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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of

the Securities Exchange Act of 1934 (Amendment No.        )

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PTC Therapeutics, Inc.

100 Corporate Court

South Plainfield, New Jersey 07080

April 29, 2021

Dear Stockholder:

You are cordially invited to attend the 2021 Annual Meeting of Stockholders of PTC Therapeutics, Inc., on Tuesday, June 8, 2021 at 9:00 a.m., Eastern Time. Due to the public health impact of the COVID-19 pandemic and governmental restrictions limiting the number of people who may gather together, and to support the health and well-being of our stockholders, directors, employees and communities, the Annual Meeting will be held over the Internet in a virtual meeting format, via live webcast at www.virtualshareholdermeeting.com/PTCT2021. There will not be a physical meeting location for the Annual Meeting and stockholders will not be able to attend the Annual Meeting in person.

The attached Notice of the Annual Meeting and proxy statement provide important information about the Annual Meeting and will serve as your guide to the business to be conducted at the meeting. Your vote is very important to us. We urge you to read the accompanying materials regarding the matters to be voted on at the Annual Meeting and to submit your voting instructions by proxy. Our Board of Directors recommends that you vote "for" each of the proposals listed on the attached Notice.

You may submit your proxy by Internet, by telephone or by requesting, prior to May 25, 2021, a printed or emailed copy of the proxy materials and using the enclosed proxy card. If you submit your proxy before the meeting but later decide to virtually attend the Annual Meeting, you may still vote at the Annual Meeting.

On behalf of our Board of Directors, management and all of our employees, I thank you for your continuing support and confidence.

As always, we encourage you to vote your shares prior to the Annual Meeting regardless of whether you intend to attend.

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PTC Therapeutics, Inc.

100 Corporate Court

South Plainfield, New Jersey 07080

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NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

To be held on June 8, 2021

To the Stockholders of PTC Therapeutics, Inc.:

This proxy statement contains information about the 2021 Annual Meeting of Stockholders of PTC Therapeutics, Inc., which we refer to as the Annual Meeting. Due to the public health impact of the COVID-19 pandemic and governmental restrictions limiting the number of people who may gather together, and to support the health and well-being of our stockholders, directors, employees and communities, the Annual Meeting will be held on Tuesday, June 8, 2021 at 9:00 a.m., Eastern Time, over the Internet in a virtual format, via live webcast at www.virtualshareholdermeeting.com/PTCT2021. There will not be a physical meeting location for the Annual Meeting, and stockholders will not be able to attend the Annual Meeting in person.

At the Annual Meeting, stockholders will consider and act upon the following matters:

Instead of mailing a printed copy of our proxy materials to all of our stockholders, we provide access to these materials via the Internet. This reduces the amount of paper necessary to produce these materials as well as the costs associated with mailing these materials to all stockholders. Accordingly, on or about April 29, 2021, we will begin mailing a Notice of Internet Availability of Proxy Materials, or Notice, to stockholders of record at the close of business on April 16, 2021, the record date for the Annual Meeting, and will post our proxy materials on the website referenced in the Notice. As more fully described in the Notice, stockholders may choose to access our proxy materials on the website referred to in the Notice or may request, prior to May 25, 2021, to receive a printed or emailed set of our proxy materials.

We encourage you to vote in one of the following ways:

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If your shares are held in “street name,” meaning that they are held for your account by a broker or other nominee, you may receive additional instructions from your broker or other nominee on how to vote your shares.

Whether or not you plan to virtually attend the Annual Meeting, we urge you to take the time to vote your shares.

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PTC Therapeutics, Inc.

100 Corporate Court

South Plainfield, New Jersey 07080

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PROXY STATEMENT FOR THE ANNUAL MEETING OF STOCKHOLDERS

To be held on June 8, 2021

These proxy materials are being furnished in connection with the solicitation of proxies by our Board of Directors for use at the 2021 Annual Meeting to be held on Tuesday, June 8, 2021 at 9:00 a.m., Eastern Time, via live webcast at www.virtualshareholdermeeting.com/PTCT2021, or the Annual Meeting Website, and at any adjournment or postponement thereof. Due to the public health impact of the COVID-19 pandemic and governmental restrictions limiting the number of people who may gather together, and to support the health and well-being of our stockholders, directors, employees and communities, the Annual Meeting will be conducted over the Internet in a virtual format. There will not be a physical meeting location for the Annual Meeting, and stockholders will not be able to attend the Annual Meeting in person.

All proxies will be voted in accordance with the instructions contained in those proxies. If no choice is specified, the proxies will be voted "for" each of the director nominees and "for" each of the proposals set forth in the accompanying Notice of Annual Meeting of Stockholders. You may revoke your proxy at any time before it is exercised at the meeting by giving our Secretary written notice to that effect.

The Notice of Annual Meeting and proxy statement are first being mailed and/or made available to stockholders on or about April 29, 2021 in conjunction with the delivery of our 2020 Annual Report to Stockholders.

In this proxy statement, unless expressly stated otherwise or the context otherwise requires, the use of "PTC," "the Company," "our," "we" or "us" refers to PTC Therapeutics, Inc., and its subsidiaries. Certain information contained in this proxy statement relating to the occupations and security holdings of our directors and officers is based upon information received from the individual directors and officers.

Whether or not you expect to virtually attend the Annual Meeting, please vote as promptly as possible to ensure your representation and the presence of a quorum at the Annual Meeting. You may vote your shares on the Internet by visiting www.proxyvote.com or by telephone by calling 1-800-690-6903 and following the recorded instructions, by requesting, prior to May 25, 2021, a printed or emailed copy of the proxy materials and using the enclosed proxy card or by voting via the Annual Meeting Website at the Annual Meeting. Your proxy is revocable in accordance with the procedures set forth in this proxy statement.

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All website addresses given in this proxy statement are for information only and are not intended to be an active link or to incorporate any website information into this document.

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IMPORTANT INFORMATION ABOUT THE ANNUAL MEETING AND VOTING

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CORPORATE GOVERNANCE

Our Board believes that good corporate governance is important to ensure that our Company is managed for the long-term benefit of our stockholders. This section describes key corporate governance guidelines and practices that we have adopted to further this goal. Complete copies of the committee charters, Code of Business Conduct and Ethics and Corporate Governance Guidelines described below are available on the Corporate Governance page of the Investors section of our website, www.ptcbio.com. Alternatively, you can request a copy of any of these documents by writing to our Vice President, Corporate Communications, PTC Therapeutics, Inc., 100 Corporate Court, South Plainfield, New Jersey 07080.

Code of Business Conduct and Ethics

We have adopted a written Code of Business Conduct and Ethics, which is a code of ethics that applies to our directors, officers and employees, including our principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions. We have posted a current copy of the Code of Business Conduct and Ethics on the Corporate Governance page of the Investors section of our website, www.ptcbio.com. In addition, we intend to post on our website all disclosures that are required by law or Nasdaq’s listing standards concerning any amendments to, or waivers from, any provision of the Code of Business Conduct and Ethics.

Corporate Responsibility

As we seek to maximize value for our shareholders, patients and other stakeholders, we do so with a concerted and constant effort to embody the PTC Expectations within our culture and every aspect of our business.

As part of the PTC Expectations, we have focused on the need to be responsible corporate citizens, including in the following areas:

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Corporate Governance Guidelines

Our Board has adopted Corporate Governance Guidelines to assist it in the exercise of its duties and responsibilities and to serve the best interests of our Company and our stockholders. We have posted a current copy of the Corporate Governance Guidelines on the Corporate Governance page of the Investors section of our website, www.ptcbio.com. These principles, which provide a framework for the conduct of our Board’s business, provide that:

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Director Independence

Our Board has determined that all of our directors and director nominees, other than Dr. Peltz, our Chief Executive Officer, are independent as defined under applicable Nasdaq rules. In making such determination, our Board considered the relationships that each such person has with our Company and all other facts and circumstances that our Board deemed relevant in determining independence, including beneficial ownership of our common stock by our non-employee directors.

Director Nominations

Process

Our Nominating and Corporate Governance Committee is responsible for identifying individuals qualified to serve as directors, consistent with criteria approved by our Board, and recommending the persons to be nominated for election as directors.

The process followed by our Nominating and Corporate Governance Committee to identify and evaluate director candidates includes requests to members of our Board, search firms and others for recommendations, meetings from time to time to evaluate biographical information and background material relating to potential candidates and interviews of selected candidates by members of our Nominating and Corporate Governance Committee and our Board.

Criteria and Diversity

In considering whether to recommend any particular candidate for inclusion in our Board’s slate of recommended director nominees, our Nominating and Corporate Governance Committee applies the criteria specified in our Corporate Governance Guidelines. These criteria include the candidate’s integrity, business acumen, knowledge of our business and industry, experience, diligence, conflicts of interest with us, and ability to act in the interests of stockholders. Our Nominating and Corporate Governance Committee does not assign specific weight to particular criteria and no particular criterion is a prerequisite for any prospective director nominee.

Our Board does not have a formal policy with respect to diversity, but our Corporate Governance Guidelines provide that an objective of Board composition is to bring to our Company a variety of perspectives and skills derived from high quality business and professional experience. Our Board recognizes its responsibility to ensure that director nominees possess appropriate qualifications and reflect a reasonable diversity of personal and professional experience, skills, backgrounds and perspectives. We believe that the backgrounds and qualifications of our directors, considered as a group, should provide a composite mix of experience, knowledge and abilities that will allow our Board to promote our strategic objectives and to fulfill its responsibilities to our stockholders.

If all of the director nominees that are nominated for election at the Annual Meeting by our Board are elected, our Board will be composed of 40% women and 10% of individuals that self-identify as a member of an underrepresented minority.

The director biographies presented under "Proposal 1: Election of Directors" indicate each director nominee’s experience, qualifications, attributes and skills that led our Board to conclude that he or she should be nominated to serve as a member of our Board or, in the case of our continuing directors, that he or she is qualified to serve on our Board. Our Board believes that each of the director nominees and continuing directors has had substantial achievement in his or her professional and personal pursuits, and possesses the background, talents and experience that our Board desires and that will contribute to the best interests of our Company and to long-term stockholder value.

Stockholder Nominations

Stockholders may recommend individuals to our Nominating and Corporate Governance Committee for consideration as potential director candidates by submitting their names, together with appropriate biographical information and background materials as of the date such recommendation is made, to our Nominating and Corporate

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Governance Committee, c/o Secretary, PTC Therapeutics, Inc., 100 Corporate Court, South Plainfield, New Jersey 07080. Assuming that appropriate biographical and background material has been provided on a timely basis, our Nominating and Corporate Governance Committee will evaluate stockholder-recommended candidates by following substantially the same process, and applying substantially the same criteria, as it follows for candidates submitted by others.

Stockholders also have the right under our bylaws to directly nominate director candidates, without any action or recommendation on the part of our Nominating and Corporate Governance Committee or our Board, by following the procedures set forth under "Stockholder Proposals and Nominations for Director."

Board Meeting and Annual Meeting Attendance

Our Board held 9 meetings during 2020.

During 2020, each of our directors attended at least 75% of the Board meetings and the meetings of the committees on which such director then served.

Our Corporate Governance Guidelines provide that our directors are expected to attend the Annual Meeting. All of our directors attended our 2020 annual meeting of stockholders.

