Exhibit 99.1 Repligen Acquistion of BioFlex Solutions* December 16, 2021 *Acquisition of BioFlex Solutions, LLC includes the company’s manufacturing arm, Newton T&M

Safe Harbor This presentation contains forward-looking statements within the meaning of the federal securities laws. Investors are cautioned that statements in this presentation which are not strictly historical statements including, without limitation, express or implied statements or guidance regarding the expected results of the proposed acquisition of BioFlex Solutions, LLC (BioFlex Solutions) on Repligen’s future financial performance, including the accretive nature and the timing of the accretive nature of the acquisition, expected synergies following the acquisition of BioFlex Solutions, customer adoption of BioFlex Solutions’ products, the expected expansion of Repligen’s product lines, and other statements identified by words like “believe,” “expect,” “anticipate,” “may,” “will,” “should,” “targeted,” “seek,” or “could” and similar expressions, constitute forward-looking statements. 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: the risk that the proposed acquisition may not be completed in a timely manner, or at all; the occurrence of any event, change or other circumstance that could give rise to the termination of the acquisition; our ability to integrate BioFlex Solutions’ business and personnel and to achieve expected synergies; our ability to maintain or expand BioFlex Solutions’ historical sales; our ability to accurately forecast the acquisition, related restructuring costs and allocation of the purchase price, goodwill and other intangibles acquisition related and other asset adjustments; and other risks detailed in Repligen’s most recent Annual Report on Form 10-K and the most recently filed Quarterly Report on Form-10-Q 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. Therefore, you should not rely on any of these forward- looking statements. These forward-looking statements reflect management’s current views and are based only on information currently available to us. Repligen does not undertake to update, whether written or oral, any of these forward-looking statements to reflect a change in its views or events or circumstances, whether as a result of new information or otherwise, that occur after the date hereof except as required by law. The industry and market data contained in this presentation are based on management’s own estimates, independent publications, government publications, reports by market research firms or other published independent sources, and, in each case, are believed by management to be reasonable estimates. Although we believe these sources are reliable, we have not independently verified the information. 2 2 2

Complements and Expands Secures and Simplifies BioFlex Solutions Our Fluid Management Offerings Our Supply Chain Strengthens Builds on 2020 acquisitions - Significant opportunities for insourcing of Repligen’s ARTeSYN, EMT, NMS components multiple Repligen components Single-Use Fluid Strengthens fluid management platform Potential to drive shorter lead-times for Management upstream/downstream Repligen single-use fluid management products Product Adds superior engineering and design capabilities Portfolio, Platform and Capabilities Accelerates Market Adoption Meets Our Strict through Repligen’s Commercial channel M&A criteria Immediate opportunity to go direct Near 100% bioprocessing Expands portfolio for dedicated Strong revenue growth commercial team Immediately accretive to adjusted EPS Complements Repligen single-use fluid management offering. Further integrates components and assemblies and supports our systems strategy. 3 3 3

BioFlex ü Differentiated fluid management solutions Solutions • Key components used in single-use flow path assemblies Meets ü Supports integration of Repligen supply chain for systems, filtration and Repligen’s Acquisition chromatography products Criteria ü Complements and expands current offerings from ARTeSYN, NMS and EMT ü Underinvested in commercial; immediate opportunity to go direct through Acquisition Repligen bioprocessing sales team Closed December 16, 2021 ü Strong revenue growth and margin profile • Revenue doubled in 2021 • Expected gross margin in range of 50%-55% with path to expansion • Accretive adjusted operating margin ü Immediately accretive to adjusted EPS (2022) All cash, accretive acquisition, undisclosed purchase price 4 4 4

Financial Highlights BioFlex Solutions Headquarters: Newton, NJ Company Founded: 2003 Revenue 2022 Revenue Profile Founder: Jason Nisler & Ralph Meola Growth est. ~$11M Employees: ~35 2021e +20% Manufacturing facilities: Newton, NJ Sales offices: US Distributors: NA, EU Products and Capabilities Revenue Breakdown (2021e) Distributors • Single-use clamps, adapters, end 4% OEM Customers caps and hose assemblies BioFlex End Users clamps • High precision injection molding and endcaps 39% • Engineering & design of components and tooling 57% • Rapid prototyping (machining and 3D printing) 5 5 5

BioFlex Solutions Adds Critical Components to Repligen Hollow Fiber Flat Sheet Molded clamps and connectors BioFlex Solutions Advances Over-molded Repligen as a tubing Engineered Single-Use Molding Technologies Fluid Molded Management bottles and Solutions assemblies Non-Metallic Leader Solutions 6

Tuck-in Acquisition Expands our single-use fluid management capabilities and product Expected to portfolio; further secures our fluid management supply chain. add ~2 points Underinvested in commercial with opportunity to expand customer of Revenue base be leveraging Repligen’s sales channel and extensive market Growth in 2022 reach. Expected to add ~$13M of incremental revenue in 2022. Expected gross margins 50%-55%; clear to expansion following investment. Adjusted operating margins above Repligen corporate average. Expected to be accretive to adjusted EPS for 2022 and thereafter. 8ϳϳ

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