Bayer shares have taken a bit of a hit after it was revealed that the firm and partner Onyx Pharmaceuticals have called a halt to a late-stage trial of its potential blockbuster Nexavar in patients with non-small cell lung cancer.

The Leverkusen-based company said that a Phase III trial evaluating Nexavar (sorafenib) in patients with non-small cell lung cancer (NSCLC) was stopped early when the independent data monitoring committee (DMC) concluded that the study would not meet its primary endpoint of improved overall survival. Data from the more-than-900-patient trial, called ESCAPE, evaluated Nexavar in combination with the chemotherapeutic agents carboplatin and paclitaxel and higher mortality was observed in the subset of patients with squamous cell carcinoma of the lung treated with sorafenib and carboplatin and paclitaxel versus those treated with the latter two agents alone.

Bayer and Onyx noted that they will review the findings of the analysis and DMC recommendation “to determine what, if any, impact they have on other ongoing Nexavar lung cancer trials”. Susan Kelley, vice president of oncology at Bayer, said that while the companies are disappointed about the outcome, they “remain committed to our comprehensive pan-tumour clinical trial programme for Nexavar”.

The drug has already been approved for kidney and advanced liver cancer but the NSCLC indication could be a major earner. Bayer has previously forecast peak sales of around 750 million euros from Nexavar in the NSCLC indication alone and a launch was pencilled in for 2009.

Not all is lost, however, as ESCAPE forms only part of the programme of clinical trials studying Nexavar for the treatment of NSCLC. These include a second ongoing Phase III study, known as NExUS, looking at the drug in combination with gemcitabine and cisplatin, while a Phase II trial in patients who have failed two or more therapeutic regimens has also completed enrollment.

Bayer shares ended the day down 2.3% at 54.15 euros.