Board Leadership Structure

The positions of Chair of the Board and Chief Executive Officer are currently separate. Mr. Schmertzler serves as our Chair of the Board and Dr. Peltz serves as our Chief Executive Officer. This leadership structure allows our Chief Executive Officer to focus on our day-to-day business and allows our Chair of the Board to lead our Board in its fundamental role of providing advice to and independent oversight of management. Our Board recognizes the time, effort and energy that our Chief Executive Officer must devote to his position, as well as the commitment required by Mr. Schmertzler to serve as our Chair of the Board, particularly as our Board’s oversight responsibilities continue to grow. Our Board also believes that this structure ensures a greater role for the independent directors in the oversight of our Company and active participation of the independent directors in setting agendas and establishing priorities and procedures for the work of our Board.

Our bylaws do not require the position of Chair of our Board and Chief Executive Officer to be separate. Our Board believes that its leadership structure demonstrates our commitment to good corporate governance, and is appropriate at present because it strikes an effective balance between strategy development, independent leadership and management oversight. Our Board believes its leadership structure positively affects its administration of its risk oversight function.

Board Committees

Our Board has established three standing committees: our Audit Committee, our Compensation Committee and our Nominating and Corporate Governance Committee. Each of these committees operates under a charter that has been approved by our Board. Each committee’s charter is posted on the Corporate Governance page of the Investors section of our website, www.ptcbio.com.

Our Board has determined that all of the members of each of its three committees are independent as defined under applicable Nasdaq rules, including, in the case of all members of our Audit Committee, the independence requirements contemplated by Rule 10A-3 under the Securities Exchange Act of 1934, as amended, or the Exchange Act, and, in the case of all members of our Compensation Committee, the independence requirements contemplated by Rule 10C-1 under the Exchange Act.

Audit Committee

The members of our Audit Committee are Ms. Reeve, Mr. Southwell and Ms. Svoronos. Ms. Reeve chairs our Audit Committee. Our Audit Committee held six meetings in 2020.

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Our Audit Committee’s responsibilities include:

Our Board has determined that Ms. Reeve, Mr. Southwell and Ms. Svoronos are "audit committee financial experts" as defined in applicable SEC rules.

Compensation Committee

The members of our Compensation Committee are Messrs. Schmertzler and Southwell and Dr. Steele. Mr. Schmertzler chairs our Compensation Committee. Our Compensation Committee held 14 meetings in 2020.

Our Compensation Committee’s responsibilities include:

Compensation Processes and Procedures

Our Compensation Committee makes all compensation decisions regarding our Chief Executive Officer and each of his direct reports, including salary, annual cash incentive compensation and long-term equity compensation (or, when the Compensation Committee deems it appropriate, makes recommendations concerning such matters to our Board). If

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the Compensation Committee deems it appropriate, it may delegate any of its responsibilities to one or more Compensation Committee members or subcommittees.

Our Compensation Committee relies on management for legal, tax, compliance, finance and human resource recommendations, data and analysis for the design and administration of the compensation and benefits programs for our executive officers. As a result, our Chief Executive Officer, our Chief Financial Officer, our Senior Vice President, Human Resources and our Executive Vice President & Chief Legal Officer generally attend Compensation Committee meetings upon the invitation of the Compensation Committee. The Compensation Committee also establishes, with input from the Chief Executive Officer and other members of the executive team, the corporate goals applicable to our annual cash incentive awards.

On an annual basis our Chief Executive Officer meets with the executive officers to discuss the Company’s accomplishments as well as the individual officer’s performance and contributions over the year. Based on these discussions and input from others within the Company, our Chief Executive Officer, with respect to each executive officer other than himself, prepares an evaluation of the executive officer as to the level of contribution made to the management and success of our Company. In addition, our Chief Executive Officer, with the participation of other members of senior management, prepares information concerning the Company’s achievements and our performance against corporate goals during the fiscal year.

The Compensation Committee is presented with this information and the Chief Executive Officer’s recommendations with respect to each executive officer, other than himself, as to each element of compensation. The Chief Executive Officer’s recommendations, information concerning the Company’s performance over the applicable fiscal period, expectations concerning performance in the coming year, and advice and information from its independent compensation consultant are all taken into account by the Compensation Committee when it makes final determinations on executive compensation matters.

Our Chief Executive Officer’s performance and salary, annual cash incentive compensation and long-term equity compensation are discussed by the Compensation Committee in executive session, with advice and participation from the Compensation Committee’s independent compensation consultant as requested by the Compensation Committee. Our Chief Executive Officer does not participate in decisions regarding his own compensation.

For additional information concerning our executive compensation program, see Compensation Discussion and Analysis on page 40.

Our Compensation Committee has delegated to the Chief Executive Officer limited authority to make equity award grants to employees of the Company or any of its present or future subsidiaries, other than to himself, any other named executive officer, or any employee who is a voting member of the executive committee of the Company or above the level of Executive Vice President or its equivalent, without necessity for any further action by the Board, Compensation Committee or any other committee of the Board. Any such awards must be reported to our Compensation Committee at its next meeting. During 2020, our Chief Executive Officer made equity award grants with an underlying aggregate amount of 15,500 shares of our common stock pursuant to this delegated authority.

Role of Independent Compensation Consultants

Our Compensation Committee may, in its sole discretion, retain or obtain the advice of one or more compensation consultants. In 2020, our Compensation Committee engaged Frederic W. Cook & Co., Inc., or FW Cook, as its independent compensation consultant, to provide comparative data on executive compensation practices in our industry, to assist the Compensation Committee in developing an appropriate list of peer companies against which to conduct compensation benchmarking, and to advise on our executive compensation program generally. The Compensation Committee also engaged FW Cook for recommendations and review of non-employee director compensation in 2020.

Although our Compensation Committee considers the advice and recommendations of independent compensation consultants as to our executive compensation program, our Compensation Committee ultimately makes its own decisions about these matters. In the future, we expect that our Compensation Committee will continue to engage independent

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compensation consultants to provide additional guidance on our executive compensation programs and to conduct further competitive benchmarking against a peer group of publicly traded companies.

The Compensation Committee has reviewed information regarding the independence and potential conflicts of interest of FW Cook during 2020 and 2021, taking into account, among other things, the factors set forth in the Nasdaq listing standards. Based on such reviews, the Compensation Committee concluded that the engagement of FW Cook did not raise any conflict of interest. FW Cook did not provide services to the Company outside of services provided at the request of the Compensation Committee in 2020.

Nominating and Corporate Governance Committee

The members of our Nominating and Corporate Governance Committee are Dr. Zeldis, Mr. Schmertzler and Ms. Okey. Mr. Schmertzler chairs our Nominating and Corporate Governance Committee. Our Nominating and Corporate Governance Committee held two meetings in 2020.

Our Nominating and Corporate Governance Committee’s responsibilities include:

Risk Oversight

Risk is inherent with every business and how well a business manages risk can ultimately determine its success. We face a number of risks, including those described under "Risk Factors" in our Annual Report on Form 10-K for the fiscal year ended December 31, 2020, and those described in our Quarterly Reports on Form 10-Q and our Current Reports on Form 8-K. Our Board is actively involved in oversight of risks that could affect us.

Role of Our Board in Management of Risk

Our Board administers its risk oversight function directly and through its Audit Committee and receives regular reports from members of senior management, including our Chief Executive Officer, Chief Financial Officer and Chief Legal Officer, on areas of material risk to our Company, including operational, financial, legal and regulatory, cybersecurity, and strategic and reputational risks and has direct access to our Chief Compliance Officer, Chief Information Officer, Senior Vice President, Quality and our Senior Vice President, Global Regulatory Affairs. As part of its charter, our Audit Committee regularly discusses with management our major risk exposures, their potential financial impact on our Company and the steps we take to manage them. Our Board believes that full and open communication between our management and our Board is essential for effective risk management and oversight.

In addition, our Compensation Committee assists our Board in fulfilling its oversight responsibilities with respect to the management and risks arising from our compensation policies and programs. Our Nominating and Corporate Governance Committee assists our Board in fulfilling its oversight responsibilities with respect to the management of risks associated with board organization, membership and structure, succession planning for our directors and executive officers and corporate governance.

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Communicating with our Directors

Our Board will give appropriate attention to written communications that are submitted by stockholders, and will respond if and as appropriate. Our Chair of the Board and the Chair of our Nominating and Corporate Governance Committee, with the assistance of our Chief Legal Officer and Vice President, Corporate Communications, are primarily responsible for monitoring communications from stockholders and for providing copies or summaries to the other directors as they consider appropriate.

Communications are forwarded to all directors if they relate to important substantive matters. In general, communications relating to corporate governance and corporate strategy are more likely to be forwarded than communications relating to ordinary business affairs, personal grievances and matters that are duplicative communications. Items that are unrelated to the duties and responsibilities of the Board may be excluded or redirected, as appropriate, such as business solicitations, job inquiries or advertisements, mass mailings, new product suggestions, or communications that have no rational relevance to our business or operations. In addition, material that is unduly hostile, threatening or similarly unsuitable will be excluded; however, any communication will be made available to any director upon her or his request.

Stockholders who wish to send communications on any topic to our Board should address such communications to the Board of Directors c/o PTC Therapeutics, Inc., 100 Corporate Court, South Plainfield, New Jersey 07080, Attn: Secretary.

Compensation Committee Interlocks and Insider Participation

Messrs. Schmertzler and Southwell and Dr. Steele served as members of the Compensation Committee during the last completed fiscal year.

None of our executive officers serves as a member of the board of directors or compensation committee, or other committee serving an equivalent function, of any other entity that has one or more of its executive officers serving as a member of our Board or our Compensation Committee. None of the members of our Compensation Committee is, or has ever been, an officer or employee of PTC.

Policies and Procedures for Related Person Transactions

Our Board has adopted a written related person policy, which sets forth our policies and procedures for the review of any transaction, arrangement or relationship in which the Company is a participant, the amount involved exceeds $120,000 and one of our executive officers, directors, director nominees or 5% stockholders, or their immediate family members, each of whom we refer to as a "related person," has a direct or indirect material interest.

If a related person proposes to enter into such a transaction, arrangement or relationship, which we refer to as a "related person transaction," the related person must report the proposed related person transaction to our Chief Legal Officer. Our related person policy calls for the proposed related person transaction to be reviewed and, if deemed appropriate, approved by our Audit Committee. Whenever practicable, the reporting, review and approval will occur prior to entry into the transaction. If advance review and approval is not practicable, the Audit Committee will review, and, in its discretion, may ratify the related person transaction. Our related person policy also permits the Chair of our Audit Committee to review and, if deemed appropriate, approve proposed related person transactions that arise between Audit Committee meetings, subject to ratification by the Audit Committee at its next meeting. Any related person transactions that are ongoing in nature will be reviewed annually.

A related person transaction reviewed under the policy will be considered approved or ratified if it is authorized by our Audit Committee after full disclosure of the related person’s interest in the transaction. As appropriate for the circumstances, the Audit Committee will review and consider:

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Our Audit Committee may approve or ratify the transaction only if the Audit Committee determines that, under all of the circumstances, the transaction is in our best interests. The Audit Committee may impose any conditions on the related person transaction that it deems appropriate.

In addition to the transactions that are excluded by the instructions to the SEC’s related person transaction disclosure rule, our Board has determined that the following transactions do not create a material direct or indirect interest on behalf of related persons and, therefore, are not related person transactions for purposes of this policy:

Our related person policy provides that transactions involving compensation of executive officers shall be reviewed and approved by our Compensation Committee in the manner specified in its charter.

All of the transactions discussed below under the heading "Related Person Transactions" that occurred during 2020 were reviewed and approved by our Audit Committee or, with respect to compensation matters, our Compensation Committee, in each case in accordance with our policy.

Related Person Transactions

Since January 1, 2020, we have engaged in the following transactions in which our directors, executive officers and holders of more than 5% of our voting securities, and affiliates of our directors, executive officers and holders of more than 5% of our voting securities may have a direct or indirect material interest. We believe that all of these transactions were on terms as favorable to us as could have been obtained from unrelated third parties.

