Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2018 Commission File Number 000-14656 REPLIGEN CORPORATION (Exact name of registrant as specified in its charter) (State or other jurisdiction of incorporation or organization) 41 Seyon Street, Bldg. 1, Suite 100 Waltham, MA 02453 (Address of principal executive offices) (Zip Code) OR ...

Financial Data and Key Metrics Changes - The company reported a record quarter with revenues of $51.9 million for Q4 2018 and $194 million for the full year 2018, reflecting organic revenue growth of 25% in Q4 and 17% for the year [28][29] - Adjusted operating income increased by 31% year-over-year in Q4, and by 25% for the full year [29][39] - Adjusted net income for Q4 was $9.8 million, a 12% increase compared to the same period in 2017, while full year adjusted net income was $33.3 million, a 23% increase [39][40] Business Line Data and Key Metrics Changes - Filtration and chromatography product lines grew over 30% organically in Q4, with the ATF product line up over 60% year-over-year [17][20] - The Spectrum portfolio had a good quarter, up 14% to 15%, with full year sales up 24% on a pro forma basis [19] - The OEM proteins business was flat for the full year, with expectations for a decline of 5% in 2019 due to GE transitioning to in-house manufacturing [23][44] Market Data and Key Metrics Changes - Direct revenue growth in Q4 was strongest in Asia and North America, up over 47% and 38% respectively [32] - For the full year, direct products in Asia, Europe, and North America accounted for approximately 16%, 29%, and 55% of sales respectively [32] - The company expects its direct to customer filtration and chromatography businesses to grow at 20% to 25% in 2019 [44] Company Strategy and Development Direction - The company aims to build out a systems team focused on TFF solutions and to win market share in perfusion and clarification applications [24] - Continued investment in R&D is planned to develop disruptive technologies across three franchises [24] - The company is actively evaluating M&A opportunities to supplement organic growth [70] Management's Comments on Operating Environment and Future Outlook - Management expressed confidence in the company's position to gain market share as the industry pivots towards flexible solutions and continuous processing [11] - The company anticipates a strong start to 2019, supported by a robust order demand and the opening of the Marlborough facility [18][19] - Management expects the first half of 2019 to be stronger than the second half, particularly for the proteins business [90] Other Important Information - The company increased its R&D spend to 8% of revenue in 2018, reflecting a commitment to innovation [15] - Adjusted gross margin for Q4 was 55.9%, down from 57.1% in the same period in 2017, while full year adjusted gross margin improved to 56.1% [33][34] - The company expects 2019 adjusted gross margin to be in the range of 56% to 57% [45] Q&A Session Summary Question: Can you break down the moving pieces between the GE transition in-house versus the growth factor in the protein business? - Management expects a strong first half for proteins, with ligands expected to decline while growth factors show reasonable growth. GE's transition will impact future volumes [51][52] Question: What revenue expectations do you have for TangenX and TFF this year? - The filtration portfolio is expected to see strong demand, with new products stimulating growth [54] Question: Can you provide an update on current capacity utilization and future investments? - The company has been diligent in capacity investments, with the Marlborough facility adding significant capacity. Future investments will focus on manpower rather than space [56][57] Question: What are the expectations for gene therapy in 2019 and 2020? - Management is enthusiastic about gene therapy, seeing demand for various products in this area [66] Question: What are the synergies expected from the Spectrum acquisition in 2019? - The target for 2019 is $5 million to $7 million in synergies, with a focus on cross-selling and geographic expansion [68][69] Question: How is the field service and applications team expected to impact revenue? - The field service team is growing rapidly, providing essential support and potentially impacting top-line growth [74] Question: What is the outlook for the OPUS product line? - The OPUS product line is expected to expand into larger commercial processes, benefiting from recent integrations and new product offerings [77] Question: How is the company addressing the growth of perfusion in the market? - Perfusion is growing, now accounting for about 25% of the market, with increasing applications in fed-batch processes [84] Question: What is the long-term outlook for the protein business? - The protein business is expected to remain flat to down 5% in 2019, with potential for recovery depending on new product introductions [92]