A Study of HST-1011 Given as Monotherapy and in Combination With an Anti-PD1 Antibody

This is a Phase 1/2 study of HST-1011, a CBL-B inhibitor, being developed for the treatment of patients with advanced solid tumors, who relapsed while on or are refractory to approved anti-PD(L)1 therapies or other standard of care.

Key Inclusion Criteria:Patient is at least 18 years of age.Patient is capable of understanding and complying with protocol requirements.Patient has signed and dated ICF.Patient has histologically confirmed advanced solid tumor, who is 1) anti-PD(L)1 relapsed/refractory; 2) platinum-resistant ovarian; 3) anal and rectal cancer; or 4) castrate-resistant prostate cancer.Patient has failed prior standard of care therapies appropriate for their metastatic disease.Patient has at least 1 measurable non-central nervous system (CNS) lesions per RECIST 1.1.Patient has provided consent for pre- and on-treatment biopsies.Eastern Cooperative Performance Status of 0 or 1.Key Exclusion Criteria:Patient has active autoimmune disease or other medical conditions requiring chronic systemic steroid therapy at the time of screening.Patient has an unacceptable intolerance to anti-PD(L)1 monoclonal antibody (Part B Only).Patient has previously participated in a clinical study evaluating a CBL-B inhibitor.Patients has untreated and/or symptomatic metastatic CNS disease.Patient is currently taking any concomitant medications at Screening that have the potential to cause a clinically relevant drug-drug interaction with HST-1011.Patients with a history of gastrointestinal disease that may affect absorption of the study drug, or patients who are not able to take oral medications.Patient has an active infection requiring systemic therapy.Patient has known or suspected infection with SARS-CoV-2 virus.