Abstract 3197: Addressing drug metabolism and pharmacokinetics (DMPK) challenges of small molecule-drug conjugates (SMDCs)

Abstract Background: SMDCs are gaining momentum with potential advantages over antibody-drug conjugates (ADCs), eg, better tumor penetration and lack of immunogenicity. We have developed a novel platform technology with tailored solutions for ADCs and SMDCs with intracellular and extracellular cleavage options. Key features of the SMDC technology comprise of a small molecule ligand such as an αvβ3 integrin binder showing efficient tumor homing and a linker extracellularly cleaved by neutrophil elastase (NE) in the tumor microenvironment allowing for seamless release of different payload classes. 1 Our lead SMDC VIP2362 is currently in a Phase 1 clinical trial for the treatment of advanced solid tumors (NCT05712889). SMDCs often have a shorter half-life compared with ADCs, which may result in more frequent dosing schedules. Here we show significant reduction of clearance and drastic prolongation of half-life of SMDCs achieved by adding a second binding moiety. Methods: Payloads such as kinesin spindle protein inhibitors (KSPi), cyclin-dependent kinase 9 inhibitors (CDK9i), and monomethyl auristatin E (MMAE) have been linked via elastase-cleavable linkers to one or, via a branched linker, to two αvβ3 integrin binding moieties. Cytotoxicity of SMDCs was measured in cell lines with or without NE. Monovalent and bivalent SMDCs were investigated in DMPK studies in rats while monitoring the conjugate and the released payload. Results: Payloads were coupled to the NE-cleavable peptides via different linkages. MMAE was conjugated via sterically hindered ester bonds, CDK9i was conjugated via sulfoximide bonds, and KSPi payloads were coupled via amide bonds. Each of these SMDCs was highly stable in plasma and buffer. Without NE, in vitro cytotoxicity of SMDCs in each cell line was poor with IC50 in the micromolar range. In contrast, in the presence of NE, potency increased, and cytotoxicity (IC50) was in the low nanomolar to picomolar range depending on the cell line and payload. In each case, the SMDCs reached similar potency as the free payload indicating efficient cleavage of the SMDC by NE. In DMPK studies of SMDCs in rat, none or trace levels of free payload (0. 1% as compared to the respective conjugates) was measured. With each of the SMDCs and independent of the conjugated payloads, a remarkable impact on exposure was observed when attaching a second binding ligand. The SMDCs with two ligands showed a 37- to 81-fold reduced plasma clearance as compared with the respective monovalent SMDCs, which parallels a 12- to 57-fold increase in half-life (eg, 2. 1 h and 28 h for mono and bivalent MMAE SMDCs respectively). Initial in vivo studies in a cell line-derived xenograft model showed efficacy of bivalent SMDCs with once weekly dosing. Conclusion: Our technology platform comprises NE-cleavable SMDCs with promising options to tune the DMPK profile for a longer half-life. 1. Lerchen et al, AACR (2023). 2. Lerchen et al, Cancers (2023). Citation Format: Anne-Sophie Rebstock, Hans-Georg Lerchen, Harvey Wong, Beatrix Stelte-Ludwig, Mareike Wiedmann, Amy J. Johnson, Raquel Izumi, Ahmed Hamdy. Addressing drug metabolism and pharmacokinetics (DMPK) challenges of small molecule-drug conjugates (SMDCs) abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3197.