Study of EO-3021 in Adult Patients With Solid Tumors Likely to Express CLDN18.2

Key Inclusion Criteria: Availability of tumor tissue (archived and fresh tumor biopsy, if medically feasible) Select advanced or metastatic solid tumor that is likely to express CLDN18.2 such as gastric/GEJ, pancreatic and esophageal cancer ≥ 18 years of age ECOG performance status (PS) 0 or 1 at Screening Progressed on or after standard therapy, or are intolerable for available standard therapy, or there is no available standard therapy Have at least one measurable extra-cranial lesion as defined by RECIST v1.1 Adequate organ function Life expectancy > 12 weeks Ability to understand the nature of this study, comply with protocol requirements, and give written informed consent Willingness of men and women of reproductive potential to observe conventional and effective birth control for the duration of treatment and for 3 months following study completion Key Exclusion Criteria: Pregnant or breastfeeding Symptomatic or untreated brain metastases Have previously received CLDN18.2 antibody drug conjugates (ADCs) or any ADC containing an auristatin payload (prior monoclonocal antibody against CLDN18.2 may be eligible) Have peripheral neuropathy Grade ≥2 Have history of non-infectious pneumonitis/interstitial lung disease Have diagnosis of another malignancy, or history of systemic treatment for invasive cancer within last 3 years. Note: Patients with Stage I cancer who have received definitive local treatment and are considered unlikely to recur are eligible. Diagnosis of non-melanoma skin cancer, carcinoma in situ of the cervix or breast, or noninvasive tumor does not affect eligibility Have active ocular surface disease at baseline (based on screening ophthalmic examination) Have serious concurrent illness or clinically relevant active bacterial, fungal or viral infection Have previous hypersensitivity to any known components of EO-3021 or history of severe infusion reaction or hypersensitivity (CTCAE Grade 3 or higher) with monoclonal antibody treatment Clinically significant cardiac disease, including but not limited to symptomatic congestive heart failure, unstable angina, acute myocardial infarction within 6 months of planned first dose, or unstable cardiac arrhythmia requiring therapy (including torsades de pointes) Have history of allogenic hematopoietic stem cell transplantation or solid organ transplantation with ongoing systemic immunosuppressive therapy Patients who are not appropriate candidates for participation in this clinical study for any other reason as deemed by the Investigator