Ferring Pharmaceuticals (FORT LAUDERDALE, Florida), a privately-owned, international pharmaceutical company and part of the Ferring Group, announced the results of two clinical studies on the efficacy of Euflexxaâ„¢, an intra-articular hyaluronic acid (IA-HA) for the relief of pain in knee osteoarthritis (OA). One study showed that the agent is equally effective in different radiographic stages of knee OA severity. The other demonstrated that based on patients' perceptions, the agent is effective in reducing the amount that knee OA pain interferes with patients' activities of daily living (ADLs) and social/leisure activities, for up to 6 months.

As a subset analysis of a larger double-blind trial, the study comparing Euflexxa and SynviscR (Genzyme Corp) demonstrated that an IA-HA treatment for knee OA is equally effective whether the disease severity is two or three on the Kellgren-Lawrence (K-L) radiographic scale. The study also showed a trend toward greater pain relief and patient satisfaction with Euflexxa. Patients having a K-L score of two or three and treated with Euflexxa had numerically more improvement than those given Synvisc (33.6 vs 27.2, P = .05), and reported greater satisfaction (3.24 vs 3.05 on a 4-point scale, P = .08).

The original study was a prospective, multicenter, randomized, double-blind trial evaluating patients with confirmed knee OA and a K-L score of two or three, using the WOMAC pain subscale as the primary effectiveness measure. Both products were administered in 3 weekly injections. This subset analysis, comparing Synvisc with Euflexxa, uses the K-L radiographic scale to define disease severity and treatment groups to see if the pain caused by OA is more resistant or responsive to IA-HA treatment at different stages of OA. The 167 patients with a K-L score of two had a mean change on the pain subscale of the WOMAC of 29.1; the 147 patients with a K-L score of three had a change of 30.2. The K-L two patients in both groups had comparable improvements (28.4 vs 29.9, P = .66). Euflexxa patients also reported greater satisfaction (3.24 vs 3.04 on a 4-point scale, P = .08).

The results of the second study revealed that patients perceive the agent as being effective in reducing the amount that knee OA pain interferes with ADLs, as well as social and leisure activities, and maintains its effectiveness through 6 months. In this ongoing prospective study, 1261 physicians gave survey materials to their patients eligible for Euflexxa. Patients voluntarily participated in a voice-response telephone survey about their condition at baseline and after 3 and 6 months. A total of 161 patients (mean age 65) completed all three surveys. Patients receiving Euflexxa reported a decrease in the amount that their knee pain interfered with their ADLs, with a mean baseline score of 5.8 (0 = least interference, 10 = most interference), decreasing to 3.7 at 3 months and maintaining 3.9 at 6 months. Patients receiving the agent also reported a decrease in the amount that their knee pain interfered with their social and leisure activities, with a mean baseline score of 5.6, decreasing to 3.6 at 3 months and maintaining 3.7 at 6 months.

Euflexxa is the first and only nonavian-derived hyaluronic acid approved in the US for the treatment of pain caused by knee OA and is indicated for a 3-injection treatment regimen for patients who have failed to respond adequately to conservative nonpharmacologic therapy and simple analgesics (eg, acetaminophen). Because it is not derived from an avian source (chicken or rooster combs), the risk of allergic reactions related to avian proteins is eliminated. The agent received premarket approval (PMA) from the US FDA on December 3, 2004, and became available to the public in late 2005. PMA is the FDA process of scientific and regulatory review to evaluate the safety and effectiveness of Class III medical devices.