A Study of HFB301001 in Adult Patients With Advanced Solid Tumors

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 * Melanoma: * BRAF V600E mutant: must have received at least 2 lines of therapy * BRAF V600E wild type: must have received at least 1 line 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 only: prior immune therapy or immune agonist antibodies * For 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.