Sanofi's dengue vaccine falters in clinical trial

Sanofi got lackluster results from a mid-stage study of its dengue fever vaccine, potentially hurting the Big Pharma company's blockbuster case for the experimental product.

Results from a Phase IIb study conducted in Thailand revealed the vaccine had about 30% overall efficacy against dengue fever type 2, way short of the more than 70% efficacy estimate Sanofi ($SNY) banked on, according to Reuters. And while the vaccine did show strong efficacy against types 1, 3 and 4 of the mosquito-borne disease, type 2 was the most prevalent in Thailand at the time of the study. The vaccine candidate is meant to protect against all four types viruses that cause dengue.

The meagre results place a question mark on Sanofi's future earnings from the vaccine. The French pharma giant invested €350 million in a factory to manufacture the vaccine, with hopes it will bring in about €1 billion ($1.3 billion) annually once it reaches the market in 2015 or so, Reuters notes. Still, the vaccine shows promise and Phase III studies involving more than 31,000 children and adults are under way in 10 countries across Asia and Latin America.

Given that there are upward of about 100 million new infections every year, the vaccines market for dengue is tremendous, not to mention competitive. BioDiem, the U.S. Navy and others are working on some sort of vaccine or another for dengue, but Sanofi's is the first-of-its-kind designed to prevent all four types, upping the ante on its potential success.

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