Brief Summary: Open label first-in-human study of TH1902 in solid cancer, with 4 sequential parts: Part 1 (dose escalation): patients with recurrent advanced solid tumors (all comers) that have relapsed or are refractory to standard chemotherapy, surgery, radiation therapy, and for which no known effective therapies exist. Part 2 (expansion): selected patient populations with recurrent advanced TNBC, HR+ breast cancer, epithelial ovarian cancer, endometrial cancer, cutaneous melanoma, thyroid cancer, SCLC, prostate cancer and other cancers known to express SORT1 that are refractory to standard therapy. Part 3 (optimization): patients diagnosed with histologically or cytologically confirmed high grade serous ovarian cancer, including high grade peritoneal or fallopian tube cancer, or high grade endometrioid cancer, that is refractory or resistant to standard therapies, should not be considered platinum sensitive, and where current therapy is not considered to be providing benefit. Part 4 (basket expansion): selected cancer type diagnosed with histologically or cytologically confirmed cancers, where TH1902 has been studied and/or showed activity (in Parts 1 to 3), that is refractory or resistant to standard therapies, and where current therapy is not considered to be providing benefit.

Detailed Description: This first-in-human study was initially designed as a Phase 1, multi-center, open-label study, with 2 sequential parts in which TH1902 was administered once every 3 weeks (Q3W): Part 1 (dose escalation): was comprised of 18 patients with recurrent advanced solid tumors (all comers) that had relapsed or were refractory to standard chemotherapy, surgery, radiation therapy, and for which no known effective therapies existed. Part 2 (dose expansion): was comprised of 18 patients from selected populations with recurrent advanced TNBC, HR+ breast cancer, epithelial ovarian cancer, endometrial cancer, cutaneous melanoma, thyroid cancer, SCLC, prostate cancer, and other cancers known to express SORT1 that are refractory to standard therapy. Following emerging data from Parts 1 and 2, the Sponsor has made the decision to pause the enrollment of patients in Part 2 of the study and revisit the study design to improve the risk-benefit ratio. Patients who were enrolled in Part 2 of the study that are still benefiting from TH1902 administration will continue following the protocol for Part 2. The study will resume with enrollment in Part 3 and TH1902 will be administered on 3 consecutive weeks followed by 1 week of rest (3/1), i.e., on Days 1, 8 and 15 of a 28-day cycle, and in the following population: Part 3 (dose optimization): will comprise approximately 16 patients diagnosed with histologically or cytologically confirmed high grade serous ovarian cancer, including high grade peritoneal or fallopian tube cancer, or high grade endometrioid cancer, that is refractory or resistant to standard therapies, should not be considered platinum sensitive, and where current therapy is not considered to be providing benefit. Upon completion of Part 3, an ad hoc interim analysis will be conducted to select at least 2 dosing arms that will offer an acceptable risk-benefit ratio for dose expansion in Part 4 with the following population: Part 4 (basket expansion): will comprise approximately 20 patients per dose level, per selected cancer type diagnosed with histologically or cytologically confirmed cancers, where TH1902 has been studied and/or showed activity (in Parts 1 to 3), that is refractory or resistant to standard therapies, and where current therapy is not considered to be providing benefit.