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Rational Design of Azastatin as a Potential ADC Payload with Reduced Bystander Killing.

ABSTRACT: Auristatins are a class of ultrapotent microtubule inhibitors, whose growing clinical popularity in oncology is based upon their use as payloads in antibody-drug conjugates (ADCs). The most widely utilized auristatin, MMAE, has however been shown to cause apoptosis in non-pathological cells proximal to the tumour ("bystander killing"). Herein, we introduce azastatins, a new class of auristatin derivatives encompassing a side chain amine for antibody conjugation. The synthesis of Cbz-azastatin methyl ester, which included the C2-elongation and diastereoselective reduction of two proteinogenic amino acids as key transformations, was accomplished in 22 steps and 0.76?% overall yield. While Cbz-protected azastatin methyl ester (0.13-3.0?nM) inhibited proliferation more potently than MMAE (0.47-6.5?nM), removal of the Cbz-group yielded dramatically increased IC₅₀ -values (9.8-170?nM). We attribute the reduced apparent cytotoxicity of the deprotected azastatin methyl esters to a lack of membrane permeability. These results clearly establish the azastatins as a novel class of cytotoxic payloads ideally suited for use in next-generation ADC development.

SUBMITTER: Hartmann RW

PROVIDER: S-EPMC7756782 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Rational Design of Azastatin as a Potential ADC Payload with Reduced Bystander Killing.

Hartmann Rafael W RW Fahrner Raphael R Shevshenko Denys D Fyrknäs Mårten M Larsson Rolf R Lehmann Fredrik F Odell Luke R LR

ChemMedChem 20201016 24

Auristatins are a class of ultrapotent microtubule inhibitors, whose growing clinical popularity in oncology is based upon their use as payloads in antibody-drug conjugates (ADCs). The most widely utilized auristatin, MMAE, has however been shown to cause apoptosis in non-pathological cells proximal to the tumour ("bystander killing"). Herein, we introduce azastatins, a new class of auristatin derivatives encompassing a side chain amine for antibody conjugation. The synthesis of Cbz-azastatin me ...[more]

PMID: 33063934

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Project description:BackgroundAntibody-drug conjugates (ADCs) are intended to bind to specific positive target antigens and eradicate only tumor cells from an intracellular released payload through the lysosomal protease. Payloads, such as MMAE, have the capacity to kill adjacent antigen-negative (Ag-) tumor cells, which is called the bystander-killing effect, as well as directly kill antigen-positive (Ag+) tumor cells. We propose that a dose-response curve should be independently considered to account for target antigen-positive/negative tumor cells.MethodsA model was developed to account for the payload in Ag+/Ag- cells and the associated parameters were applied. A tumor growth inhibition (TGI) effect was explored based on an ordinary differential equation (ODE) after substituting the payload concentration in Ag+/Ag- cells into an Emax model, which accounts for the dose-response curve. To observe the bystander-killing effects based on the amount of Ag+/Ag- cells, the Emax model is used independently. TGI models based on ODE are unsuitable for describing the initial delay through a tumor-drug interaction. This was solved using an age-structured model based on the stochastic process.Resultsβ∈(0,1] is a fraction parameter that determines the proportion of cells that consist of Ag+/Ag- cells. The payload concentration decreases when the ratio of efflux to influx increases. The bystander-killing effect differs with varying amounts of Ag+ cells. The larger β is, the less bystander-killing effect. The decrease of the bystander-killing effect becomes stronger as Ag+ cells become larger than the Ag- cells. Overall, the ratio of efflux to influx, the amount of released payload, and the proportion of Ag+ cells determine the efficacy of the ADC. The tumor inhibition delay through a payload-tumor interaction, which goes through several stages, may be solved using an age-structured model.ConclusionsThe bystander-killing effect, one of the most important topics of ADCs, has been explored in several studies without the use of modeling. We propose that the bystander-killing effect can be captured through a mathematical model when considering the Ag+ and Ag- cells. In addition, the TGI model based on the age-structure can capture the initial delay through a drug interaction as well as the bystander-killing effect.

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Rational Design of Azastatin as a Potential ADC Payload with Reduced Bystander Killing.

Publications

Rational Design of Azastatin as a Potential ADC Payload with Reduced Bystander Killing.

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