A Study to Evaluate ARV-806 in Adults With Advanced Cancer That Has the KRAS G12D Mutation

Inclusion Criteria: Part A: * Histological or cytological diagnosis of unresectable or metastatic solid tumor malignancy, AND * Must have evidence of KRAS G12D mutation in tumor tissue or blood (circulating tumor deoxyribonucleic acid \[ctDNA\]), AND * Must have received prior standard-of-care (SOC) therapy appropriate for their type and stage of disease and have no other available treatment options with curative intent, or, in the opinion of the investigator, would be unlikely to tolerate or derive clinically meaningful benefit from appropriate SOC therapy, AND * Must have at least 1 measurable lesion Part B: * Histological or cytological diagnosis of unresectable or metastatic pancreatic ductal adenocarcinoma (PDAC) with KRAS G12D mutation status confirmed by local testing of tumor tissue using a validated molecular or next-generation sequencing (NGS) testing, AND * Must be willing to provide archival tumor tissue or willing to undergo pretreatment biopsy, AND * Must have received at least one prior standard of care systemic therapy for PDAC (systemic therapy received in the neoadjuvant or adjuvant setting is allowed), AND * Participants must have at least 1 measurable lesion Part A / Part B: * Eastern Cooperative Oncology Group performance status of 0 or 1, * Participants with adequate organ function, * Participants must accept and follow pregnancy prevention guidance. Exclusion Criteria: Part A / Part B: * Active brain metastases * Carcinomatous meningitis * Uncontrolled hypertension despite optimal medical therapy * Prior treatment with a KRAS G12D or a KRAS G12C targeting therapy (pan-KRAS inhibitor/degrader included) * Participants with an inability to comply with listed prohibited treatments * Systemic anticancer therapy within 2 weeks or 5 half-lives (whichever is shorter) or radiation therapy (excluding palliative radiation) within 2 weeks prior to the study intervention treatment. If the last immediate anticancer treatment contained an antibody-based agent(s), then an interval of 28 days or 5 half-lives (whichever is shorter) of the agent(s) is required prior to receiving the study intervention treatment. * Standard 12-lead electrocardiogram that demonstrates clinically relevant abnormalities that may affect participant safety or interpretation of study results