The purpose of this study is to assess the efficacy and safety of RO7771950 in combination with trastuzumab and capecitabine, compared to tucatinib in combination with trastuzumab and capecitabine.
Pathologically documented locally advanced inoperable (LAI) or metastatic breast cancer (MBC) with confirmed HER2-positive status by central laboratory.
Measurable disease as per by RECIST v1.1 in stage 1. Non-measurable disease allowed in stage 2.
Previously treated (stable or progressive) or previously untreated CNS metastases, or leptomeningeal metastases.
At least one prior line of anti-HER2-based therapy for LAI or metastatic disease.
Concurrent anti-cancer treatment, or treatment with investigational therapy within 28 days prior to initiation of study treatment.
Known active/untreated hepatitis B or C or chronic liver disease.
Clinically significant cardiovascular disease or risk, including heart failure (New York Heart Association (NYHA) ≥ II), ischemic heart disease or recent coronary events/interventions, clinically significant arrhythmias or electrocardiogram (ECG) abnormalities, QT prolongation or risk of ventricular dysrhythmias, poorly controlled hypertension, peripheral arterial disease, dilated cardiomyopathy, or unstable angina.
Clinically significant electrolyte abnormalities (e.g., hypokalemia, hypomagnesemia, hypocalcemia), or family history of sudden unexplained death or long QT syndrome.
Parallel
RO7771950
DrugParticipants will receive one of two doses of RO7771950 orally (PO) twice a day (BID).
Tucatinib
DrugParticipants will receive a dose of tucatinib PO BID.
Trastuzumab
DrugParticipants will receive trastuzumab in accordance with local prescribing information, either through intravenous (IV) or subcutaneously (SC).
Capecitabine
DrugParticipants will receive capecitabine according to local prescribing information. Capecitabine will be administered PO BID.
Progression-free Survival (PFS) as Determined by Blinded Independent Central Review (BICR)
Time from randomization to disease progression or death, according to standard criteria (Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST v1.1)).
Progression-free Survival in Participants with Central Nervous System Metastases (PFS-CNS) by BICR
Time from randomization to disease progression or death, according to standard criteria (RECIST v1.1).
Overall Survival in Full Analysis Set (OS-FAS)
Time from randomization to death from any cause.
Objective Response Rate (ORR) by BICR
Proportion of participants with a complete response (CR), partial response (PR) according to standard criteria (RECIST v1.1).
Duration of Response (DOR) as per BICR
Time from the first occurrence of an objective response (CR or PR) to disease progression or death from any cause according to standard criteria (RECIST v1.1).
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