Abstract OT2-3-01: SGN-LIV1A: A phase 1 trial evaluating a novel antibody-drug conjugate in patients with LIV-1-positive breast cancer

Abstract

Abstract Background First identified as an estrogen-inducible gene in a breast cancer cell line, LIV-1 is a multispan transmembrane protein of the solute-carrier family 39 with putative zinc transporter and metalloproteinase activity. As a downstream target of STAT3, it promotes the epithelial-to-mesenchymal transition that is important in the malignant progression to metastasis. LIV-1 is expressed in a number of cancers with the highest prevalence and level of expression in breast, prostate, and melanoma. Additionally, LIV-1 has been linked with malignant progression to metastasis and associated with lymph node involvement in breast cancer. Normal tissue expression is predominantly limited to hormonally regulated tissues, including breast and prostate. In metastatic breast cancer tissue samples, the current validated immunohistochemistry assay for LIV-1 has detected moderate to high expression in 82% of samples tested, with 88% positivity in hormone receptor-positive tumors and 73% in triple-negative tumors. SGN-LIV1A is an antibody-drug conjugate (ADC) composed of a humanized anti-LIV-1 monoclonal antibody conjugated to the microtubule-disrupting agent monomethyl auristatin E (MMAE) via a protease-cleavable linker. In vitro, SGN-LIV1A shows target-specific internalization and cytotoxic activity against LIV-1-positive neoplastic cell lines. Significant dose-dependent tumor regression was demonstrated in mouse xenograft models. Methods The primary objective of this first-in-human phase 1, open label, multicenter study is to evaluate the safety and tolerability, and to identify the maximum tolerated dose of SGN-LIV1A using a 3+3 dose-escalation study design. Pharmacokinetics, immunogenicity, and antitumor activity will also be evaluated (ClinicalTrials.gov #NCT01969643). Enrollment to this US-based trial began in late 2013. Eligible patients are adult females who have hormone receptor-positive/HER2-negative or triple-negative metastatic breast cancer. Tumor tissue must be positive for expression of LIV-1 per central assessment. Patients must have received at least 2 prior cytotoxic regimens in the metastatic setting and have measurable disease per RECIST v1.1. Pre-existing neuropathy ≥ Grade 2 is not permitted. SGN-LIV1A is administered intravenously every 3 weeks at protocol-defined doses starting at 0.5 mg/kg. Patients who achieve an objective response or stable disease per RECIST v1.1 are eligible to continue treatment until disease progression. At the completion of dose escalation, expansion cohorts may be opened to enroll patients with specific breast cancer subtypes to further define safety and antitumor activity. Tumor biopsies are being obtained at baseline and after one cycle of treatment to evaluate the role of LIV-1 expression, target saturation, and other tumor-specific measurements in the antitumor activity of SGN-LIV1A. Citation Format: Andres Forero, Howard Burris III, Patricia LoRusso, Jennifer Specht, Kathy Miller, Monica Mita, Minetta C Liu, Shanu Modi, Lajos Pusztai, Django Sussman, Ana Kostic. SGN-LIV1A: A phase 1 trial evaluating a novel antibody-drug conjugate in patients with LIV-1-positive breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr OT2-3-01.