SecProbe.io

April 15, 2013

Via E -mail
Stuart M. Peltz, Ph.D.
Chief Executive Officer
PTC Therapeutics, Inc.
100 Corporate Court
South Plainfield, NJ  07080

Re: PTC Therapeutics, Inc.
Draft Registration Statement on Form S -1
Submitted March 18, 2013
  CIK No. 0001070081

Dear Dr. Peltz :

We have reviewed your draft registration statement  and have the following comments.  In
some of our comments, we may ask you to provide us with information so we may better
understand your disclosure.

Please respond to this le tter by providing the requested information and either submitting
an amended draft registration statement or  publicly  filing your registration statement on
EDGAR.  If you do not believe our comments apply to your facts and circumstances or do not
believe an amendment is appropriate, please tell us why in your response.

After reviewing the information you provide in re sponse to these  comments  and your
amended draft registration statement or filed registration statement,  we may have  additional
comments.

General

1. Please submit all exhibits as soon as practicable.  We may have further comments upon
examination of these exhibits.

2. Please provide us proofs of all graphic, visual or photographic information you will
provide in the printed prospectus prior to its use, for example in a preliminary prospectus.
Please note that we may have comments regarding this material.

3. Please supplementally provide us with copies of all written communications, as defined
in Rule 405 under the Securities Act, that you , or anyone authorized to do so on your
behalf , present to potential investors in reliance on Section 5(d) of the Securities Act,
whether or not they retain copies of the communications.   Similarly, please
supplementally provide us with any research reports about you that are published or

Stuart W. Peltz, Ph.D.
PTC Therapeutics, Inc.
April 1 5, 2013
Page 2

 distributed in reliance upon Section 2(a)(3) of the Securities Act of 1933 added by
Section  105(a) of the Jumpstart Our Business Startups Act by any broker or dealer that is
participating or will participate in your offering.

4. Comments to your application for confidential treatment will be delivered under separate
cover.

Prospectus Summary, pa ge 1
Risks associated with our business, page 5

5. Please expand the second bullet point in this section to note that certain of your prior
clinical trials were not successful in achieving specified primary endpoints.

Our corporation information, page 5

6. Please note that it is not appropriate to state or imply that you do not have liability for the
statements in your registration statement. The statement “we have not independently
verified” data obtained from third -party sources appears to imply that you a re not taking
liability for the statistical and other industry and market data included in your registration
statement. In order to eliminate any inference that you are not liable for all of the
information in your registration statement, please delete thi s statement or include a
statement specifically accepting liability for these statements.

Risk Factors, page 11

7. Please include a risk factor discussing the risks associated with conducting a retrospective
analysis after unblinding test results and explain why r egulatory authorities typically give
greatest weight to results from pre -specified analyses and adjusted p -values and less
weight to results from post -hoc, retrospective analyses and  nominal p -values.

“If clinical trials of our product candidates…,” page 14

8. This extensive and lengthy risk factor highlights many material risks with more specific
discussion than the heading may indicate.  Please divide this risk factor into separate risk
factors or provide subheadings highlighting more sp ecifically each of the risks addressed.
For example, you should include a separately headed risk factor or subheading discussing
the possibility that the EMA will not grant conditional approval of ataluren for the
treatment of DMD and that you may experie nce unforeseen events that could delay or
prevent your ability to receive marketing approval or commercialize your product
candidates.

Stuart W. Peltz, Ph.D.
PTC Therapeutics, Inc.
April 1 5, 2013
Page 3

 Management’s discussion and analysis of financial condition and results of operations, page 55
Critical accounting p olicies and significant judgments and estimates, page 59

9. Please disclose your election with respect to Section 107(b) of the JOBS Act and include
a statement highlighting the risk that your financial statements may not be comparable to
companies that com ply with public company effective dates .

Share -based Compensation, page 60

10. Please provide the following information separate ly for each equity instrument  issuance
through the date of your response:
 The date of the transaction,
 The number of equity ins truments granted or shares issued,
 The exercise price of equity instruments granted if any,
 Management’s estimated fair market value per share and how the estimate was
developed.  Please disclose the judgments made regarding future trends and factors
and i ndicate w hether or not the valuation was contemporaneous or re trospective ,
 The identity of the recipient, indicating if the recipient was a related party,
 The nature and terms of concurrent transactions; and,
 The amount of any compensation or interest expe nse element.

