Safety and Efficacy of Repeat Administration of Triamcinolone Acetonide Extended-release in Osteoarthritis of the Knee: A Phase 3b, Open-label Study.

Introduction: The aim of this work is to assess the safety and efficacy of repeat administration of triamcinolone acetonide extended-release (TA-ER) in patients with symptomatic knee osteoarthritis (OA), including those with advanced radiographic severity.

Methods: In this phase 3b, single-arm, open-label study, patients aged ≥ 40 years received the first intra-articular TA-ER injection on day 1. Patients received the second injection timed to the response to the first injection (at either week 12, 16, 20, or 24). Patients who received two injections were evaluated every 4 weeks for 52 weeks. Safety was evaluated via treatment-emergent adverse events and any change at 52 weeks in index-knee radiographs (chondrolysis, osteonecrosis, insufficiency fractures, subchondral bone changes). Exploratory efficacy endpoints included Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)-A (pain), -B (stiffness), -C (function), and Knee Injury and Osteoarthritis Outcome Score-Quality of Life (KOOS-QoL) after each injection. Initiative in Methods, Measurements and Pain Assessment in Clinical Trials (IMMPACT) criteria were used to determine moderate and substantial treatment response.

Results: A total of 208 patients were enrolled and received the first injection of TA-ER; 179 (86.1%) received the second injection (median time to second injection: 16.6 weeks). Both injections were well tolerated, with no unexpected adverse events or significant radiographic changes at week 52. The magnitude and duration of clinical benefit after the first and second injections were similar, and most patients reported a substantial (≥ 50%) analgesic response after both doses.

Conclusions: Repeat administration of TA-ER using a flexible dosing schedule timed to patient response was well tolerated, with no radiographic evidence of cartilage impact. Both injections resulted in similar improvements in OA symptoms across a broad spectrum of disease severity reflective of that seen in clinical practice.

Trial Registration Information: ClinicalTrials.gov identifier: NCT03046446.

Funding: Flexion Therapeutics, Inc. Plain language summary available for this article.