1. Optimization of a pendant-shaped PEGylated linker for antibody-drug conjugates.
- Author
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Tedeschini, T., Campara, B., Grigoletto, A., Zanotto, I., Cannella, L., Gabbia, D., Matsuno, Y., Suzuki, A., Yoshioka, H., Armirotti, A., De Martin, S., and Pasut, G.
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ANTIBODY-drug conjugates , *CATHEPSIN B , *AMINO acid sequence , *PEPTIDE drugs , *CYTOTOXINS - Abstract
In this work, we conceived and developed antibody-drug conjugates (ADCs) that could efficiently release the drug after enzymatic cleavage of the linker moiety by tumoral proteases. The antibody-drug linkers we used are the result of a rational optimization of a previously reported PEGylated linker, PUREBRIGHT® MA-P12-PS, which showed excellent drug loading capacities but lacked an inbuilt drug discharge mechanism, thus limiting the potency of the resulting ADCs. To address this limitation, we chose to incorporate a protease-sensitive trigger into the linker to favor the release of a "PEGless" drug inside the tumor cells and, therefore, obtain potent ADCs. Currently, most marketed ADCs are based on the Val-Cit dipeptide followed by a self-immolative spacer for releasing the drug in its unmodified form. Here, we selected two untraditional peptide sequences, a Phe-Gly dipeptide and a Val-Ala-Gly tripeptide and placed one or the other in between the drug on one side (N-terminus) and the rest of the linker, including the PEG moiety, on the other side (C-terminus), without a self-immolative group. We found that both linkers responded to cathepsin B, a reference lysosomal enzyme, and liberated a PEG-free drug catabolite, as desired. We then used the two linkers to generate ADCs based on trastuzumab (a HER2-targeting antibody) and DM1 (a microtubule-targeted cytotoxic agent) with an average drug-to-antibody ratio (DAR) of 4 or 8. The ADCs showed restored cytotoxicity in vitro , which was proportional to the DM1 loading and generally higher for the ADCs bearing Val-Ala-Gly in their structure. In an ovarian cancer mouse model, the DAR 8 ADC based on Val-Ala-Gly behaved better than Kadcyla® (an approved ADC of DAR 3.5 used as control throughout this study), leading to a higher tumor volume reduction and more prolonged median survival. Taken together, our results depict a successful linker optimization process and encourage the application of the Val-Ala-Gly tripeptide as an alternative to other existing protease-sensitive triggers for ADCs. [Display omitted] • Hydrophilic linkers are necessary to accommodate high drug loadings on antibodies. • The proposed linker features two pendant PEG arms to create a hydrated shell around the drug. • The proposed linker uses a protease-sensitive trigger for controlled "PEGless" drug release. • The linker optimization process led to a DAR 8 ADC active in a xenograft tumor model. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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