SecProbe.io

Mail Stop 4546
December 22, 2016

Via E -mail
Mr. Jon Snodgres
Chief Financial Officer
Repligen Corporation
41 Seyon Street
Bldg. 1, Suite 100
Waltham, MA  0245 3

Re: Repligen Corporation
 Form 10-K for the fiscal year ended December 31, 2015
Filed February  25, 2016
File No. 0 -14656

Dear Mr. Snodgres :

We have reviewed your filing an d have the following comment.  In our comment, we ask
you to provide us with information so we may better understand your disclosure.

Please respond to this comment  within ten busine ss days by providing the requested
information or advis e us as soon as possible when you will respond.  If you do not believe our
comment appl ies to your facts and circumstances, please tell us why in your response.

After reviewing your response and any amendment you may file in response to th is
comment , we may have  additional comments.

Financial Statements
Segment Reporting, page 65

1. Please p rovide us, for the fiscal years 2015 and 2014 and for the nine months ended
September 30, 2016, product revenues for :
 Protein A ligands ;
 OPUS® pre -packed chromatography column line ;
 Protein A chromatography resins ;
 LONG®R3 IGF -1; and
 ATF System
as discuss ed under “Our Products” on page 3.  Also, te ll us your consideration for
providing product revenue disclosures pursuant to  ASC 280 -10-50-40.

Mr. Jon Snodgres
Repligen Corporation
December 22, 2016
Page 2

 We remind you that the company and its management are responsible for the accuracy
and adequacy of their disclosur es, notwithstanding any review, comments, action or absence of
action by the staff.

You may contact Lisa Vanjoske, Assistant Chief Accountant  at (202) 551 -3614  or Mary
Mast, Senior Accountant  at (202) 551 -3613  if you have questions regarding comments on  the
financial statements and related matters.   In this regard, do not hesitate to contact me at (202)
551-3679 .

Sincerely,

 /s/ Jim B. Rosenberg

Jim B. Rosenberg
Senior Assistant Chief Accountant
Office of Healthcare and Insurance