Abstract 1544: MBK-103, a potent novel conjugation platform-based antibody-drug conjugate, changing therapeutic options in folate receptor alpha positive cancer patients

Abstract Folate receptor alpha (FOLR1) is a clinically validated target, that is overexpressed extracellularly in numerous solid malignancies with a high unmet medical need. Ovarian, non-small cell lung and breast adenocarcinomas are among indications with the highest frequency of FOLR1-positive patients with one out of two patients showing upregulated topoisomerase I expression. MBK-103, an antibody-drug conjugate targeting FOLR1, is based on Mablink’s novel proprietary hydrophilic drug-linker platform. It is comprised of: (i) an Fc-attenuated humanized IgG1 monoclonal antibody, that selectively binds to FOLR1; (ii) a polysarcosine hydrophobicity masking entity allowing for a high drug-to-antibody ratio (DAR) of 8, while improving the pharmacokinetics and tolerability of the drug; (iii) a proprietary dipeptide cleavable unit and iv) exatecan, a potent topoisomerase I inhibitor. MBK-103 showed excellent ex vivo stability in human plasma enabling a prolonged half-life, similar to that of the unconjugated monoclonal antibody. This led to an increased drug exposure, resulting in a potent antitumor efficacy observed in a collection of more than ten in vivo mouse tumor models with a diverse FOLR1 expression, already at doses as low as 1-3 mg/kg. In addition, the distinct mode of action of exatecan along with the unique characteristics of the proprietary drug-linker platform resulted in the in vivo antitumor potency obtained also in colorectal cancer models, in which tubulin-inhibiting agents exhibit only limited therapeutic effects. The compound was also very well tolerated in cynomolgus monkeys with HNSTD at 50 mg/kg and even when administered repeatedly. High conjugation yields along with 100% homogeneity are major drivers of the successful ongoing manufacturing process with planned IND submission in Q4/2023. Citation Format: Warren Viricel, Louise Conilh, Edouard Leroy, Jean-Guillaume Lafay, Frederique Brune, Lenka Kyrych Sadilkova, Charles Dumontet. MBK-103, a potent novel conjugation platform-based antibody-drug conjugate, changing therapeutic options in folate receptor alpha positive cancer patients [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 1544.