A Phase 1/1B Study of ST-01156, a Small Molecule RBM39 Degrader, in Patients With Advanced Solid Malignancies

Inclusion Criteria: * Age ≥ 18 years on the day of signing the consent form, except for adolescents with Ewing Sarcoma or other malignancies for which there is a biological rationale to support participation, in which case the participant is ≥ 16 years old. * Has a metastatic or locally advanced and unresectable solid tumor. * Has at least 1 measurable lesion or evaluable disease per RECIST v1.1. * Has an ECOG performance status ≤ 2 at screening. * Has adequate organ function as defined in the protocol. Exclusion Criteria: * Has received prior radiotherapy within 2 weeks of treatment. * Has known active CNS metastases and/or carcinomatous meningitis. Participants with previously treated brain metastases may participate, provided they are radiologically stable * Has received treatment with any local or systemic anticancer therapy or investigational anticancer agent within 14 days or 5 half-lives, whichever is shorter. * Had major surgery within 28 days before study therapy administration * Has toxicities from previous anticancer therapies that have not resolved to baseline levels, with the exception of alopecia and peripheral neuropathy. * Has previously received a RBM39 inhibitor/degrader.