A reader asks, via Twitter: "Do you know why a company would choose to approach the FDA advisory panel vs. going direct to FDA for approval?"

This isn't an either/or situation. In fact, the company has zero say in whether an advisory panel is held. It's the FDA that sets up the panel of outside experts when the agency wants a little extra help deciding on an approval.

The advisory committee meeting consists of presentations from the company and the agency, and there's usually time for patients to speak as well. The meeting culminates with questions proposed to the committee of outside experts. The voting questions are just an advisory vote; there are plenty of examples of the agency going against the panel's vote, especially when the vote is in favor of recommending approval.

Advisory panels can help investors get a better read on the likelihood of approval, but make sure you don't just focus on the vote. The briefing documents prepared by the FDA for the committee members offer a good look at what the FDA is thinking, and the agency also considers the comments made by the experts during the advisory committee in addition to the final vote.

But what about drugs where the FDA doesn't schedule an advisory panel? Can you read anything into the lack of an advisory panel?

A big, fat maybe
If the FDA doesn't schedule an advisory panel, it seems safe to assume that the FDA is comfortable with making the decision on its own. Whether that means an approval or a rejection, however, depends on the drug. It's likely good news for companies with good data and bad news for companies with questionable data.

Amarin (Nasdaq: AMRN), for instance, said this week that the FDA had informed it that no advisory panel would be scheduled for AMR101. The treatment for high triglycerides passed two clinical trials. Both trials were conducted under a Special Protocol Assessment, so the FDA had already signed off on the trial design. An approval already seemed pretty likely; the lack of an advisory panel is just piling on top of those expectations.

Similarly Ironwood Pharmaceuticals (Nasdaq: IRWD) and Forest Labs said earlier this month that the FDA wouldn't convene a panel to review their anti-constipation drug linaclotide. The drug underwent four phase 3 trials and more than 2,000 patients have been on it for at least a year, making its efficacy and safety profile fairly clear.

In general, the FDA is more likely not to bother with advisory panels for drugs that will be approved, but keep in mind that there's more to an approval than just the issues that would be reviewed by an advisory panel. Manufacturing issues, fine points of a REMS, and other issues can trip up an approval even when the clinical data looks pretty good.

Second time, same as the first
Most of the time drugmakers don't have to undergo an advisory panel meeting when they reapply for approval after receiving a complete response letter. The agency is, hopefully, confident enough with its rejection and the requirements to reverse the decision that it doesn't need any outside help.

Recently, though, a few drugmakers have had advisory panels scheduled to review their second applications. Again, considering them on a case by case basis is the best solution.

Cell Therapeutics (Nasdaq: CTIC) had an advisory panel scheduled for its cancer drug pixantrone after the company appealed to the FDA higher-ups to ask that the data be reconsidered. At the first advisory panel meeting, the committee members voted unanimously to recommend rejection of the drug. Without substantially new data, it might be difficult to convince a new panel to offer a different opinion. Cell Therapeutics is hoping a little more time will help; last month, it withdrew its application to get the advisory panel rescheduled.

Two obesity drugs, VIVUS' (Nasdaq: VVUS) Qnexa and Arena Pharmaceuticals' (Nasdaq: ARNA) lorcaserin, are back in front of the FDA after being rejected a little over a year ago. Both will get a second look from an advisory panel as well. VIVUS' meeting is next week on Feb. 22 and Arena expects its meeting to be held in the second quarter.

These are a tough call, considering the controversy around obesity drugs. While you could interpret the second advisory panel as a sign the companies didn't satisfy the FDA requirements, I think it's possible the FDA might be looking for a little backing from the experts to justify approving the drugs.

Final Foolish thoughts
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