Indian researchers find CDKN1B changes impair p27 reducing tamoxifen effectiveness

Technology Apr 27, 2026

Indian researchers have discovered that changes in a gene called CDKN1B can make hormone therapies like tamoxifen less effective for people with hormone receptor-positive (HR+) breast cancer, a type that makes up about 70% of cases in India.
The CDKN1B gene helps create a protein called p27, which these treatments rely on to work properly.

Study finds CDKN1B repair restores tamoxifen

The study, which looked at 186 patients, found that fixing the CDKN1B gene could help tamoxifen work again in those who'd become resistant.
Even better, another group of drugs called CDK4/6 inhibitors (like palbociclib) seems to work even when p27 is missing.
Researchers think checking p27 levels could help doctors personalize treatments for patients with low p27 levels or at high risk of resistance.