Repligen Corporation 41 Seyon Street Building #1, Suite 100 Waltham, Massachusetts 02453 Repligen Reports First Quarter 2017 Financial Results Record quarterly revenue of $30.6 million reflects 22% year-over-year growth

Repligen Reports First Quarter 2017 Financial Results

Record quarterly revenue of $30.6 million reflects 22% year-over-year growth or 24% at constant currency

Company increases net income and EPS guidance

WALTHAM, MA May 4, 2017 Repligen Corporation (NASDAQ:RGEN), a life sciences company focused on bioprocessing

technology leadership, today reported financial results for its first quarter ended March 31, 2017. Detailed in this press release are the Company s performance highlights for the quarter, followed by financial guidance for the year 2017

and access information for today s webcast and conference call.

Tony J. Hunt, President and Chief Executive Officer said We had a strong start

to the year, reporting first quarter revenue growth of 24% at constant currency. Our Chromatography and Filtration businesses were major drivers of growth in the quarter, with our two acquisitions from 2016 Atoll GmbH and TangenX Technology

Corporation contributing to the overall success. With a positive outlook for 2017, we are today reaffirming our full year revenue guidance and increasing our net income and EPS guidance.

Financial Highlights for the First Quarter of 2017

GROSS PROFIT and GROSS MARGIN

Adjusted net income and adjusted EPS figures, detailed in the reconciliation tables accompanying this release, exclude the impact of the above mentioned

acquisition costs, intangible amortization expenses and contingent consideration expenses. In addition, these figures exclude the non-cash portion of debt-related interest expense ($1.0 million during the

first quarter of 2017) and the tax effect of intangible amortization (negative $0.1 million for each of the first quarters of 2016 and 2017).

Financial Guidance for 2017

Based on our current

projections, we are adjusting our income tax guidance and increasing our net income and earnings per share guidance for the year 2017. We are otherwise maintaining our financial guidance as provided on our February 22 earnings call. Our current

guidance is based on expectations for our existing business and does not include the financial impact of potential new acquisitions or future fluctuations in foreign currency exchange rates.

As a reminder, as of this first quarter of 2017 earnings report we are excluding intangible amortization costs from our

non-GAAP reporting, on the basis that our recent acquisitions and potential new acquisitions are creating higher levels of this non-cash

non-operational expense. Intangible amortization was not excluded in our 2016 non-GAAP reporting and therefore, we are providing restated GAAP to non-GAAP reconciliation tables for 2016, starting with this first quarter report. We expect intangible amortization expense of approximately $2.9 million for the year 2017 ($0.6 million in cost of goods,

$2.3 million in G&A). In 2016, actual intangible amortization expense was $2.1 million ($0.6 million in cost of goods, $1.5 million in G&A).

Financial guidance highlights for the year 2017:

Our non-GAAP guidance excludes the following items:

Repligen will host a conference call and

webcast today, May 4, 2017, at 8:30 a.m. EDT, to discuss first quarter of 2017 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 11424546. 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 11424546.

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 release: revenue growth rate at constant currency, adjusted income from operations, 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

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 non-GAAP measures exclude the impact of contingent consideration related to the Company s June 2014 asset

purchase agreement with Refine Technology, the impact of acquisition costs related to the Company s April 2016 acquisition of Atoll GmBH and December 2016 acquisition of TangenX Technology Corporation, the impact of intangible amortization

costs, the impact of non-cash, and in the case of EBITDA, cash interest expense related to the Company s May 2016 convertible debt issuance. These costs are excluded because management believes that such

expenses do not have a direct correlation to future business operations, nor do the resulting charges recorded accurately reflect the performance of our ongoing operations for the period in which such charges are recorded. Refine contingent

consideration was triggered by the achievement of annual XCell ATF system sales milestones through 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.

About Repligen Corporation

Repligen Corporation

(NASDAQ:RGEN) is a bioprocessing company focused on the development, manufacture and commercialization of highly innovative products used to improve the interconnected phases of the biological drug manufacturing process. Our portfolio includes

protein products (Protein A affinity ligands, cell culture growth factors), chromatography products (OPUS pre-packed columns, chromatography resins,

ELISA kits) and filtration products (XCell ATF Systems, TangenX Sius TFF cassettes). Our bioprocessing products are sold to major life sciences companies, biopharmaceutical development companies and contract manufacturing

organizations worldwide. The Protein A ligands and growth factor products that we manufacture are components of chromatography resins and cell culture media, respectively. We are the leading manufacturer of Protein A ligands, a critical component of

Protein A resins that are the industry standard for downstream separation and purification of monoclonal antibody-based therapeutics. Our growth factors are used in upstream processes to accelerate cell growth and productivity. Our innovative line

of OPUS chromatography columns, used in downstream processes for bench-scale through clinical-scale purification needs, are delivered pre-packed with

our customers choice of resin and bed height. Our XCell ATF Systems, available in stainless steel and single-use configurations, continuously eliminate waste from a bioreactor to concentrate cells

and increase productivity in upstream processes. TangenX Sius TFF single-use cassettes and hardware are used for biologic drug concentration in downstream processes. Repligen s corporate

headquarters are in Waltham, MA (USA) and our manufacturing facilities are located in Waltham, MA, Shrewsbury, 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, including, without limitation, express or implied statements or guidance regarding current or future financial performance and position, including cash and investment position, 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 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 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.

Senior Director Investor Relations

REPLIGEN CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

REPLIGEN CORPORATION

RECONCILIATION OF GAAP INCOME FROM OPERATIONS TO NON-GAAP (ADJUSTED) INCOME FROM OPERATIONS

REPLIGEN CORPORATION

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

REPLIGEN CORPORATION

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

REPLIGEN CORPORATION

RECONCILIATION OF GAAP NET INCOME TO ADJUSTED EBITDA