Contribution to the Improvement of an Oral Formulation of Niclosamide, an Antihelmintic Drug Candidate for Repurposing in SARS-CoV-2 and Other Viruses

Niclosamide (NCL) is an effective anthelmintic agent that has been shown to possess broad-spectrum antiviral activity, including against SARS-CoV-2. Due to its poor solubility in aqueous medium, however, the commercially available NCL formulations can act only locally in gastrointestinal worms and are not suitable to achieve plasmatic levels to treat systemic diseases. Consequently, the repurposing of this drug represents a challenge for formulation development with serious risks to the biological availability and can compromise preclinical and clinical outcomes. Herein, we report possible formulation, through the research and development, of stable amorphous solid dispersions to improve its solubility. The results of exploratory screening of NCL-polymer dispersions (performed through X-ray powder diffraction and kinetic solubility studies) indicate that soluplus-niclosamide dispersions can increase its aqueous solubility and, consequently, have the potential to enhance NCL bioavailability. This outcome can be used for the development of oral dosage forms for clinical trials in SARS-CoV-2 and other viruses.