Familial Relationship

Jane (Zheng) Yang Almstead, the wife of Neil Almstead, our Chief Technical Operations Officer, is employed by us as a Senior Manager, Analytical Sciences; Joeli Mansim, the wife of Marcio Souza, who served as our Chief Operating Officer until his resignation in April 2020, is employed by us as General Manager, SAM; and Ellen Welch, Ph.D., the

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wife of Stuart W. Peltz, our Chief Executive Officer, is employed by us as Senior Vice President, Research & Translational Medicine. For their services to the Company during fiscal 2020, these employees received compensation of $204,696 to $1,906,337, comprised of base salary and non-equity incentive compensation (paid in fiscal 2021 based on 2020 performance), equity awards in the form of stock options and restricted stock units (based on the grant-date fair value), vested stock appreciation rights, company 401(k) matching contributions, with respect to Ms. Welch, a bonus paid under our employment anniversary program, and with respect to Ms. Mansim, amounts paid under an employee-wide travel incentive program. These amounts reflect the full grant-date fair value of equity compensation awarded in 2020 (computed in accordance with the provisions of ASC 718), and do not represent the actual value realized by the employee during the year. Each of these individuals participated in our benefit programs generally available to U.S. employees during 2020. None of Dr. Peltz, Dr. Almstead nor Mr. Souza (prior to his resignation from the Company) participate in the compensation decisions regarding their family members, and we believe that the compensation paid to Ms. Almstead, Ms. Mansim and Dr. Welch is fair and commensurate with what their compensation would be if they had no relationship to an executive officer of the Company.

During 2020, our IT, human resources and finance departments each engaged RSM US LLP, a provider of audit, tax and consulting services, for IT and tax services and audit services with respect to our 401(k) plan for aggregate fees of approximately $347,289. Dr. Peltz’s brother is a principal in a different business unit at RSM, and we have been advised that he does not receive a direct economic benefit from these service agreements. We have, and anticipate that we will continue to, engage RSM for these types of services during 2021. We believe that the fees paid are fair and have been unaffected by this relationship.

BioElectron Acquisition

As previously disclosed, on October 25, 2019 we completed the acquisition, or the Acquisition, of substantially all of the assets of BioElectron Technology Corporation, or BioElectron, pursuant to an Asset Purchase Agreement by and between us and BioElectron, dated October 1, 2019, or the Asset Purchase Agreement.

Upon the closing of the Acquisition, we paid to BioElectron total upfront consideration of $10.0 million, funded with cash on hand, less (i) transaction expenses incurred by BioElectron, (ii) the amount of outstanding indebtedness of BioElectron and (iii) $1.5 million to be held in an escrow account to secure potential indemnification obligations owed to us. Subject to the terms and conditions of the Asset Purchase Agreement, BioElectron may become entitled to receive contingent milestone payments of up to $200.0 million (in cash or in shares of our common stock, as determined by us) from us based on the achievement of certain regulatory and net sales milestones. Subject to the terms and conditions of the Asset Purchase Agreement, BioElectron may also become entitled to receive contingent payments of a low single digit percentage of net sales of certain products.

In April 2020, Matthew B. Klein was named our Chief Development Officer. At the time of the Acquisition, Dr. Klein was the Chief Executive Officer and director of BioElectron, and was, and remains as of the date of this proxy statement, a shareholder of BioElectron, owning approximately six percent of its outstanding shares. As a shareholder of BioElectron, Dr. Klein is entitled to receive a portion of any payments made to BioElectron pursuant to the Asset Purchase Agreement. No such payments were made to BioElectron in 2020. Dr. Klein was not a related party at the time of the Acquisition.

Indemnification Agreements

Our restated certificate of incorporation, or certificate of incorporation, provides that we will indemnify our directors and officers to the fullest extent permitted by Delaware law. In addition, we have entered into indemnification agreements with our directors and executive officers. These indemnification agreements may require us, among other things, to indemnify each such director and executive officer for some expenses, including attorneys’ fees, judgments, fines and settlement amounts incurred by him or her in any action or proceeding arising out of his or her service as one of our directors and/or executive officers.

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PRINCIPAL STOCKHOLDERS

The following table sets forth information, to the extent known by us or ascertainable from public filings, with respect to the beneficial ownership of our common stock as of April 16, 2021, except as otherwise indicated in the table below, by each of our directors and director nominees; each of our named executive officers; all of our directors, director nominees and executive officers as a group; and each person, or group of affiliated persons, who is known by us to beneficially own more than 5% of our common stock.

The column entitled "Percentage of shares beneficially owned" is based on a total of 70,418,067 shares of our common stock outstanding as of April 16, 2021.

Beneficial ownership is determined in accordance with the rules and regulations of the SEC and includes voting or investment power with respect to our common stock. Shares of our common stock subject to (i) options that are currently exercisable or exercisable within 60 days of April 16, 2021 or (ii) restricted stock units that will vest within 60 days of April 16, 2021 are considered outstanding and beneficially owned by the person holding the options or restricted stock units for the purpose of calculating the percentage ownership of that person but not for the purpose of calculating the percentage ownership of any other person. Except as otherwise noted, the persons and entities in this table have sole voting and investing power with respect to all of the shares of our common stock beneficially owned by them, subject to community property laws, where applicable.

Except as otherwise indicated in the table below, addresses of named beneficial owners are in care of PTC Therapeutics Inc., 100 Corporate Court, South Plainfield, New Jersey 07080.

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PROPOSAL 1: ELECTION OF DIRECTORS

Information Regarding Directors and Director Nominees

Board Composition

We currently have a classified board of directors consisting of three classes: Class I, Class II, and Class III. The terms of service of the three classes are staggered so that the term of one class expires each year. At each annual meeting of stockholders, directors are elected for a full term of three years to continue in office or to succeed those directors whose terms are expiring. Our directors hold office until their successors have been elected and qualified, or until the earlier of their resignation or removal.

Our certificate of incorporation and bylaws provide that the authorized number of directors may be changed only by resolution of our Board; that our directors may be removed only for cause by the affirmative vote of the holders of at least 75% of the votes entitled to be cast in an annual election of directors; and that any vacancy on our Board, including a vacancy resulting from an enlargement of our Board, may be filled only by vote of a majority of our directors then in office. Our Board is authorized to have ten directors and currently consists of nine directors, three Class I directors, three Class II directors, and three Class III directors with one vacancy, which the Board intends to fill at the Annual Meeting.

There are no family relationships between or among any of our executive officers, directors or director nominees. The principal occupation and employment during the past five years of each of our directors and director nominees was carried on, in each case except as specifically identified below, with a corporation or organization that is not a parent, subsidiary or other affiliate of us. There is no arrangement or understanding between any of our directors or director nominees and any other person or persons pursuant to which he was or is to be selected as a director or director nominee.

Director Nominees

At the Annual Meeting, stockholders will be asked to consider the election of Emma Reeve, Michael Schmertzler, Glenn D. Steele Jr., M.D., Ph.D. and Mary Smith. Upon the recommendation of our Nominating and Corporate Governance Committee, our Board has nominated Ms. Reeve, Mr. Schmertzler, Dr. Steele and Ms. Smith for election at the Annual Meeting as Class II directors, each to serve until 2024.

Each of Ms. Reeve, Mr. Schmertzler, Dr. Steele and Ms. Smith, our director nominees, has indicated his or her willingness to serve on our Board, if elected. If any director nominee should be unable to serve, the person acting under the proxy may vote the proxy for a substitute director nominee designated by our Board. We do not contemplate that any of our director nominees will be unable to serve if elected.

Unless otherwise instructed in the proxy, all proxies will be voted "FOR" the election of each of the director nominees identified above to a three-year term ending in 2024, each such director nominee to hold office until his or her successor has been duly elected and qualified.

A plurality of the voting power of the shares of common stock present in person or represented by proxy at the Annual Meeting and entitled to vote is required to elect each director nominee as a director. Proxies cannot be voted for a greater number of persons than the number of nominees named.

Our Board Recommends that You Vote "FOR" the Election of Emma Reeve, Michael Schmertzler, Glenn D. Steele Jr., M.D., Ph.D. and Mary Smith

Biographical Information

The following table and biographical descriptions provide information as of April 16, 2021 relating to each director nominee and each director continuing in office, including age and period of service as a director of our Company; committee memberships; business experience during the past five years, including directorships at other public

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companies; community activities; and the other experience, qualifications, attributes or skills that led our Board to conclude that such director should serve as a director of PTC.

Class II Director nominees to be elected at the Annual Meeting (current terms expiring in 2021)

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Class I Directors (terms expiring in 2023)

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Class III Directors (terms expiring in 2022)

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PROPOSAL 2: AMENDMENT TO THE COMPANY’S RESTATED CERTIFICATE OF INCORPORATION TO INCREASE THE NUMBER OF AUTHORIZED SHARES OF COMMON STOCK FROM 125,000,000 TO 250,000,000

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On March 23, 2021, upon the recommendation of our Nominating and Corporate Governance Committee, our Board approved the adoption of and declared advisable to the Company and its stockholders, subject to stockholder approval, an amendment to the Company’s Restated Certificate of Incorporation, or the Restated Certificate, to increase the number of authorized shares of common stock, par value $0.001 per share, from 125,000,000 shares to 250,000,000 shares. The proposed amendment to the Restated Certificate would not increase or otherwise affect our authorized preferred stock.

Our Board believes it is in the best interest of the Company and its stockholders to increase the number of authorized shares of common stock to give the Company greater flexibility in considering and planning for future potential business needs and pursuing our strategic goals. We currently have no specific plans, arrangements or understandings to issue additional shares of our common stock, except for the issuance of shares of common stock pursuant to our equity incentive plans to persons eligible to participate in those plans, including pursuant to the proposed amendment to our 2016 Employee Stock Purchase Plan, and potential future issuances pursuant to our at-the-market sales agreement with Cantor Fitzgerald & Co. and RBC Capital Markets, LLC, dated August 7, 2019, or our at-the-market sales agreement. However, the availability of additional shares of common stock for issuance is, in the Board's view, prudent and will afford the company with flexibility in acting upon financing transactions to strengthen our financial position and/or commercial partnership opportunities that may arise. The increase in the number of authorized but unissued shares of common stock would enable our Board, without the expense and delay of seeking stockholder approval, to issue shares from time to time as may be required for proper business purposes. The additional shares of common stock will be available for issuance by our Board for various corporate purposes, including but not limited to, grants under our equity incentive award plans, financings such as public or private offerings of common stock or convertible securities, including issuances under our at-the-market sales agreement, satisfaction of potential milestone payment obligations, potential settlement of conversions of our 3.00% convertible senior notes due August 15, 2022 and our 1.50% convertible senior notes due September 15, 2026, potential strategic transactions, including mergers, acquisitions, strategic partnerships, collaborations, strategic investments, joint ventures, divestitures, business combinations, stock splits, stock dividends as well as other general corporate transactions and other corporate purposes that have not yet been identified. If the authorization of an increase in the available common stock is postponed until the foregoing specific needs arise, the delay and expense incident to obtaining approval of the stockholders at that time could impair our ability to achieve the corporate purposes set forth above.

