On Aug. 30, 2021, OPKO announced completion of enrollment in its Phase 2 trial with RAYALDEEﾮ as a treatment for mild-to-moderate COVID-19. The U.S. trial was expected to enroll approximately 160 subjects, including some with stage 3 or 4 chronic kidney disease who are at higher risk for developing more severe illness. Final enrollment reached 171 subjects and topline data was expected later in 2021.

The REsCue trial randomized symptomatic COVID-19 outpatients in a 1:1 ratio to 4 weeks of treatment with RAYALDEE or placebo and a 2-week follow-up. Dosing with RAYALDEE begins with 300 mcg per day on Days 1, 2 and 3 followed by 60 mcg per day on Days 4 through 27. This dosing regimen is modelled to raise serum total 25-hydroxyvitamin D (25D) within the range of 50-100 ng/mL. The trial’s primary efficacy endpoints are attainment of the targeted 25D level and time to resolution of COVID-19 symptoms. Secondary endpoints include incidence of emergency room or urgent care visits, oxygen saturation below 94%, need for and duration of hospitalization, requirement for mechanical ventilation, mortality rate and severity and duration of illness evidenced by quality-of-life and biochemical measures.

RAYALDEE is an extended-release oral formulation of calcifediol, a prohormone of calcitriol, the active form of vitamin D₃. The product is the first and only medicine approved by the U.S. Food and Drug Administration (FDA) for raising serum total 25D and lowering blood levels of intact parathyroid hormone (iPTH). RAYALDEE, approved to treat secondary hyperparathyroidism (SHPT) in adults with stage 3 or 4 CKD and vitamin D insufficiency, was launched in the U.S. in November 2016.