<p><strong>Mechanism of Action</strong>: Mycophenolate mofetil is the 2-morpholinoethyl ester of mycophenolic acid (MPA). MPA is a potent, selective, uncompetitive and reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), and therefore inhibits the de novo pathway of guanosine nucleotide synthesis. The mechanism by which MPA inhibits the enzymatic activity of IMPDH appears to be related to the ability of MPA to structurally mimic both nicotinamide adenine dinucleotide cofactor and a catalytic water molecule. This prevents the oxidation of IMP to xanthose-5&rsquo;-monophosphate which is the committed step in de novo guanosine nucleotide biosynthesis. MPA has more potent cytostatic effects on lymphocytes than on other cells because T- and B lymphocytes are critically dependent for their proliferation on de novo synthesis of purines whereas other cell types can utilize salvage pathways.<br />
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<strong>Pharmacodynamics</strong>: Mycophenolic acid, the active metabolite of mycophenolate mofetil, is a non-competitive, reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH). Inhibition of IMPDH blocks the de novo synthesis of guanosine nucleotides which are necessary substrates for DNA and RNA synthesis. Unlike other cell types which can use the salvage pathway, B and T lymphocytes are dependent upon the de novo pathway for the generation of guanosine. Data from in vitro studies indicate that mycophenolic acid and/or mycophenolate mofetil inhibit mixed lymphocyte responses and human peripheral blood lymphocyte proliferation induced by a variety of mitogens and antigens. Mycophenolic acid decreases intracellular pools of guanosine triphosphate (GTP) and deoxyguanosine triphosphate (dGTP) in mitogen-stimulated human peripheral blood monocytes or T lymphocytic cell lines but has no effect on GTP concentrations in human neutrophils.</p>