<SEC-DOCUMENT>0001193125-15-014374.txt : 20150325
<SEC-HEADER>0001193125-15-014374.hdr.sgml : 20150325
<ACCEPTANCE-DATETIME>20150120114900
<PRIVATE-TO-PUBLIC>
ACCESSION NUMBER:		0001193125-15-014374
CONFORMED SUBMISSION TYPE:	CORRESP
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20150120

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			REPLIGEN CORP
		CENTRAL INDEX KEY:			0000730272
		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
		IRS NUMBER:				042729386
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		CORRESP

	BUSINESS ADDRESS:	
		STREET 1:		41 SEYON STREET
		STREET 2:		BUILDING 1, SUITE 100
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02453
		BUSINESS PHONE:		7814499560

	MAIL ADDRESS:	
		STREET 1:		41 SEYON STREET
		STREET 2:		BUILDING 1, SUITE 100
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02453
</SEC-HEADER>
<DOCUMENT>
<TYPE>CORRESP
<SEQUENCE>1
<FILENAME>filename1.htm
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<HTML><HEAD>
<TITLE>Correspondence</TITLE>
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 <P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:56%; font-size:10pt; font-family:Times New Roman" ALIGN="center">January&nbsp;20, 2015 </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B><U>Via EDGAR </U></B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Jeffrey Riedler </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Assistant Director </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Division of Corporation Finance </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">U.S. Securities and Exchange Commission </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">100 F Street, N.E. </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Washington, DC 20549 </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>Re:</B></TD>
<TD ALIGN="left" VALIGN="top"><B>Repligen Corporation </B></TD></TR></TABLE> <P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:8%; font-size:10pt; font-family:Times New Roman"><B>Form 10-K for the fiscal year ended December&nbsp;31, 2013
</B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:8%; font-size:10pt; font-family:Times New Roman"><B>Filed March&nbsp;14, 2014 </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; margin-left:8%; font-size:10pt; font-family:Times New Roman"><B>File No. 000-14656 </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Dear
Mr.&nbsp;Riedler: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This letter is submitted on behalf of Repligen Corporation (the &#147;<B>Company</B>&#148;) in response to comments of
the staff of the Division of Corporation Finance (the &#147;<B>Staff</B>&#148;) of the Securities and Exchange Commission (the &#147;<B>Commission</B>&#148;) with respect to the Company&#146;s Form 10-K for the fiscal year ended December&nbsp;31,
2013 (the &#147;<B>Form 10-K</B>&#148;) as set forth in your letter, dated December&nbsp;23, 2014 (the &#147;<B>Comment Letter</B>&#148;). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">For reference purposes, the Staff&#146;s numbered comments have been reproduced in italics herein with responses immediately following such
comment. Page references in the responses refer to the pages in the Form 10-K as filed with the Commission. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><U>Our Products for the Manufacturing of
Biologic Drugs, page 2 </U></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I></I>1. <I>We note that your Strategic Supplier Alliance Agreement with GE Healthcare appears to be a
material agreement as it has been filed as an exhibit pursuant to Item&nbsp;601(b)(10) of Regulation S-K. Please expand your disclosure regarding the agreement to provide the material terms, including the parties&#146; rights and obligations, the
duration of the agreement, termination provisions, and any payment provisions. </I></P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Mr. Jeffrey Riedler </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Securities and Exchange Commission </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">January 20, 2015 </P>
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 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><U>Response to Comment No.&nbsp;1</U>: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Company acknowledges the Staff&#146;s comment. In future filings, the Company will expand its disclosure regarding the GE Healthcare
Strategic Supplier Alliance Agreement substantially as set forth below in italicized and underlined text, which disclosure the Company respectfully notes was included in its Current Report on Form 8-K announcing its entry into the agreement. The
Company respectfully directs the Staff&#146;s attention to the application for confidential treatment, dated February&nbsp;12, 1999, and the application for continued confidential treatment, dated December&nbsp;16, 2008, in which the Company
petitioned the Staff for confidential treatment for, in addition to other things, certain payment provisions and terms under the GE Healthcare Strategic Supplier Alliance Agreement. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Our Products for the Manufacturing of Biologic Drugs </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Repligen is a leading developer and manufacturer of certain consumable bioprocessing products used in the production of monoclonal antibodies
