Forest Laboratories, Inc. and Gedeon Richter Plc. announced top-line results from a phase II placebo and positive comparator-controlled, parallel-arm, double-blind, dose-response clinical trial of the novel, investigational NR2B-selective NMDA (N-methyl D-aspartate) receptor antagonist, radiprodil (RGH-896), for the treatment of neuropathic pain associated with diabetic peripheral neuropathy (DPNP). Treatment with radiprodil did not show statistically significant or clinically meaningful reductions in mean daily pain scores, the primary endpoint, compared to placebo for any of the dosages studied.

The companies will review the complete study database over the coming weeks to determine the appropriate next steps regarding the development of radiprodil.

This was a randomized placebo and active-controlled parallel-arm, double-blind, dose-response study in patients with diabetic peripheral neuropathic pain (DPNP) who were clinically diagnosed with painful polyneuropathy (greater-than or equal to 6 months) due to type I or type II diabetes mellitus. Patients had a minimum daily pain rating of at least four at screening, and an average daily pain rating of at least four (on an eleven-point scale) during the one week before baseline.

Following a five-week screening/washout period during which all analgesic medications used for DPNP were discontinued, a total of 458 male or female outpatients between 18 and 75 years of age were randomized to one of three radiprodil doses (15mg, 30mg, 45mg), an active comparator (100mg pregabalin), or placebo given three times a day (TID) for 14 weeks.

The protocol-specified primary endpoint was the change from baseline to Week 14 in mean daily pain rating for the individual radiprodil treatment groups compared to placebo treatment. A secondary endpoint was the rate of 50 per cent pain responders (defined as patients with a greater-than or equal to 50 per cent reduction in mean daily pain rating from baseline to Week 14). Both endpoints were analyzed using the last observation carried forward approach (LOCF).

Across the different dosing groups the most common adverse events observed after treatment with radiprodil were dizziness, fatigue, and insomnia.

Radiprodil is a novel, potent, orally active NR2B (a subunit of the NMDA receptor) antagonist. Radiprodil was discovered by Gedeon Richter and is currently being co-developed with Forest Laboratories as a candidate for the treatment of chronic neuropathic pain conditions, including neuropathic pain caused by diabetes mellitus. Forest Laboratories has licensed US and Canadian rights for radiprodil from Gedeon Richter.

Gedeon Richter, headquartered in Budapest/Hungary, is a major pharmaceutical company in Hungary and one of the largest in Central Eastern Europe, with consolidated sales of approximately 1 billion EUR (1,3 billion USD) and 3 billion EUR (4 billion USD) market capitalization in 2009.

Forest Laboratories is a US-based pharmaceutical company with a long track record of building partnerships and developing and marketing products that make a positive difference in people's lives.