Figure shows DLD1 xenograft study comparing Biaryl PBD ADCs hR-13 vs hR-DGN549

Table shows TROP2 receptor quantification on DLD1 and HT29 cells

Table shows Cytotoxicity Data for Platforms 18 vs 19

Figure shows Plasma stability comparing indole-linked ADC T-13 to N10-linked ADC T-BH

Figure shows Structures of Platforms 6, and 8-16

Figure shows Efficacy in OVCAR-3 xenograft for A) targeted ADCs X-17 and X-19 and B) their corresponding non-binding control ADCs NB-17 and NB-19

Table shows Cytotoxicity comparisons between Biaryl PBD ADCs vs DGN549 ADCs

Table shows Tabulated cell growth inhibition data for NCI-N87 and MDA-MB231 cells in monoculture and coculture when treated with ADCs T-16, T-17, and T-18

Table shows Impact of Tether length and Hydrophilic Modifier on ADC Aggregation and Hydrophobicity

Table shows Payload in vitro potency in various cell lines.

Figure shows Cytotoxicity of Mesothelin ADCs M-16, M-17, and M-19 in NCI-N87 cell line

Structures of PBD Platform 5 and AF-HPA Platform 7 (known as Dolaflexin)

Figure shows In vitro activity of NaPi2b ADCs X-BG and X-19 and payload 4 in the OVCAR3 cell line

Extinction coefficient used to determine DAR for ADCs

Abstract Although microtubule inhibitors (MTI) remain a therapeutically valuable payload option for antibody–drug conjugates (ADC), some cancers do not respond to MTI-based ADCs. Efforts to fill this therapeutic gap have led to a recent expansion of the ADC payload “toolbox” to include payloads with novel mechanisms of action such as topoisomerase inhibition and DNA cross-linking. We present here the development of a novel DNA mono-alkylator ADC platform that exhibits sustained tumor growth suppression at single doses in MTI-resistant tumors and is well tolerated in the rat upon repeat dosing. A phosphoramidate prodrug of the payload enables low ADC aggregation even at drug-to-antibody ratios of 5:1 while still delivering a bystander-capable payload that is effective in multidrug resistant (MDR)-overexpressing cell lines. The platform was comparable in xenograft studies to the clinical benchmark DNA mono-alkylator ADC platform DGN459 but with a significantly better tolerability profile in rats. Thus, the activity and tolerability profile of this new platform make it a viable option for the development of ADCs.