and other biologic drugs. The Company manufactures multiple forms of Protein A ligand, a critical component of Protein A media that is used in the downstream purification process for monoclonal antibodies, on behalf of several major life sciences
companies. We also manufacture and sell growth factors, used to increase cell growth and productivity during upstream fermentation, and chromatography products. Our chromatography products include OPUS pre-packed columns for biologics purification,
proprietary Protein A media and quality test kits. These products are sold to life sciences companies, contract manufacturing organizations and biopharmaceutical companies for use in the biologic drug production. Demand for our bioprocessing
products has grown in concert with the expanding global market for biologics, particularly monoclonal antibodies, and also as a result of new product offerings through our acquisition of the Novozymes Biopharma business in December 2011. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">In 2012, the global biologics market was valued at approximately $175 billion and is expected to grow at a rate in the high single digits
annually. Market research indicates that the monoclonal antibody segment comprised over 40% of the overall biologics market in 2012 and is growing more rapidly than the overall market. Six of the ten worldwide best-selling drugs in 2012 were
monoclonal antibodies, including blockbuster products such as Enbrel<SUP STYLE="font-size:85%; vertical-align:top">&reg;</SUP> and Remicade<SUP STYLE="font-size:85%; vertical-align:top">&reg;</SUP> for the treatment of rheumatoid arthritis and other
inflammatory disorders, Rituxan<SUP STYLE="font-size:85%; vertical-align:top">&reg;</SUP> for non-Hodgkin&#146;s lymphoma and Herceptin<SUP STYLE="font-size:85%; vertical-align:top">&reg;</SUP> for the treatment of breast cancer. There are more than
35 approved monoclonal antibody products and over 350 product candidates currently in clinical development, most of which are manufactured using Protein A. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I></I>Repligen has been a leading manufacturer of Protein A for over fifteen years and manufactures multiple forms of Protein A for major
life sciences companies including GE Healthcare and EMD Millipore under long-term supply agreements which extend to dates between 2016 and 2021. <I><U>Pursuant to Repligen&#146;s Strategic Supplier Alliance Agreement with GE Healthcare, Repligen has
agreed to manufacture and sell to GE Healthcare two forms of GE Healthcare proprietary recombinant Protein A through January&nbsp;28, 2015, with a right to extend the agreement through 2021. Repligen&#146;s Strategic Supplier Alliance Agreement with
GE Healthcare is terminable by either party upon written notice of breach or insolvency</U>. <U>In addition,</U> </I></P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Mr. Jeffrey Riedler </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Securities and Exchange Commission </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">January 20, 2015 </P>
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 3
 </P> <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P>
 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><I>
<U>pursuant to the Strategic Supplier Alliance Agreement, or Sweden Supplier Agreement, by and between Repligen Sweden AB (as successor-in-interest to Novozymes Biopharma Sweden AB) and GE
Healthcare, Repligen agrees to manufacture and sell to GE Healthcare three forms of GE Healthcare proprietary recombinant Protein A through December&nbsp;31, 2016. Either party may terminate the Sweden Supplier Agreement unilaterally for convenience
upon two years&#146; written notice or upon written notice of material default or breach of the agreement and bankruptcy or insolvency . GE Healthcare may terminate the Sweden Supplier Agreement if Repligen markets or sells any chromatography media
products, transfers control of the Sweden Supplier Agreement or upon delay or defect in the proprietary recombinant Protein A products.</U> </I>To be useful in the monoclonal antibody manufacturing process, Protein A is chemically bound to
proprietary microscopic beads that are manufactured by life sciences companies, such as those mentioned above. These beads provide the rigid support required to use Protein A ligands. The combination of Protein A ligands bound to the beads is known
as Protein A chromatographic media, which is packed by end-users into cylindrical columns and used to purify monoclonal antibodies. For example, after a fermentation process that produces monoclonal antibodies, the broth containing the monoclonal of
interest, as well as numerous fermentation by-products and contaminants, is pumped through a column filled with Protein A chromatographic media. The Protein A media selectively binds to or &#147;captures&#148; the monoclonal antibody. Protein A has
