The FDA's agonizing over Amgen's (NASDAQ:AMGN) lead drugs looks like it will continue into 2008. On Thursday, Amgen announced that the FDA would be holding yet another oncologic advisory panel hearing to discuss top-selling drug Aranesp and Johnson & Johnson's (NYSE:JNJ) Procrit.

For Amgen, 2007 can best be described as the year that its erythropoiesis-stimulating agents (ESAs), Epogen and Aranesp, first came under serious regulatory, competitive, and payor resistance (and its stock price shows this). Aranesp and Procrit are used to help treat chemotherapy-related anemia. Amgen also markets Aranesp and its other ESA, Epogen (the exact same compound as Procrit) to treat kidney failure-related anemia.

The upcoming advisory committee meeting will take place in the first quarter of next year. This will be the third meeting held to discuss Amgen's ESAs since May. The May advisory meeting was also an oncologic advisory panel to discuss when best to use ESAs in treating cancer patients.

That hearing didn't go so well when, in reaction to the meeting, the Center for Medicaid and Medicare Services, which accounts for about a third of all health-care expenditures in the U.S., decided to enact stricter rules on when it would reimburse doctors' use of ESAs in cancer patients.

The second FDA advisory panel meeting this year over the ESAs was in September, and it was held to discuss the benefits and risks of Epogen and Aranesp in kidney-failure patients. This meeting was less harmful to Amgen, as the main negative conclusion was to tighten and remove some of the quality-of-life claims on the ESA labels.

What's clear from the FDA briefing documents and transcripts of these past advisory panels is that the FDA is confused over when to recommend the use of the ESAs, as well as over which patients will benefit from the drugs enough to outweigh any adverse effects.

There are numerous studies showing that renal failure patients and cancer sufferers with certain hemoglobin levels do benefit from the use of the ESAs. Until Amgen, J&J, and the FDA are able to reach a definitive consensus over which patients these are, though, expect the ESA sales to continue coming under fire as the panel hearings and stricter labeling revisions continue. Thankfully, Amgen has other drugs, like its Wyeth (NYSE:WYE)-partnered Enbrel, to help pick up the slack.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. Johnson & Johnson is an active Income Investor pick. The Fool has an A+ disclosure policy.