Abstract OT1-03-06: Phase 1b/2 study of ladiratuzumab vedotin (LV) in combination with pembrolizumab for first-line treatment of triple-negative breast cancer (SGNLVA-002, trial in progress)

Abstract Background Patients with metastatic triple-negative breast cancer (mTNBC) have a poor prognosis. Treatment combinations of anti-programmed death protein 1 (anti–PD-1) agents with chemotherapy have shown promise in mTNBC. Ladiratuzumab vedotin (LV) is an investigational antibody-drug conjugate directed to LIV-1, a protein highly expressed on breast cancer cells, via a humanized IgG1 monoclonal antibody conjugated to approximately 4 molecules of monomethyl auristatin E (MMAE) by a protease-cleavable linker. LIV-1–mediated delivery of MMAE disrupts microtubules and induces cell cycle arrest and apoptosis. LV has also been shown to drive immunogenic cell death (ICD) to elicit an immune response. LV + pembrolizumab may result in synergistic activity through LV-induced ICD, creating a microenvironment favorable for enhanced anti–PD-1 activity. Interim results from an ongoing, multi-part, open-label study investigating the safety and efficacy of LV in patients with metastatic breast cancer (SGNLVA-001, NCT01969643), showed weekly LV monotherapy at doses up to 1.5 mg/kg were clinically active and generally well tolerated (Tsai 2021). Based on pharmacokinetic and pharmacodynamic modeling and simulation analysis, an intermittent LV + pembrolizumab dosing regimen is being evaluated to further enhance efficacy and improve the tolerability profile. Due to an unmet medical need for patients with unresectable locally advanced (LA)/mTNBC who are programmed death ligand 1 (PD-L1) low or negative, Part D will focus on this patient population. Trial Design SGNLVA-002 (NCT03310957) is an ongoing global single-arm, open-label phase 1b/2 study of LV + pembrolizumab as 1L therapy for patients with unresectable LA/mTNBC. Part D is currently enrolling ~40 patients. Eligible patients must have advanced disease with no prior cytotoxic/anti–PD-1 treatment, PD-L1 combined positive score < 10, measurable disease per RECIST v1.1, and an ECOG performance status ≤1. Patients with Grade ≥2 pre-existing neuropathy or active central nervous system metastases are not permitted. Patients will receive LV at 1.5 mg/kg on Days 1 and 8 every 21 days plus pembrolizumab 200 mg on Day 1 q3w. The primary objectives are to evaluate the safety/tolerability and objective response rate of LV + pembrolizumab. Secondary objectives include duration of response, disease control rate, progression-free survival, and overall survival. Safety and efficacy endpoints will be summarized with descriptive statistics. Global enrollment is ongoing in the US, EU, and Asia. Citation Format: Patrick Dillon, Reva Basho, Hyo S. Han, Hans-Christian Kolberg, Katherine Tkaczuk, George Zahrah, Maria Gion, Herman Voss, Jane Meisel, Timothy Pluard, Jenny Fox, Mafalda Oliveira, Ursa Brown-Glaberman, Erica Stringer-Reasor, Luis Manso, Sherko Küemmel, Lin Chi Chen, Sheng Wu, Brandon Croft, Valentina Boni. Phase 1b/2 study of ladiratuzumab vedotin (LV) in combination with pembrolizumab for first-line treatment of triple-negative breast cancer (SGNLVA-002, trial in progress) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT1-03-06.