a high affinity for the monoclonal antibody and as a result, the antibody remains bound to the Protein A media while impurities flow through the column and are discarded. Once the impurities are removed, a change in pH conditions releases the
purified antibody from the Protein A media. As a result, the monoclonal antibody product is highly purified and concentrated from a single purification step. Further purification steps are usually necessary to increase purity to a level greater than
98%. Over the past three years, the majority of our product sales have been sales of Protein A products.<I> </I></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Most biopharmaceuticals
are produced through mammalian cell fermentation. In order to spur increased cell growth, manufacturers add growth factors and nutrients to the fermentor. As part of the Novozymes Acquisition, the Company acquired four cell culture growth factor
products. Among those products is LONG<SUP STYLE="font-size:85%; vertical-align:top">&reg;</SUP>R3 IGF-I, a growth factor that is more biologically potent than insulin, and that has been shown to significantly increase recombinant protein production
in fermentation applications. LONG<SUP STYLE="font-size:85%; vertical-align:top">&reg;</SUP>R3 IGF-I is currently used in the manufacture of several commercial biopharmaceutical products and is sold under a distribution agreement with Sigma-Aldrich
Corporation (&#147;Sigma&#148;) which extends to 2021. Sigma has distribution rights for industrial cell culture applications while Repligen sells the product for use in stem cell and other cell-based therapies. In addition, we acquired long
epidermal growth factor (LONG<SUP STYLE="font-size:85%; vertical-align:top">&reg;</SUP>EGF) and transforming growth factor alpha (LONG<SUP STYLE="font-size:85%; vertical-align:top">&reg;</SUP>TGF-a) supplements for serum-free or low serum culture in
cell-based therapy applications, as well as recombinant transferrin (rTransferrin) which has been developed as an iron supplement for cell culture. There may be applications for these growth factors in stem cell and other cell-based therapies. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">We also sell a number of products used in purification and quality control applications to contract manufacturers and biopharmaceutical
companies. These products include: OPUS pre-packed, disposable chromatography columns, proprietary Protein A chromatography media and </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Mr. Jeffrey Riedler </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Securities and Exchange Commission </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">January 20, 2015 </P>
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quality test kits. Our pre-packed chromatography columns are sold in a variety of sizes with the customer&#146;s choice of media. This product line&#146;s smaller sizes consist of proprietary
technology that we acquired from BioFlash Partners, LLC (&#147;BioFlash&#148;) in January 2010 while the larger sizes encompass products and technology that we developed as a result of our internal research and development efforts. The OPUS brand
stands for &#147;Open Platform, User Specified.&#148; OPUS columns have the potential to improve manufacturing efficiencies and lower costs by reducing labor and time spent on column packing, validation, set-up and cleaning. In addition, because
OPUS columns are &#147;plug-and-play&#148; we believe they offer customers significantly greater manufacturing efficiency and flexibility when used with other flexible, disposable technologies. In early 2012, we introduced new, process-scale OPUS
chromatography columns with diameters of 20cm and 30cm. These new products are well suited for the production of a broad range of clinical trial material and niche commercial products such as orphan biologics. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Our proprietary Protein A chromatography media is used by contract manufacturers and biopharmaceutical companies in a variety of applications,
including in the purification of some currently marketed biotherapeutics. Customers use our Protein A and Growth Factor ELISA test kits to ensure that there are minimal levels of residual Protein A and growth factor, respectively, in the final bulk
drug product. </P> <P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><U>Research and Development, page 4 </U></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I></I>2. <I>Please expand your disclosure for your HDAC Agreement with BioMarin to describe the material terms of the agreement, including the
parties&#146; rights and obligations, the duration of the agreement, termination provisions and royalty rates. Also, please file the agreement as an exhibit pursuant to Item&nbsp;601(b)(10) of Regulation S-K. </I></P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><U>Response to Comment No.&nbsp;2</U>: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Company acknowledges the Staff&#146;s comment. In future filings, the Company will expand its disclosure regarding the HDAC Agreement with
BioMarin substantially as set forth below in italicized and underlined text. The Company respectfully informs the Staff that because the HDAC Agreement with BioMarin was entered into during the quarter ended March&nbsp;31, 2014, it is filed as
