Inclusion Criteria.  Provision of full informed consent prior to any study-specific procedures. Patients must be ≥18 years of age, at the time of signing informed consent. Dose escalation phase, patients with histologically and/or cytologically confirmed malignant solid tumor whose disease has progressed following at least one standard therapy and who have no other acceptable standard treatment options. Tumor types will include breast, ovarian, fallopian tube, or peritoneal cancer, extensive-stage small cell lung cancer (ES-SCLC), prostate, pancreatic, colorectal gastric, biliary tract, and endometrial cancer. Dose-expansion phase patients with histologically and/or cytologically confirmed malignant solid tumor (breast, ovarian, fallopian tube, or peritoneal cancer, extensive-stage small cell lung cancer (ES-SCLC), with one of the documented deleterious mutations of specified HRR genes and whose disease has progressed following at least one standard therapy. Patients with at least one measurable lesion per RECIST version 1.1 at baseline that can be accurately assessed by CT-scan or MRI and is suitable for repeated assessment at follow up-visits. ECOG performance status 0 to 2. Use of contraception measures  Exclusion Criteria:  Patients with HER2 positive breast cancer Patients receiving anticancer therapy Patient who has not recovered from acute toxicities of previous therapy except treatment-related alopecia. Prior treatment with a PARP inhibitor Major surgery within 4 weeks of starting study treatment or any patient who has not recovered from the effects of major surgery. Patient with symptomatic uncontrolled brain metastasis. Pregnancy and lactation Patients with uncontrolled disease