Drug Repurposing of the Antiviral Drug Acyclovir: New Pharmaceutical Salts

Abstract

Drug repurposing is becoming interesting in terms of offering advantages over the traditional drug development, once drug discovery is a costly, time-consuming, and highly risky process. In particular, with the coronavirus disease (COVID-19) declared by World Health Organization as a global pandemic, there has emerged a considerable need to develop therapeutic agents capable of preventing viral outbreaks. Concomitantly, well-known and long-used drugs such as acyclovir (Acv) have been tested against COVID-19. Acv is a guanosine analogue that acts as an antiviral drug, commonly used to treat herpes simplex virus (HSV), genital herpes, and varicella zoster virus (VZV). Acv showed to inhibit viral proteases, multiple viral genes expression, and RNA-Dependent RNA Polymerase, helping to recover COVID-19 patients. However, ACV is a BCS class III/IV drug, with low permeability and/or slight water solubility (concentration-dependent). Given the repurposing eligibility of Acv, in this work, two new salts of this drug are presented (nitrate and sulfate), with the aim of improving its pharmacokinetic properties. The new salts were evaluated by X-ray diffraction, and thermal and spectroscopic analyses. A third salt, a chloride one, was also characterized and used for comparison.