Manufacturers: Wyeth pharmaceuticals inc
Sirolimus is an mTOR inhibitor immunosuppressant used to prevent organ transplant rejections, treat lymphangioleiomyomatosis, and treat adults with perivascular epithelioid cell tumors.
Sirolimus is an mTOR inhibitor immunosuppressant used to prevent organ transplant rejections, treat lymphangioleiomyomatosis, and treat adults with perivascular epithelioid cell tumors.
Sirolimus works by inhibiting T-lymphocyte activation and proliferation stimulated by antigens and cytokines such as interleukin (IL)-2, IL-4, and IL-15. In target cells, sirolimus binds to the cytoplasmic receptor FK506-binding protein-12 (FKBP12), an immunophilin, to form an immunosuppressive complex. FKBP12-sirolimus complex binds to and inhibits the activation of the mammalian target of rapamycin (mTOR), which is a serine/threonine-specific protein kinase that regulates cell growth, proliferation, survival, mobility, and angiogenesis. mTOR regulates the downstream signalling pathways involved in cell survival, such as the phosphatidylinositol-3 kinase (PI3K)/Akt signalling pathway. Inhibition of mTOR leads to the suppression of cytokine-driven T-cell proliferation, thus the progression from the G1 to the S phase of the cell cycle is inhibited. Sirolimus also inhibits antibody production. In vitro, sirolimus and other mTOR inhibitors inhibit the production of certain growth factors that may affect angiogenesis, fibroblast proliferation, and vascular permeability. Lymphangioleiomyomatosis is a disorder that primarily affects the lungs. It is characterized by lung tissue infiltration, unregulated alveolar smooth muscle proliferation, and cystic destruction of parenchyma. Although infrequent, it occurs as a symptomatic pulmonary complication in tuberous sclerosis complex (TSC), which is an inherited disorder caused by mutations in TSC genes. Loss of functional TSC gene leads to the aberrant activation of the mTOR signalling pathway, resulting in cellular proliferation and release of lymphangiogenic growth factors. Sirolimus inhibits the activated mTOR pathway and proliferation of alveolar smooth muscle cell proliferation.
Sirolimus is indicated for the prophylaxis of organ rejection in patients aged 13 years or older receiving renal transplants. In patients at low-to moderate-immunologic risk, it is recommended that sirolimus be used initially in a regimen with cyclosporine and corticosteroids; cyclosporine should be withdrawn two to four months after transplantation. In patients at high-immunologic risk (defined as Black recipients and/or repeat renal transplant recipients who lost a previous allograft for immunologic reason and/or patients with high panel-reactive antibodies [PRA; peak PRA level > 80%]), it is recommended that sirolimus be used in combination with cyclosporine and corticosteroids for the first year following transplantation. It is also used to treat lymphangioleiomyomatosis. In the US, albumin-bound sirolimus for intravenous injection is indicated for the treatment of adult patients with locally advanced unresectable or metastatic malignant perivascular epithelioid cell tumour (PEComa). In Europe, it is recommended that sirolimus for the prophylaxis of organ rejection in renal transplants is used in combination with cyclosporin microemulsion and corticosteroids for two to three months. Sirolimus may be continued as maintenance therapy with corticosteroids only if cyclosporin microemulsion can be progressively discontinued. Topical sirolimus is indicated for the treatment of facial angiofibroma associated with tuberous sclerosis in adults and pediatric patients six years of age and older.
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