11. After your IPO price range has been set, disclose  each significant factor contributing to
the difference between the fair value as of the date of each grant  of equity instrument
issued, including options, any warrants classified as equity instruments, and preferred
stock  and the estimated IPO price or when a contemporaneous valuation by an unrelated
valuation specialist was obtained subsequent to the grants b ut prior to the IPO, the fair
value as determined by that valuatio n.  Reconcile and explain the differences between the
mid-point of your estimated offering price range and the fair values included in your
analysis.  Please ensure that all of your equity i nstruments issued during the periods
presented are included in your tabular disclosure.  Revise your tabular disclosure as
necessary to include information for all equity instruments issued subsequent to the
balance sheet date through the date of your late st response.

Liquidity and Capital Resources, page 65

12. Please include a summary of all of the equity financing activities completed in the
periods presented and through the date of your response.  Please also clarify and discuss
the “additional financing event” that is referred to in your Subsequent events not e on
page F -25.

Stuart W. Peltz, Ph.D.
PTC Therapeutics, Inc.
April 1 5, 2013
Page 4

 Business, page 69
Our product development programs, page 72

13. Please expand your disclosure to indicate whether you have an IND for ataluren in each
indication.  Please also add disclosure regarding orphan designations.

Planned  Phase 3 clinical trial of ataluren for nmDMD, page 76

14. Please describe how you intend to attract or recruit patients for your trials.

Regulatory status and strategy for nmDMD, page 79

15. Please expand your disclosure to discuss the extent to which you and potential investors
may rely on the statement that “the FDA indicated that … the study design for the
proposed clinical trial, in general, was appropriate for providing evidence of efficacy of
ataluren.”

Post-hoc analysis of Phase 2b clinical trial data, page 84

16. Please explain on page 86 why r egulatory authorities typically give greatest weight to
results from pre -specified analyses and adjusted p -values and less weight to results from
post-hoc, retrospective analyses and  nominal p -values.

Safety  and tolerability, page 91

17. Please specifically describe the adverse events observed during the trial, with particular
focus on the serious adverse events.  In addition, please explain how you determined that
these serious adverse events were not ataluren -related.

Completed Phase 3 clinical trial of ataluren for nmCF, page 96

18. Please disclose why 34 patients withdrew prematurely from the trial.

19. You disclose on page 96 that the EMA has advised you of certain matters that may need
to be further a ddressed in your MAA. Please briefly elaborate on the items provided in
the bulleted list on page 96 to give added context to each of the matters to clarify the
nature of the FDA’s concerns and how you plan to address these in your MAA.

Safety and toler ability, page 99

20. Please specifically describe the adverse events observed during the trial, with particular
focus on the serious adverse events.  In addition, please explain how you determined that
the most serious adverse events were “unrelated to study drug treatment.”

Stuart W. Peltz, Ph.D.
PTC Therapeutics, Inc.
April 1 5, 2013
Page 5

 Open label extension trial of ataluren for treatment of nmCF, page 100

21. Your disclosure indicates that you have not observed increases in frequency of previously
reported adverse events or significant numbers of new adverse events in the  open label
extension trial.  Please expand your discussion to disclose the adverse events you have
observed noting the new adverse events particularly.

Intellectual Property, page 113

22. Your disclosure in the third paragraph of this section discusses the patent rights relating
to ataluren owned by you.  Please add similar disclosure regarding any material patent
rights relating to ataluren that you license.

Competition , page 115

23. Please explain why you do not believe Kalydeco or the two other product candidates that
Vertex is developing for the treatment of cystic fibrosis are applicable for the treatment of
patients with nmCF.

Director compensation, page 142

24. We note your disclosure on page 143 that you intend to approve a compensation policy
for n on-employee directors that will become effective upon closing of the offering.  Once
approved, please update your disclosure to describe the adopted compensation plan.

Lock -up agreements, page 159

25. Once available, please file copies of each of the lock -up agreements.

Financial Statements
Statements of Operations, page F -4

26. Please tell us why you excluded the gain on exchange of convertible preferred stock in
connection with your recapitalization and the beneficial conversion charge from your Net
Loss for  2012.

Notes to Financial Statements
Revenue Recognition, page F -10

27. Please tell us how the accounting policy that you recognize grant and collaboration
revenue when invoiced is appropriate.  Please also clarify whether there are any refund  or
repayment obligations associated with your grants.  If so, please disclose the nature of
these obligations and tell us how the recognition of revenue is appropriate.   Please also
tell us why you have classified the grant received as revenue as opposed to o ther income.

