Discovery of new drug indications for COVID-19: A drug repurposing approach

International regulatory and publicly-funded initiatives to advance drug repurposing

Introduction

Although drug repurposing holds great potential in addressing unmet needs, successful practical implementation is challenging and has been less widespread than anticipated. Regulators may play a critical role in addressing this, and recent years have seen the conception of regulator-initiated and publicly-funded repurposing initiatives, with significant regulator involvement.

Methods

International regulators and public funders (n = 8) were interviewed to obtain insight in how repurposing can be advanced from a regulatory perspective. Transcripts were thematically analyzed.

Results

Most initiatives employed a broad concept of repurposing. While patient access was the main focus, label extension remained the gold standard. Commonly perceived barriers were a lack of regulatory expertise, limited downstream drug development, insufficient financial incentives, inadequate awareness of challenges, and poor collaboration. Ways for regulators to facilitate repurposing include early and accessible involvement fostering education, collaboration, and awareness. Increased stakeholder engagement, including internationally, was recommended. Legislative changes may enable the current repurposing ecosystem to evolve.

Discussion

Regulators may play a central role in advancing repurposing by reconsidering their responsibilities within the current regulatory framework, both in mitigating repurposing pitfalls and actively encouraging repurposing initiatives by industry and non-traditional drug developers.

Polypharmacology guided drug repositioning approach for SARS-CoV2

Drug repurposing has emerged as an important strategy and it has a great potential in identifying therapeutic applications for COVID-19. An extensive virtual screening of 4193 FDA approved drugs has been carried out against 24 proteins of SARS-CoV2 (NSP1-10 and NSP12-16, envelope, membrane, nucleoprotein, spike, ORF3a, ORF6, ORF7a, ORF8, and ORF9b). The drugs were classified into top 10 and bottom 10 drugs based on the docking scores followed by the distribution of their therapeutic indications. As a result, the top 10 drugs were found to have therapeutic indications for cancer, pain, neurological disorders, and viral and bacterial diseases. As drug resistance is one of the major challenges in antiviral drug discovery, polypharmacology and network pharmacology approaches were employed in the study to identify drugs interacting with multiple targets and drugs such as dihydroergotamine, ergotamine, bisdequalinium chloride, midostaurin, temoporfin, tirilazad, and venetoclax were identified among the multi-targeting drugs. Further, a pathway analysis of the genes related to the multi-targeting drugs was carried which provides insight into the mechanism of drugs and identifying targetable genes and biological pathways involved in SARS-CoV2.

In Silico Models for Anti-COVID-19 Drug Discovery: A Systematic Review

The coronavirus disease 2019 (COVID-19) is a severe worldwide pandemic. Due to the emergence of various SARS-CoV-2 variants and the presence of only one Food and Drug Administration (FDA) approved anti-COVID-19 drug (remdesivir), the disease remains a mindboggling global public health problem. Developing anti-COVID-19 drug candidates that are effective against SARS-CoV-2 and its various variants is a pressing need that should be satisfied. This systematic review assesses the existing literature that used in silico models during the discovery procedure of anti-COVID-19 drugs. Cochrane Library, Science Direct, Google Scholar, and PubMed were used to conduct a literature search to find the relevant articles utilizing the search terms "In silico model," "COVID-19," "Anti-COVID-19 drug," "Drug discovery," "Computational drug designing," and "Computer-aided drug design." Studies published in English between 2019 and December 2022 were included in the systematic review. From the 1120 articles retrieved from the databases and reference lists, only 33 were included in the review after the removal of duplicates, screening, and eligibility assessment. Most of the articles are studies that use SARS-CoV-2 proteins as drug targets. Both ligand-based and structure-based methods were utilized to obtain lead anti-COVID-19 drug candidates. Sixteen articles also assessed absorption, distribution, metabolism, excretion, toxicity (ADMET), and drug-likeness properties. Confirmation of the inhibitory ability of the candidate leads by in vivo or in vitro assays was reported in only five articles. Virtual screening, molecular docking (MD), and molecular dynamics simulation (MDS) emerged as the most commonly utilized in silico models for anti-COVID-19 drug discovery.

