Flexion Therapeutics to Advance Investigational Gene Therapy FX201 into High Dose Cohort of Phase 1 Clinical Trial in Knee Osteoarthritis and Expand Low and Mid Dose Treatment Groups - Seite 2

The open-label, expansion phase of the study is expected to enroll up to an additional 20 patients, in both the low and mid dose treatment groups. Each patient will receive one injection of FX201 into the knee joint and will be followed for 104 weeks. The DMC will continue to review safety data of all enrolled patients in all dose levels.

Data through Week 52 for patients treated in the initial low and mid dose cohorts of the single ascending dose phase are expected by the end of 2021. In addition, preliminary data from the high dose cohort and expanded treatment groups are also anticipated before year-end.

About FX201
FX201 is an investigational gene therapy which utilizes a helper-dependent adenovirus (HDAd) vector devoid of all viral genes that carries a coding sequence for an anti-inflammatory protein called interleukin-1 receptor antagonist (IL-1Ra) under the control of an inflammation-responsive promoter. FX201 is injected directly into the joint space (also termed the intra-articular space) and is intended to deliver as-needed anti-inflammatory activity to joint tissues over the long-term, with the goal to improve outcomes for OA patients.

About Flexion Therapeutics
Flexion Therapeutics (Nasdaq:FLXN) is a biopharmaceutical company focused on the development and commercialization of novel, local therapies for the treatment of patients with musculoskeletal conditions, beginning with osteoarthritis, the most common form arthritis. The Company's core values are focus, ingenuity, tenacity, transparency and fun. Please visit flexiontherapeutics.com.

Forward-Looking Statements
This release contains forward-looking statements that are based on the current expectations and beliefs of Flexion. Statements in this press release regarding matters that are not historical facts, including, but not limited to, statements relating to the future of Flexion; timing and plans with respect to the Phase 1 clinical trial of FX201; and the potential therapeutic and other benefits of FX201, are forward looking statements. These forward-looking statements are based on management’s expectations and assumptions as of the date of this press release and are subject to numerous risks and uncertainties, which could cause actual results to differ materially from those expressed or implied by such statements. These risks and uncertainties include, without limitation, the fact that the impacts and expected duration of the COVID-19 pandemic are uncertain and rapidly changing; the risk that we may not be able to maintain and enforce our intellectual property, including intellectual property related to FX201; risks related to clinical trials, including potential delays, safety issues or negative results; and other risks and uncertainties described in our filings with the Securities and Exchange Commission (SEC), including under the heading “Risk Factors” in our Quarterly Report on Form 10-Q for the quarter ended September 30, 2020 filed with the SEC on November 4, 2020 and subsequent filings with the SEC. The forward-looking statements in this press release speak only as of the date of this press release, and we undertake no obligation to update or revise any of the statements. We caution investors not to place considerable reliance on the forward-looking statements contained in this press release.