This study is looking at patients with advanced solid tumors and patients with advanced HR-positive HER2-negative breast cancer. HR-positive means the cancer cells have receptors for hormones that help them grow, and HER2-negative means the cancer cells do not have too much of a certain protein called HER2. The study will test a medicine called ECI830, which will be given either alone or in combination with other treatments. The combinations being studied include ECI830 with ribociclib and fulvestrant, which are medicines used to treat breast cancer. Some patients may also receive hormone treatments such as goserelin or leuprorelin acetate, which help reduce the amount of hormones in the body that can make cancer grow. ECI830 is taken by mouth as a capsule, fulvestrant is given as an injection into the muscle, and ribociclib is taken by mouth as a tablet.
The purpose of this study is to find out if ECI830 is safe when given alone or with other treatments, to determine the right dose to use, and to see if the combination of ECI830 with ribociclib and fulvestrant can help stop the cancer from getting worse in patients with HR-positive HER2-negative breast cancer who have already received treatment with a type of medicine called a CDK4/6 inhibitor. The study will also look at how well these treatments work against the cancer by measuring things like whether tumors shrink or stop growing.
The study has two parts. The first part will test different doses of ECI830 to see what side effects occur and to find the best dose to use. The second part will give the chosen dose of ECI830 in combination with ribociclib and fulvestrant to a larger group of patients with breast cancer to see how well this combination works. During the study, patients will have regular check-ups where doctors will monitor their health, take blood samples, check heart activity, and use imaging scans to see how the cancer is responding to treatment. The study will track how long patients live without their cancer getting worse and how long they survive overall.



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