Puma preps its once-vaunted cancer drug for European submission

Puma CEO Alan Auerbach

Puma Biotechnology ($PBYI) said European regulators have opened a path to approval for its in-development breast cancer drug, clearing the way for a treatment that has divided analysts over the past few years.

The drug, neratinib, is a tyrosine kinase inhibitor designed to block the engines of cellular growth that help cancer spread throughout the body. In a meeting with the European Medicines Agency, Puma got the green light to submit neratinib for review as a treatment for early-stage breast cancer in patients with HER2 gene mutations who have already received Roche's ($RHHBY) Herceptin. The company plans to file its drug in the first half of 2016.

Neratinib was once considered a potential blockbuster based on top-line Phase III data released last year, in which adding the drug to Herceptin made a significant difference in progression-free survival for HER2-positive breast cancer sufferers. The case for neratinib's commercial success slowly came apart starting later that year when the drug failed to top Herceptin in a Phase II trial. Shortly afterward, Puma disclosed that it was pushing back its expected FDA filing date by a year, to the first quarter of 2016, to fulfill the agency's request for additional preclinical data. And in new results presented at the summer's ASCO conference, neratinib made only a minor difference in preventing the return of cancer in pretreated patients, disappointing analysts.

The ongoing neratinib saga has dragged Puma's share price down nearly 75% from its all-time high of $275 in 2014, as the drug's perceived underperformance has come coupled with the emergence of some serious side effects. In the Phase III data disclosed at ASCO, Puma's drug led to severe diarrhea in about 40% of patients in the treatment arm, a consistent effect in neratinib's clinical program that analysts worry could be a debilitating flaw if and when the drug reaches the market.

Puma is expecting to report final data from its Phase III, post-Herceptin trial by year's end, planning to assemble its FDA and EMA applications based on those results.

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