COVID-19 Drug Development: A Therapeutic Prescription Drug Overview

Several existing antiviral medications used for HIV/AIDS, malaria, Middle East respiratory syndrome (MERS), and severe acute respiratory syndrome (SARS) are currently being researched as COVID-19 treatments. Some of them have already been moved to clinical trials for COVID-19 treatment. As stated by the author Charlotte Harrison at Canterbury, UK, “Existing antivirals and knowledge gained from the SARS and MERS outbreaks gain traction as the fastest route to fight the current coronavirus epidemic." Similarly Vincent Munster, Chief of the Viral Ecology Unit at the US National Institute of Health, noted, “The general genomic layout and the general replication kinetics and the biology of the MERS, SARS, and [SARS-CoV-2] viruses are very similar, so testing drugs which target relatively generic parts of these coronaviruses is a logical step.”

During the pandemic, the World Health Organization (WHO), European Medicines Agency (EMA), US Food and Drug Administration (FDA), and the Chinese government and drug manufacturers have coordinated with academic and industry researchers to speed development of vaccines, antiviral drugs, and post-infection therapies. The International Clinical Trials Registry Platform of the WHO recorded 536 clinical studies to develop post-infection therapies for COVID-19 infections, with numerous established antiviral compounds that treat other infections undergoing clinical research to be repurposed.

For small-molecule drugs such as antivirals, antibiotics, or antiparasitics, the process of drug discovery, synthesis, and production generally involves three stages.

  • The first yields the active ingredient in the drug, leading to discovery and synthesis of the active ingredient.
  • The second modifies the drug to make it stable and readily absorbed by the body.
  • The third involves drug packaging (e.g., into tablets or vials).

Here we present a quick summary of journal articles published by various authors on small-molecule drugs that are being repurposed for COVID-19 treatment in clinical trials around the world.

Repurposed small molecule drug for COVID-19 treatment

Research objective

Experimental details

Link to the article

antiviral; adenosine nucleotide analog inhibiting RNA synthesis in coronaviruses

In this article, the authors describe in detail the structure-activity relationships (SAR) of the parent nucleoside, prodrug optimization and selection, and synthesis optimization of the development candidate, G. A robust diastereoselective synthesis provided enough quantities of Remdesivir (GS-5734) to enable preclinical efficacy studies.

High-resolution mass spectrometry (HRMS) was performed on an Agilent model 6230 accurate mass time of flight mass spectrometer featuring Agilent Jet Stream Thermal Focusing Technology, with an Agilent 1200 Rapid Resolution HPLC. HRMS chromatography was performed using an Agilent Zorbax Eclipse Plus C18 RRHD 1.8 μm, 2.1 × 50 mm column at 30°C.

Discovery and synthesis of a phosphoramidate prodrug of a pyrrolo[2,1-f][triazin-4-amino] adenine C-nucleoside (GS-5734) for the treatment of Ebola and emerging viruses.


In this article, the authors report GS-5734 antiviral activity against multiple variants of EBOV and other filoviruses in cell-based assays. GS-5734 pharmacokinetics, metabolism, and distribution (DMPK) were examined in non-human primates.

In this DMPK study, the plasma samples were protein precipitated and filtered through an Agilent Captiva 96 well 0.2 μm filter plate. Samples were analyzed on a UPLC coupled to triple quadrupole mass spectrometry.

Therapeutic efficacy of the small molecule GS-5734 against Ebola virus in rhesus monkeys.

tyrosine kinase inhibitor, antineoplastic agent

The authors developed a simple and sensitive method for the simultaneous detection of imatinib mesylate (IM) and its active metabolite, N-desmethyl imatinib (M1), in human serum samples. The method was successfully applied to calculate the pharmacokinetic parameters of chronic myeloid leukemia patients receiving imatinib.

The separation was successfully achieved on an Agilent 1200 series rapid resolution liquid chromatography system (RRLC) using an Agilent ZORBAX Eclipse plus C18 reversed-phase column (50 mm × 2.1 mm, i.d.; 1.8 μm).

Method development and validation for the simultaneous determination of imatinib mesylate and N-desmethyl imatinib using rapid resolution high-performance liquid chromatography coupled with UV-detection.

antiviral, immune suppression

An isocratic reverse phase liquid chromatographic (RP-LC) assay method was developed for the quantitative determination of lopinavir in bulk drug and in pharmaceutical dosage form.

Authors used Agilent Zorbax SB- C18 250´ 4.6 mm, 5 mm for chromatographic separation on an HPLC System.

A stability indicating LC method for Lopinavir.

antiviral, immune suppression

Authors developed a method for rapid, simultaneous determination of Lopinavir and Ritonavir in human plasma with stacked protein precipitations and salting-out assisted extraction (SALLE), and ultrafast LC-MS/MS detection.

The authors used Agilent Zorbax Extend-C18 Rapid Resolution HT column (1.8 μm, 2.1 mm × 30 mm) for ultrafast separation with an LC run of 48 sec.

Rapid, simultaneous determination of Lopinavir and Ritonavir in human plasma by stacking protein precipitations and salting-out assisted liquid/liquid extraction, and ultrafast LC-MS/MS.

antiviral treatment for influenza infection

A new stability-indicating RP-UFLC method was proposed for the determination of Umifenovir in bulk and tablet dosage forms. The method was validated and used for forced degradation studies.

Chromatographic separation was achieved through Agilent C18 column (150 mm × 4.6 mm i.d., 3.5 μm particle size).

New stability indicating ultrafast liquid chromatographic method for the determination of Umifenovir in tablets.

macrolide-type antibiotic

Authors develop and validate a new rapid and more sensitive reverse-phase High-Performance Liquid Chromatography (RP-HPLC) method for the simultaneous estimation of azithromycin, fluconazole, and ornidazole in bulk and pharmaceutical dosage forms

Authors used Agilent Zorbax SB C18 (250 mm x 4.6 mm, 5 µm) for chromatographic separation.

Development and validation of stability-indicating liquid chromatographic method for the simultaneous estimation of azithromycin, fluconazole, and ornidazole in the combined dosage form. 

macrolide-type antibiotic

In this study, a novel and high-throughput liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay was developed and validated for the simultaneous determination of two glycopeptides (vancomycin, teicoplanin) and two small molecule compounds (meropenem, voriconazole) in human plasma.

Target compounds were separated on an Agilent Zorbax SB-C18 column (4.6 × 50 mm, 2.7 μm) and analyzed in positive ion mode using a triple quadrupole mass spectrometer.

An LC-MS-MS Assay for Simultaneous Determination of Two Glycopeptides and Two Small Molecule Compounds in Human Plasma

antimalarial drug

Authors study the affinity of antimalarials for efflux transporters such as P-glycoprotein (P-gp) to understand the drug absorption and pharmacokinetic drug interactions during oral absorption in drug combination therapies. In-vitro Caco-2 cell monolayers were used here as a model for potential drug absorption related problems and P-gp mediated transport of drugs.

In this study, the HPLC analysis was performed using an Agilent 1200 series and a reverse phase chromatographic separation. Agilent Bond Elute OMIX 96 C4 100 μL pipette tips were used for removing salt content in HBSS.

The Interactions of P-glycoprotein with antimalarial drugs, including substrate affinity, inhibition and regulation.