Salix Pharmaceuticals, Ltd. (SLXP">SLXP) and Progenics Pharmaceuticals, Inc. (PGNX">PGNX) recently received good news on the pipeline front with their opioid-induced constipation (OIC) treatment, oral Relistor (methylnaltrexone) achieving its primary endpoints in a phase III study.

The 804-patient phase III trial was conducted to evaluate the safety and efficacy of oral Relistor for the treatment of (OIC) in patients with chronic, non-cancer pain. Three once-daily dosing regimens of oral Relistor were evaluated: 150, 300 and 450mg.

US Filing in Mid-2012

Highly statistically significant results were achieved for the primary endpoint in two of the three treatment arms compared to placebo. In addition to showing highly statistically significant improvements in rescue-free bowel movement (RFBM) within 4 hours of administration over 28 days, the 300 and 450 mg arms also demonstrated highly statistically significant improvements in RFBM within 4 hours of administration following the first dose compared to placebo.

The 300 and 450 mg arms also achieved statistical significance for two key secondary efficacy endpoints. Oral Relistor’s safety profile was comparable to placebo. With these results in hand, Salix and Progenics intend to file for US Food and Drug Administration (FDA) approval for the oral formulation in mid-2012.

Relistor Deal Signed in Feb

Salix acquired worldwide (excluding Japan) rights to Relistor from Progenics in February 2011. Relistor is already available as a subcutaneous injection for the treatment of OIC in patients with advanced illness who are receiving palliative care, when response to laxative therapy has not been sufficient. Relistor is approved in more than 50 countries including the US. Relistor sales came in at $16 million in 2010.

While Salix’s sales force started marketing the product in the US from April, Salix granted a license to Link Healthcare in October 2011 to market Relistor in Australia, New Zealand, South Africa and Asia. The company is currently looking for a distribution partner in Europe.

Salix is looking to drive Relistor sales through label expansions and focused promotion efforts. While initial focus will be on gastroenterologists, Salix intends to expand Relistor’s use among primary care physicians eventually. Salix’s presence in the gastroenterology space should increase awareness of the product.

Besides developing an oral formulation of Relistor, Salix filed a supplemental new drug application (sNDA) seeking approval for the use of Relistor in chronic non-cancer pain patients with OIC. A response should be out by April 27, 2012. According to the company, Relistor could achieve peak sales of $1 billion in the US provided the company gains approval for label expansions and the oral formulation.

Outperform on Salix

We currently have an Outperform recommendation on Salix, which carries a Zacks #1 rank (short-term Strong Buy rating). We are encouraged by the positive data on oral Relistor. The Relistor deal should help drive long-term growth at Salix.