The bad news never seems to end for pharmaceutical giant Pfizer (NYSE:PFE). Yesterday, it received news that its novel HIV treatment maraviroc was issued an approvable letter from the FDA.

Maraviroc is supposed to be Pfizer's next big hit. It has a unique mechanism of action compared to other HIV treatments, and as Pfizer likes to state, it would be the first drug in a new class of oral HIV therapies to gain regulatory approval in more than a decade. Earlier in the year, an FDA advisory committee reviewing the drug unanimously recommended that it be approved.

This approvable letter doesn't necessarily mean maraviroc won't be on the market shortly; these letters are very common for drugs with new mechanisms of action like maraviroc. But it'd be nice if Pfizer could throw investors a bone and provide a few details on the nature of the approvable letter.

If it was some simple issue necessitating only a class 1 response, it could mean a delay of a couple of weeks or months at most. However, a call for more data and clinical trial work could mean years of delay. Based on the unanimously positive FDA advisory review, it almost assuredly is the former, not the latter. I'd guess that investors shouldn't worry too much.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has a disclosure policy.