The Restated Certificate currently authorizes the issuance of up to 125,000,000 shares of common stock, par value $0.001 per share, and 5,000,000 shares of preferred stock, par value $0.001 per share. As of April 16, 2021, 70,418,067 shares of our common stock were outstanding and our Board had reserved 12,623,895 shares of common stock for issuance upon the exercise of outstanding stock options and unvested restricted stock units, 752,366 shares of common stock for issuance pursuant to our 2013 Long Term Incentive Plan, 1,096,710 shares of common stock for issuance pursuant to our 2020 Inducement Stock Incentive Plan, as amended, and 359,167 shares of common stock for issuance pursuant to our 2016 Employee Stock Purchase Plan. In addition, our Board has reserved up to 10,577,310 shares of common stock for issuance upon conversion of our 3.00% convertible senior notes due August 15, 2022 and our 1.50% convertible senior notes due September 15, 2026. As a result, the Company has only 29,172,485 shares of common stock available for future issuance out of the 125,000,000 shares of common stock currently authorized as of March 31, 2021. Additionally, we have the option to pay our contingent obligations of (i) up to $200.0 million in potential milestone payments to BioElectron pursuant to an Asset Purchase Agreement by and between us and BioElectron, dated October 1, 2019 and (ii) a $30.0 million development milestone payment upon the completion of enrollment of a Phase 3 clinical trial for PTC923 for PKU to former Censa securityholders pursuant to an Agreement and Plan of Merger, dated as of May 5, 2020, by and among us, Hydro Merger Sub, Inc., our wholly owned, indirect subsidiary, and, solely in its capacity as the representative, agent and attorney-in-fact of the securityholders of Censa, Shareholder Representatives Services LLC, in shares of our common stock rather than in cash. Our Board has also approved, and we are seeking stockholder approval of, an increase of 1,000,000 shares of common stock to be reserved for issuance under the 2016 Employee Stock Purchase Plan, as described in Proposal 3.

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If this proposal is approved, the additional authorized shares may be issued at the discretion of our Board without further stockholder action, except as may be required by law or the rules of Nasdaq. The adoption of the proposed amendment to the Restated Certificate would not have any immediate dilutive effect on the proportionate voting power or other rights of existing stockholders. However, the issuance of shares of common stock, other than on a pro-rata basis to all stockholders, would reduce each stockholder’s proportionate interest in the Company and the issuance of additional shares of common stock may, among other things, have a dilutive effect on earnings per share and on stockholders' equity and voting rights. Furthermore, future sales of substantial amounts of our common stock, or the perception that these sales might occur, could adversely affect the prevailing market price of our common stock or limit our ability to raise additional capital. Stockholders should recognize that, as a result of this proposal, they will own a smaller percentage of shares relative to the total authorized shares of the company than they presently own. The holders of any of the additional shares of common stock issued in the future would have the same rights and privileges as the holders of the shares of common stock currently authorized and outstanding. Those rights do not include preemptive rights with respect to the future issuance of any additional shares. The holders of shares of our common stock will have no dissenters' rights of appraisal under Delaware law, our Restated Certificate or our Bylaws with respect to the proposed amendment to the Restated Certificate.

The issuance of additional shares of common stock could have the effect of making it more difficult for a third party to acquire, or discouraging a third party from attempting to acquire, control of the company. We are not aware of any attempts on the part of a third party to effect a takeover of the company, and the proposed amendment to the Restated Certificate has been proposed for the reasons stated above and not with the intention that any increase in the authorized shares of common stock be used as a type of anti-takeover device.

A copy of the proposed amendment to the Restated Certificate is attached as Exhibit A to this proxy statement. If the proposed amendment to the Restated Certificate is approved, subject to the discretion of the Board of Directors, as soon as practicable after the Annual Meeting, the Company will file the amendment to the Restated Certificate with the office of the Secretary of State of Delaware to reflect the increase in the authorized number of shares of our common stock. Upon approval and following such filing with the Secretary of State of Delaware, the amendment to the Restated Certificate will become effective on the date it is filed. Our Board reserves the right to abandon or delay the filing of the amendment to the Restated Certificate even if it is approved by the stockholders. If the proposed amendment to the Restated Certificate is approved and becomes effective, the first paragraph of Article FOURTH of our Restated Certificate, which sets forth our currently authorized capital stock, will be amended to read in its entirety as follows:

“FOURTH: The total number of shares of all classes of stock which the Corporation shall have authority to issue is Two Hundred Fifty-Five Million (255,000,000) shares, consisting of (i) Two Hundred Fifty Million (250,000,000) shares of Common Stock, $0.001 par value per share (“Common Stock”), and (ii) Five Million (5,000,000) shares of Preferred Stock, $0.001 par value per share (“Preferred Stock”).”

The affirmative vote of the holders of at least a majority of the shares of common stock entitled to vote at the Annual Meeting will be required to approve this proposal. Abstentions will have the practical effect of a vote against the amendment to the Restated Certificate. Our Board urges stockholders to vote for this proposal as failure to obtain the vote of a majority of outstanding shares may limit the Company’s abilities to operate and execute on future business plans.

Our Board Recommends that You Vote "FOR" the Approval of an Amendment to the Company’s Restated Certificate of Incorporation to Increase the Number of Authorized Shares of Common Stock from 125,000,000 to 250,000,000.

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PROPOSAL 3: AMENDMENT TO THE COMPANY’S 2016 EMPLOYEE STOCK PURCHASE PLAN TO INCREASE THE NUMBER OF AUTHORIZED SHARES OF COMMON STOCK UNDER THE PLAN FROM 1,000,000 TO 2,000,000

On March 23, 2021, upon the recommendation of our Compensation Committee, our Board approved the adoption of and declared advisable to the Company and its stockholders, subject to stockholder approval, an amendment to the Company’s 2016 Employee Stock Purchase Plan, or the ESPP, to increase the number of authorized shares of common stock authorized for issuance under the ESPP from 1,000,000 shares to 2,000,000 shares (we refer to the ESPP as so amended, as the Amended ESPP).

A description of the material terms of the Amended ESPP are summarized below. The only difference between the terms of the ESPP and the Amended ESPP is that the Amended ESPP provides that an additional 1,000,000 shares of our common stock may be issued pursuant to the Amended ESPP.

The Amended ESPP is intended to benefit our company and our stockholders by attracting, retaining and motivating talented employees, which we believe to be critical for our success, and aligning the interests of participating employees with our stockholders. We believe that the ability to participate in the Amended ESPP is an attractive feature for current and potential employees by affording them the opportunity to share in the growth and success of the Company. The Amended ESPP also helps to attract and retain employees because employee stock purchase plans are commonly offered by our peers and other industry leaders. In 2018, 2019 and 2020, we issued a total of 139,181, 107,145 and 124,736 shares of common stock under the ESPP, respectively. As of April 16, 2021, 359,167 shares were available for future issuance under the ESPP without giving effect to the approval of the Amended ESPP. As our employee population continues to grow, if the Amended ESPP is not approved by our stockholders, our ability to recruit and retain employees could be negatively impacted if we do not have sufficient authorized shares available for future issuance under our ESPP for our employees’ participation. To further encourage stock ownership among our employees while providing our employees a benefit that is common in the companies with which we compete for talent, our Board has adopted the Amended ESPP.

A majority of the voting power of the shares of common stock cast on this matter is required to approve this proposal. Our Board urges stockholders to vote for this proposal as failure to obtain the required vote may limit the Company’s ability to attract, retain and motivate talented employees.

Our Board Recommends that You Vote "FOR" the Approval of an Amendment to the Company’s 2016 Employee Stock Purchase Plan to Increase the Number of Authorized Shares of Common Stock under the Plan from 1,000,000 to 2,000,000.

Description of the Amended ESPP

The following is a brief summary of the Amended ESPP. The following description is only a summary of the material terms of the Amended ESPP, and is qualified in its entirety by reference to the Amended ESPP, a copy of which is attached to this proxy statement as Exhibit B. You can request a copy of the Amended ESPP by writing to PTC Therapeutics, Inc., Attn: Corporate Communications, 100 Corporate Court, South Plainfield, New Jersey 07080. A copy of the Amended ESPP, which is attached to the electronic copy of this proxy statement filed with the SEC, also may be accessed from the SEC's home page (www.sec.gov).

Eligibility

All employees of the Company and any subsidiary of the Company designated by our Board or Compensation Committee are eligible to participate in the Amended ESPP provided that they work more than twenty (20) hours per week and for more than five (5) months in a calendar year, are employees for at least two (2) years prior to enrolling in the Amended ESPP and are employees on the first day of the applicable offering period; provided, that we may permit employees who work fewer hours per week, fewer months per calendar year or who have been employed for a shorter period of time prior to participating in the Amended ESPP, in accordance with the terms of the Amended ESPP, Section 423 of the Code and guidelines that we establish under the Amended ESPP. No employee can be granted an option under

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the Amended ESPP that would result in the employee owning common stock and/or options to purchase common stock representing five percent or more of the total combined voting power or value for all classes of our outstanding capital stock. As of March 31, 2021, approximately 957 employees would have been eligible to participate in the Amended ESPP, including our currently employed named executive officers.

Amended ESPP Operation

The Amended ESPP permits eligible employees to purchase shares of our common stock at a discount. Eligible employees may elect to participate by completing an enrollment form, timely filing it with our payroll office and authorizing after-tax payroll deductions from their pay. Participants can elect to contribute from 1 to 15 percent (or such higher or lower maximum percentage as we may determine in accordance with the terms of the Amended ESPP, Section 423 of the Code and guidelines that we establish under the Amended ESPP), in whole percentages only, of their compensation (as defined in the Amended ESPP) received on each pay day during the offering period. Our Board or Compensation Committee may also, in its discretion, establish a different minimum payroll deduction percentage.

The Amended ESPP will be implemented by consecutive six (6) month offering periods. Our Board or Compensation Committee may, in its discretion, choose a different offering period of not more than twenty-seven (27) months.

Offering periods will begin at such time as our Compensation Committee may determine and establish in the Amended ESPP's guidelines. The guidelines currently contemplate that offering periods will begin on the first day on which national stock exchanges and Nasdaq are open for trading on or after July 1 and January 1 of each year. On the first day of each offering period, each employee who is enrolled in the Amended ESPP will automatically receive an option to purchase, on the last business day of the offering period, up to that number of shares of our common stock determined by multiplying $2,083 by the number of full months in the plan period and dividing the result by the closing price of our common stock on the first day of the offering period, or such lesser number of shares set by the Board or Compensation Committee. We refer to these as the option shares.

However, no eligible employee may be granted an option under the Amended ESPP that permits the employee's rights to purchase shares under the Amended ESPP to accrue at a rate that exceeds $25,000 in fair market value (based on the value of the stock on the first day of the offering period) of our common stock in any given calendar year in which such option is outstanding at any time.

Unless a participant withdraws from the Amended ESPP, the participant's option will be exercised automatically on the last business day of the offering period as to the largest whole number of shares that are exercisable and can be purchased with the deductions accumulated as of the last business day of the offering period.

Our Board or Compensation Committee will determine the purchase price of each of the shares purchased in a given offering period. The purchase price will be at least 85% of (i) the closing price of a share of our common stock on the first business day of the offering period or the last business day of the offering period, whichever is lower or (ii) the closing price of a share of our common stock on the last business day of the offering period. If the total number of shares of common stock with respect to which options are to be exercised exceeds the number of shares remaining available for issuance under the Amended ESPP, we will only issue to participants in that offering that number of shares remaining available for issuance, on a pro-rata basis.

