This is a phase 1/1b open-label, multicenter, dose-selection study of ciforadenant, an oral small molecule targeting the adenosine-A2A receptor on T-lymphocytes and other cells of the immune system. This trial will study the safety, tolerability, and anti-tumor activity of ciforadenant as a single agent and in combination with atezolizumab, a PD-L1 inhibitor against various solid tumors. Ciforadenant blocks adenosine from binding to the A2A receptor. Adenosine suppresses the anti-tumor activity of T cells and other immune cells.

This is a phase 1/1b open-label, multicenter, dose-selection study of ciforadenant, an oral small molecule targeting the adenosine-A2A receptor on T-lymphocytes and other cells of the immune system. This trial will study the safety, tolerability, and anti-tumor activity of ciforadenant as a single agent and in combination with atezolizumab, an intravenous PD-L1 inhibitor. Ciforadenant blocks adenosine from binding to the A2A receptor. Adenosine suppresses the anti-tumor activity of T cells and other immune cells.

Renal Cell Carcinoma Inclusion Criteria

1. Eastern Cooperative Oncology Group (ECOG) Performance Status 0-2.
2. Documented pathologic diagnosis of clear cell RCC.
3. Relapsed or refractory to 1-2 prior lines of therapy containing at least an anti-PD-(L)1 agent.
4. Measurable disease according to RECIST v1.1
5. Mandatory newly collected tumor biopsy sample obtained prior to treatment initiation.

Renal Cell Carcinoma Exclusion Criteria

1. History of severe hypersensitivity reaction to monoclonal antibodies.
2. Has immunodeficiency or requires treatment with systemic immunosuppressive medication within 2 weeks prior to initiation of study treatment or anticipation of need for systemic immunosuppressant medication during study treatment.
3. Has an active autoimmune disease requiring systemic treatment with in the past 2 years OR a documented history of clinically severe autoimmune disease.

Metastatic Castration-Resistant Prostate Cancer Inclusion Criteria

1. Documentation of disease: progressive CRPC with histologically or cytologically confirmed adenocarcinoma of the prostate.

2. Patients must have radiologically evident metastatic disease, but it can be measurable or non-measurable disease:

   • Measurable disease: nodal, visceral, or extra nodal lesions according to RECIST v1.1 using a diagnostic computed tomography
   • Non-measurable disease: bone only disease (up to 1/3 of study population) per PCWG3 criteria

3. 1-3 prior lines of therapy, including at least one newer generation androgen synthesis inhibitor (e.g., abiraterone) or androgen receptor antagonist (e.g., enzalutamide, apalutamide, darolutamide).

4. Mandatory newly collected tumor biopsy sample obtained prior to treatment initiation.

5. Eastern Cooperative Oncology Group (ECOG) Performance Status 0-2.

Metastatic Castration-Resistant Prostate Cancer Exclusion Criteria

1. Has pure small-cell histology and variants with predominant (≥ 50%) neuroendocrine differentiation.
2. Has a history of severe hypersensitivity reaction to monoclonal antibodies.
3. Has immunodeficiency or requires treatment with systemic immunosuppressive medication within 2 weeks prior to initiation of study treatment or anticipation of need for systemic immunosuppressant medication during study treatment.
4. Has an active autoimmune disease requiring systemic treatment with in the past 2 years OR a documented history of clinically severe autoimmune disease.