GEN-001 (Live Biotherapeutic Product) and Avelumab Combination Study for Patients With Solid Tumors Who Have Progressed on Anti-PD-(L)1 Therapy

Inclusion Criteria: * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 * Have adequate organ functions as defined in the protocol * Negative childbearing potential * Have ability to swallow and retain oral medication and no clinically significant gastrointestinal abnormalities * Patients with diseases for which no curative therapies are available, and who have progressed on at least two lines of approved therapy for their histological subtypes which includes an anti-PD-1 or anti-PD-L1 based therapy (as mono or combination) * Disease progression on anti-PD-(L)1 based therapy (as monotherapy or combination therapy) and must meet criteria for acquired resistance as defined in the protocol * Patients who have completely recovered from any clinically significant AEs that occurred during prior immunotherapy * Estimated life expectancy of at least 3 months * Objective evidence of disease progression at baseline (Dose Escalation) * Histologically or cytologically confirmed, unresectable, locally advanced, or metastatic NSCLC, SCCHN, and UC (Dose Expansion) * Measurable disease as per RECIST v1.1 defined as at least 1 lesion (Dose Expansion) Exclusion Criteria: * Have experienced primary resistance to anti-PD-(L)1 based therapy * Has experienced a toxicity that led to permanent discontinuation of prior anti-PD-(L)1 based therapy or other immunotherapies * Has active autoimmune disease that has required systemic treatment in the past 2 years * Current use of immunosuppressive medication at time of study entry * Have an active infection requiring antibiotics, antifungal or antiviral agents or have received a course of antibiotics within the previous 4 weeks of starting study treatment * Has received a live vaccine within 4 weeks of starting of study treatment * Known history of, or any evidence of active, non-infectious pneumonitis * Prior solid organ or allogeneic stem cell transplantation * Has had any investigational or anti-tumor treatment within 4 weeks or 5 half-life periods of starting study treatment, had any major surgeries within 4 weeks of starting study treatment * Has received proton pump inhibitors (PPIs) within 2 weeks prior to dosing study treatments * Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis * Has clinically significant (i.e., active) cardiovascular disease * Has known history of uncontrolled intercurrent illness * Has any psychiatric condition that would prohibit the understanding or rendering of informed consent or that would limit compliance with study requirements.