All payroll deductions received or held by the Company under the Amended ESPP may be used by us for any corporate purpose, and we will not be obligated to segregate such payroll deductions. No interest will accrue on the payroll deductions (except as our Board or Compensation Committee may otherwise provide), and an employee participating in the Amended ESPP may not increase or decrease payroll deductions, except as permitted by the Amended ESPP. Employees may purchase common stock under the Amended ESPP only through payroll deductions. A participant's payroll deduction elections remain in effect for successive offering periods. Except to the extent provided by our Board or Compensation Committee in accordance with the Amended ESPP, Section 423 of the Code and guidelines with respect to the Amended ESPP a participant's payroll deduction may be decreased, increased or terminated by the participant only with respect to the next offering period. A participant may decrease or increase the

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rate of his or her payroll deductions for subsequent offering periods by filing a new enrollment form with our payroll office authorizing a change in payroll deduction rate. In addition, a participant may elect to discontinue his or her payroll deductions during an offering period but not elect to withdraw his or her funds. In such cases, funds deducted prior to his or her election to discontinue shall be applied to the purchase of common stock on the last day of the purchase period in which the funds were deducted. If an employee withdraws from participation during an offering period, the amounts contributed to the Amended ESPP will be refunded promptly without interest and the employee's option granted for such offering period will automatically terminate. At the end of the offering period, the accumulated payroll contributions of each employee who continues to participate in the plan as of such date will be used to purchase shares of common stock (at the option price described above) subject to the limitations described above. A participant's withdrawal from an offering period will not have any effect upon his or her eligibility to participate in succeeding offering periods or in any other similar plan which the Company may adopt.

The value of the common stock purchased will vary based on the fair market value of our common stock on the last day of the offering period. Accordingly, the dollar value and the number of shares that may be purchased in the future pursuant to the Amended ESPP are not currently determinable.

We are required to make equitable adjustments to the number and class of securities available under the Amended ESPP, the share limitations under the Amended ESPP and the purchase price for an offering period under the Amended ESPP to reflect stock splits, reverse stock splits, stock dividends, recapitalizations, combinations of shares, reclassifications of shares, spin-offs and other similar changes in capitalization or events or any dividends or distributions to holders of our common stock other than ordinary cash dividends.

In connection with a merger or other reorganization event (as defined in the Amended ESPP), our Board or a committee appointed by our Board may take any one or more of the following actions as to outstanding options to purchase shares of our common stock under the Amended ESPP on such terms as our Board or committee determines:

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Administration

The Amended ESPP shall be administered by our Board or by a committee appointed by the Board. Our Board or such committee has authority to make rules and regulations for the administration of the Amended ESPP, and its interpretation and decisions with respect to the Amended ESPP shall be final and conclusive.

The Board or such committee may delegate to one or more officers of the Company the authority to implement and administer the Amended ESPP, subject to the terms of the Amended ESPP and any guidelines approved by the Board or such committee. The Board has appointed the Compensation Committee to administer the ESPP, and the Compensation Committee has delegated authority over certain administrative matters with respect to the ESPP to the Company's Employee Benefit Plan Committee, subject to the terms of the ESPP and the guidelines adopted by the Compensation Committee. Such delegations will remain in effect if the Amended ESPP is approved by the stockholders.

Our Board or Compensation Committee has the ability to change offering periods (including the commencement dates and length thereof) with respect to future offerings without stockholder approval. Our Board may terminate or amend the Amended ESPP at any time and for any reason. The Board may amend the Amended ESPP at any time, but the plan may not be amended in any way that will cause rights issued thereunder to fail to meet the requirements for employee stock purchase plans as defined in Section 423 of the Code including stockholder approval if required.

Our Board or the Compensation Committee may allow employees who are citizens or residents of foreign jurisdictions to participate in an offering period or establish sub-plans for the benefit of such foreign employees to the extent such actions are in compliance with Section 423 of the Code.

New Plan Benefits

Benefits and purchases of shares of our common stock under the Amended ESPP depend on elections made by employees and the fair market value of our common stock on dates in the future. As a result, it is not possible to determine the benefits that will be received by executive officers and other employees in the future under the Amended ESPP.

For illustrative purposes only, the following table sets forth certain information regarding the number of shares of our common stock purchased during the fiscal year 2020 offering periods pursuant to our ESPP by each of (i) the NEOs identified in the Summary Compensation Table of this proxy statement, (ii) all current executive officers, as a group, and (iii) all employees, other than executive officers, as a group. Non-executive members of our Board are not eligible to participate in the ESPP.

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Since the ESPP was approved by our stockholders in 2016: Dr. Peltz has purchased 0 shares of our common stock under the ESPP, Ms. Hill has purchased 0 shares of our common stock under the ESPP, Dr. Almstead has purchased 2,490 shares of our common stock under the ESPP, Mr. Boulding has purchased 2,490 shares of our common stock under the ESPP, Mr. Pauwels has purchased 3,774 shares of our common stock under the ESPP, Mr. Souza has purchased 3,505 shares of our common stock under the ESPP, all of our current executive officers, as a group have purchased 13,068 shares of our common stock under the ESPP, all of our non-executive directors and director nominees, as a group have purchased 0 shares of our common stock under the ESPP and all of our employees, other than current executive officers, as a group have purchased 627,765 shares of our common stock under the ESPP.

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Federal Income Tax Consequences

The following generally summarizes the United States federal income tax consequences that will arise with respect to participation in the Amended ESPP and with respect to the sale of common stock acquired under the plan. This summary is based on the tax laws in effect as of the date of this proxy statement. The Amended ESPP is intended to qualify as an "employee stock purchase plan" as defined in Section 423 of the Code. This summary assumes that the Amended ESPP complies with Section 423 of the Code. Further, this summary assumes that the purchase price for shares is 85% of the closing price of a share of our common stock on the first day of the offering period or the last day of the offering period, whichever is lower. Changes to these laws could alter the tax consequences described below.

Tax Consequences to Participants

A participant will not have income upon enrolling in the Amended ESPP or upon purchasing stock at the end of a purchase period. A participant may have both compensation income and a capital gain or loss upon the sale of stock that was acquired under the Amended ESPP. The amount of each type of income and loss will depend on whether the participant disposes of the stock in a qualifying or disqualifying disposition. A qualifying disposition is when the participant sells the stock more than two years after the commencement of the offering during which the stock was purchased and more than one year after the date on which the participant purchased the stock at a profit (i.e., the sales proceeds exceed the purchase price). In a qualifying disposition, the participant will have compensation income equal to the lesser of:

Any profit in excess of compensation income will be long-term capital gain. If the participant sells the stock at a loss (i.e., if sales proceeds are less than the purchase price) after satisfying these waiting periods, then the loss will be a long-term capital loss.

If the participant sells the stock prior to satisfying these waiting periods, then he or she will have engaged in a disqualifying disposition. Upon a disqualifying disposition, the participant will have compensation income equal to the value of the stock on the day he or she purchased the stock less the purchase price. The participant also will have a capital gain or loss equal to the difference between the sales proceeds and the value of the stock on the day he or she purchased the stock. This capital gain or loss will be long-term if the participant has held the stock for more than one year and short-term if held one year or less.

Tax Consequences to Us

There will be no tax consequences to us except that we will be entitled to a deduction when a participant recognizes compensation income upon a disqualifying disposition. Any such deduction will be subject to the limitations of Section 162(m) of the Code.

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PROPOSAL 4: RATIFICATION OF SELECTION OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Our Audit Committee has appointed the firm of Ernst & Young LLP, an independent registered public accounting firm, to audit our books, records and accounts for the fiscal year ending December 31, 2021. This appointment is being presented to the stockholders for ratification at the Annual Meeting.

Ernst & Young LLP has served as our auditor consecutively since 2010, and has served as our independent registered public accounting firm beginning in connection with our initial public offering in 2013. Ernst & Young LLP has no direct or indirect material financial interest in our Company or our subsidiaries. Representatives of Ernst & Young LLP are expected to be present at the Annual Meeting and will be given the opportunity to make a statement on the firm’s behalf if they so desire. The representatives also will be available to respond to appropriate questions.

Our Audit Committee is solely responsible for selecting our independent registered public accounting firm for 2021. Although we are not required to submit the appointment to a vote of the stockholders, our Board believes that it is appropriate as a matter of good corporate governance to request that the stockholders ratify the appointment of Ernst & Young LLP as our independent registered public accounting firm.

If the stockholders do not ratify the appointment, our Audit Committee will investigate the reasons for stockholder rejection and may reconsider its appointment of Ernst & Young LLP as our independent registered public accounting firm for 2021 and may appoint another independent registered public accounting firm. Even if the appointment is ratified, our Audit Committee in their discretion may direct the appointment of a different independent registered public accounting firm at any time during the year if they determine that such a change would be in the best interests of our Company and our stockholders.

A majority of the voting power of the shares of common stock cast on this matter is required to approve this proposal. Unless otherwise instructed in the proxy, all proxies will be voted "FOR" the ratification of Ernst & Young LLP.

Our Board Recommends that You Vote "FOR" the Ratification of Ernst & Young LLP as our Independent Registered Public Accounting Firm for the Fiscal Year Ending December 31, 2021.

Fees Paid to Independent Registered Public Accounting Firm

The following table sets forth the fees incurred for services performed by Ernst & Young LLP during fiscal years 2020 and 2019:

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Our Audit Committee determined that the provision of the non-audit services by Ernst & Young LLP described above is compatible with maintaining Ernst & Young LLP’s independence.

Audit Committee Pre-Approval Policy and Procedures

Our Audit Committee as a whole, or through its Chair, pre-approves all audit and non-audit services (including fees) to be provided by the independent registered public accounting firm. Our Audit Committee has delegated to the Chair of our Audit Committee the authority to pre-approve non-audit services not prohibited by law to be performed by Ernst & Young LLP and associated fees, provided that the Chair of our Audit Committee reports any decisions to pre-approve such services and fees to the full Audit Committee at its next regular meeting. All services provided by Ernst & Young LLP during 2020 and 2019 were pre-approved by the Audit Committee.

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REPORT OF THE AUDIT COMMITTEE OF THE BOARD OF DIRECTORS

The Audit Committee has reviewed and discussed the audited financial statements of PTC Therapeutics, Inc. for the fiscal year ended December 31, 2020 with management.

The Audit Committee has discussed with Ernst & Young LLP, our independent registered public accounting firm, the matters required to be discussed by the applicable requirements of the Public Company Accounting Oversight Board and the SEC.

The Audit Committee has received the written disclosures and the letter from Ernst & Young LLP required by Public Company Accounting Oversight Board Rule 3526 regarding Ernst & Young LLP’s communications with the Audit Committee concerning independence, and has discussed Ernst & Young LLP’s independence from us with Ernst & Young LLP.

Based on the review and discussions referred to in the foregoing paragraphs, the Audit Committee recommended to the Board that the audited financial statements as of and for the year ended December 31, 2020 be included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020.

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EXECUTIVE OFFICERS

The following table and biographical descriptions provide information as of April 16, 2021 relating to each of our executive officers, other than Dr. Peltz, who also serves as a director of the Company. Dr. Peltz’s biographical information is presented above in this proxy statement under the heading "Proposal 1: Election of Directors—Biographical Information."

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There are no family relationships between or among any of our executive officers or directors. There is no arrangement or understanding between any of our executive officers and any other person or persons pursuant to which he was or is to be selected as an executive officer.

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EXECUTIVE COMPENSATION

This section describes the material elements of compensation awarded to, earned by or paid to our named executive officers, who, for fiscal year 2020, are:

Additionally, this section discusses the principles underlying our decisions with respect to the compensation of our named executive officers and the most important factors relevant to an analysis of these decisions, as well as qualitative information regarding the manner and context in which compensation is awarded to and earned by our named executive officers, and is intended to provide context for the data presented in the tables and narrative that follow.

Compensation Discussion and Analysis

Executive Summary

Our executive compensation program is intended to be competitive with our peers and to motivate our executive team to achieve our short-term and long-term strategy for creating stockholder value. Our executive compensation program consists of three primary elements: base salary, annual cash incentive and annual equity award.

