NCT07100106

A Study to Evaluate the Effect of GDC-4198 Alone and in Combination With Giredestrant Versus Abemaciclib and Giredestrant in Participants With Locally Advanced or Metastatic Estrogen Receptor-Positive (ER+), Human Epidermal Growth Factor Receptor-Negative (HER2-) Breast Cancer

A Phase Ib/II Multicenter, Open-Label, Randomized Study Evaluating the Safety, Pharmacokinetics, and Activity of GDC-4198 Alone and in Combination With Giredestrant in Comparison With Abemaciclib and Giredestrant in Participants With Locally Advanced or Metastatic Estrogen Receptor-Positive, HER2-Negative Breast Cancer Who Have Previously Progressed During or After a CDK4/6 Inhibitor

• Status: Recruiting
• Phase: Phase 1 / Phase 2
• Study type: Interventional
• Enrollment: 285 (estimated)
• Sponsor: Genentech, Inc. · Industry
• Sex: All
• Age: 18 Years
• Healthy volunteers: Not accepted

Summary

The purpose of this study is to assess the safety of GDC-4198 alone and in combination with giredestrant and also the efficacy of GDC-4198 + giredestrant versus abemaciclib + giredestrant in participants with locally advanced or metastatic ER+, HER2- breast cancer. The study consists of 2 phases: Phase Ib and Phase II. Phase Ib will evaluate the safety and pharmacokinetics (PK) of GDC-4198 alone and in combination with giredestrant. Phase II stage will compare the activity and safety of GDC-4198 and giredestrant with abemaciclib and giredestrant.

Conditions

• Breast Cancer

Interventions

Type	Name	Description
DRUG	GDC-4198	GDC-4198 will be administered orally.
DRUG	Giredestrant	Giredestrant will be administered orally.
DRUG	Abemaciclib	Abemaciclib will be administered orally.

Timeline

• Start date: 2025-10-07
• Primary completion: 2028-08-31
• Completion: 2028-08-31
• First posted: 2025-08-03
• Last updated: 2026-03-12

Locations

21 sites across 6 countries: United States, Australia, Canada, France, Germany, Spain

Regulatory

• FDA-regulated drug study