Progenics (NASDAQ:PGNX) and partner Wyeth (NYSE:WYE) have announced plans to start three new clinical trials for Progenics' constipation-relieving drug methylnaltrexone.

Two of the trials will investigate the use of the drug under the skin as a way to treat constipation in patients taking certain painkillers. The trials -- one a phase 2 and the other a phase 3 -- will test subcutaneous methylnaltrexone in patients taking opioids for back pain or for pain after orthopedic surgery.

The third trial will test methylnaltrexone administered intravenously in managing a condition that sometimes comes about after hernia surgery. The condition, known as post-operative ileus (POI), impairs a patient's bowel motility. Methylnaltrexone is currently in phase 3 trials for treating POI after a colectomy. Because POI occurs most often after abdominal surgery, being able to market the drug to gastrointestinal surgeons for both of those indications should help the companies expand sales.

The patient treatment time for the trials is relatively short, so investors won't have to wait too long to see how the drug performs; the results from all three trials are expected in mid- to late 2008.

Finding more patients
These trials are designed to expand the label indications to more patient populations than the palliative care patients included in Progenics' March 2007 New Drug Application submission. The company expects to hear about an approval from the FDA by the end of January.

Wyeth, which has worldwide marketing rights for the drug, has already submitted a Marketing Authorization Application in Europe to EMEA. It should be reviewed sometime next year.

The companies are also working on an oral version of the drug, which showed successful results in a phase 1 trial recently. An oral version probably won't be useful for patients suffering from POI (you just had surgery, what's one more shot going to hurt you?), but it should benefit the company in the OIC market. Patients with pain are often on opioids for extended periods of time, and no one likes to give themselves shots again and again.

I think the companies are taking the right track by trying to get subcutaneous methylnaltrexone approved for as many indications as possible as fast as possible. Once doctors start prescribing the injectable version, it should be easy to get them to switch to the oral version after it's approved. That should help it compete with Adolor's (NASDAQ:ADLR) and GlaxoSmithKline's (NYSE:GSK) Entereg if it receives marketing approval.

Want to know the latest drug stock we've picked for the Fool's market-beating Rule Breakers newsletter? Click here to take a look at all our recommendations with a free 30-day trial.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Glaxo is an Income Investor selection. The Fool's disclosure policy eats a bowl of bran flakes every morning.