placebo + fulvestrant

Placebo + fulvestrant is a combination regimen utilized as the control arm in the Phase III LEONARDA-1 clinical trial (NCT05054751) sponsored by Genor Biopharma. This regimen consists of fulvestrant, a selective estrogen receptor degrader (SERD), and an oral placebo designed to match the administration of the CDK4/6 inhibitor lerociclib (GB491). Fulvestrant is an intramuscularly administered small molecule that competitively binds to estrogen receptors (ER), leading to their down-regulation and degradation, which inhibits the growth of hormone receptor-positive (HR+) breast cancer cells. The combination was evaluated in patients with HR-positive, HER2-negative locally advanced or metastatic breast cancer who had progressed on prior endocrine therapy, serving as the baseline to demonstrate the superior progression-free survival of the lerociclib-containing arm.