NCT07100106 · Genentech, Inc.
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
(MoonROSE)
What this study is about
The purpose of this study is to assess the safety of GDC-4198 alone and in combination with giredestrant and also the effectiveness 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.
View original scientific description
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.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Histologically and/or cytologically confirmed adenocarcinoma of the breast that is locally advanced or metastatic.
- Previously documented ER+ and HER2- tumor according to American Society of Clinical Oncology (ASCO)/ College of American Pathologists (CAP) or European Society of Medical Oncology (ESMO) guidelines or any national guidelines with criteria conforming to ASCO/CAP or ESMO guidelines.
- Disease progression during or after treatment with an approved cyclin-dependent kinase 4/6 (CDK4/6) inhibitor and approved endocrine therapy (ET) in the locally advanced or metastatic setting.
- Measurable or non-measurable evaluable, disease per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1).
- Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.
- Life expectancy \>= 6 months.
Exclusion criteria
- Advanced, symptomatic, visceral spread that is at risk of life-threatening complications in the short term appropriate for treatment with cytotoxic chemotherapy at time of entry into the study, as per national or local treatment guidelines.
- Have received more than one-line of therapy for locally advanced or metastatic disease.
- Have received prior chemotherapy for metastatic breast cancer.
- Treatment with an approved oral ET within 7 days prior to initiation of study drug; treatment with fulvestrant or an approved CDK4/6 inhibitor within 21 days prior to initiation of study drug.
- Malabsorption condition or other gastrointestinal (GI) conditions/surgeries that the investigator assesses may significantly interfere with enteral absorption
- History of malignancy within 3 years prior to screening, except for cancer under investigation in this study and malignancies with a negligible risk of metastasis or death.
- Known allergy or hypersensitivity to any component of the study treatments.
Where
- Duarte, California
- Irvine, California
- La Jolla, California
- San Francisco, California
- Tampa, Florida
- Atlanta, Georgia
- Zion, Illinois
- Detroit, Maine
- St Louis, Missouri
- New Brunswick, New Jersey
- East Patchogue, New York
- Charlotte, North Carolina
And 5 more locations — see the full list below.
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Jun 16, 2026 · Source of record for eligibility and locations