SecProbe.io

December 7, 2012

Via E -mail
Dale Schenk, PhD
President and Chief Executive Officer
Prothena Corporation plc
650 Gateway Boulevard
San Francisco, CA 94080

Re: Prothena Corporation plc
Amendment No. 2 to Registration Statement on Form 10
Filed November 30, 2012
 File No. 001 -35676

Dear Dr. Schenk :

We have reviewed amendment n o. 2 to your  registration statement on Form 10 and
response letter filed on November 30, 2012 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 letter by amending your registration statement and providing the
requested informati on.  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 any amendment to your registration statement and the information you
provid e in response to these  comments, we may have  additional comments.

Exhibit 99.1

Annual Audited Carve -out Combined Financial Statements
Report of Independent Registered Public Accounting Firm, page F -16

1. As a public company, your auditor is required by l aw to undergo regular Public Company
Accounting Oversight Board (PCAOB) inspections to assess its compliance with U.S. law
and professional standards in connection with its audits of financial statements filed with the
SEC.   The PCAOB, however, is currentl y unable to inspect the audit work and practices of
your auditor (see
http://pcaobus.org/International/Inspections/Pages/IssuerClientsWithoutAccessList.a spx).  As
a result of this obstacle, investors in U.S. markets who rely on your auditor’s audit reports are
deprived of the benefits of PCAOB inspections of auditors. Therefore, please state this fact

Dale Schenk, PhD
Prothena Corporation plc
December 7, 2012
Page 2

 under a separate risk factor heading.   Explain that thi s lack of inspection prevents the
PCAOB from regularly evaluating your auditor’s audits and its quality control procedures.

2. Your auditor’s report indicates that their audit was conducted in accordance with the
auditing standards of the PCAOB.   As auditors  of issuers must comply with all standards
of the PCAOB and not just the auditing standards, please have your auditors revise their
report to remove the word “auditing” in the context of the standards under which they
conducted their audit.   Otherwise, exp lain to us why your financial statements are not
required to be reaudited by an auditor who complies with all the standards of the
PCAOB.

You may contact Tabatha Akins at (202) 551 -3658  or Mark Brunhofer at (202) 551 -3638
if you have questions regarding c omments on the financial statements and related matters.
Please contact Johnny Gharib at (202) 551 -3170, Jennifer Riegel at (202) 551 -3575 or me at
(202) 551 -3715  with any other questions.

Sincerely,

 /s/ Jennifer Riegel for

 Jeffrey P. Riedler
Assistant Director

cc: Via E-mail
 Christopher T. Cox, Esq.
 Cadwalader, Wickersham & Taft LLP
 One World Financial Center
 New York, New York 10281