Exhibit 10.01 to the Company&#146;s quarterly report on form 10-Q for the quarter ended March&nbsp;31, 2014, filed with the Commission on May&nbsp;9, 2014. The Company respectfully directs the Staff&#146;s attention to the application for
confidential treatment, dated May&nbsp;9, 2014, in which the Company petitioned the Staff for confidential treatment for, in addition to other things, certain provisions and terms under the HDAC Agreement with BioMarin. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>HDAC Agreement with BioMarin </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">On
January&nbsp;21, 2014, we out-licensed our HDACi portfolio, which includes the Friedreich&#146;s ataxia program, to BioMarin Pharmaceuticals Inc. Friedreich&#146;s ataxia is an inherited </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Mr. Jeffrey Riedler </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Securities and Exchange Commission </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">January 20, 2015 </P>
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disease that causes progressive damage to the nervous system resulting in symptoms ranging from impaired walking and speech problems to heart disease. Under the terms of the agreement, Repligen
received an upfront payment of $2 million in January 2014 from BioMarin and we have the potential to receive up to $160 million in future milestone payments for the development, regulatory approval and commercial sale of portfolio compounds included
in the agreement. <I><U>These potential milestone payments are approximately 37% related to clinical development and 63% related to initial commercial sales in specific geographies.</U></I> In addition, Repligen is eligible to receive royalties on
sales of qualified products developed. <I><U>The royalty rates are tiered and begin in the mid-single-digits for the first HDACi portfolio product and for the first non-HDACi portfolio product with lesser amounts for any backup products developed
under the agreement. Repligen&#146;s receipt of these royalties is subject to customary offsets and deductions. There are no refund provisions in this agreement. </U></I> </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I></I>3. <I>Please expand your disclosure for your SMA Agreement with Pfizer to describe the termination provisions of the agreement. With
regard to the duration of the agreement, we note that the royalty term of the agreement is based on the later of (a)&nbsp;expiration of the licensed patents or (b)&nbsp;a predetermined time after the first commercial sale of the first product in a
country. Please revise the duration disclosure to provide the expiration date of the last to expire patent and the &#147;predetermined time&#148; referenced in your disclosure. </I></P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><U>Response to Comment No.&nbsp;3</U>: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Company acknowledges the Staff&#146;s comment. In future filings, the Company will expand its disclosure regarding the SMA Agreement with
Pfizer substantially as set forth below in italicized and underlined text. The Company respectfully directs the Staff&#146;s attention to the application for confidential treatment, dated March&nbsp;15, 2013, as amended on May&nbsp;2, 2013, in which
the Company petitioned the Staff for confidential treatment for, in addition to other things, certain royalty adjustment and cessation provisions and terms under the Pfizer Inc. License Agreement. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>SMA Agreement with Pfizer </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">On
December&nbsp;28, 2012, we entered into an exclusive worldwide licensing agreement (the &#147;License Agreement&#148;) with Pfizer to advance the SMA program, which is led by RG3039 and also includes backup compounds and enabling technologies. Under
the terms of the License Agreement, we received $5 million from Pfizer as an upfront payment on January&nbsp;22, 2013 and a $1 million milestone payment on September&nbsp;4, 2013. We are entitled to receive up to $64 million in potential future
milestone payments, a portion of which may be owed to third parties. These potential payments are approximately equally divided between milestones related to clinical development and initial commercial sales in specific geographies.&nbsp;In
addition, we are entitled to receive royalties on any future sales of RG3039 or any SMA compounds developed under the License Agreement.&nbsp;The License Agreement also provides for tiered and increasing royalty rates which begin in the high
single-digits for RG-3039 or lesser amounts for any backup compounds </P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Mr. Jeffrey Riedler </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Securities and Exchange Commission </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">January 20, 2015 </P>
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developed under the License Agreement.&nbsp;Our receipt of these royalties is subject to an obligation under an existing in-license agreement&nbsp;and other customary offsets and deductions.
