Sanofi’s experimental cancer medicine amcenestrant failed in an intermediate clinical test for breast cancer, dealing a blow to one of the French drugmaker’s potential future blockbusters.
The patients who got the drug, rather than endocrine treatment, didn’t live longer without the disease progressing -- a key benefit measure known as progession-free survival -- in the phase 2 trial, Sanofi said Monday. The stock fell as much as 6.2% in Paris trading, the steepest drop in almost two years.
The medicine is one of six "potentially transformative” products Sanofi has touted and prioritized. The disappointing result doesn’t mean it’s the end of the road for amcenestrant, but it increases the risk of failure for the other trials, according to analysts at Bloomberg Intelligence. The company said it would press ahead with other trials.
"Competition is hot” and the announcement puts in doubt the $1 billion sales consensus for 2026 for the medicine, BI’s John Murphy and Sam Fazeli wrote in a note.
In the trial, the patients had advanced disease and few treatment options remaining, and the medicine wasn’t combined with another as is often the case in cancer.
"We continue to investigate amcenestrant in patients with earlier stages of breast cancer with different tumor profiles and where different standard of care treatments are used,” said John Reed, the company’s head of research.
Other trials of the drug include one called Ameera-5, an advanced study in which it’s combined with Pfizer Inc.’s Ibrance as a first-line treatment of breast cancer that has spread.
