Background: LIV-1 is a transmembrane protein expressed in a variety of cancer types. SGN-LIV1A, or ladiratuzumab vedotin (LV), is a novel investigational humanized IgG1 antibody-drug conjugate (ADC) directed against LIV-1. LV mediates delivery of monomethyl auristatin E (MMAE), which drives antitumor activity through cytotoxic cell killing and induces immunogenic cell death. In a phase 1 study, LV was tolerable and active in heavily pretreated patients with metastatic breast cancer (Modi 2017). This study is currently evaluating the safety and efficacy of LV in different advanced solid tumors with various LIV-1 expression, including metastatic castration-resistant prostate cancer (mCRPC), advanced gastric and gastroesophageal junction (GEJ) adenocarcinoma, esophageal squamous cell carcinoma, small cell lung cancer (SCLC), non-small cell lung cancer (squamous and nonsquamous), head and neck squamous cell carcinoma, and melanoma. Methods: SGNLVA-005 (NCT04032704) is an open-label, phase 2 study evaluating LV monotherapy in patients with previously treated, locally advanced unresectable or metastatic advanced solid tumors, including mCRPC. Patients with mCRPC will receive LV administered as a 30 minute intravenous infusion (IV) at 1.25 mg/kg every 1 week. Up to 30 patients with mCRPC will be enrolled. Patients in the mCRPC cohort must have metastatic castration-resistant disease, have received no more than 1 prior line of androgen receptor-targeted therapy, have ≥28 days between androgen receptor-targeted therapy and start of study treatment, an Eastern Cooperative Oncology Group (ECOG) score of 0 or 1, and adequate organ function. In addition, mCRPC patients with measurable and non-measurable disease are eligible if the protocol-defined criteria are met. mCRPC patients must not have BRCA gene mutations, prior cytotoxic chemotherapy in the metastatic mCRPC setting, prior radioisotope therapy, or radiotherapy to ≥30% of bone marrow. Patients are not preselected based on tumor LIV-1 expression. Their tumor samples will be analyzed for correlation between LIV-1 expression and response. Safety and efficacy will be monitored throughout the study. Study objectives include objective tumor response rate per RECIST 1.1 and prostate-specific antigen (PSA) response rate per Prostate Cancer Clinical Trials Working Group 3 (both primary); safety and tolerability, disease control rate, duration of response, progression-free and overall survival, and pharmacokinetics and immunogenicity (all secondary); and pharmacodynamics. Study accrual is ongoing in the USA, Italy, South Korea, Taiwan, Australia, and the UK. Clinical trial information: NCT04032704