Pfizer has suffered a clinical setback after its investigational lung cancer drug dacomitinib failed in two late-stage studies.

The drugs giant announced top-line results from two Phase III trials of the irreversible pan-HER kinase inhibitor in patients with advanced non-small cell lung cancer. In the first, which included patients previously treated with chemotherapy, dacomitinib did not meet its objective of demonstrating statistically significant improvement in progression-free survival (PFS) when compared with Roche's epidermal growth factor receptor (EGFR) inhibitor Tarceva (erlotinib).

In the second trial, which included patients with advanced NSCLC after standard therapy with both chemotherapy and an EGFR tyrosine kinase inhibitor had failed, dacomitinib failed to prolong overall survival versus placebo.

Mace Rothenberg, chief medical officer for Pfizer Oncology, said that "while we are disappointed in the results, lung cancer is a complex disease, and the use of targeted agents to treat specific patient populations continues to evolve". The full data set from the trials will be submitted for presentation at an upcoming medical meeting.

However, Pfizer has not pulled the plug on dacomitinib just yet and an ongoing, third Phase III trial, is evaluating PFS in a different patient population ie versus AstraZeneca's Iressa (gefitinib) in treatment-naive patients with EGFR-mutant advanced NSCLC. The results are expected in 2015.

However some observers believe the end is nigh for the drug which Pfizer had hailed as a jewel in its pipeline. ISI analyst Mark Schoenebaum issued a research note saying "we believe consensus expectations (for dacomitinib) will be close to zero given today's readout".

He added that there has been little investor interest in the treatment and Pfizer stock did not slide on the news, down just 1.4%.