Safety and efficacy of retreatment with a bioengineered hyaluronate for painful osteoarthritis of the knee: results of the open-label Extension Study of the FLEXX Trial

Objective

To evaluate the safety of repeated intra-articular (IA) injections of Euflexxa^® (1% sodium hyaluronate; IA--BioHA) for painful knee osteoarthritis (OA).

Design

Participants who completed the randomized, double-blind, 26-week FLEXX Trial comparing IA-BioHA to IA saline (IA-SA) for knee OA¹ received three weekly IA-BioHA injections in a 26-week Extension Study. Adverse events (AEs) were recorded and the effect of treatment on knee pain was measured immediately following a 50-foot walk test using a 100 mm visual analog scale (VAS). Responder rate, Medical Outcomes Study Short Form 36 scores, Patient’s Global Assessment, and intake of rescue medication were also evaluated.

Results

The Extension Study included 433 subjects, 219 who received IA-BioHA and 214 who received IA-SA during the FLEXX Trial. Safety results from the Extension Study indicated that 43.4% (188/433) of subjects had AEs, of which 4.8% (21/433) were deemed treatment-related AEs. Two AEs in the Extension Study led to discontinuation, and no joint effusion was reported. Patients who continued with IA-BioHA in the Extension Study maintained their improvement from baseline, with an average reduction in pain in the VAS score of −3.5 mm. Patients initially treated with IA-SA in the FLEXX Trial also had a reduction in VAS score of −9.0 mm. Secondary efficacy variables also improved during the Extension Study.

Conclusions

Repeat injections of IA-BioHA were effective, safe, well tolerated, and not associated with an increase in AEs, such as synovial effusions. Additional symptom improvements were noted for subjects who received either IA-BioHA or IA-SA in the FLEXX Trial.Clinical Trial Registration Number: NCT00379236