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Flexion Therapeutics Announces Publication of Analysis of Patients with Unilateral Knee OA from Pivotal Trial of ZILRETTA® (triamcinolone acetonide extended-release injectable suspension)

  • Post-hoc analysis published in Advances in Therapy indicated patients with unilateral knee osteoarthritis experienced significant and durable reductions in pain with ZILRETTA vs. immediate-release triamcinolone acetonide
  • Patients in ZILRETTA arm experienced profound magnitude of analgesic effect with pain scores reduced by >60%, as measured by Average Daily Pain
  • Analysis indicated improvements on OA-specific measures of pain, stiffness, function (WOMAC A, B, C), and quality of life scores lasting up to six months
  • Paper examines the debilitating consequences of knee OA among military personnel and highlights ZILRETTA as an important non-opioid option to help manage OA pain

BURLINGTON, Mass., April 24, 2019 (GLOBE NEWSWIRE) -- Flexion Therapeutics, Inc. (FLXN) today announced that the results from a post-hoc analysis of data from the pivotal Phase 3 trial of ZILRETTA (triamcinolone acetonide extended-release injectable suspension) were published in Advances in Therapy. The findings indicated that patients with unilateral osteoarthritis (OA) knee pain experienced significant and durable pain relief with a single intra-articular injection of ZILRETTA compared to immediate-release triamcinolone acetonide in crystalline suspension (TAcs), as measured by Average Daily Pain (ADP) intensity scores. The analysis also indicated that ZILRETTA patients in this subgroup experienced improvements on OA-specific measures of pain, stiffness, function, and quality of life scores that lasted up to six months. 

The objective of the analysis was to characterize the primary endpoint of the trial, change in ADP, within a subgroup of randomized patients with unilateral OA knee pain. The analysis showed that patients in this subgroup who were treated with ZILRETTA experienced a profound magnitude of analgesic effect, with ADP scores that were reduced by >60% at Week 3-17. These results suggest that bilateral knee pain may have been a confounding factor in the pivotal trial, which assessed the impact of ZILRETTA treatment in only one knee.

The authors, led by Michael J. Langworthy, M.D., Department of Orthopedics & Orthopedic Surgery, Southcoast Health Systems, Dartmouth, MA and leading advisor on arthritic joint disease to the U.S. military, conducted this additional analysis to gain a deeper understanding of the potential benefit of ZILRETTA and apply these crucial insights to members of the armed forces. OA of the knee affects more than 15 million Americans, including active-duty military personnel, who frequently experience a higher incidence of unilateral OA, as a result of previous injury. Approximately 11,000 active-duty military personnel are diagnosed with OA each year, and it is the leading cause of disability discharge due to the chronic and painful nature of the disease.1,2

“Military service members and others working in physically demanding professions often must modify their activity or change roles as a result of persistent OA knee pain, thus highlighting a large unmet medical need for active professionals,” said Dr. Langworthy. “I believe the results of this subgroup analysis lend even further support for ZILRETTA as an effective non-opioid alternative for people suffering from painful knee OA.”

Key topline results from the post-hoc analysis of the Phase 3 study:

  • A single intra-articular injection of ZILRETTA provided significant improvement in pain at Week 12 compared with placebo (P<0.0001) and TAcs (P<0.01) to patients with unilateral knee OA, as measured by ADP-intensity scores;
  • ZILRETTA provided participants with unilateral knee OA improvements in WOMAC-A (pain), WOMAC-B (stiffness), WOMAC-C (physical function), and quality of life scores (KOOS-QoL) at Weeks 4, 8, and 12 (measured through standardized, verified instruments; P<0.05 for all instruments) compared with TAcs and up to six months compared with placebo (P<0.05); 3,4
  • Patients treated with ZILRETTA used less rescue medication for pain compared with both the placebo and TAcs groups; and
  • Adverse events (AEs) were similar in frequency across treatment groups, with most AEs reported as mild or moderate and unrelated to the study agent.

“We are pleased to have this post-hoc analysis published in a peer-reviewed journal, as it further reinforces ZILRETTA as an important and effective treatment option offering pain relief to those suffering from OA of the knee,” said Michael Clayman, M.D., President and Chief Executive Officer of Flexion. “This analysis provides us with important insight into the significant benefit ZILRETTA may confer when used to treat isolated knee pain, where the impact is more easily discerned.”

Indication and Select Important Safety Information for ZILRETTA

Indication: ZILRETTA is indicated as an intra-articular injection for the management of osteoarthritis pain of the knee. It is not intended for repeat administration.

