SecProbe.io

September 26, 2012

Via E -mail
Jay R. Luly, Ph.D.
President and Chief Executive Officer
Enanta Pharmaceuticals, Inc.
500 Arsenal Street
Watertown, Massachusetts 02472

Re: Enanta Pharmaceuticals, Inc.
Confidential Draft Registration Statement on Form  S-1
Submitted August 31, 2012
  CIK No. 0001177648

Dear Dr. Luly:

We have reviewed your confidential 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 u nderstand your disclosure.

Please respond to this letter by providing the requested information and either submitting
an amended confidential draft registration statement or 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 response to these comments and your
amended confidential draft registration statemen t or filed registration statement, we may have
additional comments.

General

1. We note that your draft filing omits disclosure  and exhibits that you intend to provide  at a
later date . Please provide this information with your next submission  or as soon as
possible thereafter in order to expedite the review of your filing.

2. We further note that you have submitted an application for confidential treatment relating
to certain of your exhibits. Please be advised that we will be performing a separate review
of this application and that the review of your registration statement will not be complete
until all comments concerning your confidential treatment request, if any, have been
cleared.

Jay R. Luly, Ph.D.
Enanta Pharmaceuticals, Inc.
September 26, 2012
Page 2

 Prospectus Summary

Overview,  page 1

3. Please state here and wherever else applicable in your registration statement, including
the risk factor beginning on page 16, that none of your product candidates has yet
advanced beyond the Phase 2 stage of clinical testing  and that Phase 3 clin ical trials are
lengthy and typically involve at least several hundred people, if not more ; please also
provide an estimate of the minimum amount of time it would take from now until a New
Drug Application for one of your products could be approved.

ABT -450/r, a Protease Inhibitor for HCV Infection, page 2

4. Please include a statement in the last paragraph under this heading on page 3 that Abbot
Laboratories’ projection may be mistaken and that your clinical trials may take longer
than anticipated to comp lete, that the FDA may refuse to approve your New Drug
Application as submitted for a variety of reasons, and that you may be request ed to
perform additional clinical trials.

Risk Factors

“We may require substantial additional financing to achieve our goals if the development and
commercialization of ABT -450 or EDP -239 is delayed or terminated . . .,” page 13

5. Please include in this risk factor an estimate of the amount you intend to alloc ate toward
product development in the next fiscal year.

“We have incurred a substantial cumulative net loss since our inception and we anticipate that
we may incur substantial operating losses in the future . . .,” page 14

6. Please state in this risk factor and wherever else applicable in your registration statement
the reason(s) your former collaborator opted to terminate its agreement with you in 2010,
to the best of your knowledge.

“Clinical drug development involves a l engthy and expensive process with uncertain timelines
and uncertain outcomes . . .,” page 16

7. Please expand the discussion in this risk factor to state, if known, the reason for the
clinical hold on Novartis’ cyclophilin inhibitor.

Jay R. Luly, Ph.D.
Enanta Pharmaceuticals, Inc.
September 26, 2012
Page 3

 “If we or our collab orators are required to suspend or discontinue clinical trials due to side
effects or other safety risks associated with our product candidates . . .,” page 17

8. If you are aware of any instance where a clinical trial for one of your product candidates
was suspended or terminated for safety reasons, please disclose it here.

“Even if we or our collaborators are able to commercialize any product candidates, the resulting
products may become subject to unfavorable pricing regulations . . .,” page 21

9. Please i nclude in this risk factor a brief but specific discussion of the ramifications of the
Patient Protection and Affordable Care Act on your commercial prospects.

“Because a portion of our manufacturing takes place in China through third -party manufacturers
. . .,” page 24

10. Please amend your disclosure to state to which of your product candidates that your third -
party manufacturing and supply agreements relate.

“Issued patents covering one or more of our product candidates could be found invalid or
unenforc eable if challenged in court,” page 26

11. We note your disclosure on page 96 and in Note 16 to your financial statements that you
are not currently party to any actual or threatened litigation. If there has been any
litigation in the past concerning one of y our material patents, please describe the nature
of this litigation and its resolution in this risk factor.

“We will incur increased costs as a result of operating as a public company, and our management
will be required to devote substantial time to new  compliance initiatives,” page 34

12. Please include in this risk factor an estimate of the expenses you expect to incur in
completing your public offering as well as of the annual compliance costs associated with
your reporting obligations.

Use of Proceeds,  page 40

13. Please amend your disclosure to include an approximate amount of the proceeds you plan
to allocate to each of the bulleted expenditures and the stage of clinical development you
anticipate you will attain with such allocation.

Management’s Discussion and Analysis of Financial Condition and Results of Operations
Research and Development Expenses, page 63

14. Please disclose on pages 61 and 63 the costs incurred from inception to date for each
program or clarify why the inception to date amounts have not been provided.

Jay R. Luly, Ph.D.
Enanta Pharmaceuticals, Inc.
September 26, 2012
Page 4

Business

Our Research and Development Pipeline, page 71

15. In your discussion of the scientific background of your product portfolio beginning on
page 73, please state expressly whether the research you have performed and the
discoveries you have made either independently or in collaboration with Abbott
Laboratories or Novartis into protease inhibitors provides conclusive evidence that your
product candidates can offer an interferon -free or interferon/ribavirin -free approach to
HCV.  If controversy remains in the scientific community as to any of your hypotheses,
you should amend your disclosure to note this and to discuss any potential ramifications,
particularly how these uncertainties cast doubt upon the possibility of develo ping ABT -
450/ABT -450/r. To the extent appropriate, any such controversy should also be addressed
in your prospectus summary and in an independent risk factor.  Please provide a similar
discussion for EDP -788, Bicyclolides and their therapeutic effects rela ting to MRSA and
other skin infections.

