Genentech’s blockbuster cancer drug Avastin faces a big challenge from ImClone Systems’ Erbitux in lung cancer, according to a Morgan Stanley investor note that cites unpublished data, Reuters reports. The brokerage has learned from what it calls “a reliable public source” that ImClone’s med had demonstrated an unexpected survival benefit in a second Phase III trial - the so-called BMS-099 trial for first line metastatic lung cancer.

The disclosure came as Genentech announced fresh findings from a clinical trial called Avail showing that Avastin improved progression-free survival in patients with non-small cell lung cancer (NSCLC), but did not prolong overall survival. The results mean Erbitux has two Phase III trials with proven survival benefit compared with only one for Avastin, increasing the chances that Erbitux could pose a serious threat to Avastin in the lung cancer treatment market in future.

Avastin, which is vital to the future prospects of both Genentech and Roche is already approved in NSCLC in the US and Europe. Erbitux, which is sold in the US by Bristol-Myers Squibb and in Europe by Germany’s Merck KGaA, was initially developed for colon cancer but the drugmakers now want to use it in a wider range of tumour types.