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 at a recommended dose of 2.5 mg/kg every 21 days (Modi 2017). More frequent, fractionated dosing has improved the activity and/or safety of other ADCs. Thus, this study is currently evaluating the safety and efficacy of weekly LV dosing (Days 1, 8, and 15 of every 3-week cycle) in different advanced solid tumors with various LIV-1 expression, including 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, castration resistant prostate cancer, and melanoma. Methods: SGNLVA-005 (NCT04032704) is an open-label, phase 2 study evaluating LV monotherapy in patients with 8 different advanced solid tumors in two parts (administered as a 30 minute intravenous infusion [IV]: Part A LV 2.5 mg/kg IV every 3 weeks [up to n = 72 total]; Part B LV 1.0 or 1.25 mg/kg every 1 week [up to n = 252 total]). The study is enrolling previously treated patients with unresectable locally advanced or metastatic disease. Patients must have measurable disease per RECIST v1.1, an Eastern Cooperative Oncology Group (ECOG) score of 0 or 1, and adequate organ function. Cohort specific inclusion criteria require that patients in the gastric and GEJ adenocarcinoma and esophageal squamous cell carcinoma cohorts must have received and progressed during or after no more than 1 prior line of platinum based cytotoxic chemotherapy. Patients in the gastric and GEJ adenocarcinoma cohort may have received prior anti-programmed cell death (ligand) 1 (anti-PD[L]1) therapy (unless contraindicated), and patients with known human epidermal growth factor receptor 2 (HER2) overexpression must have received prior HER2-targeted therapy. Patients are not preselected based on tumor LIV-1 expression. Tumor samples will be analyzed for correlation between LIV-1 expression and tumor response. Safety and efficacy will be monitored throughout the study. Study objectives include objective response rate (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