Abstract 2514: Towards homogenous adcs: A new site-specific antibody conjugation using bacterial transglutaminase (btg-adc)

Abstract

Abstract Purpose : Bacterial Transglutaminase (BTG) allows coupling on endogenous Q295 from an aglycosylated antibody. Here, the work relates to ADCs synthesis through BTG approach on mAbs with single point mutations and the study of stability, pharmacokinetics, as well as in vitro and in vivo efficacy of resulting BTG-ADCs. AdcetriS®, brentuximab vedotin, has been used as comparator, hence for consistency BTG-ADCs have been conjugated with the different linkage strategies (one step and two step) containing distally the same protease sensitive moiety compared to ADCETRIS®, i.e. valine-citrulline-PAB-MMAE. Methods : . For synthesis, a two-step process has been designed consisting of coupling first a linker and coming back with a toxin, and affording versatility and efficiency. The DAR stability was monitored over one week in human and cynomolgus plasma by affinity capture/LC/MS. The pharmacokinetic profile was studied in rat and monitored by affinity capture/LC/MS for conjugated antibody and ELISA for total antibody. In vitro efficacy of ADCs conjugated using BTG was compared side-by-side with ADCETRIS® on Karpas 299 cells. In vivo efficacy was studied in xenogenic nude mice engrafted with Karpas 299 in SC with BTG ADCs or ADCETRIS at doses of 0.6mg/kg. Results: BTG two-step process leads to ADCs with DAR of exactly 2.0 or 4.0 for antibodies with N297S or N297Q single point mutation respectively. The BTG ADCs were stable in human and cynomolgus plasma, with no degradation observed over 15 days in rats and furthermore with favorable total antibody clearance. In vitro efficacy for BTG ADCs DAR=4.0 was comparable to ADCETRIS (mean DAR=4) with respect to EC50 and plateau. In vivo efficacy for BTG ADC was demonstrated to be at least equivalent to ADCETRIS®. Conclusions: Pre-clinical proof of concept is demonstrated for BTG coupling. When considering versatility, speed and efficiency of the process, BTG-ADC coupling should provide a promising technology for the next generation of homogeneous ADCs. Citation Format: Florence Lhospice, Delphine Bregeon, Christian Belmant, Agnes Represa, Angelique Boedec, Yannis Morel, Patrick Dennler, Roger Schibli, François Romagne. Towards homogenous adcs: A new site-specific antibody conjugation using bacterial transglutaminase (btg-adc). [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 2514. doi:10.1158/1538-7445.AM2014-2514