Royalties are payable, on a country-by-country basis, for a duration based upon the later of (a)&nbsp;expiration of the licensed patent(s) <I><U>and</U></I> (b)&nbsp;a predetermined time after the first commercial sale of the first such product in
such country. Pursuant to this License Agreement, Pfizer has assumed full responsibility for the SMA program moving forward, including the conduct of the clinical trials necessary for any product approvals. Pfizer may terminate the license agreement
at any time for convenience <I><U>or for cause upon written notice to Repligen. In addition, the License Agreement shall terminate upon the termination of the Exclusive License Agreement by and between Repligen and Families of Spinal Muscular
Atrophy (&#147;FSMA&#148;), dated October&nbsp;22, 2009, which is terminable at will by Repligen and will otherwise terminate upon the later of (i)&nbsp;the expiration or abandonment of all underlying patent rights, (ii)&nbsp;10 years following the
first commercial sale of the licensed product, and (iii)&nbsp;the expiration or termination of all obligations pursuant to FSMA&#146;s existing licenses with Vertex Pharmaceuticals Incorporated and deCode Chemistry, Inc.</U></I> </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><U>Significant Customers and Geographic Reporting, page 5 </U></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I></I>4. <I>Please revise your disclosure in this section to identify the customer which accounted for 35% of your revenues for the fiscal
year ended December&nbsp;31, 2013. Also, please identify customers A, B and C in the section entitled &#147;Concentrations of Credit Risk and Significant Customers&#148; on page 67. </I></P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><U>Response to Comment No.&nbsp;4</U>: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Company respectfully directs the Staff&#146;s attention to the section entitled &#147;Sales and Marketing&#148; on page 5, in which the
Company identifies large bioprocessing customers with specificity. The Company has disclosed its relationship with Customer A, GE Healthcare, extensively throughout its periodic reports. In reliance on Item&nbsp;101(c)(vii) of Regulation S-K,
Customer B and Customer C are not identified with specificity because although these customers are significant, the loss of either such customer would not have a material adverse effect on the Company as a whole. Accordingly, the Company
respectfully submits that it is similarly not appropriate to identify Customer B or Customer C with additional specificity in the section entitled &#147;Concentrations of Credit Risk and Significant Customers&#148; on page 67. In future filings, the
Company will more expressly identify GE Healthcare as a substantial customer, as well as any other customer, the loss of which would have a material adverse effect on the Company. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><U>Patent, Licenses and Proprietary Rights, page 6 </U></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I></I>5. <I>Please expand your disclosure for your material patents and patent applications to include the following information: </I></P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"><I>the type of patent protection such as composition of matter, use or process for your U.S. Patent No.&nbsp;7,691,608 B2;</I> </TD></TR></TABLE>

<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">


 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Mr. Jeffrey Riedler </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Securities and Exchange Commission </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">January 20, 2015 </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"> Page
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<TR>
<TD WIDTH="1%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left"><I>&#149;</I></TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"><I>the jurisdiction where your OPUS pre-packed column patent application is pending and the expected expiration date if the patent is issued; </I></TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="1%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left"><I>&#149;</I></TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"><I>the expiration dates of U.S. Patent Nos. 7,888,366 and 7,985,755; and </I></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="1%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left"><I>&#149;</I></TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top"><I>the jurisdiction where your histone deacetylase inhibitors patent application is pending and the expected expiration date if the patent is issued. </I></TD></TR></TABLE>
<P STYLE="margin-top:18pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><U>Response to Comment No.&nbsp;5</U>: </P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Company acknowledges the Staff&#146;s comment. In future filings, the Company will expand its disclosure regarding its material patents and
patent applications substantially as set forth below in italicized and underlined text: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top">The type of patent protection such as composition of matter, use, or process for your U.S. Patent No.&nbsp;7,691,608 B2 </TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I><U>The claims of U.S. Patent No.&nbsp;7,691,608 cover compositions of matter including isolated nucleic acids, expression vectors,
