Calcineurin

Class

Calcineurin inhibitor

Calcineurin is a calcium- and calmodulin-dependent phosphatase found in most cells, but its activity is especially consequential in T lymphocytes, a class of immune cells central to adaptive immunity. When a T-cell receptor is engaged, intracellular calcium rises and activates calcineurin, which removes phosphate groups from a transcription factor called NFAT (nuclear factor of activated T cells). Dephosphorylated NFAT moves into the nucleus and switches on genes needed for T-cell activation and proliferation, including interleukin-2. Calcineurin inhibitors block this phosphatase step, preventing NFAT activation and thereby dampening the T-cell response without killing the cells outright. This mechanism became foundational for controlling the immune system therapeutically, most classically in preventing organ transplant rejection, and it is also relevant in autoimmune and inflammatory diseases where an overactive T-cell response drives tissue damage, such as certain forms of kidney inflammation. Because calcineurin inhibition acts broadly on T-cell signaling rather than on a single disease-specific pathway, it is used across a range of conditions where suppressing cellular immunity is the therapeutic goal. Different chemical entities and formulations within this class vary in pharmacokinetic properties, such as how steadily drug levels are maintained or where in the gastrointestinal tract the drug is released, which can influence dosing convenience and exposure variability.