Flexion's pain drug comes through in Phase III after a prior pivotal failure

Flexion Therapeutics ($FLXN), on the rebound after a stinging clinical setback, said its lead painkiller hit the mark in a Phase III trial in patients with osteoarthritis, a success the company believes will clear the way for an FDA submission.

The injected drug, called FX006, met its primary endpoint of beating out placebo in reducing patients' pain after 12 weeks, Flexion said.

CEO Michael Clayman

The company enrolled 486 patients with knee pain related to osteoarthritis, giving one-third FX006, one-third the corticosteroid triamcinolone acetonide and the rest placebo. Flexion's drug led to a statistically significant improvement in pain over placebo, the company said, and, in a secondary measure of efficacy, topped the corticosteroid on measures of pain, stiffness and function after 12 weeks. FX006 missed a secondary goal of significantly improving patient scores on a daily pain rating scale compared with triamcinolone acetonide, according to the company.

The results sent Flexion's shares up more than 35% in after-hours trading on Tuesday, a positive note after FX006's earlier failure. In Phase IIb results disclosed in September, the drug failed to meet its primary endpoint of beating placebo after 12 weeks, a misstep that roughly halved Flexion's share price at the time.

Now the company believes it has the data necessary to support an FDA application, and management said it's planning to sit down with regulators in hopes of filing FX006 in the second half of this year.

The treatment, which Flexion plans to market as Zilretta, is a revamped take on triamcinolone acetonide, using a polymer technology the company claims can extend the old drug's half-life and amplify its efficacy.

"We believe that Zilretta has the potential to become an important new non-opioid treatment in a therapeutic area that hasn't seen meaningful innovation in many years," Flexion CEO Dr. Michael Clayman said in a statement.

Flexion, headquartered in Burlington, MA, pulled off a $60 million IPO in 2014 on the strength of its lead candidate. The biotech is also at work on FX005, a Phase II treatment for end-stage osteoarthritis, and FX007, a preclinical candidate for postoperative pain.

- read the statement