Inclusion Criteria:

- Previously received the following lines of systemic therapy for the
advanced/metastatic disease:

- Soft tissue sarcoma: at least 1 line of therapy

- Renal cell carcinoma: at least 2 lines of therapy;

- Uterine carcinosarcoma: at least 1 line of therapy;

- Hepatocellular carcinoma: at least 1 line of therapy

- Head and neck squamous cell carcinoma: at least 2 lines of therapy

- Suitable site to biopsy at pre-treatment and on-treatment

- Measurable disease as determined by Response Evaluation Criteria in Solid Tumors
(RECIST) 1.1 and immune-RECIST (iRECIST)

- Eastern Cooperative Oncology Group performance status of 0 or 1.

Exclusion Criteria:

- Systemic anti-cancer therapy within 2 weeks prior to start of study drug.

- For soft tissue sarcoma and uterine carcinosarcoma patients only: prior immune therapy

- Therapeutic radiation therapy within the past 2 weeks

- Prior exposure to agents targeting the OX40 receptor;

- Active autoimmune disease requiring systemic treatment in the previous 2 years;

- Systemic steroid therapy (>10 mg/day of prednisone or equivalent) or any immune
suppressive therapy.

- Persisting toxicity of >Grade 1 relating to prior anti cancer therapy with the
following exceptions:

- All grades of alopecia are acceptable;

- Endocrine dysfunction on replacement therapy is acceptable.

- Severe or unstable medical condition, including uncontrolled diabetes, coagulopathy,
or unstable psychiatric condition;

- Major surgery within 2 weeks of the first dose of study drug;

- History or presence of drug or non-drug induced interstitial lung disease or
pneumonitis ≥Grade 2;

- History of allergic reactions attributed to compounds of similar chemical or biologic
composition to monoclonal antibodies or any excipient of HFB301001;

- Known active malignancy, with the exception of the specific cancer under investigation
in this trial, that required treatment within the previous 2 years.

Note: Other protocol defined Inclusion/Exclusion criteria may apply.

Eligibility last updated 1/19/23. Questions regarding updates should be directed to the study team contact.