Puma shrugs off an 'expected' Phase II failure for its breast cancer drug

Puma Biotechnology's ($PBYI) closely watched neratinib failed to beat out the blockbuster Herceptin in a mid-stage breast cancer trial, a miss the company said was no surprise as it touted success on a secondary goal.

The company recruited 479 patients with HER2- positive breast cancer, testing whether a combination of neratinib and paclitaxel could better prolong progression-free survival (PFS) than a cocktail of Roche's ($RHHBY) Herceptin and paclitaxel. In the end, median PFS for Puma's drug came in at 16.6 months, while Herceptin clocked 16.7. And neratinib fared no better on its secondary endpoint, charting a 74.8% overall response rate compared to Herceptin's 75.1%.

Puma CEO Alan Auerbach

But Puma is "very pleased with the results," CEO Alan Auerbach said in a statement, pointing to the secondary endpoint in which neratinib succeeded. The drug contributed to a 52.6% reduction in the incidence of central nervous system metastases--for instance cancer spreading to the brain--compared to the Herceptin arm, a statistically significant result that Puma believes could help differentiate neratinib on the market for breast cancer therapies.

"As expected, there was no statistically significant difference in progression-free survival and objective response rate for the paclitaxel plus neratinib arm compared to the paclitaxel plus trastuzumab arm," Auerbach said. "However ... while the development of other HER2-targeted drugs has produced a clinically meaningful benefit to patients with HER2 positive breast cancer, these drugs have had little impact on CNS metastases. As a result, we believe that there remains an unmet clinical need for reducing the incidence of CNS metastases, and the results of the NEfERTT study demonstrate that we may be able to provide this type of improvement with neratinib."

Puma's shares fell as much as 15% on the news but made up some ground overnight, trading roughly 8% down on Friday morning.

What the Phase II failure will mean for neratinib's long-term potential remains unclear. The company's shares more than tripled over the summer in response to Phase III results in which neratinib, delivered as an adjuvant to Herceptin, contributed to a 33% improvement in PFS. Puma has now demonstrated that its drug isn't any better at Roche's in prolonging disease progression, but that doesn't change its proven efficacy as a follow-on treatment.

The company remains on track to file an FDA application for the drug in the first half of next year.

- read the statement