INTRODUCTION
Coronavirus disease 2019 (COVID-19), an infectious viral disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first reported in Wuhan in the Hubei province of China in December 2019 (Lu et al., 2020). It was declared a public health emergency of international concern and subsequently a global pandemic by World Health Organisation on 20th January 2020 and 11th March 2020 respectively (WHOa, 2020). As at 17th May 2020, there were about 4.5 million confirmed cases of COVID-19 and well over 300 000 deaths resulting from the pandemic globally (WHOb, 2020).
Most of the cases of COVID-19 (about 80%) are asymptomatic (Crosby et al., 2020). In the initial symptomatic phase of the disease, there could be flu-like clinical features like sore throat, dry cough, rhinorrhea, fever and fatigue. Myalgia, shortness of breath, haemoptysis, chest pain, diarrhea, nausea and vomiting, headache and confusion may set in subsequently. In the later phase, complications like acute respiratory distress syndrome (ARDS), pneumonia, arrhythmia and septic shock may set in (Chen et al., 2020; Yan et al., 2020; Huang et al., 2020; Wang, D. et al, 2020). It has also been observed that the symptoms are usually more severe in elderly patients with co-morbidities, in patients with allergic conditions like asthma, and patients with chronic obstructive pulmonary disease (Yang et al., 2020).
As at date, neither drug nor vaccine has been approved for the treatment or prevention of this dreaded pandemic that has plunged the entire world into confusion and fear as well as socio-economic straits.However, a combination of oxygen therapy, mechanical ventilation, drugs like antivirals, antibiotics and other supportive therapies appear to give promising clinical outcomes in the management of COVID-19 patients (Yan et al., 2020). These therapeutic agents are being used on “off-label” basis as they have not been approved for use in COVID-19 patients. This “off-label” use is a way of drug repurposing (drug repositioning) in the bid to find fast-tracked remedy for the disease. Drug repurposing can be said to be the process of identifying and developing new uses for existing drugs (Ashburn & Thor, 2004).
A recent study shows that as at 20th March 2020, about 344 interventional studies had been registered on clinical trials registries including ClinicalTrials.gov, WHO ICTRP, EU Clinical Trials Register, and Cochrane Central Register of Controlled Trials (Lythgoe & Middleton, 2020). Also, WHO had on 18th March 2020 launched a clinical trial called SOLIDARITY to trial the four most promising drug candidates for COVID-19 treatment, namely: chloroquine/hydroxychloroquine, remdesvir, lopinavir/ritonavir and lopinavir/ritonavir/interferon beta-1a. This mega clinical trial is involving participants across over 90 countries (WHOc, 2020). Also, as at 14th April 2020, over 600 clinical trials on this subject matter had been registered with the WHO with about 133 of them being for therapeutic purposes.12 Putting the therapeutic drug candidates together, they fall into about four major therapeutic groups: antivirals, antimalarials, immunosuppressants/immunomodulators and antibiotics. The antiviral candidates include remdesvir, favipiravir, lopinavir/ritonavir, ostelmavir, ganciclovir, peniclovir, umifenovir, triazavirin, baloxavir marboxil, danoprevir/ritonavir, azvudine, sofosbuvir/ledipasvir, sofosbuvir/daclatasvir, darunavir/cobicistat, emtricitabine/tenofovir and ribavarin. The antibiotics include azithromycin, pirfenidone, carimycin and teicoplanin. The antimalarials are the chloroquine/ hydroxychloroquine whereas the immunosuppressants/immunomodulators include glucocorticoids (corticosteroids, methylprednisolone, dexamethasone), anti-cytokines (tocilizumab, adalimumab, eculizumab, sarilumab, ixekizumab) pegylated interferon with ribavarin, lopinavir/ritonavir/interferon beta-1a (Lythgoe & Middleton, 2020; WHOc, 2020). This list is not exhaustive but enough to show that the race to find effective therapeutics for COVID-19 is certainly on and hopefully, some of these drug candidates will make it through the clinical trials and get formal approval.