Onyx Pharmaceuticals has posted a narrowing in losses for the fourth quarter but that did nothing to stop the stock from crumbling as investors absorbed the news that a lung cancer trial using Nexavar, which is partnered with Bayer, has been halted.

Onyx's fourth-quarter 2007 net loss narrowed 43.5% to $11.7 million, or $0.21 per share, and product revenue, ie from Nexavar (sorafenib) almost doubled to $124.9 million. Onyx and Bayer evenly split revenue and R&D expenses from the drug, which is approved for kidney and liver cancer, but only Bayer reports total revenue from Nexavar on its balance sheet.

The results disappointed analysts but not as much as the company’s refusal to give any sales guidance for 2008 on Nexavar. The problem stems from the massively disappointing news the day before that a Phase III trial the drug in patients with non-small cell lung cancer was stopped early because the study would not meet its primary endpoint of improved overall survival.

Bayer’s shares rebounded from the declines of the day before as the firm noted that it has other ongoing trials of Nexavar in NSCLC, but Onyx’ reluctance to give any sort of projected sales figures saw its stock end down over 26% to $33.09.