VLS-101, a ROR1-Targeting Antibody-Drug Conjugate, Demonstrates a Predictable Safety Profile and Clinical Efficacy in Patients with Heavily Pretreated Mantle Cell Lymphoma and Diffuse Large B-Cell Lymphoma

Introduction: Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncofetal protein that is physiologically expressed during embryogenesis, largely disappears by birth, but can be reexpressed pathologically in transformed tissues of many hematological and solid cancers. VLS-101 is an antibody-drug conjugate (ADC) comprising a rapidly internalizing, humanized monoclonal antibody (UC-961) that recognizes extracellular ROR1, a cleavable linker, and the anti-microtubule cytotoxin, monomethyl auristatin E (MMAE). Methods: This first-in-human, Phase 1 study evaluated the safety, pharmacokinetics (PK), pharmacodynamics (PD), immunogenicity, and efficacy of VLS-101 in patients unselected for tumor ROR1 expression who had previously treated chronic lymphocytic leukemia (CLL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), mantle cell lymphoma (MCL), marginal zone lymphoma (MZL), or Richter transformation lymphoma (RTL). VLS-101 was infused over 30 min every 3 wk until cancer progression or intolerable toxicity. After accrual of 1 patient at the first dose level, cohorts were enrolled by 3+3 dose escalation with additional patients accrued and intrapatient dose escalation permitted to refine estimates of maximum tolerated dose and recommended dosing regimen (RDR). Results: 32 patients were enrolled, including 19 males and 13 females with median (range) ages of 70 (54-84) ys; ECOG performance status (n) of 0 (18), 1 (10), or 2 (4); and tumor types (n) of MCL (15), CLL (7), DLBCL (5), FL (3), MZL (1), and RTL (1). Patients had received a median (range) of 4 (1-24) prior systemic therapies including hematopoietic stem cell transplantation (5) and/or chimeric antigen receptor (CAR)-T or -natural killer (NK) cells (6). Among patients with MCL, 15/15 (100%) had received a Bruton tyrosine kinase inhibitor (BTKi), 13/15 (87%) discontinued the BTKi due to progressive disease, and 2/15 (13%) discontinued for atrial fibrillation after 15.6 or 68.5 months of BTKi therapy. Patients (n) by VLS-101 starting dose were 0.5 (1), 1.0 (3), 1.5 (3), 2.25 (11), and 2.5 (14) mg/kg. With intrapatient dose escalation, many patients (n) received a maximum of 2.25 mg/kg (12) or 2.5 mg/kg (17) during VLS-101 therapy (range: 1 to 13 cycles). Cycle 1 DLTs (n/N) by mg/kg dose level were 0.5 (0/1), 1.0 (0/3), 1.5 (0/3), 2.25 (1/11 [9%] Gr 4 neutropenia), and 2.5 (2/14 [14%]; one Gr 4 neutropenia; one Gr 3 diarrhea of uncertain cause). Gr 4 neutropenia occurred in 9/32 (2