Sanofi’s dengue vaccine slams into a safety issue, triggering a $120M write-off and eviscerating old blockbuster projections

Sanofi spent $1.5 billion over about 20 long years to develop its dengue vaccine, believing that it had a blockbuster product headed to a massive global market.

But their in-house development team missed something important.

On Wednesday, Sanofi $SNY said that their investigators had determined that Dengvaxia presented a real threat to patients who were vaccinated against dengue without having first been exposed to it. As a result, these subjects could experience a significantly worse reaction when exposed to a new infection — with their body reacting to the first exposure as if it were the second, due to the vaccination.

Sanofi said in their statement:

There are many factors that can lead to severe dengue infection. However, the highest risk of getting more severe disease has been observed in people infected for the second time by a different dengue virus.

And now Sanofi — which has Takeda nipping at its heels with a Phase III rival — wants to limit its use to protect people who have had a prior infection.

Sanofi is taking a $120 million write-off on the setback, which dwarfs the amount the pharma giant has earned in its first anemic rounds of revenue — which fell far behind its own projections as well as the analysts who had been cheering them on.

The jarring reversal on Dengvaxia underscores yet again the deep-seating problems that the pharma giant has experienced in developing and fielding new therapies out of its own pipeline. While Sanofi has been bullishly making advances in hand with its partner at Regeneron, its R&D operations in Boston and France haven’t been able to generate blockbuster new medicines for years.

Dengvaxia was supposed to help change that rep. Dengue affects 390 million people globally each year, costing billions of dollars and claiming 20,000 lives. That was supposed to ignite a major new market for Sanofi, but sales started at $60 million last year and then started to dwindle.

Sanofi’s setback, though, is Takeda’s gain. Just weeks ago Takeda posted new data underscoring TAK-003’s ability to generate antibodies to dengue. It’s now in Phase III being tested among 20,000 subjects.

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Research Scientist - Immunology
Recursion Pharmaceuticals Salt Lake City, UT
Director of Operations
Atlas Venture Cambridge, MA

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