The easiest way to see where a drug company might get tripped up by a Food and Drug Administration advisory panel is to look at the questions the agency has for the panel of outside experts. There are often four or five -- sometimes more -- questions about different issues the FDA has with the drug. Some have requests for a vote, others just ask for a discussion, and there's always the ultimate question on whether the committee recommends approval of the drug.

So you could tell the FDA is fairly impressed with Seattle Genetics' (Nasdaq: SGEN) lymphompa drug brentuximab vedotin when there were just two questions for each of the indications that Seattle Genetics has applied for. Sure, there's mention in the briefing documents about side effects, but the lack of a question about them leads me to think the FDA probably isn't that worried about the potential for nerve damage or depletion of immune cells.

The two questions on the docket:

  1. Should brentuximab vedotin get a full approval, an accelerated approval, or no approval at all?
  2. What should a confirmatory trial look like if an accelerated approval is given?

I think we can take a regular approval off the table for both types of lymphoma. The drug was tested in relatively small clinical trials without control arms. The response rates produced by brentuximab vedotin are sufficient to be convinced that the drug is working, but the panel members will want to see more data before giving the drug a full approval. Except for having to run an additional trial, there's no downside to getting an accelerated approval.

Seattle Genetics has already started a confirmatory trial in Hodgkin's lymphoma; it remains to be seen whether the FDA panel likes the design. If worse comes to worst, Seattle Genetics has to modify the trial or run an entirely different trial altogether. For anaplastic large-cell lymphoma, the other indication it's applying for, the company hasn't started a confirmatory trial yet.

At this point, the confirmatory trials seem like the only stumbling block that could trip up Seattle Genetics. Eli Lilly (NYSE: LLY), Bristol-Myers Squibb (NYSE: BMY), Amgen (Nasdaq: AMGN), and many others have failed to complete confirmatory trials after their cancer drugs received accelerated approvals, which doesn't make the FDA very happy. The agency may want to see Seattle Genetics' trials in process before giving brentuximab vedotin an accelerated approval for the indications.

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Fool contributor Brian Orelli holds no position in any company mentioned. Check out his holdings and a short bio. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.