FDA approves Flexion's Zilretta for osteoarthritis knee pain

Flexion Therapeutics announced Friday that it received FDA approval for Zilretta, a modified formulation of the corticosteroid triamcinolone, making it the first and only extended-release, intra-articular injection for osteoarthritis knee pain. CEO Michael Clayman said the non-opioid therapy "has the potential to be a transformative medicine for the more than five million patients who receive an intra-articular injection for osteoarthritis knee pain each year." Company shares gained as much as 18 percent on the news.

Approval of the marketing application for the drug, also known as FX006, was based on data from a late-stage trial of 484 patients with osteoarthritis of the knee. Results demonstrated that patients treated with Zilretta, which uses Flexion's microsphere technology to provide pain relief over 12 weeks, achieved significantly improved pain, stiffness and function compared to placebo and an immediate-release steroid.

The drugmaker noted that Zilretta's label also includes data from a Phase II parallel-group trial that examined blood glucose concentrations in patients with type 2 diabetes. Study author Steven Russell said "our trial demonstrated that Zilretta may avoid the disruptive blood glucose spikes that can be seen with corticosteroid use in patients coping with both knee osteoarthritis and type 2 diabetes."

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Flexion stated in a US Securities and Exchange Commission filing that it plans to introduce Zilretta in the US later this month at a wholesale acquisition price of $570 per dose, with a full commercial launch expected in mid-November. The company, which employs around 140 staff, plans to add around 100 field representatives to sell the therapy.

Northland Capital Markets analyst Carl Byrnes predicted that Zilretta could generate potential peak sales of more than $750 million. Meanwhile, analyst David Maris of Wells Fargo suggested the drug, which the FDA reviewed under a fast-track designation, "has the potential to be a game-changer in osteoarthritis knee pain treatment."

Sanofi, which markets the osteoarthritis knee pain injection Synvisc-One (hylan G-F 20), was rumoured earlier this year to have submitted a non-binding buyout offer for Flexion potentially worth more than $1 billion. For additional analysis, see ViewPoints: Reading the tea leaves on Sanofi’s possible takeout of Flexion.

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