In 2020, we set the salary below the median, and the target total cash compensation opportunity, which is the sum of salary and target bonus, near the median of our 2019 peer group for our Chief Executive Officer. The total target direct compensation opportunity for our Chief Executive Officer, which is the sum of target cash and the fair value of stock options and restricted stock units awarded in January 2020, was higher than the total target direct compensation opportunity for our Chief Executive Officer in 2019. This was primarily due to two factors. First, our annual equity grants made in January 2020 to our Chief Executive Officer and other named executive officers were granted when the price of our common stock was 55% higher than the price of our common stock in January 2019 at the time the annual equity grants were made, which followed total shareholder return, or TSR, of 40% during 2019 (which was itself followed by a year of 26% TSR in 2020). Second, in January 2020, we awarded larger annual equity awards to our named executive officers than in January 2019 because we felt that corporate accomplishments during 2019 were exceptional. The 2019 accomplishments included the acquisition of substantially all of the assets of BioElectron and the establishment of our Bio-e platform. For a discussion of how we determine our peer groups, see "Peer Group Composition" on page 42.

2020 Say on Pay Vote

Pursuant to Section 14A of the Exchange Act, at our 2020 annual meeting of stockholders, our stockholders voted, in an advisory manner, on a proposal to approve our named executive officers’ compensation, which is commonly referred to as the “say-on-pay” vote.

The 2020 say-on-pay vote was approved by our stockholders, with approximately 98.5% of the votes cast in favor of the overall compensation of our named executive officers, including related compensation philosophy, policies and practices. We were pleased with the continued strong support from our stockholders, which we believe resulted from

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changes we made to our executive compensation program over the past several years, and we will continue to evaluate our executive compensation program going forward.

Executive Compensation Objectives and Philosophy

Our compensation policies and programs are intended to:

"At-risk" compensation drives executive focus on achievement of our short- and long-term goals. Under our executive compensation program, a significant majority (92.9% and 87.1%, respectively) of our Chief Executive Officer’s and other named executive officers’ (for those who were named executive officers for the full year) primary compensation elements in 2020 (comprised of base salary, annual cash incentive at target, and the grant date fair market value of the annual equity award) were variable based on our annual performance against pre-established goals or our stock price, as shown below:

Primary compensation elements in 2020

(base salary, annual cash incentive at target, and annual equity award)

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The variable portion of our compensation program was higher in 2020 than in 2019, while the portion of total compensation represented by base salary compensation was lower in 2020 compared to 2019. This reflects our desire to keep base salary levels in a median range of our then peer group year over year, and a focus of granting our named executive officers equity grants and non-equity incentive compensation that are contingent upon achieving corporate

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goals and increasing shareholder value, which we believe helps to align named executive officers’ interests with the interests of our stockholders.

We believe that our annual cash incentive program contributes to the achievement of key short-term goals that drive the success of our long-term growth strategy. Our Compensation Committee works with management to establish corporate objectives under our annual cash incentive program that highlight the Company’s strategic goals and provide appropriate motivation toward the achievement of significant milestones that we believe directly correlate to the long-term enhancement of stockholder value.

In addition, since becoming a public company in June 2013, our executive compensation program has included an annual equity award that generally vests over a period of four years, traditionally in the form of stock options and, in 2017 and 2020, restricted stock awards and restricted stock units, respectively. Equity awards are made at the start of the new year, which is after performance results for the previous year are known and before the results for the new year. The January 2020 equity grant was influenced by our company’s strong performance in 2019 during which our share price increased by 40% year-over-year and by our 64% three-year compound annual growth rate return at the end of 2019.

The equity awards granted to our named executive officers in 2018 and 2019 who were named executive officers at the time of grant were comprised of stock options. The Compensation Committee utilized stock options to encourage the execution of our long-term growth strategy as these equity awards only provide value if our stock price increases after the grants are made and the applicable award has vested. In 2020, the Compensation Committee split the equity awards between options and restricted stock units, with 70% in options and 30% in restricted stock units, in order to use fewer dilutive shares and to include some immediate retention with restricted stock units through short-term market volatility.

We do not maintain an executive perquisite program or any guaranteed or funded retirement plan benefits other than a matching contribution under our 401(k) savings and retirement plan, or our 401(k) plan, that we make available to all employees. Additionally, in light of travel safety concerns due to the COVID-19 pandemic, our Compensation Committee determined that Dr. Peltz is required to use private chartered aircraft for all aircraft travel, including any personal travel, during the duration of the COVID-19 pandemic, see "Other Elements of Compensation" below.

Attract and retain well-qualified executive management.  We believe the Company’s growth and success can only be achieved through the contributions of our employees, as led by our executive officers. Our Compensation Committee regularly works with an independent compensation consultant to understand the competitive landscape and design a compensation program intended to attract, engage and retain high caliber, talented executives capable of executing on our short- and long-term growth strategy.

For compensation in 2020, our Compensation Committee utilized data from the 2019 peer group developed with the assistance of its independent compensation consultant as one tool to assist the Compensation Committee with respect to competitive positioning and internal parity for base salary, bonus target under our annual incentive program, and equity awards. Peer group data is viewed as a reference point in making compensation decisions, but the Compensation Committee does not utilize peer data in a formulaic manner. As a result, individual pay levels vary based on individual experience, scope of responsibilities, past performance and expectations with respect to future performance and future leadership potential.

Strengthen the alignment of the interests of our executive officers and stockholders.  A stock option only has value if our stock price increases above the option exercise price and such increased value is maintained through the vesting and exercise date. The Compensation Committee believes that this form of equity award is most effective at rewarding successful execution of our long-term growth strategy and has historically relied primarily on granting stock option equity awards to our named executive officers.

Peer Group Composition

General.  Our Compensation Committee uses peer group benchmark information developed in coordination with an independent compensation consultant to assist it in understanding the range of base salary, target annual incentive compensation, and equity grant levels offered for comparable roles at peer companies. Our Compensation Committee

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considers the relevance of its compensation peer group based on factors that include the Company’s stage of development, therapeutics focus, market capitalization, revenue, and headcount.

Analysis of the level and types of compensation our peer group companies offer for positions similar to those of our named executive officers is only one factor taken into account by the Compensation Committee when determining executive compensation. Our Compensation Committee also considers the performance of the Company and each named executive officer’s individual performance over the past year, their contributions to the execution of the Company’s short-term goals and long-term strategy, the Board’s expectations of performance against key strategic, financial and operational objectives in the coming year, the long-term retention of the named executive officer, and demonstration of executive leadership at the Company as well as matters of internal parity.

2019 Peer Group. Our Compensation Committee retained FW Cook as its independent compensation consultant in 2019 and directed FW Cook to assist it in the development of a reference peer group, which we refer to as the 2019 peer group, for compensation decisions to be made effective in January 2020, including 2020 base salary adjustments, annual cash incentive targets for 2020, and the annual equity awards granted on January 29, 2020 for 2019 performance.

In developing the 2019 peer group, the Compensation Committee, with input from FW Cook, selected companies within what it considered a relevant market cap range, that have at least one commercial product and are headquartered on the east coast or the west coast of the United States to align cost-of-living and labor market. Acorda Therapeutics, Inc. and Omeros Corp. were removed from the peer group because their market caps were no longer in the relevant market cap range. The Medicines Company was removed since it no longer owned commercial drugs. Two new companies, Spark Therapeutics, Inc. and Pacira BioSciences, Inc., with market caps in a similar range as ours were added, for a total of 15 peer companies. The 2019 peer group had a median market cap of approximately $2.48 billion on average in 2018 when the selected companies made the compensation decisions disclosed in their 2019 proxy statements. PTC’s market cap at the time of the 2019 peer group review was $2.61 billion, which was near the 75th percentile of the 2019 peer group. PTC’s employee population was above the 75th percentile of the 2019 peer group and PTC’s trailing 12 month revenue was aligned with the median of the 2019 peer group. The 2019 peer group consisted of:

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2020 Peer Group. Our Compensation Committee retained FW Cook as its independent compensation consultant in 2020 and directed FW Cook to assist in the development of a reference peer group, which we refer to as the 2020 peer group, for compensation decisions to be made effective in January 2021, including 2021 base salary revisions, annual cash incentive targets for 2021, and the annual equity awards granted on January 6, 2021 for 2020 performance.

In developing the 2020 reference peer group, the Compensation Committee again selected companies within what it considered a relevant market cap range, that have at least one commercial product and are headquartered on the east coast or the west coast of the United States to align cost-of-living and labor market. A 2020 review of the 2019 peer group showed PTC was above the 60th percentile of the average market cap and that continuing with 12 companies from the 2019 peer group maintained year-over-year consistency. Momenta Pharmaceuticals, Inc. and Spark Therapeutics, Inc. were removed from the peer group because they were acquired by other companies in 2020. Halozyme Therapeutics, Inc. was removed from the peer group because of its shift in focus away from traditional drug development. Four new companies, Agios Pharmaceuticals, Inc., bluebird bio, Inc., Fibrogen, Inc. and Neurocrine Biosciences, Inc., with market caps in a similar range as ours were added, for a total of 16 peer companies. The selected companies had a median market cap of approximately $3.49 billion on average in 2019 when they made the

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compensation decisions disclosed in their 2020 proxy statements. PTC’s market cap at the time of the 2020 peer group review was $3.28 billion, which was near the median of the 2020 peer group. PTC’s employee population was near the 85th percentile of the 2020 peer group and PTC’s trailing 12 month revenue was slightly below the median of the 2020 peer group. The 2020 peer group consisted of:

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Individual and Company Performance

When making annual compensation determinations, the Compensation Committee considers each named executive officer’s individual performance over the past year, his or her contributions to the execution of the Company’s short-term goals and long-term strategy, the Board’s expectations of performance against key strategic, financial and operational objectives in the coming year, and demonstration of executive leadership at the Company.

Individual performance is used together with other information resources to assist in a holistic evaluation of executive compensation. In connection with the close of each fiscal year, our Compensation Committee considers the Company’s performance against the objectives and metrics established for that fiscal year and assigns a corporate rating value, defined as a percentage against goals, to corporate performance based on their assessment of results. This corporate rating is applied, together with the individual performance modifier described below, to determine the amounts earned by each named executive officer under the annual incentive program for the last closed (or closing) fiscal year. Awards under the 2020 annual cash incentive program were finalized in January 2021 based on the Compensation Committee’s assessment of individual and Company performance during 2020.

While individual performance is considered in connection with all aspects of executive compensation, the individual performance modifier only directly impacts the value of cash incentive compensation received by our named executive officers under our annual incentive program. Quantitative weight is assigned to individual performance in the form of an individual performance modifier, which, for 2020 compensation, could range from 1.10, for top performers, to 1.0, for employees who consistently deliver on their position requirements and expectations. Performance below these levels can result in the application of an individual performance modifier that is less than 1.0, reducing the annual incentive award below the level determined by corporate performance.

Our Compensation Committee generally considers Dr. Peltz’s assessment of each named executive officer’s performance, other than himself, around the end of the fiscal year at the same time that it considers the Company’s performance against the corporate goals established by the Compensation Committee and Dr. Peltz’s performance for the applicable fiscal year. As our Chief Executive Officer, Dr. Peltz has overall responsibility for our business strategy, operations and corporate vision and our Compensation Committee generally assesses his performance in the context of the execution of our business strategy and the performance of the Company as a whole over the applicable fiscal year.

