Another drug targeting epidermal growth factor tyrosine kinase has failed to live up to early promise as a treatment for cancer.
Roche's Tarceva (erlotinib) has followed in the footsteps of another EGF inhibitor, AstraZeneca's Iressa (gefitinib), by failing to show a significant effect on survival in a Phase III study involving patients with non-small cell lung cancer. Both are oral derivatives of the quinazoline family and bind competitively and reversibly to the ATP binding site of the EGF tk enzyme.
The fact that two drugs sharing this mechanism of action have yielded only partial efficacy raises questions about the validity of the approach in NSCLC treatment.
Tarceva, and Iressa before it, was widely tipped to become blockbuster drugs with sales in excess of $1 billion a year when they were in mid-stage development. Roche itself had tipped the product to make peak sales of between SF 1 billion (€650m) and SF 1.5 billion.
However, the results of the TALENT and TRIBUTE studies found no benefit in terms of patient survival when Tarceva was given alongside chemotherapy and compared to chemotherapy alone. Earlier, Phase II trial data in patients with glioma (brain cancer) suggested that the EGF blocker had some benefit.
"Tarceva is now falling back from a potential first- line treatment for NSCLC to a potential third-line treatment," said Denise Gugerli-Etter of Swiss broker Sarasin.
She has reduced her peak sales projections for Tarceva from SF 1 billion to SF 500 million on the back of the trial disappointment, noting that the drug may still find a market in glioma and as a monotherapy in NSCLC. A Phase III trial looking at the latter indication is ongoing.
The drug is being developed in collaboration with US companies Genentech and OSI Pharmaceuticals.