Calcifediol in the Treatment of COVID 19. Modification of Therapeutic Response by Best Available Treatment or Other Treatment or Clinical Variables

The ongoing pandemic of coronavirus disease-19 (COVID-19), caused by the β-coronavirus SARS-CoV-2, is the greatest challenge ever faced by modern medicine and public health systems worldwide. In early outbreaks, approximately 20% progressed to severe symptomatology, of which 5% developed acute respiratory distress syndrome (ARDS), septic shock and multi-organ failure accompanied by a high risk of death. In this scenario, the scientific community employed strong social containment measures and developed vaccines effective in preventing severe clinical forms of COVID-19. Vaccines against the causative virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have shown a preventive effect against the occurrence and severity of COVID-19, and social and economic activities are gradually recovering worldwide.

The rapid mutation rate of this virus family including multiple mutations in the receptor binding domain of the spike protein that have been associated with increased transmissibility and immune evasion after natural infection and vaccination, calls into question both the efficacy of vaccines and their long-term safety and the efficacy of monoclonal antibodies withdrawn for lack of effectiveness. Moreover, the cost/benefit of newly licensed oral antivirals for high-risk patients in higher-income countries remains inadequately documented.

These data update the repositioning strategy employed since the beginning of the pandemic for the use of safe drugs, approved for another indication and reproposed to improve symptoms and clinical outcomes in COVID-19 patients.

Numerous drugs have been investigated with this strategy and many studies have been published. Calcifediol (25OH vitamin D3) is one of them. Calcifediol is the prohormone of the vitamin D endocrine system (VDES). It requires hydroxylation to convert to calcitriol (1,25(OH)2 vitamin D3) , the active form that exerts its functions by activating the vitamin D receptor (VDR), which is expressed in the immune system and many other affected organs in COVID, including the lungs.

Available data strongly suggest that treatment with calcifediol can decrease the severity of COVID-19, decreasing the need for intensive care unit (ICU) admissions and decreasing the risk of mortality. It is a cost-effective treatment, without major adverse effects, and widely available, which could have positive implications for the treatment of the disease worldwide.