Ranitidine for COVID-19

With the rollout of multiple COVID-19 vaccines, adjunctive treatments for COVID-19 have received less attention. Breakthrough infections post-vaccination (including boosters) underscore the need to continue evaluating repurposed drugs and nutraceuticals as candidate adjunctive treatments. Early clinical studies of antihistamines hypothesized that targeting mast cells (and/or histamine receptors) might benefit COVID-19 patients. In cultured human coronary artery endothelial cells, histamine potentiated spike-mediated angiotensin-converting enzyme 2 internalization; this effect can be blocked by the antihistamine famotidine. This literature review focuses on clinical studies of antihistamines, mast cell stabilizers, and leukotriene receptor antagonists for COVID-19 patients. Several antihistamines and mast cell-targeting agents, including fluvoxamine, cyproheptadine, hydroxyzine, and antihistamines used alone or with azithromycin (dexchlorpheniramine, cetirizine, loratadine, and ebastine), as well as azelastine, famotidine (standard or high-dose), high-dose famotidine with celecoxib, and the flavonoid mast cell stabilizer quercetin, have been reported to be associated with clinical benefits in COVID-19 patients. Multiple studies have reported mixed results for aspirin, montelukast, and normal-dose famotidine; patients taking aspirin often have associated COVID-19 risk factors. In the context of current standard-of-care treatments, clinical studies evaluating candidate adjunctive treatments should carefully consider and avoid known drug–drug interactions, such as those involving celecoxib and dexamethasone. Further clinical studies of the identified treatments targeting mast cells and/or histamine receptors in COVID-19 patients associated with clinical benefits are therefore strongly recommended.

Drug repurposing requires distinguishing established drug class targets from novel molecule-specific mechanisms and rapidly derisking their therapeutic potential in a time-critical manner, particularly in a pandemic scenario. In response to the challenge to rapidly identify treatment options for COVID-19, several studies reported that statins, as a drug class, reduce mortality in these patients. However, it is unknown if different statins exhibit consistent function or may have varying therapeutic benefit. A Bayesian network tool was used to predict drugs that shift the host transcriptomic response to SARS-CoV-2 infection towards a healthy state. Drugs were predicted using 14 RNA-sequencing datasets from 72 autopsy tissues and 465 COVID-19 patient samples or from cultured human cells and organoids infected with SARS-CoV-2. Top drug predictions included statins, which were then assessed using electronic medical records containing over 4,000 COVID-19 patients on statins to determine mortality risk in patients prescribed specific statins versus untreated matched controls. The same drugs were tested in Vero E6 cells infected with SARS-CoV-2 and human endothelial cells infected with a related OC43 coronavirus. Simvastatin was among the most highly predicted compounds (14/14 datasets) and five other statins, including atorvastatin, were predicted to be active in > 50% of analyses. Analysis of the clinical database revealed that reduced mortality risk was only observed in COVID-19 patients prescribed a subset of statins, including simvastatin and atorvastatin. In vitro testing of SARS-CoV-2 infected cells revealed simvastatin to be a potent direct inhibitor whereas most other statins were less effective. Simvastatin also inhibited OC43 infection and reduced cytokine production in endothelial cells. Statins may differ in their ability to sustain the lives of COVID-19 patients despite having a shared drug target and lipid-modifying mechanism of action. These findings highlight the value of target-agnostic drug prediction coupled with patient databases to identify and clinically evaluate non-obvious mechanisms and derisk and accelerate drug repurposing opportunities.