SecProbe.io

March 13 , 2013

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.
Amendment No. 4 to Registration Statement on Form S -1
Filed March 5 , 2012
  File No. 333 -184779

Dear Dr. Luly:

We have reviewed your amendment dated March 5 , 2013 and have the following
comment.  Please respond to this letter by amending your registration statemen t as requested.   If
you do not believe th is comment app lies to your facts and circumstances or do not believe a n
amendment is appropriate, please tell us why in a response.

After reviewing any further amendment to your  registration statement and the
information you provide in response to this comment, we may have additional comments.

Dilution, page 45

1. Please revise the dilution disclosure to present line items for historical net tangible book
value per share and the  amounts attributable to pro forma adjustments to arrive at pro
forma net tangible book value per share.

We urge all persons who are responsible for the accuracy and adequacy of the disclosure
in the filing to be certain that the filing includes the infor mation the Securities Act of 1933 and
all applicable Securities Act rules require.   Since the company and its management are in
possession of all facts relating to a company’s disclosure, they are responsible for the accuracy
and adequacy of the disclosure s they have made.

Notwithstanding our comment, in the event you request acceleration of the effective date
of the pending registration statement please provide a written statement from the company
acknowledging that:

 should the Commission or the staff,  acting pursuant to delegated authority, declare the
filing effective, it does not foreclose the Commission from taking any action with respect
to the filing;

Jay R. Luly, Ph.D.
Enanta Pharmaceuticals, Inc.
March 13 , 2013
Page 2

  the action of the Commission or the staff, acting pursuant to delegated authority, in
declaring the filing effective, does not relieve the company from its full responsibility for
the adequacy and accuracy of the disclosure in the filing; and

 the company may not assert staff comments and the declaration of effectiveness as a
defense in any proceedi ng initiated by the Commission or any person under the federal
securities laws of the United States.

Please refer to Rules 460 and 461 regarding requests for acceleration.  We will consider a
written request for acceleration of the effective date of the registration statement as confirmation
of the fact that those requesting acceleration are aware of thei r respective responsibilities under
the Securities Act of 1933 and the Securities Exchange Act of 1934 as they relate to the proposed
public offering of the securities specified in the above registration statement.  Please allow
adequate time for us to rev iew any amendment prior to the requested effective date of the
registration statement.

Sincerely,

 /s/ Jeffrey P. Riedler

Jeffrey Riedler
Assistant Director

cc: Nathaniel S. Gardiner, Esq.
 Stacie S. Aarestad, Esq.
Edwards Wildman Palmer LLP
111 Huntington Avenue
Boston, Massachusetts 02199