The Quest for Secondary Pharmaceuticals: Drug Repurposing/Chiral-Switches Combination Strategy

Drug repurposing toward new medical uses and chiral switches are elements of secondary pharmaceuticals. The drug repurposing and chiral-switches strategies have mostly been applied independently in drug discovery. Drug repurposing has peaked in the search for therapeutic treatments of the Coronavirus Disease 2019 pandemic, whereas chiral switches have been overlooked. The current Perspective introduces the drug repurposing/chiral-switches combination strategy, overviewing representative cases of chiral drugs that have undergone this combination: ketamine, flurbiprofen, fenfluramine, and milnacipran. The deuterium-enabled chiral switches of racemic thalidomide analogs, a variation of the repurposing/chiral-switch combination strategy, is also included. Patenting and regulatory-exclusivity considerations of the combination strategy in the discovery of new medical uses are considered. The proposed combination creates a new synergy of its two elements, overcoming arguments against chiral switches, with better prospects for validation of patents and regulatory exclusivities. The combination strategy may be applied to chiral switches to paired enantiomers. Repurposing/chiral-switch drugs may be 'obvious-to-try'; however, their inventions may be unexpected and their patents nonobvious. Patenting repurposing/chiral-switch combination drugs is not 'evergreening', 'product hopping', and 'me-too'. The expected benefits and opportunities of the combined repurposing/chiral-switch strategy vis-à-vis its two elements are superior pharmacological properties, overcoming arguments against patent validities, challenges of chiral-switch patents, reduced expenses, shortened approval procedures, and higher expectations of regulatory exclusivities.

Deuterated Drugs and Biomarkers in the COVID-19 Pandemic

Coronavirus disease 2019 (COVID-19) is a highly contagious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Initially identified in Wuhan (China) in December 2019, COVID-19 rapidly spread globally, resulting in the COVID-19 pandemic. Carriers of the SARS-CoV-2 can experience symptoms ranging from mild to severe (or no symptoms whatsoever). Although vaccination provides extra immunity toward SARS-CoV-2, there has been an urgent need to develop treatments for COVID-19 to alleviate symptoms for carriers of the disease. In seeking a potential treatment, deuterated compounds have played a critical role either as therapeutic agents or as internal MS standards for studying the pharmacological properties of new drugs by quantifying the parent compounds and metabolites. We have identified >70 examples of deuterium-labeled compounds associated with treatment of COVID-19. Of these, we found 9 repurposed drugs and >20 novel drugs studied for potential therapeutic roles along with a total of 38 compounds (drugs, biomarkers, and lipids) explored as internal mass spectrometry standards. This review details the synthetic pathways and modes of action of these compounds (if known), and a brief analysis of each study.

Hybrid Approach to Identifying Druglikeness Leading Compounds against COVID-19 3CL Protease

SARS-CoV-2 is a positive single-strand RNA-based macromolecule that has caused the death of more than 6.3 million people since June 2022. Moreover, by disturbing global supply chains through lockdowns, the virus has indirectly caused devastating damage to the global economy. It is vital to design and develop drugs for this virus and its various variants. In this paper, we developed an in silico study-based hybrid framework to repurpose existing therapeutic agents in finding drug-like bioactive molecules that would cure COVID-19. In the first step, a total of 133 drug-likeness bioactive molecules are retrieved from the ChEMBL database against SARS coronavirus 3CL Protease. Based on the standard IC50, the dataset is divided into three classes: active, inactive, and intermediate. Our comparative analysis demonstrated that the proposed Extra Tree Regressor (ETR)-based QSAR model has improved prediction results related to the bioactivity of chemical compounds as compared to Gradient Boosting-, XGBoost-, Support Vector-, Decision Tree-, and Random Forest-based regressor models. ADMET analysis is carried out to identify thirteen bioactive molecules with the ChEMBL IDs 187460, 190743, 222234, 222628, 222735, 222769, 222840, 222893, 225515, 358279, 363535, 365134, and 426898. These molecules are highly suitable drug candidates for SARS-CoV-2 3CL Protease. In the next step, the efficacy of the bioactive molecules is computed in terms of binding affinity using molecular docking, and then six bioactive molecules are shortlisted, with the ChEMBL IDs 187460, 222769, 225515, 358279, 363535, and 365134. These molecules can be suitable drug candidates for SARS-CoV-2. It is anticipated that the pharmacologist and/or drug manufacturer would further investigate these six molecules to find suitable drug candidates for SARS-CoV-2. They can adopt these promising compounds for their downstream drug development stages.