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Mycophenolate mofetil


ACCESSION NB: DB00688 (APRD01602)


TYPE: small molecule


GROUP: approved


DESCRIPTION:
Mycophenolate mofetil is the 2-morpholinoethyl ester of mycophenolic acid (MPA), an immunosuppressive agent, inosine monophosphate dehydrogenase (IMPDH) inhibitor.

VOLUME OF DISTRIBUTION: 3.6 ±1.5 L/kg [intravenous] 4 ±1.2 L/kg [oral administration]

CATEGORIES:
Antineoplastic Agents Enzyme Inhibitors Dermatologic Agents Immunosuppressive Agents

ABSORPTION: Rapidly absorbed following oral administration. In 12 healthy volunteers, the mean absolute bioavailability of oral mycophenolate mofetil relative to intravenous mycophenolate mofetil (based on MPA AUC) was 94%. Food (27 g fat, 650 calories) has no effect on the extent of absorption (MPA AUC) of mycophenolate mofetil.

INDICATION:
For the prophylaxis of organ rejection in patients receiving allogeneic renal, cardiac or hepatic transplants. Mycophenolate mofetil should be used concomitantly with cyclosporine and corticosteroids.

PHARMACODYNAMICS:
Mycophenolate mofetil is a prodrug of mycophenolic acid, an antibiotic substance derived from Penicillium stoloniferum. It blocks de novo biosynthesis of purine nucleotides by inhibition of the enzyme inosine monophosphate dehydrogenase. Mycophenolic acid is important because of its selective effects on the immune system. It prevents the proliferation of T-cells, lymphocytes, and the formation of antibodies from B-cells. It also may inhibit recruitment of leukocytes to inflammatory sites.

MECHANISM OF ACTION:
Mycophenolate mofetil is hydrolyzed to form mycophenolic acid (MPA), which is the active metabolite. 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 without incorporation into DNA. 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, MPA has potent cytostatic effects on lymphocytes. MPA inhibits proliferative responses of T- and B-lymphocytes to both mitogenic and allospecific stimulation. Addition of guanosine or deoxyguanosine reverses the cytostatic effects of MPA on lymphocytes. MPA also suppresses antibody formation by B-lymphocytes. MPA prevents the glycosylation of lymphocyte and monocyte glycoproteins that are involved in intercellular adhesion to endothelial cells and may inhibit recruitment of leukocytes into sites of inflammation and graft rejection. Mycophenolate mofetil did not inhibit early events in the activation of human peripheral blood mononuclear cells, such as the production of interleukin-1 (IL-1) and interleukin-2 (IL-2), but did block the coupling of these events to DNA synthesis and proliferation.

PROTEIN BINDING:
MPA (the active metabolite), at clinically relevant concentrations, is over 98% bound to plasma albumin.

METABOLISM:
Following oral and intravenous dosing, mycophenolate mofetil undergoes complete metabolism to MPA, the active metabolite. Metabolism to MPA occurs presystemically after oral dosing. MPA is metabolized principally by glucuronyl transferase to form the phenolic glucuronide of MPA (MPAG) which is not pharmacologically active. In vivo, MPAG is converted to MPA via enterohepatic recirculation. The following metabolites of the 2-hydroxyethyl-morpholino moiety are also recovered in the urine following oral administration of mycophenolate mofetil to healthy subjects: N-(2-carboxymethyl)-morpholine, N-(2-hydroxyethyl)-morpholine, and the N-oxide of N-(2-hydroxyethyl)-morpholine.

TOXICITY:
Oral (LD50): Acute: 352 mg/kg [Rat], 1000 mg/kg [Mouse], and >6000 mg/kg [Rabbit]. Possible signs and symptoms of acute overdose could include the following: hematological abnormalities such as leukopenia and neutropenia, and gastrointestinal symptoms such as abdominal pain, diarrhea, nausea and vomiting, and dyspepsia.

AFECTED ORGANISMS:
Humans and other mammals