Nothing can be more frustrating for a drugmaker like Theravance (Nasdaq: THRX) than having to deal with a partially schizophrenic FDA.

In December the FDA called for a hearing of its advisory panel to review the company's lead drug, Telavancin. Earlier this week Theravance got word that the FDA had canceled the meeting.

When the FDA requests an advisory panel hearing, it's a sign that the agency is on the ropes whether to approve a drug or the extent of a drug's approval, as it was in the case of Cardiome (Nasdaq: CRME) several months ago. So when Theravance's antibiotic Telavancin was hit with the December hearing notice, investors knocked Theravance shares down several percent.

If an advisory panel hearing means a drug is less likely to be approved (data show this to be true for drugs facing a first-time approval decision), then does canceling a panel hearing bode well for Telavancin's approval chances? Well, maybe. 

The official reason for canceling Telavacin's hearing was "to allow time for the FDA to review and resolve several outstanding issues." No mention was made by the FDA whether those outstanding issues were related to Telavancin, its class of antibiotics in general, or all drugs reviewed by the anti-infective drugs division -- the FDA had also canceled a panel hearing for a Johnson & Johnson (NYSE: JNJ) antibiotic.

Considering that the J&J panel hearing was canceled too, I'd bet the FDA is having persistent issues with all antibiotic drugs. In October the agency issued a guidance document for the proper way to perform clinical trials for antibacterial drugs, and this guidance document could be causing internal conflicts over the approval of Telavancin and similar antibiotics. 

My FDA advisory panel prognostication powers have been down lately, so I won't try to read too much into what the tea leaves on the canceled meeting mean. Optimistic Theravance investors can consider that the FDA might have resolved the problems it had about Telavancin and not needed the hearing after all.

But Theravance bears can point at the ominous FDA guidance document and determine that this might be a delay and an omen for a future, unannounced advisory panel hearing for Telavancin.

Nothing can move a biotech's stock price more than a binary FDA regulatory decision. Come to the Motley Fool's CAPS database and rate Theravance outperform or underperform. You can also see what other investors have to say about Theravance and other stocks. Best of all, CAPS is free.

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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 that did get a flu shot.