Calcifediol Anhydrous is the anhydrous form of calcifediol, an orally available synthetic form of the calcitriol prohormone calcifediol (25-hydroxyvitamin D), which can be used for vitamin D supplementation, and with potential immunomodulating activity. Upon oral administration, calcifediol is taken up by the body and converted, in the kidneys, to the active form calcitriol (1,25-dihydroxyvitamin D or 1,25(OH)2D). This form increases and normalizes vitamin D plasma levels, which, in turn, regulates calcium plasma levels, and normalizes elevated parathyroid hormone (PTH) levels by suppressing both PTH synthesis, and secretion. Vitamin D modulates and enhances the innate and adaptive immune responses. This may improve unregulated inflammation and prevents the production of pro-inflammatory cytokines. Specifically, vitamin D binds to its receptor vitamin D receptor (VDR) which is widely expressed on immune cells and epithelial cells. This stimulates neutrophils, macrophages, and natural killer (NK) cells, and activates epithelial cells to produce antimicrobial peptides (AMPs). In addition, upon infection, vitamin D promotes the migration of myeloid dendritic cells (mDCs) to lymphoid organs where they activate B- and T-lymphocytes.