Release Details

SOUTH PLAINFIELD, NJ – August 8, 2013 – PTC Therapeutics, Inc. (NASDAQ:PTCT) today announced the selection of a development candidate in its spinal muscular atrophy (SMA) collaboration with Roche and the SMA Foundation. The achievement of the milestone triggers a $10 million payment to PTC from Roche.

"We are excited about this important achievement in our SMA program", stated Stuart Peltz, Ph.D., Chief Executive Officer of PTC Therapeutics. "This program exemplifies PTC's technology platform and its chemistry and biology expertise applied in an area of great unmet medical need. We are grateful for the exceptional commitment and dedication from our PTC team, as well as from our partners, Roche and the SMA Foundation. The discovery and advancement of a potential new treatment for SMA is a significant milestone for SMA patients and their families."

SMA is caused by a missing or defective SMN1 gene, which results in reduced levels of the survival motor neuron (SMN) protein. It is a genetic neuromuscular disease responsible for the early death of motor neuron cells within the spinal cord leading to muscle atrophy and eventually death in the most severe form of the disease. The oral small molecule compounds in the program target the underlying cause of the disorder by increasing SMN protein levels in the nervous system, muscles, and other tissues. It is estimated that SMA affects approximately 10,000 to 25,000 children and adults in the United States, and that between one in 6,000 and one in 10,000 children are born with this rare disorder.

Luca Santarelli, Head of Neuroscience and Small Molecule Research at Roche commented: "The compelling science behind this project and the highly synergistic alliance between Roche, PTC Therapeutics and the SMA Foundation are the groundwork for this potential therapeutic program. We consider every step towards a treatment option in SMA of high importance for patients and families affected by this devastating and currently incurable condition."

The SMA program was initially developed by PTC Therapeutics' in partnership with the SMA Foundation. The SMA Foundation was established in 2003 to accelerate the development of a treatment for SMA. In November 2011, Roche gained an exclusive worldwide license to PTC's SMA program. PTC received a $30 million upfront payment, is entitled to $10 million based upon the selection of a development candidate and may receive up to an additional $450 million upon successful completion of other development and commercialization milestones, plus tiered royalties on worldwide net product sales. Development is overseen by a joint steering committee comprised of members from Roche, PTC and the SMA Foundation.

Karen Chen, Chief Scientific Officer of the SMA Foundation, stated, "We are highly encouraged by the continued progress. Achieving this milestone brings us closer to developing a treatment for thousands of patients with SMA. The SMA Foundation is eager to support and propel treatments forward for patients and look forward to the continued success of our collaboration with Roche and PTC."

ABOUT PTC THERAPEUTICS, INC. PTC is biopharmaceutical company focused on the discovery and development of orally-administered, proprietary small molecule drugs that target post-transcriptional control processes. While PTC's discovery programs are directed at targets in multiple therapeutic areas, PTC is focusing particularly on the development and commercialization of treatments for orphan and ultra-orphan disorders. Post-transcriptional control processes regulate the rate and timing of protein production and are essential to proper cellular function. PTC's internally-discovered pipeline addresses multiple therapeutic areas, including neuromuscular disorders, oncology and infectious diseases. For more information on the company, please visit our website www.ptcbio.com.

FOR MORE INFORMATION PLEASE CONTACT: Jane Baj +1 (908) 912-9167 jbaj@ptcbio.com

FORWARD LOOKING STATEMENTS: Any statements in this press release about future expectations, plans and prospects for the Company, including statements about the receipt of a milestone payment from Roche, the development of and potential market for the Company's SMA product candidate and other statements containing the words "anticipate," "believe," "estimate," "expect," "intend," "may," "plan" "predict," "project," "target," "potential," "will," "would," "could," "should," "continue," and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Forward-looking statements involve substantial risks and uncertainties that could cause our future results, performance or achievements to differ significantly from those expressed or implied by these forward-looking statements. Such risks and uncertainties include, among others, those related to the initiation and conduct of clinical trials, availability of data from clinical trials, expectations for regulatory approvals, our scientific approach and general development progress, the availability or commercial potential of our product candidates and other factors discussed in the "Risk Factors" section of the final prospectus for our initial public offering, which is on file with the Securities and Exchange Commission. In addition, the forward-looking statements included in this press release represent the Company's views only as of the date of this release. The Company anticipates that subsequent events and developments will cause the Company's views to change. However, while the Company may elect to update these forward-looking statements at some point in the future, the Company specifically disclaims any obligation to do so. These forward-looking statements should not be relied upon as representing the Company's views as of any date subsequent to the date of this release.