Hydrogen Sulfate Guided Therapy With STS for COVID-19 Patients in Need of Critical Care: The H4COVID Open-label, Randomized, Triple-arm Trial

With the appearance of the COVID-19 pandemic, a race for the discovery of effective treatments to combat SARS-CoV-2 infection and its sequelae commenced. Some patients with COVID-19 develop severe acute respiratory syndrome which is the main reason for death. The aim of this study is to spearhead pharmacotherapeutic solutions for COVID-19 patients in the intensive care which have proven to be the hardest to treat due to the high death rate, the long-term allocation of patients in ICU, and the slow recovery that oftentimes leads to residual symptoms and signs. The ever-increasing pressure on the health care system requires finding an effective treatment that can benefit even advanced-stage patients such as those in the intensive care unit.

It was not until recently that the published literature about hydrogen sulfide shifted from revolving around its toxicity to its recognition as an endogenous gaseous signaling molecule and its biological roles. Hydrogen Sulfide (H2S) is a novel gaseous signaling molecule (gasotransmitter) that regulates a variety of physiological functions and provides protection against organ damage (anti-inflammatory, prolonged survival, cardioprotection, antioxidant, and more). H2S also displays beneficial roles in preventing lung disorders such as pneumonia, lung injury (acute/ chronic), and chronic obstructive pulmonary disease and limits viral replication. H2S has been shown to be effective in reversing lung inflammation and improving pulmonary function in various animal models. Based on preclinical data, cystathionine-γ-lyase (CSE)-derived H2S or exogenously applied H2S may block Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) entry into the host cells by interrupting Angiotensin-Converting Enzyme-2 (ACE2) and transmembrane protease serine-2 (TMPRSS2), inhibiting viral replication by attenuating syncytium formation and virus assembly/release, and thus may protect SARS-CoV-2-induced lung damage by suppressing the immune response and the development of inflammation.

Lymphopenia is a key characteristic of COVID-19 patients. Serum H2S was positively correlated with the lymphocyte count and is considered a predictor of mortality. Additionally reduced H2S bioavailability has been suggested as an indicator of enhanced pro-inflammatory responses and endothelial dysfunction. Both these conditions often accompany severe COVID-19. Interleukin-6 (IL-6) has been proposed as the principle pro-inflammatory cytokine involved in the cytokine storm that leads to severe lung injury, respiratory failure, and death by COVID-19. A negative association between IL-6 and serum H2S has been shown to exist. The above-mentioned results led to further evaluation of admission H2S levels as a marker of survival in a recent study. Results showed that serum levels of H2S on day 1 lower than 150.44 micromolars (μM) had the best tradeoff for sensitivity and specificity for death. Thus, administration of a H2S-donor could be a potential remedy for COVID-19 by relieving the damage in lungs and other organs.

Sodium thiosulfate (STS) is a H2S-donor with known safety and efficacy profile in humans for other diseases, including calciphylaxis and cyanide poisoning. STS can be metabolized to H2S and acts as a precursor for H2S signaling. Moreover, in patients presenting with acute coronary syndrome, a phase 1 study was conducted, showing that STS was well tolerated, even with concomitant use of blood pressure lowering drugs. Additionally, the Groningen Intervention study for Preservation of cardiac function with Sodium thiosulfate in ST-elevation myocardial infarction (GIPS-IV trial) is the first trial in humans designed to test the hypothesis that STS provides protection against I/R injury in patients presenting with ST-segment elevation myocardial infarction