Contraindication: ZILRETTA is contraindicated in patients who are hypersensitive to triamcinolone acetonide, corticosteroids or any components of the product.

Warnings and Precautions:

  • Intra-articular Use Only: ZILRETTA has not been evaluated and should not be administered by epidural, intrathecal, intravenous, intraocular, intramuscular, intradermal, or subcutaneous routes. ZILRETTA should not be considered safe for epidural or intrathecal administration.
  • Serious Neurologic Adverse Reactions with Epidural and Intrathecal Administration: Serious neurologic events have been reported following epidural or intrathecal corticosteroid administration. Corticosteroids are not approved for this use.
  • Hypersensitivity reactions: Serious reactions have been reported with triamcinolone acetonide injection. Institute appropriate care if an anaphylactic reaction occurs.
  • Joint infection and damage: A marked increase in joint pain, joint swelling, restricted motion, fever and malaise may suggest septic arthritis. If this occurs, conduct appropriate evaluation and if confirmed, institute appropriate antimicrobial treatment.

Adverse Reactions: The most commonly reported adverse reactions (incidence ≥1%) in clinical studies included sinusitis, cough, and contusions.

Please see ZilrettaLabel.com for full Prescribing Information.

On October 6, 2017, ZILRETTA was approved by the U.S. FDA as the first and only extended-release intra-articular therapy for patients confronting osteoarthritis-related knee pain. ZILRETTA employs proprietary microsphere technology combining triamcinolone acetonide — a commonly administered, short-acting corticosteroid — with a poly lactic-co-glycolic acid (PLGA) matrix to provide extended pain relief. The pivotal Phase 3 trial on which the approval of ZILRETTA was based showed that ZILRETTA significantly reduced knee pain for 12 weeks, with some people experiencing pain relief through Week 16. Learn more at www.zilretta.com.

About Osteoarthritis (OA) of the Knee
OA, also known as degenerative joint disease, affects more than 30 million Americans and accounts for more than $185 billion in annual expenditures. In 2016, more than 15 million Americans were diagnosed with OA of the knee and the average age of physician-diagnosed knee OA has fallen by 16 years, from 72 in the 1990s to 56 in the 2010s. The prevalence of OA is expected to continue to increase as a result of aging, obesity and sports injuries. Each year, more than 15 million Americans are treated for OA-related knee pain, and approximately five million OA patients receive either an immediate-release corticosteroid or hyaluronic acid intra-articular injection to manage their knee pain.

About Flexion Therapeutics
Flexion Therapeutics (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, a type of degenerative arthritis. The company's core values are focus, ingenuity, tenacity, transparency and fun. For the past two years, Flexion has been named one of the Best Places to Work by the Boston Business Journal, and a Top Place to Work in Massachusetts by The Boston Globe.

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; ZILRETTA's market potential and potential benefits; and expected increases in the rate of individuals with OA of the knee, 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 associated with commercializing new pharmaceutical products in the United States; the risk that we may not be able to successfully maintain an effective sales force or product supply to commercialize ZILRETTA; competition from alternative therapies; the risk that we may not be able to maintain and enforce our intellectual property, including intellectual property related to ZILRETTA; the risk that ZILRETTA may not be successfully commercialized, including as a result of limitations in ZILRETTA's label and package insert information; risks regarding our ability to obtain adequate reimbursement from payers for ZILRETTA; risks related to the manufacture and distribution of ZILRETTA, including our reliance on sole sources of supply and distribution; risks related to key employees, markets, economic conditions, health care reform, prices and reimbursement rates; the risk that we may use our capital resources in ways that we do not currently expect; 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 for the year ended December 31, 2018 filed with the SEC on February 28, 2019 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.


1. Cameron KL, Driban JB, Svoboda SJ. Osteoarthritis and the tactical athlete: A systematic review. J Athl Train. 2016; 51(11).
2. Cameron KL, Hsiao MS, Owens BD, Burks R, Svoboda SJ. Incidence of physician-diagnosed osteoarthritis among active duty United States military service members. Arthritis Rheum. 2011; 63(10): 2974-82.
3. WOMAC (Western Ontario and McMaster Universities Arthritis Index) is a validated, widely used, proprietary set of standardized questionnaires used by health professionals to evaluate the condition of patients with osteoarthritis of the knee and hip, including pain, stiffness and physical functioning of the joints.
4. The KOOS (Knee Injury and Osteoarthritis Outcome Score) QoL (Quality of Life) subscale Assesses patients' perceptions about their treated knee and associated problems related to quality of life.


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

Julie Downs
Senior Manager, Corporate Communications & Investor Relations
Flexion Therapeutics, Inc.
T: 781-305-7137