Flexion Therapeutics, Inc. announced that, on December 26, 2018, the first patient was enrolled in a Phase 3 clinical trial to evaluate the safety and efficacy of ZILRETTA (triamcinolone acetonide extended-release injectable suspension) in patients with hip osteoarthritis (OA). Similar to knee OA, hip OA is a degenerative disease which has no cure, and it is estimated that roughly 25% of the U.S. population may develop symptomatic hip OA in their lifetime. The initiation of the Phase 3 hip registration trial was supported by findings from a Phase 2, randomized, open-label, pharmacokinetic (PK) study in the shoulder and hip joints, known as the SHIP study. The results from the SHIP study demonstrated that ZILRETTA was generally safe and well tolerated, and the PK profile of ZILRETTA observed in both joints was consistent with previous PK studies in the knee. Results also showed that an injection of ZILRETTA into the hip resulted in 6-fold lower peak plasma levels and reduced systemic exposure compared to immediate-release triamcinolone acetonide in crystalline suspension (TAcs). The data on the hip cohort have been submitted for presentation. The double-blind, placebo-controlled Phase 3 trial will evaluate the efficacy and safety of ZILRETTA in 440 patients with hip OA pain. Patients will be randomized to one of two treatment groups (1:1) and treated with a single intra-articular (IA) injection of either ZILRETTA or normal saline (placebo). The primary endpoint of the trial is the magnitude of pain relief versus placebo as measured on the WOMAC A (pain) subscale at Week 12. Following initial injection of ZILRETTA or placebo, participants will be evaluated at Weeks 12, 16, 20 and 24 to determine if a second IA injection for hip OA pain is clinically indicated. If eligible for a second injection, patients will receive open label ZILRETTA at the time of recurrent symptoms and will be followed for 12 weeks after that injection. Patients who do not receive a second injection will be followed for up to 24 weeks after their first injection. Flexion also plans to initiate additional Phase 2 studies of ZILRETTA in the shoulder later this year. The company intends to initially investigate ZILRETTA in both OA of the shoulder and adhesive capsulitis (frozen shoulder). ZILRETTA is indicated as an intra-articular injection for the management of osteoarthritis pain of the knee. It is not intended for repeat administration. ZILRETTA is contraindicated in patients who are hypersensitive to triamcinolone acetonide, corticosteroids or any components of the product.