Stuart W. Peltz, Ph.D.
PTC Therapeutics, Inc.
April 1 5, 2013
Page 6

Beneficial conversion, page F -11

28. You disclose that the beneficial conversion feature results from the excess of the
proceeds allocated to the Series Three convertible preferred stock.  Please provide us with
the computation of the benefici al conversion charge in 2012.

Fair value of financial instruments and investments, page F -13

29. Please disclose th e assumptions used to determine the fair value of the warrant liability in
2012 and 2011.

Recapitalization, page F -17

30. Please disclose how y ou determined the value of the Series One, Series Two and Series
Three preferred stock issued in connection with the July 2012 recapitalization.  Please be
sure to describe the model used to estimate the fair values and all of the relevant
assumptions.  Pl ease also provide us with the computations of how you determined the
fair value of the Series One, Series two and Series Three preferred stock.

31. Please tell us the business purpose of the recapitalization transaction completed in July
2012 from the perspec tive of the Series A though G holders of convertible preferred stock
and the Series One, Series Two and Series Three convertible preferred stockholders and
why the recapitalization made economic sense for each series of preferred stockholders.
Please also  tell us why only the Series One preferred stockholders contributed proceeds
of $29.7 million in the recapitalization transaction and why the Series A through G
holders of preferred stock exchanged all of their interest for Series Two and Series Three
preferred stock.

32. Please provide us with an analysis that supports your accounting for the gain of $160
million in 2012 on the exchange of convertible preferred stock.

10.  Collaborations and Grants
Terminated Collaborations
Genzyme, page F -21

33. Please di sclose the amount of the additional payment received in exchange for an option
to commercialize ataluren in indications other than nonsense mutation Duchenne
muscular dystrophy outside the United States and Canada.  Please also disclose how you
accounted f or deferred revenue when you received notification that Genzyme terminated
the collaboration agreement.

34. You disclose that you recorded a one -time adjustment to your deferred revenue balance
upon the restructuring of your agreement with Genzyme in August 2011 “ to reflect the

Stuart W. Peltz, Ph.D.
PTC Therapeutics, Inc.
April 1 5, 2013
Page 7

 value of the remaining performance obligations under the restructured agreement as
represented by the best estimate of selling price .”  Please tell us how y ou calculated the
adjustment to your deferred revenue in connection with this r estructuring and all of the
relevant assumptions.

35. While you disclose on page F -10 that you use the “updated multiple element revenue
recognition guidance” for material modifications to your collaborations, it is unclear how
you determined that there was  a material modification.  Please revise your disclosures to
clarify how you determined that the modifications were material.

Roche and SMA Foundation, page F -22

36. Please disclose the estimated performance period and the factors considered in
determining  what appears to be a relatively short performance period.

14.  Subsequent events, page F -25

37. You disclose that in March 7, 2013 you issued and sold 4,497,035 shares of series four
senior preferred stock and an aggregate of 502,919 shares of your series f our senior
preferred stock upon conversion of the convertible promissory notes issued in January
and February 2013.  Please disclose how you plan to account for the January and
February 2013 convertible promissory note issuances, for the conversion of the
convertible promissory notes, for the issuance of warrants at an exercise price of $.01 and
for the exchange of the outstanding preferred stock that resulted in  another
recapitalization event.

38. Please disclose how you determined the value of the Series O ne, Series Two and Series
Three preferred stock issued in connection with the March 7, 2013 recapitalization.
Please be sure to describe the model used to estimate the fair values and all of the
relevant assumptions.  Please also provide us with the compu tations of how you
determined the fair value of the Series One, Series two and Series Three preferred stock.

General

If you intend to respond to these comments with an amended draft registration statement ,
please submit it and any associated correspondence in accordance with the guidance we provide
in the Division’s October 11 , 2012 announcement on the SEC website at
http://www.sec.gov/divisions/corpfin/cfannouncements/drsfilingprocedures101512.htm .

Please keep in mind that we may publicly post filing review correspondence in
accordance with our December 1, 2011 policy
(http://www.sec.gov/divisions/corpfin/cfannouncements/edgarcorrespondence.htm ).  If you
intend to use Rule 83 (17 CFR 200.83) to request confidential treatment of