This study has two parts. The first part tests different doses of a drug called EIS 12656 to learn about its safety and how the body handles it. The second part uses the best dose to study the drug in more people. You will be in the second part of the study. Doctors will do tests to see how your body and your cancer respond to the study drug. These tests may include physical exams, checking your vital signs, taking blood and urine samples, heart tests, scans, and tumor biopsies. You will also keep a diary to write down when you take the drug.

This study is for patients who have advanced or metastatic solid tumors. These tumors have a problem in the way their cells repair DNA, called homologous recombination deficiency, or HRD.

People can join this study if they are 18 years or older and have an advanced or metastatic solid tumor that has grown after at least one earlier treatment or if they cannot take standard treatments. Their cancer must have an HRD mutation, such as BRCA1, BRCA2, ATM, PALB2, or certain RAD51 gene changes. They must also be able to take care of themselves and be active, with only mild limits on physical activity.

This study is testing a new pill called EIS 12656. It is designed to block a protein called ALC1, which some cancers use to fix damaged DNA. Researchers want to find a safe dose, learn how the drug works inside the body, and see early signs of whether it can help shrink tumors in people with HRD positive cancers. The study is also looking at whether using EIS 12656 together with other cancer drugs, such as PARP inhibitors or T DXd, can improve treatment.