A Study With ABL103 in Subjects With Advanced or Metastatic Solid Tumors

Inclusion Criteria: * Subject must understand and be willing to provide informed consent and be able to comply with the study procedures and restrictions. * Subject must be ≥18 years of age on the day of signing the informed consent form (ICF) * Subject must have a histologically confirmed locally advanced unresectable, or metastatic solid tumor. * Subject must be relapsed or be refractory to available standard therapy or they must be intolerant of available standard therapy. * Subject must meet Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1. * Subject must have an estimated life expectancy of at least 12 weeks. * Subjects must be recovered from AEs from prior therapy to Grade 1 or the baseline grade more than 14 days prior to the first administration of the study drug, except alopecia or Grade 2 toxicities that are deemed stable or irreversible (eg, peripheral neuropathy) * Subjects must have adequate hematologic, renal, hepatic, and thyroid functions confirmed based on the screening laboratory test within 7 days prior to the first administration of ABL103. Exclusion Criteria: * Subject has received prior anticancer monoclonal antibody treatment or investigational therapy within 28 days prior to the first administration of study drug. * Subject has received prior chemotherapy or radiation therapy within 2 weeks or targeted small molecule therapy within 5 half-lives prior to the first administration of study drug. * Subject requires or has received systemic steroid therapy or any other immunosuppressive therapy within 14 days prior to study drug administration. * Subject has a history of drug-induced pneumonitis (interstitial lung disease) or currently has pneumonitis. * Subject has risk factors for bowel obstruction or bowel perforation, including, but not limited to a history of acute diverticulitis, intra-abdominal abscess, and abdominal carcinomatosis. * Subject discontinued from prior immunomodulatory therapy due to any intolerable immune-related adverse events (irAEs) requiring systemic steroid treatment. * Subject has received prior treatment with anti-B7-H4 antibody and/or anti-4-1BB antibody.