Abstract 6342: Preclinical safety & pharmacokinetics of AFVT-2101, a tetravalent FRα x CD16A bispecific innate cell engager for the treatment of solid tumors

Abstract

Abstract AFVT-2101 is a novel bispecific innate immune cell engager in development to treat solid tumors. It is comprised of bivalent folate receptor alpha (FRα) and CD16A (FcγRIIIA) binding domains with a silenced IgG1 Fc region. AFVT-2101 is engineered to exert potent and selective immune-mediated antitumor activity with minimal off-tumor toxicity by promoting NK cell and macrophage engagement of FRα-positive tumors. A comprehensive package of IND-enabling studies is currently in progress to support the preclinical safety profile of AFVT-2101. In agreement with target sequence homology, binding affinity of AFVT-2101 against human and cynomolgus monkey FRα and CD16A is highly similar, confirming non-human primate (NHP, specifically cynomolgus monkey) as the only pharmacologically relevant preclinical safety model. The toxicology program includes tissue cross-reactivity assessment against a panel of human and cynomolgus cryosections, single- and repeat-dose range finding (DRF) non-GLP studies and a 4-week IND-enabling GLP study with 4-week recovery period in NHPs. In a single-dose study AFVT-2101 demonstrated non-linear pharmacokinetics when administered as a 2-h IV infusion to male NHPs where the mean Cmax (85.1 and 1620 µg/mL) and AUC168hr (3,430 and 97,000 µg.h/mL) at 3 and 30 mg/kg, respectively, increased supra-proportionally with respect to dose, consistent with target-mediated drug disposition. Half-life was 103-155 h across doses. A DRF study was conducted to characterize toxicity, identify target organs, determine toxicokinetics (TK), immunogenicity (anti-drug antibodies, ADA), and to inform the dose selection of the subsequent 4-week study. AFVT-2101 was administered once-weekly to female NHPs via 2-h IV infusion for a total of 4 doses. Mean Cmax (1120, 3320, 7190 µg/mL) and AUC168hr (83,600, 209,000, 592,000 µg.h/mL) at 30, 75, and 150 mg/kg, respectively, increased in a generally dose-proportional manner with a trend for modest accumulation (<2-fold) upon repeated administration with a half-life of 80-230 h. Exposure did not appear to be impacted by any treatment-emergent ADA. AFVT-2101 was well-tolerated with no test article-related adverse effects on clinical observations, bodyweight, clinical chemistry, hematology, coagulation, anatomic pathology, or immunotoxicity parameters. The no observed adverse effect level (NOAEL) was determined to be 150 mg/kg under the conditions of the study. The safety profile is being further evaluated in an ongoing pivotal 4-week GLP study incorporating standard toxicology endpoints, safety pharmacology (CNS, CV, and respiratory), gross and anatomic pathology, as well as cytokine, immunophenotyping, receptor occupancy, TK, and ADA analyses. In conclusion, AFVT-2101 is well-tolerated in NHPs with a pharmacokinetic and safety profile consistent with its intended clinical application. Citation Format: Wendy Luo, Eric J. Gaukel, Janice A. Lansita, Stephen M. Laczko, Peter Sandy, Daniel J. O'Shannessy, Sudhir Penugonda, Bhavik Manocha, Daniel E. Patterson, Izabela Kozłowska, Séverine Sarlang, Stefan Knackmuss, Daniela Penston, Uwe Reusch, Zoë Johnson. Preclinical safety & pharmacokinetics of AFVT-2101, a tetravalent FRα x CD16A bispecific innate cell engager for the treatment of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6342.