Progenics' Intriguing Study Results

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Yesterday, development-stage drugmaker Progenics Pharmaceuticals (Nasdaq: PGNX) announced positive phase 1b clinical trial results for its lead HIV treatment, PRO 140.

In this 39-person safety and efficacy study, the drug reduced HIV viral loads in patients by an average maximal decrease of 1.83 log10. For you non-mathematicians out there, this means that 98.5% of the virus was cleared from patients' blood. As a comparison, Gilead's (Nasdaq: GILD) HIV treatment Viread -- which received marketing approval in 2001 -- reduced HIV viral loads by an average of 1.5 log10 in one early-stage trial in previously untreated HIV patients.

PRO 140 is in a drug class called CCR5 inhibitors. The basic mechanism employed by the drug is to stop HIV from entering cells, which is crucial to viral replication. PRO 140 wouldn't be the first CCR5 compound on the market; just last week, Pfizer (NYSE: PFE) received a unanimously positive FDA panel vote on its own CCR5 compound, Maraviroc, and is expected to get approval on the drug in the near future.

This may add competitive pressure (research suggests the CCR5 compounds may be used synergistically) for Progenics; in addition, Pfizer's compound can be dosed orally. But there is always room for novel compounds to treat HIV since many patients often become resistant to existing therapies.

PRO 140 won't ever become a front-line treatment for HIV; being a monoclonal antibody means inconvenient intravenous dosing of the drug, whereas the front-line HIV therapies can all be taken orally. Nonetheless, later-stage clinical studies are expected to start in the second half of 2007. If the drug can prove efficacious in these clinical studies, then PRO 140 will still have the opportunity to bring in sales in at least the low hundreds of millions of dollars, just like Trimeris' (Nasdaq: TRMS) equally inconveniently dosed Fuzeon compound. For a pharma the size of Progenics, with its $650 million market capitalization, this sort of revenue would be quite meaningful.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. Pfizer is an Inside Value recommendation. The Fool has a disclosure policy.