This study involves people with different types of solid tumors, which are cancers that form solid masses rather than blood cancers. The first part of the study will include people with advanced or metastatic solid tumors, which means the cancer has spread to other parts of the body, and who have tried all available standard treatments without success. The second part of the study will focus specifically on people with metastatic breast cancer that has a gBRCAmut (a specific inherited change in the BRCA gene), is HER2-negative or HER2-low (meaning the cancer has little or no HER2 protein), and who have received no more than three previous treatment plans. The study will test two medications: GSK4524101, which is an experimental drug that works by blocking an enzyme called DNA Polymerase Theta, and niraparib, which is a PARP inhibitor that prevents cancer cells from repairing their damaged genetic material. Both medications are taken by mouth as tablets.
The purpose of the study is to find out what dose of GSK4524101 can be given safely, either alone or together with niraparib, and to see if the combination of these two drugs can help slow down or stop the growth of cancer. The study is divided into two parts. In the first part, small groups of people will receive increasing doses of GSK4524101 alone or combined with niraparib to find the highest dose that can be given without causing serious side effects. This part will also include a group to test whether taking GSK4524101 with food affects how the body processes the medication. In the second part, a larger group of people with the specific type of breast cancer described above will receive the combination of GSK4524101 and niraparib at a dose determined to be safe from the first part, to learn more about whether this combination can help shrink tumors.
Throughout the study, participants will have regular check-ups where doctors will monitor for any side effects and take blood samples to measure the amount of medication in the body. The study will also assess how well the treatment works by looking at whether tumors shrink or stop growing, and how long any positive effects last. Participants in the first part will help determine the safest dose to use, while those in the second part will help show whether the combination treatment can provide benefit for people with this specific type of breast cancer who have not previously received a PARP inhibitor.



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