As a result, our Compensation Committee considers individual and Company performance during the most recent fiscal year as well as expectations for individual and Company performance during the coming year when setting base salary, target annual cash incentive opportunity and annual equity awards that will become effective in January of the coming year. For example, 2020 base salary adjustments and annual option awards were considered in late 2019 and set in January 2020 after considering Company and individual performance during 2019. At the same time, our Compensation Committee considered the demands that would be placed on our executive team in order to execute on our 2020 strategic goals.

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For a discussion of the Compensation Committee’s assessment of individual and corporate performance in 2020, which directly impacted annual cash incentive awards for 2020, see "Annual cash incentive program" on page 46. For information concerning individual and corporate performance in 2019, which directly impacted 2020 base salary and equity award, see "Base salary" below.

Elements of Executive Compensation

The material elements of compensation and the periods of time in which our Compensation Committee made determinations with respect to each element for 2020 were as follows:

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In addition, each named executive officer is entitled to severance payments and other benefits if his or her employment is terminated under the circumstances specified in his or her employment agreement and is entitled to participate in the benefit programs made available to all employees, such as health, life and disability insurance, our 401(k) plan, and the ESPP.

Base salary.  Base salary is designed to attract, motivate and retain qualified employees by providing a consistent cash flow throughout the year as compensation for performance of day-to-day responsibilities. The responsibilities of the position; background and experience; individual, team, and corporate performance and contribution; market competitive conditions; and other factors described below are taken into account by the Compensation Committee when determining this component of compensation.

Fiscal 2020 base salary determinations. Base salary determinations for 2020 were discussed in December 2019, set in January 2020 and became effective as of March 1, 2020. Our Compensation Committee set 2020 base salaries near the median of our 2019 peer group for the named executive officers overall, subject to relatively modest individual variation based on experience, proficiency, and importance of their role. These base salary adjustments for 2020 reflected 3% to 7% increases over 2019 salaries for most of our named executive officers. These increases were generally similar to the rate of increases observed for comparable roles in the 2019 peer group during the year prior. Our Compensation Committee determined that each of the named executive officers consistently delivered on their position requirements and expectations during 2019 and provided Ms. Hill with a larger salary increase to align her salary near the median of the 2019 peer group. Base salaries for our named executive officers were at or below the median of our 2019 peer group, except that Mr. Pauwels’ base salary was above the median following his promotion in April 2020.

Tabular presentation of base salary adjustments in 2020.  The table below sets forth our named executive officers salaries, as determined by our Compensation Committee for fiscal year 2020:

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*Base salary reflects new base salary following April 2020 promotion and was paid on a pro-rated basis.

^Mr. Souza received his pro-rated 2020 base salary until April 25, 2020, the date of his resignation from the Company.

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Annual cash incentive program.  Our annual cash incentive program is intended to motivate and reward our named executive officers to achieve and exceed annual goals and milestones that are expected to advance our long-term growth strategy. Both pre-established corporate goals and individual contributions toward these goals factor into the amount earned under the program. The corporate goals established under the program are tied to the Company’s operating plan for the applicable year and have typically been focused on the achievement of specific research, clinical, regulatory, commercial, financial, compliance or operational milestones developed in collaboration with our Compensation Committee. Achievement of these goals is viewed as conducive to the creation of stockholder value because the goals are designed to be consistent with our short-term and long-term strategic priorities.

Mechanics of annual cash incentive program.  Each named executive officer has the potential to realize a pre-established target value tied to a percentage of his or her salary, with the risk of earning no bonus and the ability to earn up to two times target. For 2020, the target annual cash incentive for Ms. Hill, Mr. Almstead, Mr. Boulding and, upon his April 2020 promotion, Mr. Pauwels were each increased from 40% of their base salaries to 45% of their base salaries, to align their target bonuses with the median of the 2019 peer group. The target for Dr. Peltz remained the same as the level previously established by the Board, an amount equal to 75% of his base salary. Mr. Souza resigned from the Company as of April 25, 2020 and therefore, was not eligible to receive an award. Pursuant to the terms of each of the named executive officers’ employment agreements, the target bonus level can be raised or lowered in any given year at the discretion of the Board.

In connection with the close of each fiscal year, our Compensation Committee considers the Company’s performance against the objectives and metrics established for that fiscal year in the beginning of that fiscal year and assigns a value to corporate performance based on the Compensation Committee’s assessment of results. The amounts that could be achieved under the corporate performance segment of the annual incentive program are capped at two times target. The program permits the exercise of both negative and positive discretion based on our Compensation Committee’s view of overall corporate performance during the year (subject to the maximum award cap). However, corporate performance ratings for the named executive officers under the annual cash incentive program in the last five years have ranged from a low of 85% to a high of 150%. The corporate rating for the 2020 cash incentive program, as determined in January 2021, was 135% for the named executive officers, as further discussed below.

Individual performance is considered in the manner described under "Individual and Company Performance" on page 44, with a maximum quantitative modifier for potential awards based on 2020 performance of up to 1.33. Downward adjustments made to any executive officer’s individual performance modifier may be used to make a corresponding upward adjustment to another executive officer’s individual performance modifier, although no such adjustment effecting a named executive officer was made to 2020 annual incentive awards.

The combination of corporate and individual performance is applied using the following formula:

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Company goals and results under the 2020 annual incentive program.  The Company exceeded its goals in 2020, which we viewed as a year of very high performance. The goals and key performance indicators, or KPIs, used to evaluate the goals established by our Compensation Committee for 2020, and our performance under such goals and KPIs, were as follows:

Deliver on financial performance. The purpose of this goal was to manage cash flow to support long-term growth of the Company. The KPIs established to assess achievement of this goal were to be between $320 and $340 million for 2020 Duchenne muscular dystrophy, or DMD, franchise revenue and to be between a combined $545 and $575 million for (i) 2020 non-U.S. Generally Accepted Accounting Principles (“GAAP”) research and development expenses (“R&D”), which excludes non-cash, stock-based compensation expense plus (ii) 2020 non-GAAP selling, general and administrative expenses (“SG&A”), which excludes non-cash, stock-based compensation expense less (iii) one-time transaction-related charges for 2020. This goal was achieved as 2020 DMD franchise revenue was approximately $331 million and 2020 non-GAAP R&D and SG&A, excluding one-time transaction related costs were approximately $558

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million. Please refer to Exhibit C of this proxy statement for a description and reconciliation of these non-GAAP financial measures relative to reported GAAP financial measures. In addition to the specific KPIs achieved, we furthered the purpose of this goal by strengthening our balance sheet by entering into a Royalty Purchase Agreement with RPI 2019 Intermediate Finance Trust, or RPI, pursuant to which we sold to RPI 42.933% of our right to receive sales-based royalty payments on worldwide net sales of Evrysdi and any other product developed pursuant to our License and Collaboration Agreement with Roche and the Spinal Muscular Atrophy Foundation for $650.0 million in cash consideration. Additionally, we entered into the Rights Exchange Agreement pursuant to which we issued 2,821,176 shares of our common stock and paid $36.9 million, in the aggregate, to certain former equityholders of Agilis in exchange for the cancellation and forfeiture of their rights to receive certain milestone-based contingent payments in the aggregate of approximately $225.0 million.

Advance late stage programs. The purpose of this goal was to advance our Aromatic L-Amino Acid Decarboxylase, or AADC, program, our Translarna program and our Bio-E platform. For our AADC program, the KPIs were to increase our patient finding to put us in a position to have 300 AADC patients identified should PTC-AADC receive regulatory approval and to file a biologics license application, or BLA, with the U.S. Food and Drug Administration, or FDA, for PTC-AADC by the third quarter of 2020. While the BLA filing was delayed based on FDA feedback and COVID-19 pandemic-related complications that delayed our ability to take the necessary steps in response to FDA feedback, we were successful in installing new screening programs and screening many patients in multiple countries putting us in position to have 300 AADC patients identified. For our Translarna program, the KPI was to file a New Drug Application, or NDA, by the third quarter of 2020. In order to fulfill this KPI, we first needed to complete Study 045 in order to gather data that would be part of the NDA filing. However, due to the COVID-19 pandemic, certain patients were delayed over six months in having the final study muscle biopsies performed at our clinical trial site at the University of California, Los Angeles. We consider this KPI partially completed, as even with the delays, we were able to perform the final muscle biopsies allowing us to complete Study 045 in 2020. We had two KPIs relating to our Bio-E platform consisting of initiating clinical trials for our PTC-743 mitochondrial epilepsy study and our PTC-743 Friedrich ataxia study. Both of these KPIs were completed as both trials initiated in 2020. We viewed the overall goal as achieved, due to the KPIs we did complete as well as completing other unanticipated achievements including (i) initiating our PTC299 COVID-19 clinical trial, (ii) having the European Commission approve the removal of the statement “efficacy has not been demonstrated in non-ambulatory patients” from the indication statement for Translarna, (iii) successfully filing a marketing authorization application for Waylivra in Brazil, (iv) obtaining orphan drug designation from the FDA for vatiquinone for the treatment of mitochondrial epilepsy, PTC-AS for the treatment of Angelman syndrome, PTC596 for the treatment of leiomyosarcoma and diffuse intrinsic pontine glioma, or DIPG, and PTC299 for the treatment of acute myelogenous leukemia and (v) obtaining rare pediatric disease designation from the FDA for vatiquinone for the treatment of mitochondrial epilepsy, PTC-AS for the treatment of Angelman syndrome and PTC596 for the treatment of DIPG.

Progress early stage platforms. The purpose of this goal was to advance certain of our early stage platforms through pre-clinical, clinical and manufacturing achievements. There were six primary KPIs for this goal. The first KPI required us to initiate a clinical trial for PTC-518 in Huntington Disease, which was achieved. The second KPI was to meet our enrollment plan for PTC-FA. This KPI was partially achieved as the COVID-19 pandemic has impacted the activities enabling the first-in-human studies for PTC-FA and while we did not meet our specific goal, we were able to keep moving this program forward. The third KPI was to initiate a trial for PTC-857 in our Bio-E platform, which was achieved. The fourth KPI was to finalize our gene therapy program for Angelman’s by conducting in-vivo and in-vitro studies and finalizing the non-clinical components to support an Investigational New Drug Application submission, all of which were achieved. Our fifth KPI was to initiate our first gene therapy engineering batch in our Hopewell, New Jersey facility, which was achieved. Our sixth KPI was to add three development candidates and five proof of concept programs to our portfolio. We added one development candidate and three proof of concepts to our portfolio. Overall, we considered this goal achieved due to the KPIs that were successful as well as additional achievements including, advancing six programs through the validation stage.

Continue PTC’s transformation. The purpose of this goal was to prepare the organization for long-term success by continuing to develop the Company’s people, process, systems and environment. This goal was considered satisfied due to various achievements affecting the Company’s day-to-day operations, including: creating “culture and community” and “people services” roles, which drives employee engagement and improves the employee experience; redesigning

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leadership training to fit a virtual audience and roll out “Clifton Strength Finders” to the entire organization; the design and roll out of a mentorship program, a talent pipeline internship program for recent graduates who were unable to find employment due to the COVID-19 pandemic, an equality, diversity and inclusion program and woman in leadership group, and successfully hiring and onboarding over 300 employees.

The recommendations of Dr. Peltz, our Chief Executive Officer, who, with input from the other named executive officers, assessed the Company’s performance against corporate goals for 2020, were also considered. As part of the assessment, the Compensation Committee also took into consideration how the achievement of our corporate goals expanded the long-term outlook of the Company and the impact on Company stakeholders. Additionally, the Compensation Committee considered how the Company dealt with the COVID-19 pandemic, in particular how it focused on employee safety, including closing offices and initiating a mandatory work-from-home policy even before local, state and federal governments were limiting travel and designing and executing a return-to-office strategy that has been and continues to be deployed where possible and appropriate, while at the same time keeping a commitment of excellence to stakeholders and continuing to achieve the goals described above. In January 2021, our Compensation Committee finalized its determination that 2020 performance against the overall corporate objectives, goals and metrics, including qualitative assessment of the importance of the achievements to long-term success, warranted a corporate rating of 135% for the named executive officers.

