First-in-Human, Multicenter, Phase I Study to Evaluate Safety, Tolerability, Pharmacokinetics, and Preliminary Antitumor Activity of YL-18319 Monotherapy in Patients With Locally Advanced/Metastatic Solid Tumors

First-in-Human, multicenter, phase I study to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of YL-18319 monotherapy treatment in patients with advanced solid tumors who have progressed or are intolerant to current standard-of-care therapies.

Inclusion Criteria: * Patients with advanced solid tumors that is unresectable or metastatic who have no standard therapies, or have progressed on or intolerable to standard therapies. Preferential enrollment consideration will be made for patients (at least 2 patients per cohort) with known genetic alterations causing deficiencies of BRCA1, BRCA2, and/or Homologous Recombination Defective (HRD), or selected gene mutations of genome instability or cell cycle control, based on the mechanism of YL-18319. * Patient has at least 1 measurable target lesion or evaluable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 * Demonstrate adequate organ function as defined below. The following screening laboratories should be performed within 7 days of study treatment initiation. Absolute neutrophil count (ANC) ≥1.5 × 109/L Platelets ≥100 × 109/L Hemoglobin ≥9 g/dL Measured and/or Calculated creatinine clearance (CrCl) (Cockroft-Gault) ≥ 60 mL/min Total bilirubin ≤1.5 × ULN (patients with Gilbert's syndrome, total bilirubin ≤3.0 × ULN) Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5 × ULN or ≤5 × ULN for patients with liver metastases * Has an ECOG performance status of 0-1. * Life expectancy at least 3 months. * Women of childbearing potential must have negative serum or urine pregnancy test within 72 hours prior to receiving the first study drug administration. If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required. * For women of childbearing potential, must be willing to use an adequate method of contraception from 30 days prior to the first study drug administration and at least 3 months following last day study drug administration. * Male patients of childbearing potential must be surgically sterile or must agree to use adequate method of contraception during the study and at least 3 months following the last day of study drug administration. * Age ≥18 years at screening. * Able and willing to provide written informed consent and to comply with all protocol-required visits, assessments, and procedures. * Washout from prior anti-tumor therapy: Cytotoxic therapies ≥ 3 weeks Mitomycin C or nitrosoureas ≥ 6 weeks Small molecule agents ≥2 weeks or 5x T1/2, whichever is longer Biologic agents (e.g., antibodies) ≥ 4weeks Immunotherapy (e.g., CTLA4, PD-1, PD-L1 inhibitors) ≥ 4 weeks Radiotherapy ≥ 2 weeks Limited field radiotherapy or palliative radiotherapy ≥ 2 weeks Major surgery, excluding biopsy ≥ 4 weeks (exception: patients may enroll if fully recovered without intolerable or clinically significant adverse effects, but at least 14 days must have elapsed between major surgery and first study drug administration) Study drug with an investigational product, or non-approved use of a drug or device ≥ 4 weeks (≥2 weeks or 5x T1/2, whichever is longer for small molecule agents) Exclusion Criteria: * Known symptomatic brain metastases requiring dexamethasone \>4mg (or equivalent) or requiring steroid dose increase within 14 days prior to the first dose of YL-18319. * Any concurrent chemotherapy, immunotherapy, or biologic or hormonal therapy for cancer treatment. * Unresolved toxicities from prior therapy, defined as having not resolved to NCI CTCAE v.5.0 Grade ≤1 or baseline, with exception of endocrinopathies from prior therapy and successfully treated (such as hypothyroidism), alopecia, vitiligo, and ≤ grade 2 peripheral neuropathy. * Human immunodeficiency virus (HIV) infection with a current or a known history of AIDS-defining illness or HIV infection with a CD4+ T cell count \