bacterial cells that include the nucleic acids, as well as methods of producing truncated Protein A polypeptides, methods of producing affinity chromatography resins, and methods of purifying proteins. </U></I></P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top">The jurisdictions where your OPUS pre-packed column patent application is pending and the expected expiration date if the patent is issued </TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I><U>The OPUS pre-packed column patent application is pending in the United States, Australia, Canada, Europe, India, and Japan.</U> </I></P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%">&nbsp;</TD>
<TD WIDTH="3%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top">The expiration dates of U.S. Patent Nos. 7,888,366 and 7,985,755 </TD></TR></TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I><U>The expiration date of
U.S. Patent No.&nbsp;7,888,366 (the &#145;366 patent) is in 2028 with potential for patent term extension.</U> </I></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I><U>The expiration
date of U.S. Patent No.&nbsp;7,985,755 (the &#145;755 patent) is in 2027 with potential for patent term extension.</U> </I></P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="1%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top">The jurisdiction where your histone deacetylase (HDAC) inhibitors patent application is pending and the expected expiration date if the patent is issued </TD></TR></TABLE>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I><U>On January&nbsp;21, 2014, the Company out-licensed its HDAC Inhibitor (HDACi) portfolio to BioMarin Pharmaceuticals Inc. The
Company&#146;s outlicensed HDACi portfolio included patent applications in the United States as well as patent applications in the EU, Canada, Japan and Australia.</U></I> </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">*&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;* </P>

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<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">


 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Mr. Jeffrey Riedler </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Securities and Exchange Commission </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">January 20, 2015 </P>
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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On behalf of the Company, I hereby acknowledge that: </P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="1%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top">the Company is responsible for the adequacy and accuracy of the disclosure in the filing; </TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="1%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top">Staff comments or changes to disclosure in response to Staff comments do not foreclose the Commission from taking any action with respect to the filing; and </TD></TR></TABLE>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="1%">&nbsp;</TD>
<TD WIDTH="2%" VALIGN="top" ALIGN="left">&#149;</TD>
<TD WIDTH="1%" VALIGN="top">&nbsp;</TD>
<TD ALIGN="left" VALIGN="top">the Company may not assert Staff comments as a defense in any proceeding initiated by the Commission or any person under the federal securities laws of the United States. </TD></TR></TABLE>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Mr. Jeffrey Riedler </P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Securities and Exchange Commission </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">January 20, 2015 </P>
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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Should you have any further comments or questions with regard to the foregoing, please do not
hesitate to contact the undersigned by phone at 781-419-1862 or by e-mail at jsnodgres@repligen.com or Arthur R. McGivern by phone at 617-642-5702 or by email at amcgivern@goodwinprocter.com. </P>
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<TD VALIGN="top" COLSPAN="5">Sincerely,</TD></TR>
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<TD HEIGHT="16" COLSPAN="4"></TD></TR>
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<TD VALIGN="top" COLSPAN="3"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Jon Snodgres</P></TD></TR>
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<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top">Name:</TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top">Jon Snodgres</TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top">Chief Financial Officer</TD></TR>
</TABLE></DIV> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD VALIGN="top">Cc:</TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top">Walter C. Herlihy</TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3"> <P STYLE="text-indent:5.00em; font-size:10pt; font-family:Times New Roman"><I>Repligen Corporation</I></P></TD></TR>
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<TD HEIGHT="16"></TD>
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<TD VALIGN="top">Arthur R. McGivern</TD></TR>
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<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top">Courtney M. Gaughan</TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3"> <P STYLE="text-indent:5.00em; font-size:10pt; font-family:Times New Roman"><I>Goodwin Procter LLP</I></P></TD></TR>
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