After a few quarters in the black, Onyx Pharmaceuticals (NASDAQ:ONXX) slipped back into the red this quarter, reporting a loss of $30 million for the fourth quarter.

Major issue? No, it's a drug developer, after all. Things are bound to be lumpy. Just ask Biomarin Pharmaceutical (NASDAQ:BMRN) -- it could turn a $30 million profit last year into a $15 million loss this year.

And for Onyx, lumpy is an understatement. Sales growth of the company's only drug, Nexavar, which it markets with Bayer, seemed to be coming to a screeching halt. The drug competes with Wyeth's (NYSE:WYE) Torisel, Pfizer's (NYSE:PFE) Sutent, and Genentech's (NYSE:DNA) Avastin for kidney cancer patient. It looked like the liver cancer market, which it just entered in 2007, was already getting saturated, even though it doesn't have any meaningful competition there.

 

Q1 2008

Q2

Q3

Q4

Nexavar Sales (in millions)

$151.9

$168.5

$180.9

$176.5

Quarter-Over-Quarter Increase (Decrease)

21.6%

10.9%

7.4%

(2.4%)

Source: Company press releases.

But growth should get back on track, now that launches in Europe and Asia are picking up this year. The company is guiding for sales of $850 million to $875 million this year. Based on the run rate from the second half of last year, that's a healthy 19% increase at the low end. That could certainly help the company get back in the black. Also, keep in mind that the company has been relatively conservative with guidance in the past -- for instance, management had been guiding for sales of $159 million to $174 million for the fourth quarter, and it topped the high end.

The long-term sales growth of Nexavar will be determined by how well the drug performs in phase 3 trials (against other cancers) that Onyx and Bayer are running. In the meantime, investors can probably look forward to getting back on track this year.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Pfizer is a former Income Investor pick and a current Inside Value recommendation. The Fool has a disclosure policy.