Which immunosuppressive agent binds to the same target as CsA?

The correct choice is Prograft (FK506), as this immunosuppressive agent binds to the same target as Cyclosporine A (CsA), which is calcineurin. Both CsA and FK506 inhibit T-cell activation by blocking the action of calcineurin, which is essential for the activation of the transcription factor NFAT (Nuclear Factor of Activated T-cells). This inhibition prevents the production of cytokines, particularly interleukin-2 (IL-2), which is crucial for T-cell proliferation and differentiation.

As a result, FK506 is often used as an alternative to CsA in transplant patients to prevent organ rejection, as it can offer similar efficacy with a potentially different side effect profile. Other agents listed, such as OKT3, Mycophenolate (CellCept), and azathioprine (Imuran), work through different mechanisms and do not directly target the calcineurin pathway.