Adolor Tries Again

After unexpected side effects caused a major setback with its lead compound, Entereg, drug developer Adolor (Nasdaq: ADLR  ) announced yesterday that it had advanced a second drug candidate into phase 2 testing.

This new compound is an opioid painkiller with a novel mechanism of action. The drug targets the delta opioid receptor, which is different from any other approved oral opioid painkiller and could provide a distinct marketing advantage if the drug ever makes it to market.

Adolor had completed phase 1 studies of the drug late last year and early this year. But I can't make any judgment on the drug's efficacy and safety in human studies, since results have not yet been released publicly.

Pain drug studies are notoriously difficult to run, thanks to a large amount of patient dropouts (if a drug appears ineffective) and a high placebo effect in patients in the control arm of the study. This makes the data from these studies very noisy and sometimes difficult to interpret, as other drugmakers working on pain drugs -- like Pain Therapeutics (Nasdaq: PTIE  ) -- have learned the hard way. Many a pain drug that has shown efficacy in phase 2 studies can mysteriously fail in later-stage studies.

If it can't gain regulatory approval next year to treat post-operative ileus with Entereg, then Adolor will be relying entirely on this opioid painkiller for its near-term future. Investing in drugmakers whose future rests with compounds with unproven mechanisms of action and no publicly available data is not my cup of tea. Fortunately, the newly initiated study is expected to be completed in early 2008, so investors won't have to wait long for some data to sink their teeth into on this drug.

Looking for more Foolish drug stock coverage? Check out the Fool's market-beating Rule Breakers newsletter. You can check out all our recommendations as well as get access to our message boards and exclusive content with a 30-day free trial.

Fool contributor Brian Lawler owns shares of Pain Therapeutics but no shares of other companies mentioned in this article. The Fool has a disclosure policy.