It was like looking into one of those mood rings the kids have -- right before our eyes, earnings at Onyx Pharmaceuticals (NASDAQ:ONXX) went from red to black. But will they stay black?

Sales of Onyx's only drug, Nexavar, which it markets with Bayer, exceeded $100 million in the quarter. That's an impressive increase of 29% over the last quarter and 130% over Q3 of last year.

As Nexavar sales for treating kidney cancer began to plateau due to strong competition from Pfizer's (NYSE:PFE) Sutent, its sales for treating liver cancer are on the rise. Onyx didn't break out the sales figures by treatment but hinted that most of the drug's increased sales were due to a rise in prescriptions for off-label use by liver cancer patients after stellar trial results were presented last June.

Last week, Nexavar became the only approved systemic therapy for liver cancer in Europe after a positive recommendation from the European Committee for Medicinal Products for Human Use in September. The U.S. approval is expected this quarter, which will allow the duo to market the drug to doctors who haven't started using it yet because the only information they get about products is from sales reps in exchange for free pizza. Don't laugh -- I've worked with a few of them.

In addition to expanding into liver cancer, Onyx and Bayer are working to expand into other tumor types. They have completed enrollment of a phase 3 trial testing Nexavar in combination with chemotherapeutic agents in non-small cell lung cancer patients.

Trial results are expected in the second half of next year, which, if positive, will allow them to compete with AstraZeneca's (NYSE:AZN) Iressa, and Avastin and Tarceva from Genentech (NYSE:DNA); but the market could be more congested by then given the strong results from ImClone Systems (NASDAQ:IMCL).

The big market for Nexavar will be in the treatment of breast cancer, where it's a little farther behind. It has three phase 2 breast cancer trials in progress. The primary endpoint for the trials is progression-free survival, so the results will be back sooner than if the trials measured overall survival, which should allow Bayer and Onyx to move into pivotal phase 3 trials quicker.

With these expensive trials it will be interesting to see if Onyx can stay in the black. It doesn't really matter if it totters back and forth between red and black for a quarter or two; given its pipeline-less status, the future of the company depends on Nexavar's effectiveness in treating breast and lung cancers.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Pfizer is a pick of the Inside Value newsletter service. The Fool has a disclosure policy.