Controlled masking and targeted release of redox-cycling ortho-quinones via a C–C bond-cleaving 1,6-elimination
Lavinia Dunsmore, Claudio D. Navo, Julie Becher, Enrique Gil de Montes, Ana Guerreiro, Emily Hoyt, Libby Brown, Viviane Zelenay, Sigitas Mikutis, Jonathan Cooper, Isaia Barbieri, Stefanie Lawrinowitz, Elise Siouve, Esther M. Martin, Pedro Ruivo, Tiago Rodrigues, Filipa P. da Cruz, Oliver Werz, George S. Vassiliou, Peter Ravn, Gonzalo Jiménez‐Osés, Gonçalo J. L. Bernardes
Abstract
Natural products that contain ortho-quinones show great potential as anticancer agents but have been largely discarded from clinical development because their redox-cycling behaviour results in general systemic toxicity. Here we report conjugation of ortho-quinones to a carrier, which simultaneously masks their underlying redox activity. C-benzylation at a quinone carbonyl forms a redox-inactive benzyl ketol. Upon a specific enzymatic trigger, an acid-promoted, self-immolative C-C bond-cleaving 1,6-elimination mechanism releases the redox-active hydroquinone inside cells. By using a 5-lipoxygenase modulator, β-lapachone, we created cathepsin-B-cleavable quinone prodrugs. We applied the strategy for intracellular release of β-lapachone upon antibody-mediated delivery. Conjugation of protected β-lapachone to Gem-IgG1 antibodies, which contain the variable region of gemtuzumab, results in homogeneous, systemically non-toxic and conditionally stable CD33+-specific antibody-drug conjugates with in vivo efficacy against a xenograft murine model of acute myeloid leukaemia. This protection strategy could allow the use of previously overlooked natural products as anticancer agents, thus extending the range of drugs available for next-generation targeted therapeutics.