Mycophenolic acid

Mycophenolate mofetil (MMF) is an immunosuppresant drug used to prevent rejection in organ transplantation.

It is metabolised in the liver to mycophenolic acid which inhibits inosine mononophosphate dehydrogenase, the enzyme which controls the rate of synthesis of guanine monophosphate in the de novo pathway of purine synthesis used in the proliferation of lymphocytes.

MMF is a therefore a potent anti-proliferative, and can be used in place of the older anti-proliferative azathioprine. It is usually used as part of triple therapy including a calcineurin inhibitor (cyclosporine or tacrolimus) and prednisolone.

Compared with azathioprine, it is more lymphocyte-specific, causes less bone marrow suppression and is associated with fewer opportunistic infections. It is also associated with a lower incidence of acute rejection. MMF does cause gastro-intestinal side effects, however, including severe diarrhoea.

The exact role of MMF vs. azathioprine has yet to be conclusively established, but many centres use it in place of azathioprine for high-risk patients, or patients who have already experienced an episode of acute rejection. In long-term immunosuppression, it may be used to avoid calcineurin inhibitors or steroids.