Abstract DDT01-04: SGN-CD19A: A novel Anti-CD19 antibody drug conjugate

Abstract

Abstract CD19, a member of the immunoglobulin superfamily, is a B-cell specific marker that is found on B cells as early as the pro-B cell stage. CD19 is maintained upon malignant transformation and is expressed in the majority of patients with B-lineage acute lymphocytic leukemia (ALL) and non-Hodgkin lymphoma (NHL). SGN CD19A is a novel antibody-drug conjugate (ADC) composed of a humanized anti-CD19 monoclonal antibody conjugated to the microtubule-disrupting agent monomethyl auristatin F (MMAF) via a maleimidocaproyl (mc) linker. Upon binding to CD19, SGN-CD19A internalizes and releases cys-mcMMAF, which binds to tubulin and induces G2/M arrest and apoptosis in the targeted cells. In mice bearing B-lineage ALL and lymphoma xenografts, SGN-CD19A induced dose-dependent tumor growth delay and extended survival. Two first-in-human, phase 1, dose-escalation studies are ongoing to investigate the safety, tolerability, pharmacokinetics (PK), and antitumor activity of SGN CD19A; one trial in adult and pediatric patients with relapsed or refractory (R/R) B cell ALL or highly aggressive B-cell lymphoma (CT.gov NCT01786096) and the second trial in adult patients with R/R B-cell NHL (CT.gov NCT01786135). Both trials employ a modified continual reassessment method (CRM) to estimate the dose-toxicity relationship and to estimate the maximum tolerated dose. Exploratory analyses include correlation of target (CD19) expression, target saturation, and apoptotic cellular markers with clinical response and clearance of leukemic blasts; dose and PK of SGN-CD19A will also be correlated with target saturation and intracellular levels of cys-mcMMAF. Early PK analyses indicate that plasma SGN-CD19A ADC generally increases with higher doses. Rapid clearance of ADC was observed at low doses in patients with leukemia, suggesting target-mediated drug disposition. Dose escalation of SGN-CD19A is ongoing in both clinical trials. In preliminary safety analyses, SGN-CD19A was generally tolerable at doses examined to date. Encouraging antitumor activity has been observed, with multiple patients achieving complete remissions in both trials. Citation Format: Tina M. Albertson, Lali Sandalic, Baiteng Zhao, Ana Kostic, Che-Leung Law. SGN-CD19A: A novel Anti-CD19 antibody drug conjugate. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr DDT01-04. doi:10.1158/1538-7445.AM2014-DDT01-04