Exhibit 99.1

						Repligen Corporation
						41 Seyon Street
						Building #1, Suite 100
						Waltham, Massachusetts 02453

Repligen Reports First Quarter 2016 Financial Results

- Record quarterly revenue of $25.1 million, reflecting 21% year-over-year growth -

WALTHAM, MA – May 5, 2016 – Repligen Corporation (NASDAQ:RGEN), a life sciences company focused on bioprocessing technology leadership, today reported financial results for the first quarter ended March 31, 2016. Detailed in this press release are the Company’s performance highlights for the period, followed by updated financial guidance for the year 2016 and access information for today’s webcast and conference call.

Tony J. Hunt, President and Chief Executive Officer said, “Our record revenue during the first quarter reflects overall growth of 21% year-over-year, driven by increased demand for our proprietary products, which we believe is a direct result of our commercial expansion in 2015. We continue to add best-in-class technologies to our portfolio, and we closed out the quarter by executing on our acquisition strategy with our April 1^st purchase of Atoll GmBH (“Atoll”). We are pleased with how the integration is progressing and look forward to establishing the Weingarten, Germany, facility as our European customer-facing center for many of our high-value products.”

Financial Highlights for First Quarter 2016

- more -

Non-GAAP Measures of Financial Performance

To supplement our financial statements, which are presented on the basis of U.S. generally accepted accounting principles (GAAP), the following non-GAAP measures of financial performance are included in this

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release: revenue growth rate at constant currency, adjusted operating income, earnings before interest, taxes, depreciation and amortization (EBITDA), adjusted EBITDA, adjusted net income and adjusted earnings per diluted share (EPS). The Company provides revenue growth rates in constant currency to exclude the impact of foreign currency translation in order to facilitate a comparison of its current revenue performance to its past revenue performance. To calculate revenue growth rates in constant currency, the Company converts actual net sales from local currency to U.S. dollars using constant foreign currency exchange rates in the current and prior period. The Company’s adjustments to these non-GAAP measures exclude the impact of contingent consideration and acquisition costs related to the Company’s June 2014 asset purchase agreement with Refine Technology, and acquisition costs related to the Company’s April 2016 acquisition of Atoll GmBH. These costs and revenues are excluded because management believes that such expenses do not have a direct correlation to future business operations, nor do the resulting charges and revenues recorded accurately reflect the performance of our ongoing operations for the period in which such charges and revenues are recorded. Refine contingent consideration is triggered by the achievement of annual ATF System sales milestones through the end of the year 2016.

A reconciliation of GAAP to adjusted non-GAAP financial measures is included as an attachment to this press release. When analyzing the Company’s operating performance investors should not consider non-GAAP measures as substitutable for the comparable financial measures prepared in accordance with GAAP.

Financial Guidance for 2016

Based on our first quarter performance, our acquisition of Atoll at the beginning of the second quarter of 2016, and our current projections for organic business performance, we are updating our guidance for the year 2016. This guidance is based on expectations for our existing business and does not include the financial impact of potential additional Refine or Atoll contingent consideration, potential new acquisitions or future fluctuations in foreign currency exchange rates.

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Conference Call

Repligen will host a conference call and webcast today, May 5, 2016, at 8:30 a.m. EDT, to discuss first quarter 2016 financial results and corporate developments. The conference call will be accessible by dialing toll-free (844) 835-7432 for domestic callers or (404) 537-3372 for international callers. Dial-in participants must provide the passcode 97934207. In addition, a webcast will be accessible via the Investor Relations section of the Company’s website. Both the conference call and webcast will be archived for a period of time following the live event. The replay dial-in numbers are (855) 859-2056 for domestic callers and (404) 537-3406 for international callers. Replay listeners must provide the passcode 97934207.

About Repligen Corporation

Repligen Corporation (NASDAQ:RGEN) is a life sciences company focused on the development and commercialization of high-value consumable products used in the process of manufacturing biological drugs. Our bioprocessing products are sold to major life sciences and biopharmaceutical companies worldwide. We are the leading manufacturer of Protein A affinity ligands, a critical component of Protein A media that is used to separate and purify monoclonal antibody therapeutics. Our ATF System and our growth factor products are used to increase product yield during the fermentation stage of biologic drug manufacturing. In addition, we market an innovative line of “ready-to-use” chromatography columns under our OPUS^® and MediaScout^® brands that we deliver pre-packed with our customers’ choice of purification media. Repligen’s corporate headquarters are in Waltham, MA (USA) and our manufacturing facilities are located in Waltham, MA, Lund, Sweden and Weingarten, Germany.

The following constitutes a “Safe Harbor” statement under the Private Securities Litigation Reform Act of 1995: This press release contains forward-looking statements, which are made pursuant to the safe harbor provisions of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Investors are cautioned that statements in this press release which are not strictly historical statements, constitute forward-looking statements, including, without limitation, express or implied statements or guidance regarding current or future financial performance and position, including cash and investment position, expected revenue growth from acquisitions, the potential impairment of future earnings, management’s strategy, plans and objectives for future operations or acquisitions, product development and sales, selling, general and administrative expenditures, intellectual property, development and manufacturing plans, availability of materials and product and adequacy of capital resources and financing plans constitute forward-looking statements identified by words like “believe,” “expect,” “may,” “will,” “should,” “seek,” “anticipate,” or “could” and similar expressions. Such forward-looking statements are subject to a number of risks and uncertainties that could cause actual results to differ materially from those anticipated, including, without limitation, risks associated with: our ability to successfully grow our bioprocessing business, including as a result of acquisition, commercialization or partnership opportunities; our ability to successfully integrate the Atoll business, our ability to develop and commercialize products and the market acceptance of our products; reduced demand for our products that adversely impacts our future revenues, cash flows, results of operations and financial condition; our ability to compete with larger, better financed bioprocessing, pharmaceutical and biotechnology companies; our compliance with all Food and Drug Administration and EMEA regulations; our

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volatile stock price; and other risks detailed in Repligen’s most recent Annual Report on Form 10-K on file with the Securities and Exchange Commission and the other reports that Repligen periodically files with the Securities and Exchange Commission. Actual results may differ materially from those Repligen contemplated by these forward-looking statements. These forward looking statements reflect management’s current views and Repligen does not undertake to update any of these forward-looking statements to reflect a change in its views or events or circumstances that occur after the date hereof except as required by law.

Repligen Contact:

Sondra S. Newman

Senior Director Investor Relations

(781) 419-1881

snewman@repligen.com

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REPLIGEN CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME

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REPLIGEN CORPORATION

RECONCILIATION OF GAAP INCOME FROM OPERATIONS TO NON-GAAP INCOME FROM OPERATIONS

(Unaudited)

REPLIGEN CORPORATION

RECONCILIATION OF GAAP NET INCOME TO NON-GAAP ADJUSTED EBITDA

(Unaudited)

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REPLIGEN CORPORATION

RECONCILIATION OF GAAP NET INCOME TO NON-GAAP ADJUSTED NET INCOME

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REPLIGEN CORPORATION

RECONCILIATION OF GAAP NET INCOME (LOSS) PER SHARE TO NON-GAAP ADJUSTED NET INCOME PER SHARE

(Unaudited)

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