Individual performance in 2020. For individual performance in 2020, excluding those named executive officers who ceased to be employees during 2020, our Compensation Committee considered the following key accomplishments and contributions by individual named executive officers during 2020 and Dr. Peltz’s recommendations with respect to performance ratings for all named executive officers, other than himself:

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Amounts earned under 2020 annual incentive program.  Our named executive officers earned the amounts set forth in the table below based on our Compensation Committee’s determinations with respect to the Company’s corporate rating and individual performance modifiers under the 2020 annual cash incentive program:

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*Mr. Souza was not eligible to receive an award for 2020 under our annual cash incentive program in light of his resignation from the Company on April 25, 2020.

Annual equity award. A significant portion of our executive compensation program in 2020 and in prior years has been in the form of an annual equity award that vests over a four-year period.

The “Stock Award” and "Options Awards" columns of our Summary Compensation Table set forth the full grant date fair value of the restricted stock units and stock option awards, respectively, granted to each named executive officer in January 2020, calculated in accordance with the provisions of Financial Accounting Standards Board Accounting Standard Codification, Topic 718, or FASB ASC Topic 718. These amounts do not represent the actual value realized by the named executive officers in 2020; in fact, no portion of the applicable equity awards vested until January 2021.

A stock option only has value if our stock price increases above the exercise price of the stock option and such value is maintained through the applicable vesting and exercise date. Our Compensation Committee views time-vested stock option awards as an important tool to align the interests of our named executive officers with the interests of our stockholders and believes that this form of equity is most effective at rewarding successful execution of our long-term growth strategy. The time vesting feature of the annual equity award, for both the stock options and restricted stock units, is also intended to promote employment retention of executives.

In determining the size of the annual equity awards granted to our named executive officers, our Compensation Committee considers the Company’s performance during the year prior to grant, the individual’s key contributions to our execution of our short-term and long-term goals during that year, as well as expectations for the Company’s and the individual’s performance in the new year, including the individual’s potential for enhancing the long-term creation of value for our stockholders. Our Compensation Committee also considers information provided by its independent compensation consultant, including information regarding comparative stock ownership of, and equity awards received by, the executives in our peer group and our industry. Our Compensation Committee also considers matters of internal pay equity as well as individual expectations based on historic Company practices. In addition, Dr. Peltz provides his recommendations to our Compensation Committee for each named executive officer other than himself.

Timing, pricing, material terms, of other matters related to equity awards.  All grants to our named executive officers must be approved by our Compensation Committee. Annual equity awards are generally granted at predetermined meetings of the Compensation Committee, which have historically been in January, including in 2018, 2019 and 2020. The annual equity awards consider the prior year’s performance more than the current year, because the Compensation Committee does not know the results of the coming year at the time of grant. As a result, performance in the previous year is a key factor in determining the grant amount.

Specifically, the equity awards granted in January 2020, which are disclosed in the Summary Compensation Table, were impacted by our Compensation Committee’s assessment of 2019 performance and expectations for 2020. We viewed 2019 as a year with high company performance with the acquisition of substantially all of the assets of

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BioElectron, establishment our Bio-e platform and a TSR of 40% for the year. Our Compensation Committee’s assessment of 2020 performance and expectations for 2021 were factors in determining the equity awards granted in January 2021, which will be discussed in next year’s Summary Compensation Table.

The exercise price for annual stock option awards is set at the closing price of the Company’s common stock on the date of the grant. Annual stock option awards granted to employees, including our named executive officers, since our initial public offering have generally vested over a four-year period, with 25% of the shares underlying such options vesting one year after grant and 6.25% of the shares vesting at the end of each successive three month period thereafter. A portion of the annual stock option awards that our named executive officers received in 2019 vest over four years, with 50% of the shares underlying the options vesting on the third anniversary of the grant, and the remaining 50% of the shares vesting on the fourth anniversary of the grant. The restricted stock units granted to our named executive officers in 2020 vest over a four-year period, with 25% of the shares vesting one year after grant, and an additional 25% of the shares vesting annually thereafter.

Fiscal 2020 equity award determinations. In establishing equity awards for 2020 in January 2020, our Compensation Committee, with the assistance of its independent compensation consultant, determined an aggregate share pool to be allocated to equity awards made in 2020 which was determined by reference to the median average equity compensation burn rate in the 2019 peer group for the grant of awards to named executive officers.

In allocating equity awards among the named executive officers, our Compensation Committee considered individual performance in the context of both the Company’s achievements during 2019, as described under "Annual cash incentive program" beginning on page 46 as well as Dr. Peltz’s assessment and recommendations for each of the named executive officers. The Compensation Committee also considered the prevalence of restricted stock unit grants within the 2019 peer group and the usefulness of restricted stock units in managing the Company’s burn rate and dilution overhang.

Based on the factors detailed above, our Compensation Committee granted the stock option awards and restricted stock units described under the "Tabular presentation of annual equity awards in 2020" below to our named executive officers, pursuant to our 2013 Long Term Incentive Plan, on January 29, 2020.

Tabular presentation of annual equity awards in 2020. The table below sets forth the grant date fair value of the equity awards made to each of our named executive officers who were named executive officers in January 2020, calculated in accordance with the provisions of FASB ASC Topic 718.

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Severance Benefits.  Each of our named executive officers has an employment agreement that entitles such executive to certain cash payments and other benefits in the event such officer’s employment is terminated (other than for "cause") or the Company undergoes a change in control. See "Employment Agreements with Named Executive Officers" on page 57 for additional information with respect to the employment agreements in general and "Potential Payments Upon Termination or Change in Control (2020)" on page 61 for addition information concerning specific severance payments and other benefits that our named executive officers may be entitled to receive under their employment agreements.

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We believe the benefits under these employment agreements are consistent with market practice. The change in control provisions are intended to help to promote a continuity of management during a corporate transaction, while the severance arrangements are used primarily to attract, retain and motivate well-qualified executive management. Each employment agreement includes restrictive covenants (such as non-compete and non-solicitation provisions) that would apply in the event of the named executive officer’s termination, which our Board believes helps us protect our value.

Our change in control benefits are "double trigger" benefits. A "double trigger" benefit means that a change in control, by itself, would not trigger benefits. Instead, benefits would be paid only if the employment of the named executive officer is terminated during a specified period after the change in control. We believe this structure would help us secure the continued employment and focus of our named executive officers during change in control negotiations in which they believe they may lose their jobs.

Other Elements of Compensation.  Our named executive officers are eligible to participate in all of our employee benefit plans, in each case on the same basis as other employees. We maintain broad-based benefits that are provided to eligible employees, including health, dental, life and disability insurance and our 401(k) plan. During 2020, we provided a 100% matching contribution for up to the first 6% of each contributing employee’s eligible compensation under our 401(k) plan. The matching contribution is subject to vesting at the rate of 25% at the end of each year of employment, for an employee’s first four years of employment, following which the matching contribution vests at 100% upon receipt. Our named executive officers are also eligible to participate in our ESPP, which is available on the same basis to other employees.

In light of travel safety concerns due to the COVID-19 pandemic, our Compensation Committee determined that Dr. Peltz is required to use private chartered aircraft for all aircraft travel, including any personal travel, during the duration of the COVID-19 pandemic. Our Compensation Committee believes that this focus on Dr. Peltz’s health and safety is reasonable and appropriate under the circumstances and in the best interests of our stockholders.  Dr. Peltz has been and will continue to be reimbursed for all such chartered aircraft travel and any applicable taxes related thereto.

Stock Ownership Guidelines

In December 2016, as part of our Board’s efforts to improve our governance and compensation practices, our Compensation Committee recommended, and our Board adopted, Executive and Director Stock Ownership Guidelines, or Guidelines. The purpose of the Guidelines is to encourage ownership of the Company’s common stock by our executive officers and directors, promote the alignment of the long-term interests of our executive officers and directors with the long-term interests of the Company’s stockholders, and to further promote our commitment to sound corporate governance. The Guidelines are applicable to our executive officers and our non-employee directors.

Under the Guidelines, executive officers and directors must acquire ownership of target common stock ownership levels by the end of the five-year compliance period from adoption of the Guidelines. The target common stock ownership levels are specified as shares of our common stock with a value equal to a multiple of the three-year average cash compensation (sum of base salary plus annual cash incentive program award) in the case of executive officers, and a multiple of the three-year average cash Board retainer, in the case of non-employee directors, as follows:

Individuals covered by the Guidelines are expected to achieve their target ownership level by the fifth anniversary of their becoming subject to the Guidelines, or they will become subject to a requirement to hold their after tax profit shares until compliance is achieved.

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Insider Trading, Prohibition Against Pledging, and Anti-Hedging Policies

We have an Insider Trading Policy that has been adopted in light of restrictions under applicable securities laws. This policy prohibits trades in our common stock that would violate these laws, and it also imposes other restrictions such as blackout periods and prior notification and/or clearance requirements intended to protect against inadvertent violations of these laws. This policy also prohibits all employees, executive officers and directors from purchasing Company securities on margin, borrowing against Company securities held in a margin account, or pledging Company securities as collateral for loans as well as prohibits engaging in hedging or similar transactions, engaging in any short sales of our common stock or any purchases or sales of puts or calls for speculative purposes.

Adjustment or Recovery of Awards—Clawback Provisions

The Dodd-Frank Act requires the SEC to direct the national securities exchanges to prohibit the listing of any security of an issuer that does not develop and implement a clawback policy. At this time, the SEC has not finalized rules related to clawback policies. Once the final rules are in place, we intend to adopt a clawback policy that fully complies with SEC regulations.

Further, under Section 304 of the Sarbanes-Oxley Act, if we are required to restate our financial results due to material noncompliance with any financial reporting requirements as a result of misconduct, our Chief Executive Officer and Chief Financial Officer could be required to reimburse the Company for (1) any bonus or other incentive-based or equity-based compensation received during the twelve months following the first public issuance of the non-complying document, and (2) any profits realized from the sale of our securities during those twelve months.

Tax Considerations

Section 162(m) of the Internal Revenue Code of 1986, as amended, or the Code, generally disallows a tax deduction to public companies for compensation in excess of $1.0 million paid in any taxable year to each of certain of the company’s current and former executive officers. Historically, compensation that qualified under Section 162(m) as performance-based compensation, was exempt from the deduction limitations. However, the tax reform legislation signed into law on December 22, 2017 eliminated the performance-based compensation exception. As a result, for taxable years beginning after December 31, 2017, subject to certain transition rules, all compensation in excess of $1 million paid in any taxable year to each of the specified will not be deductible by us. The Compensation Committee has and will continue to review on a periodic basis the effect of Section 162(m) and may use its judgment to authorize compensation payments that may be in excess of the limit when it believes such payments are appropriate, and in the best interests of our company and our stockholders.

Compensation Committee Report

The Compensation Committee furnishes the following report:

The Compensation Committee has reviewed and discussed the Compensation Discussion and Analysis required by Item 402(b) of Regulation S-K with our management. Based on this review and discussion, the Compensation Committee recommended to our Board of Directors that the Compensation Discussion and Analysis be included in this proxy statement.

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Summary Compensation Table

The following table sets forth information regarding compensation awarded to, earned by or paid to our named executive officers during the years indicated:

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