GSK is refusing to write off its cancer vaccine despite last year's PhIII flop

GSK CEO Andrew Witty

GlaxoSmithKline's ($GSK) MAGE-A3 cancer vaccine was viewed as a long shot by some analysts even before it missed its first co-primary endpoint last year. Yet while analysts lowered expectations in the wake of the weak data in melanoma patients, GSK is continuing to promote its prospects.

Expectations for MAGE-A3 reached new lows in September when the vaccine failed to outperform the placebo in a Phase III trial of 1,345 melanoma patients. The vaccine is designed to train immune systems to attack the MAGE-A3 protein found in many advanced melanoma cases. In doing so, GSK hoped the vaccine could prevent tumors from returning after surgery. The theory was dented by the Phase III data, but GSK is still investigating the effect of the vaccine in different patient populations.

A trial in patients with non-small cell lung cancer (NSCLC) is ongoing and GSK is continuing the melanoma study to see whether patients with a particular genetic profile are more responsive. "We still have three more sets of pivotal data to come in on the MAGE-A3 programme. Essentially we need one of those to come in for us to be in business and that is an exciting prospect," CEO Andrew Witty said Wednesday as the company reported earnings. In September Citigroup analyst Andrew Baum forecast MAGE-A3 sales of $233 million in 2018 .

Sales at GSK's vaccine unit grew 12% in the fourth quarter, largely driven by the U.S. where the introduction of its quadrivalent flu vaccine pushed turnover up 23%. GSK also benefited from a shortage of Sanofi's ($SNY) pertussis-containing vaccines. Sales of GSK's tetanus, diphtheria, and pertussis vaccine Boostrix were up 97% in the U.S. GSK faces its own issues in supplying chickenpox vaccines, but does not expect sales to drop. "That looks like it is going to be a very short-lived disruption," Witty said.

- here's Reuters' take
- read FiercePharma's coverage
- view GSK's results (PDF)
- and access the call

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