giredestrant + palbociclib

Giredestrant + palbociclib is a combination therapy being investigated for the treatment of estrogen receptor-positive (ER+), HER2-negative breast cancer. This combination pairs giredestrant, a next-generation oral selective estrogen receptor antagonist and degrader (SERD), with palbociclib, an established CDK4/6 inhibitor. ## Drug Information Giredestrant (also known as GDC-9545) is designed to target and degrade estrogen receptors, including those with mutations that cause resistance to conventional endocrine therapies. Palbociclib works by inhibiting cyclin-dependent kinases 4 and 6, which helps block cell proliferation in hormone receptor-positive breast cancer. The combination has shown promising results in clinical trials, demonstrating clinical benefit in patients who have progressed on prior endocrine therapy, including those with ESR1-mutated tumors. In the phase Ia/b GO39932 study, the combination showed a clinical benefit rate of 81.3% compared to 48.6% for giredestrant monotherapy[1]. ## Clinical Development Multiple phase III trials are evaluating this combination: 1. **persevERA Breast Cancer trial (NCT04546009)**: A double-blind, placebo-controlled study comparing giredestrant + palbociclib versus letrozole + palbociclib as first-line treatment for ER+/HER2- locally advanced or metastatic breast cancer[2][5]. 2. **pionERA BC trial (NCT06065748)**: Comparing giredestrant with fulvestrant, both in combination with a CDK4/6 inhibitor (investigator's choice of palbociclib, ribociclib, or abemaciclib), in patients with ER+/HER2- advanced breast cancer who developed resistance to adjuvant endocrine therapy[4]. 3. **coopERA BC study (NCT04436744)**: A phase II trial that evaluated giredestrant versus anastrozole followed by giredestrant + palbociclib compared with anastrozole + palbociclib in postmenopausal women with untreated, ER+/HER2- early breast cancer[7]. The combination has demonstrated a manageable safety profile, with adverse events consistent with known endocrine therapy risks. The most common side effects include asymptomatic bradycardia with giredestrant and typical CDK4/6 inhibitor-related effects from palbociclib. This combination represents an important advancement in the treatment landscape for hormone receptor-positive breast cancer, particularly for patients with endocrine therapy resistance.

Other names

GDC-9545/palbociclib