The trial was terminated for strategic business reasons; the decision was not based on any safety and/or efficacy concerns.

This study aims to evaluate the safety, and early signals of anti-tumor activity of PF-07820435 when administered alone (Part 1A) or in combination with sasanlimab (Part 1B; Part 2) in patients with selected advanced or metastatic solid tumors. Part 1 will be dose-finding and Part 2 of the study will further evaluate PF-07820435 at the recommended dose for combination expansion in patients with selected advanced solid tumors.

Inclusion Criteria:

• Histological or cytological diagnosis of advanced, unresectable, and/or metastatic or relapsed/refractory solid tumor
• Part 1A: Participants with solid tumors where anti-PD-(L)1 is an established treatment. Participants must have progressed on or following prior anti-PD-(L)1 therapy if approved, available, tolerable, and eligible
• Part 1B: Participants either meeting Part 1A criterion, or participants with "cold" solid tumors where anti-PD-(L)1 therapy is not an established treatment
• Part 2: Participants with NSCLC (Arm A) must have received platinum-based chemotherapy and anti-PD-(L)1 or have intolerability to or refusal of standard therapies. NSCLC participants with known activating mutation(s) must also have received prior approved and available targeted therapy(ies) for the associated mutation(s) or have intolerability or documented refusal of these therapies. Participants with UC (Arm B) must have received prior platinum-based chemotherapy, anti-PD-(L)1 therapy, or enfortumab vedotin, or have documented intolerability or refusal of the standard therapy(ies). Additional cohort indication(s) or dose regimens may be added and defined based on emerging data
• At least 1 measurable lesion based on RECIST 1.1 that has not been previously irradiated (Part 1 exceptions permitted after review and approval)
• Able to provide pre-treatment (and optional on-treatment) tumor tissue

Exclusion Criteria:

• Active or history of clinically significant gastrointestinal disease and other conditions that are unresolved or pose a risk to study treatment or procedures
• Active or history of pneumonitis/interstitial lung disease, pulmonary fibrosis requiring treatment with systemic steroid therapy
• Active or history of clinically significant autoimmune disease or other medical condition that required chronic systemic immunosuppressive therapy within recent 2 years
• History of severe immune-mediated adverse event or cytokine release syndrome that was considered related to prior immune modulatory therapy that required immunosuppressive therapy

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.