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Sanofi reveals setback for cancer drug acquired in Synthorx buyout

Disappointing study results have led the company to take an impairment charge and plan new early-stage trials for a drug at the center of a $2.5 billion acquisition.

Sanofi on Friday revealed a setback for the drug at the center of its $2.5 billion acquisition of biotechnology company Synthorx three years ago.

In its quarterly earnings report, the French pharmaceutical company said it’s stopped the ongoing Phase 2 tests of a prospective cancer treatment known as SAR444245 because the drug’s efficacy “was lower than projected.” Sanofi is planning new studies with a different dosing regimen, but will take a roughly $1.6 billion impairment charge because of delays to the program, the company said.

Sanofi’s drug is part of a new wave of medicines aimed at IL-2, an inflammatory protein that’s intrigued drugmakers for years because of its cancer-fighting potential. These medicines are being engineered or tweaked in ways that are meant to overcome the limitations of the only available IL-2 treatment, Proleukin. Many have drawn the interest of pharmaceutical companies as potential partner therapies.

Upon acquiring Synthorx, for instance, Sanofi R&D chief John Reed called SAR444245 “a molecule that has the potential to become a foundation for the next generation of immuno-oncology combination therapies.” Roche and Merck & Co. have each made recent deals for IL-2 medicines, too, all part of a series of recent acquisitions and biotech launches over the past five years.

Yet the newer IL-2 drugs have struggled to fulfill their potential. A multibilllion dollar partnership between Nektar Therapeutic and Bristol Myers Squibb, for instance, fell apart earlier this year after an IL-2 medicine they were co-developing failed in clinical testing. Synthorx’s drug has struggled as well, with an early profile that some analysts have described as undifferentiated from others in clinical testing.

Now Sanofi will toss out the drug’s current dosing regimen and try another approach, believing it will “solidify the foundation for a best-in-class target profile,” the company said. The drugmaker is also facing a delay for another top prospect it recently acquired in a pricey deal, the multiple sclerosis drug tolebrutinib, testing of which was recently partially halted due to safety concerns. Studies could resume in the fourth quarter, Sanofi said Friday.

The news was better on the sales side for Sanofi. The drugmaker raised its revenue outlook for the year amid stronger-than-expected sales for its vaccines and the inflammatory disease treatment Dupixent, which has generated nearly $6 billion over the first three quarters. Shares climbed about 2% in pre-market trading Friday.

Published Oct. 28, 2022

Ben Fidler

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