Controlled masking of redox cyclers: a novel β-Glucuronide- Triggered β-Lapachone prodrug for enhanced targeting Julie Becher, Gonçalo Bernardes, Lavinia Dunsmore, Nisita Dutta, Enrique Gil de Montes University of Cambridge, UK AIM: Ortho -quinone natural products have great therapeutic potential, but their clinical use has been limited due to systemic toxicity stemming from the redox activity of the ortho -quinone scaffold. This project discusses the development of a novel β-lapachone prodrug platform that detoxifies ortho -quinones while in circulation via C-alkylation, triggers site-specific release in the tumour microenvironment via β-glucuronidase activity, and controls drug release rate via para -hydroxybenzyl (PHB) self-immolative linker design. The optimized prodrugs will then be conjugated to a targeting carrier moiety for clinical use. MATERIALS AND METHOD: Four prodrug derivatives have been synthesized over 5 steps and characterized. Importantly, indium-mediated C-alkylation was utilized to attach the glucuronide linker to the ortho -quinone carbonyl under mild conditions. The pH-dependent pseudo-first-order drug release kinetics were then examined via HPLC assay, and preliminary cell viability assays were performed on a panel of cancer cell lines. RESULTS: Previously, our group published the discovery of para -aminobenzyl (PAB) C-alkylated ortho -quinone prodrugs that release via 1,6-elimination breaking a C-C bond in a pH-dependent manner. 1 Modelling shows the para -hydroxybenzyl (PHB) derivative should release 10,000X faster at physiological pH. PHB prodrug 11a was synthesized and released faster at physiological pH than the PAB derivative (t 1/2 =54±3hr vs. t 1/2 =13,000±10,000hr respectively) as expected. However, cell viability assays demonstrated incomplete restoration of toxicity due to slow drug release. To accelerate release, lowering the pKa of the PHB phenol was examined by making difluoro ( 11b ) and tetrafluoro ( 11c ) derivatives following a similar synthetic route. 11b (t 1/2 =25±2hr) released faster, while 11c (t 1/2 =1340±270hr) did not show improvement. Next, stabilizing the elimination transition state was explored via the methoxy derivative ( 11d ), which exhibited orders of magnitude faster release (t 1/2 =1.9±0.1hr). CONCLUSIONS: The release rate of a novel β-glucuronide-PHB-β-lapachone prodrug was greatly improved by modulating the pKa and transition state stabilization of the PHB linker. The first-order drug release half-life was improved 2X by lowering phenol pKa, while stabilizing the TS via addition of a methoxy group resulted in 28X faster ortho -quinone release. The synthesis of an optimized derivative combining the beneficial features of each linker and a click handle for carrier attachment is now underway. References 1. 1.Dunsmore, L., Navo, C.D., Becher, J.et al.Controlled masking and targeted release of redox-cyclingortho-quinones via a C–C bond-cleaving 1,6-elimination.Nat. Chem. 14 , 754–765 (2022). https://doi.org/10.1038/s41557-022-00964-7
P03
© The Author(s), 2023
Made with FlippingBook Learn more on our blog