Binding of the small-molecule kinase inhibitor ruxolitinib to membranes does not disturb membrane integrity

Drug-Membrane Interactions: Effects of Virus-Specific RNA-Dependent RNA Polymerase Inhibitors Remdesivir and Favipiravir on the Structure of Lipid Bilayers

The two RNA-dependent RNA polymerase inhibitors remdesivir and favipiravir were originally developed and approved as broad-spectrum antiviral drugs for the treatment of harmful viral infections such as Ebola and influenza. With the outbreak of the global SARS-CoV-2 pandemic, the two drugs were repurposed for the treatment of COVID-19 patients. Clinical studies suggested that the efficacy of the drugs is enhanced in the case of an early or even prophylactic application. Because the contact between drug molecules and the plasma membrane is essential for a successful permeation process of the substances and therefore for their intracellular efficiency, drug-induced effects on the membrane structure are likely and have already been shown for other substances. We investigated the impact of remdesivir and favipiravir on lipid bilayers in model and cell membranes via several biophysical approaches. The measurements revealed that the embedding of remdesivir molecules in the lipid bilayer results in a disturbance of the membrane structure of the tested phospholipid vesicles. Nevertheless, in a cell-based assay, the presence of remdesivir induced only weak hemolysis of the treated erythrocytes. In contrast, no experimental indication for an effect on the structure and integrity of the membrane was detected in the case of favipiravir. Regarding potential prophylactic or accompanying use of the drugs in the therapy of COVID-19, the physiologically relevant impacts associated with the drug-induced structural modifications of the membrane might be important to understand side effects and/or low effectivities.

Impact of Selected Small-Molecule Kinase Inhibitors on Lipid Membranes

Small-molecule protein kinase inhibitors are used for the treatment of various diseases. Although their effect(s) on the respective kinase are generally quite well understood, surprisingly, their interaction with membranes is only barely investigated; even though these drugs necessarily come into contact with the plasma and intracellular membranes. Using biophysical methods such as NMR, ESR, and fluorescence spectroscopy in combination with lipid vesicles, we studied the membrane interaction of the kinase inhibitors sunitinib, erlotinib, idelalisib, and lenvatinib; these drugs are characterized by medium log p values, a parameter reflecting the overall hydrophobicity of the molecules, which is one important parameter to predict the interaction with lipid membranes. While all four molecules tend to embed in a similar region of the lipid membrane, their presence has different impacts on membrane structure and dynamics. Most notably, sunitinib, exhibiting the lowest log p value of the four inhibitors, effectively influences membrane integrity, while the others do not. This shows that the estimation of the effect of drug molecules on lipid membranes can be rather complex. In this context, experimental studies on lipid membranes are necessary to (i) identify drugs that may disturb membranes and (ii) characterize drug-membrane interactions on a molecular level. Such knowledge is important for understanding the efficacy and potential side effects of respective drugs.