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

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 a histologically confirmed, advanced solid tumor (metastatic, recurrent,
and/or unresectable) in one of the following categories: 1) anti-PD-(L)1
relapsed/refractory; 2) platinum-resistant ovarian cancer; 4) anal cancer; 5) rectal
cancer; or 6) castration-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.