FDA panel advises against more clinical trials for opioid constipation drugs

An FDA panel advised the agency against requiring more large clinical studies for the cardiovascular risks of drugs that treat opioid-induced constipation, relieving drugmakers like AstraZeneca ($AZN), Salix Pharmaceuticals ($SLX) and others from bearing the burden of further clinical safety trials.

The Anesthetic and Analgesic Drug Products Advisory Committee met on June 11 and 12, after Cubist Pharmaceuticals' ($CBST) Entereg was linked with heart attacks in patients during several late-stage studies. During the meeting, most of the panelists agreed there was not enough information to link the drug class with the potentially fatal side effect. AstraZeneca and Nektar ($NKTR) are developing Movantik (naloxegol) and Salix already makes Relistor (methylnaltrexone).

The positive FDA panel vote could drive up Salix's stock $6 per share, says Sterne Agee analyst Shibani Malhotra. The World Health Organization estimates 116 million people suffered from chronic pain in the U.S. in 2011 alone. And the market for opioid constipation drugs could reach nearly $2 billion in three years, analysts at research firm GlobalData say.

Theravance ($THRX) is working on its axelopran, and Develco is looking at a sustained-release verion of naloxone--which is used in opioid addiction pills at a fixed dosage. Nektar took $70 million from AstraZeneca for the Movantik (naloxegol) drug last November. Cubist's Entereg (alvimopan) is currently restricted to hospital use only and capped at 15 doses.

Other drugs for treating opioid-induced constipation are currently available on the market, like Sucampo's Amitiza: a chloride channel activator. These drugs don't have the tie to the coronary risks presented by peripherally acting mu-opioid receptor antagonists, the drug class reviewed by the FDA advisory panel.

- here are the FDA's special advisory committee meeting materials