Boulder, Colo.-based Array BioPharma’s phase II study of ARRY-797 met its primary endpoint osteoarthritis patients suffering from moderate to severe knee pain despite the use of non-steroidal anti-inflammatory drugs (NSAIDs).

The investigational compound, ARRY-797, is a novel, oral, selective p38 inhibitor with a mechanism of action unique from that of currently approved pain medications. The randomized, placebo-controlled and active-controlled (oxycodone ER) trial enrolled 157 patients who received ARRY-797 400mg twice-daily.

The study’s resulted in a statistically significant reduction in pain over a 28-day period compared to placebo, as measured using the Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain subscale (a 0 – 10 numerical pain rating scale). Patients receiving ARRY-797 experienced a mean reduction in the WOMAC pain subscale score at day 28 vs. baseline that was 0.8 greater than those receiving placebo (2.4 vs. 1.6; one-sided p=0.0247). Additional endpoints, including WOMAC physical function, WOMAC stiffness, responder analysis and the Patient’s Global Impression of Change, also showed improvement relative to placebo.

“The study results with ARRY-797 showed promising benefit in the management of pain in osteoarthritis patients who are refractory to NSAIDS,” said Alan Kivitz, M.D., founder of the Altoona Arthritis and Osteoporosis Center and an investigator on the study. “This study was designed with a high hurdle in mind, which this drug was able to overcome.”

ARRY-797 was considered overall to be well-tolerated. The most common adverse events observed in patients treated with ARRY-797 were dizziness, diarrhea and nausea, which were mainly mild in severity.

To further explore the safety and tolerability of ARRY-797, Array BioPharma is currently conducting a multiple ascending dose trial in healthy volunteers at doses up to 2.5-fold higher than those evaluated in the osteoarthritis pain trial.