RO7771950 Versus Tucatinib in Combination With Trastuzumab and Capecitabine in People With Locally Advanced or Metastatic Breast Cancer That is Human Epidermal Growth Factor Receptor 2 (HER2)-Positive

To join this study, you must have HER2-positive breast cancer that is advanced or has spread. Your doctors must have confirmed this by looking at your cancer cells. You should have already received at least one other HER2-targeted treatment for your advanced breast cancer. This might include certain antibody-drug conjugate (ADC) therapies like trastuzumab-deruxtecan or trastuzumab emtansine, unless these aren't available to you or you have a clear medical reason not to take them. If you've had a type of tablet treatment called a TKI in the past for early-stage breast cancer, this is generally okay if it was more than a year ago. However, you can't have had a TKI for your advanced breast cancer previously.

It's important that you are generally well enough to take part. This means your major organs like your heart, liver, and kidneys are working properly, and your bone marrow is healthy enough to make blood cells. Your heart function will be checked, and it must be at a certain level. You also need to be able to carry out most of your normal daily activities without too much difficulty.

There are some reasons why you might not be able to join. For example, if you are currently receiving other cancer treatments or have recently taken part in another research study. You also wouldn't be able to join if you have certain heart conditions or have had serious heart problems before. Doctors will also check for known active or untreated hepatitis B or C, or other chronic liver diseases. They will explain all the specific requirements and make sure the study is suitable and safe for you.

If you join this study, you'll be randomly assigned to receive one of the two treatment combinations being compared. This means neither you nor your doctor will choose which combination you get, similar to flipping a coin. Both combinations involve a main study drug (either RO7771950 or tucatinib) and two other established medicines (trastuzumab and capecitabine). The treatments are typically given in cycles, which involve taking medicines for a period followed by a rest period.

Taking part will involve regular visits to the clinic. During these visits, doctors and nurses will monitor your health closely. This will include blood tests, urine tests, physical examinations, and scans (like CT or MRI scans) to see how your cancer is responding to treatment. You'll also have checks to make sure your heart is healthy. These assessments help the study team understand how safe and effective the treatments are for you.

Treatment will continue as long as it is benefiting you and you are not experiencing unacceptable side effects. After your treatment period, there will be a follow-up period where the study team will continue to monitor your health, usually through regular check-ups. The total duration of your participation in the study, including treatment and follow-up, will be explained by the study team, but it could last for several years.