In a recent study published on bioRxiv* preprint server, researchers assessed the cardiac effects of remdesivir.
Nucleoside analogues have long been used to design antiviral drugs. Nucleoside analogues inhibit viral RNA-dependent RNA polymerase (RdRp). Several analogues, such as remdesivir, favipiravir and molnupiravir, have been approved to treat coronavirus disease 2019 (COVID-19).
Remdesivir, a modified adenosine analog, is rapidly converted to a mononucleoside form upon intravenous administration. Subsequently, it is metabolized by host enzymes to the active triphosphate state. The active drug is a selective and potent inhibitor of RdRp of many viruses. Originally used to treat the Ebola virus, remdesivir was approved for COVID-19 amid the pandemic.
Although well tolerated by most patients, commonly reported side effects include rash, nausea, headache, and elevated transaminases. Additionally, cardiovascular events such as bradycardia, hypertension, T wave abnormality and QT interval prolongation have been reported.
Remdesivir distributes to multiple tissues, including the heart; however, the mechanisms underlying cardiovascular complications remain unknown.
Molnupiravir and favipiravir have been used for the treatment of COVID-19. Although various adverse events have been reported, no cardiovascular events have been reported with the use of favipiravir or molnupiravir. Nucleosides or nucleotides also act as ligands for G protein-coupled receptors (GPCRs). Since nucleoside analogs mimic structures, it is speculated that they could activate GPCRs and cause side effects.
The study and the conclusions
In the current study, researchers performed large-scale GPCR screening using the three anti-COVID-19 drugs. The nucleoside analogs were screened against 348 GPCRs in a transforming growth factor (TGF)-α loss assay. Initially, screening was performed using Ga subunits for efficient detection of receptor activation. The authors noted that remdesivir selectively activated the urotensin II receptor (UTS2R).
Concentration-response analysis showed a half-maximal effective concentration (pEC50) of 4.89 for remdesivir, although lower than that of urotensin II, the endogenous ligand of UTS2R. Intriguingly, remdesivir did not induce a β-arrestin recruitment response, unlike urotensin II, and was therefore a G protein-biased ligand. The major and minor remdesivir metabolites, GS-441524 and GS -704277, did not affect UTS2R activation.
Further investigation revealed that activation of the receptor required both the nucleoside base and the McGuigan prodrug fragment of remdesivir. In silico structural docking of UTS2R and remdesivir identified several residues in the orthosteric pocket, potentially stabilizing binding to remdesivir. Three UTS2R residues (T304, N297 and M134) have been shown to interact with remdesivir. Replacing these residues with others abolished the activating potency of remdesivir.
Next, HEK293 cells expressing UTS2R were stimulated with remdesivir and the phosphorylation of extracellular signal regulating kinase (ERK) 1/2 was examined. Remdesivir treatment induced long-lasting ERK1/2 phosphorylation in a dose-dependent manner. Remdesivir-mediated phosphorylation was abolished in the presence of a UTS2R antagonist.
The impact of remdesivir on cardiomyocytes was assessed considering the high expression of UTS2R and urotensin II in cardiovascular systems. The effect of the drug was analyzed on the field potential (FP) using cardiomyocytes derived from human induced pluripotent stem cells (iPS), in which the levels of UTS2R are comparable to those of the heart.
A multi-electrode assay showed that remdesivir-treated cells exhibited prolonged FP duration that was significantly suppressed in the presence of a UTS2R antagonist. The drug’s effects on cardiac contractility were assessed in neonatal rat cardiomyocytes (NRCM). Chronic application of remdesivir to NRCMs resulted in reduced contractility mediated by antagonist UTS2R.
The team constructed 110 missense mutants corresponding to human nucleotide variants (SNVs) in the UTS2R embarrassed. Of these, 44 SNVs showed lower susceptibility to remdesivir compared to the wild-type receptor. In contrast, 47 SNVs had reduced sensitivity to urotensin II.
Notably, four missense SNVs increased susceptibility to remdesivir compared to wild type. Of these, two SNVs had lower sensitivity to urotensin II, while the other two had a moderate/insignificant increase in sensitivity to urotensin II. Individuals with these mutations may be more susceptible to remdesivir/UTS2R-mediated cardiotoxicity.
The authors found that remdesivir selectively activated UTS2R. Activation of UTS2R by urotensin II has been implicated in cardiac dysfunction. Thus, activation of UTS2R by remdesivir in cultured cardiomyocytes induced electrical abnormalities and impaired contractility, resembling cardiac events reported in humans. Notably, adverse effects were negated by antagonizing UTS2R or blocking downstream signaling.
The results suggest that the clinical dose of remdesivir was adequate to trigger UTS2R activation. Notwithstanding the finding that UTS2R is activated by remdesivir leading to cardiotoxicity, a limitation of the study is the lack of clinical evidence.
In summary, the study provided mechanistic insights into remdesivir-mediated cardiac effects and found that it acts as a selective UTS2R agonist.
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, guide clinical practice/health-related behaviors, or treated as established information.