Collaboration and License Agreements, page 81

16. Please be more specific in your descriptions of the tiered royalties you are eligible to
receive through the Abbott Laboratories and Novartis agreements, e.g. “teens, ”
“twenties,” “thirties,” etc.

Manufacturing, page 96

17. You state here that you currently manufacture a limited amount of your active
pharmaceutical ingredients and you imply that you will only rely on third -party
manufacturers for these ingredients when you initiate clinical trials in the future. In your
risk factor on page 24, you suggest that such third -party agreements are already in place
and that you are currently receiving supplies of your APIs through them. Please reconcile
this discrepancy in your disclosure

Executive Compensation

Narrative Disclosu re to Summary Compensation Table, page 103

18. We note that you propose to file only a form executive employment agreement as an
exhibit. If there are any other material differences among these agreements other than
what you have described here, please includ e the other differences in this disclosure and
file the individual agreements as exhibits.

Jay R. Luly, Ph.D.
Enanta Pharmaceuticals, Inc.
September 26, 2012
Page 5

 Principal Stockholders, page 111

19. Please identify the individual(s) who possess(es) voting and/or investment power over the
shares held by OBP III -Holdings LLC and its affiliated entities.

Shares Eligible for Future Sale

Lock -Up Agreements and Market Standoff Provisions, page 121

20. Please file a form of the lock -up agreement as an exhibit to your registration statement.

Notes to Financial Statements

Note 8.  Coll aboration Agreements , page F -21

21. You state that you are eligible to receive additional milestones relating to the Novartis
contract.  Please clarify in Note 8, if the additional milestones are the result of your
efforts or the collaborators’ efforts.  Also , please provide the disclosure requirements of
ASC 605 -28-50-2c and d, if required.

Note 14. Stock -Based Awards

Stock Option Valuation, page F -34

22. You have issued 513,500 stock options in the six months ended June 30, 2012.  We will
evaluate the accounting treatment for these and any other equity issuances once an IPO
price has been set.

If you intend to respond to these comments with an amended draft registration statement,
please submit it and any associated correspondence in text searchable PD F files using the secure
e-mail system we describe on our website at
http://www.sec.gov/divisions/corpfin/cfannouncements/cfsecureemailinstructions.

Please use your Central Index Key, or CIK number, in your correspondence to us about
your submissio n. You will need your CIK number to make your initial filing on EDGAR and
you must take a number of steps to prepare for that filing.  Following the procedures set forth in
Section 3.3.1.1  of the EDGAR Filer Manual – Volume I at
http://www.sec.gov/info/edg ar/edgarfm -vol1-v12., you must:

 Submit a request to us to convert your EDGAR status to an electronic filer if we
generated the CIK number for you.

 Request access codes and passwords to file your registration statement on the EDGAR
system.   If you need new or replacement EDGAR access codes and passwords, we

Jay R. Luly, Ph.D.
Enanta Pharmaceuticals, Inc.
September 26, 2012
Page 6

 suggest that you complete the process to obtain them well in advance of your targeted
filing date.  Please call the Division’s Filer Support team at 202 -551-8900 (choose option
number four) if you hav e questions about this process.   If you do call, please make sure to
tell us that we have already assigned a CIK number to your company and have that
number available.

 Make any necessary changes to your contact information and business and mailing
addre sses in EDGAR prior to making your initial filing so we can contact you about your
filing.

When you publicly file your confidential draft registration statement and amendments on
EDGAR in accordance with Section 106(a) of the JOBS Act, please:

 Attach each submission, including exhibits, to your initial registration statement as a
separate Exhibit 99 document and clearly identify each confidential submission attached
as an Exhibit 99 document (e.g., “Confidential Draft # 1”) .  Do not attach submissions
marked to show changes from earlier submissions.

 Submit each item of correspondence you sent to us in connection with your confidential
draft submissions, including your responses to our comments, as a separate “CORRESP”
submission on EDGAR.

As you pre pare correspondence to us in connection with your confidential draft
registration statement, please keep in mind that we will expect you to submit that same
correspondence on EDGAR so that we may publicly post filing review correspondence in
accordance wit h our December 1, 2011 policy (SEC Staff to Release Filing Review
Correspondence Earlier ).  If you intend to use Rule 83 (17 CFR 200.83) to request confidential
treatment of information in the correspondence you submit on EDGAR, please properly mark
that information in each of your confidential submissions to us so we do not repeat or refer to
that information in our comment letters to you.

You may contact Chris tine Allen at (202) 551 -3652 or Mary Mast at (202) 551 -3613 if
you have questions regarding comments on the financial statements and related matters.  Please
contact Scot Foley at (202) 551 -3383, John Krug at (202) 551 -3862 or me at (202) 551 -3715
with any  other questions.

Sincerely,

 /s/ Jeffrey P. Riedler

Jeffrey P. Riedler
Assistant Director