Abstract 2687: Dolasynthen–a novel, homogeneous Auristatin F hydroxypropyl amide antibody-drug conjugate platform

Dolasynthen is a novel, fully synthetic, structurally homogeneous platform that enables the construction of ADCs with tunable drug-to-antibody ratios (DAR), from a low of 2 to a high of 24. The resulting ADCs exhibit excellent physicochemical properties and fully homogeneous conjugates can be created through a variety of bioconjugation chemistries. Analogous to our first platform, Dolaflexin®, Dolasynthen is loaded with the proprietary payload Auristatin F hydroxypropylamide (AF-HPA) with precisely defined numbers of the cytotoxin per Dolasynthen scaffold.Studies that evaluate the tolerability and efficacy of Dolasynthen in preclinical models are described herein. ADCs containing a range of DAR values were generated following conjugation of Dolasynthen to two different monoclonal antibodies. The DAR of the ADCs was achieved by controlled reduction of native disulfide bonds in IgG1 antibodies, chromatographic fractionation, or through use of site-specific conjugation technologies. ADCs with both DAR6 and DAR12 were evaluated in vitro and also in vivo in the mouse, rat and monkey, for efficacy, tolerability and PK. Dolasynthen conjugates had excellent physicochemical properties and displayed the expected cell binding and in vitro cytotoxicities. In vivo pharmacology of Dolasynthen ADCs in in vivo xenograft models showed dose-dependent tumor growth inhibition at low mg/kg mAb doses. Tolerability in the rat at multiple doses was determined, including histopathological evaluation. Dolasynthen ADCs showed excellent PK characteristics in mouse, rat and NHP. Overall, the Dolasynthen platform appears to offer significant potential for clinical application. Citation Format: Dorin Toader, Marc Damelin, Anouk Dirksen, Shawn P. Fesler, Scott D. Collins, Barrett J. Nehilla, Jian Xu, Ling Xu, Kalli C. Cattcott, Alex Uttard, Winnie Lee, Susan Clardy, Cheri A. Stevenson, LiuLiang Qin, Patrick R. Conlon, Mariya V. Kozytska, Chen-Ni Chin, David H. Lee, Timothy B. Lowinger. Dolasynthen–a novel, homogeneous Auristatin F hydroxypropyl amide antibody-drug conjugate platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2687.