posted on 2021-07-23, 10:14authored byIris K. Sokka, Surachet Imlimthan, Mirkka Sarparanta, Hannu Maaheimo, Mikael P. Johansson, Filip S. Ekholm
Halogenation can
be utilized for the purposes of labeling and molecular
imaging, providing a means to, e.g., follow drug distribution in an
organism through positron emission tomography (PET) or study the molecular
recognition events unfolding by nuclear magnetic resonance (NMR) spectroscopy.
For cancer therapeutics, where often highly toxic substances are employed,
it is of importance to be able to track the distribution of the drugs
and their metabolites in order to ensure minimal side effects. Labeling
should ideally have a negligible disruptive effect on the efficacy
of a given drug. Using a combination of NMR spectroscopy and cytotoxicity
assays, we identify a site susceptible to halogenation in monomethyl
auristatin F (MMAF), a widely used cytotoxic agent in the antibody–drug
conjugate (ADC) family of cancer drugs, and study the effects of fluorination
and chlorination on the physiological solution structure of the auristatins
and their cytotoxicity. We find that the cytotoxicity of the parent
drug is retained, while the conformational equilibrium is shifted
significantly toward the biologically active trans isomer, simultaneously decreasing the concentration of the inactive
and potentially disruptive cis isomer by up to 50%.
Our results may serve as a base for the future assembly of a multifunctional
toolkit for the assessment of linker technologies and exploring bystander
effects from the warhead perspective in auristatin-derived ADCs.