SecProbe.io

May 25, 2016

Glyn Edwards
Chief Executive Officer and Executive Director
Summit Therapeutics plc
85b Park Drive
Milton Park, Abingdon
Oxfordshire OX14 4RY
United Kingdom

Re: Summit Therapeutics plc
  Registration Statement on Form F-3
Filed  May 12, 2016
  File No.  333-211301

Dear Mr. Edwards :

We have limited our review of your registration statement to those issue  addressed in our
comment. Please respond to this letter by amending your registration statement as requested .  If
you do not believe our comment appl ies to your facts and circumstances or do not believe an
amendment is appropriate, please tell us why in a response.

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

Exhibit 5.1

1. We note in paragraph 5(ii) of Exhibit 5.1 that counsel opines that the ordinar y shares will
be “validly allotted and issued and fully paid .” Please file an opinion that also addresses
whether the ordinary shares will be non-assessable , as that term is understood under U.S.
law.  For guidance, p lease refer to Section II.B.1.c of Staff Legal Bulletin No. 19
(October 14, 2011) .

We urge all persons who are responsible for the accuracy and adequacy of the disclosure
in the filing to be certain that the filing inclu des the information the Securities Act of 193 3 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 t he disclosures 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:

Glyn Edwards
Summit Therapeutics plc
May 25, 2016
Page 2

 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;

 the action of the Commission or the staff, acting pursuant t o 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 effect iveness as a
defense in any proceeding 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 acceler ation of the effective date of the registration statement as confirmation
of the fact that those requesting acceleration are aware of their 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 review any amendment prior to the requested effective date of the
registration statement.

You may contact Scot Fole y at (202) 551 -3383 or Mary Beth Breslin at (202) 551 -3625
with any questions.

Sincerely,

 /s/ Mary Beth Breslin for

Suzanne Hayes
Assistant Director
Office of Healthcare and Insurance

cc: Brian A. Johnson
Wilmer Cutler Pickering Hale and Dorr LLP