Flexion Therapeutics Announces Positive Preclinical Data Supporting Development of FX301, a Locally Administered Nav1.7 Inhibitor Product Candidate for Post-Operative Pain

• New animal data show FX301 provided sustained, post-operative analgesic effect with no impairment in motor function compared to liposomal bupivacaine and placebo
• High local concentrations of funapide, the active ingredient in FX301, were measured at the site of administration for the duration of the study, consistent with the creation of a depot providing controlled drug release
• Electronic poster presentation now available on the American Society of Regional Anesthesia and Acute Pain Medicine’s website

BURLINGTON, Mass., April 27, 2020 (GLOBE NEWSWIRE) --Flexion Therapeutics Inc. (Nasdaq:FLXN) today announced new positive preclinical efficacy and pharmacokinetic (PK) data for FX301, its locally administered peripheral nerve block candidate for control of post-operative pain. Results demonstrated sustained analgesic effect in a preclinical surgical pain model for the duration of the study (72 hours) following a single injection of FX301, and no impairment of motor function. The data were presented in an electronic poster presentation available on the American Society of Regional Anesthesia and Acute Pain Medicine’s (ASRA) website.

“These compelling data bolster our excitement about the potential for FX301 to solve the issues that have plagued most pain drug candidates in the NaV1.7 inhibitor class and address a key unmet need in post-operative pain management – to provide durable and meaningful post-operative pain relief while sparing motor function,” said Michael Clayman, M.D., President and Chief Executive Officer of Flexion. “In contrast to liposomal bupivacaine, FX301, through its innovative mechanism of action, provided improved analgesic effect while preserving motor function. These results support the potential for FX301 to become a differentiated peripheral nerve block product which could enable more rapid post-operative ambulation and rehabilitation than existing nerve blocks. We look forward to advancing the FX301 GLP toxicology studies this year and intend to initiate human trials in 2021.”

The study evaluated the efficacy and PK profile of FX301 following ultrasound-guided sciatic nerve block in a validated post-operative pain model in pigs. The pigs were divided into three study groups (n=6 per group), anesthetized and given a single 10 ml injection of either FX301 (13 mg/mL; total dose 130 mg), liposomal bupivacaine (13.3 mg/mL; total dose 133 mg) or placebo (normal saline) in close proximity to the sciatic nerve prior to receiving a surgical incision on the hind limb. Pain was assessed at 1, 4, 8, 12, 24, 36, 48, and 72 hours post-injection. Motor function was evaluated at 2 and 24 hours post-injection.

Key findings from the study include:

• FX301 provided both greater analgesic effect from 12 through 72 hours and a longer duration of effect through 72 hours compared to liposomal bupivacaine or placebo;
• Treatment with FX301 did not significantly affect total walking distance in animals at 2 and 24 hours post-injection; animals treated with liposomal bupivacaine experienced a significant reduction in total walking distance compared with baseline at 2 and 24 hours post-injection; and
• Systemic plasma profile of funapide, the active ingredient in FX301, remained relatively flat throughout the study, indicative of controlled drug release from the thermosensitive gel formulation, while high local concentrations of funapide were observed at the site of administration at 72 hours.

An encore presentation of these findings was accepted at the International Anesthesia Research Society (IARS) annual meeting.

About FX301
FX301 is a locally administered NaV1.7 inhibitor product candidate, known as funapide, formulated for extended release in a thermosensitive hydrogel. The initial development of FX301 is intended to support administration as a peripheral nerve block for control of post-operative pain. Flexion believes FX301 has the potential to provide effective pain relief while preserving motor function and anticipates initiating clinical trials in 2021.

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 people with musculoskeletal conditions, beginning with osteoarthritis, the most common form of arthritis. The Company's core values are focus, ingenuity, tenacity, transparency and fun. 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; expected clinical developments and clinical trial timelines; and the potential therapeutic and other benefits of FX301, 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, risks related to clinical trials, including potential delays, safety issues or negative results; risks related to key employees, markets, economic conditions, and health care reform; and other risks and uncertainties described in our filings with the Securities and Exchange Commission (SEC), including under the heading "Risk Factors" in our Annual Report on Form 10-K filed with the SEC on March 12, 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.

Contacts:

Scott Young
Vice President, Corporate Communications & Investor Relations
Flexion Therapeutics, Inc.
T: 781-305-7194
syoung@flexiontherapeutics.com

Julie Downs
Associate Director, Corporate Communications & Investor Relations
Flexion Therapeutics, Inc.
T: 781-305-7137
jdowns@flexiontherapeutics.com