Immunosuppressants sirolimus

Concurrent immunosuppressants Sirolimus has been administered concurrently with cyclosporine and corticosteroids. The efficacy and safety of the use of sirolimus in combination with other immunosuppressive agents have not been determined. Renai function impairment Mean serum creatinine was increased and mean glomerular filtration rate was decreased in patients treated with sirolimus and cyclosporine compared with those treated with cyclosporine and placebo or azathioprine controls. Monitor renal function during the administration of maintenance immunosuppression regimens including sirolimus in combination with cyclosporine, and consider appropriate adjustment of the immunosuppression... 

To provide optimal immunosuppressant effects, sirolimus is typically combined with glucocorticoids or other immunosuppressants. Sirolimus exerts a number of other beneficial effects, including the ability to inhibit smooth muscle proliferation in blood vessel walls. For this reason, sirolimus is sometimes incorporated into drug-eluting stents that is, a supportive tubular structure (stent) is placed in the lumen of a partially occluded artery, and the drug is released slowly from the stent to help reduce vessel occlusion.64... 

Elloso MM, Azrolan N, Sehgal SN, et al. Protective effect of the immunosuppressant sirolimus against aortic atherosclerosis in apo E-deficient mice. Am J Transplant 2003 3 562-569. 

Lampen A, Zhang Y, Hackbarth I, et al. Metabolism and transport of the macrolide immunosuppressant sirolimus in the small intestine. J Pharmacol Exp Ther 1998 285 1104-1112. 

Jacobsen W, Serkova N, Hausen B, Morris RE, Benet LZ, Christians U. Comparison of the in vitro metabolism of the macrohde immunosuppressants sirolimus and RAD. Transplant Proc 2001 33 514-515. 

Oswald S, Nassif A, Modess C, Keiser M, Hanke U, Engel A, Lutjohaim D, Weitschies W, Siegmund W. Pharmacokinetic and pharmacodynamic interactions between the immunosuppressant sirolimus and the lipid-lowering drug ezetimibe in healthy volunteers. Clin Pharmacol Ther 2010 87(6) 663-7. 

A number of fungal immunosuppressives have been isolated from fermentation broths and demonstrated to have immunotherapeutic efficacy. Other than cyclosporin (35), two fungal metaboHtes, sirolimus (36), previously known as rapamycin (80), and FK-506 (37) (81) are in various stages of development (see Antibiotics, macrolides). 

Immunosuppression induced by sirolimus (36) appears to be mediated by a mechanism distincdy different from that of either cyclosporin or FK-506. Sirolimus markedly suppresses IL-2 or IL-4-driven T-ceU proliferation. The preclinical studies suggest that sirolimus is a potent immunosuppressive agent in transplantation and autoimmune disease models. The clinical potential of this agent depends on its toxicity profile (80). 

FK-506 (37) interferes with IL-2 synthesis and release and has a cyclosporin-like profile, but is considerably more potent in vitro. IC q values are approximately 100-fold lower. This neutral macroHde suppresses the mixed lymphocyte reaction T-ceU proliferation generation of cytotoxic T-ceUs production of T-ceU derived soluble mediators, such as IL-2, IL-3, and y-IFN and IL-2 receptor expression (83). StmcturaHy, FK-506 is similar to sirolimus. Mycophenolate mofetil (33), brequinar (34), and deoxyspergualin are in various phases of clinical evaluation. Identification of therapeutic efficacy and safety are important factors in the deterrnination of their utiUty as immunosuppressive agents. 

Immunophillins are abundant proteins that catalyze the cis-trans isomerization of proline residues within proteins, generally to aid in protein folding. Immunophillins are not essential proteins, are the intracellular binding proteins of several immunosuppressive drugs. Cyclosporin A exerts its action after binding to cyclophilin. Tacrolimus and sirolimus predominantly bind to the protein FKBP-12 (FK binding protein-12). 

FIGURE 52-2. Center-specific protocols may use RATG, an IL-2RA, or no induction therapy. In any situation, patients receive IV methylprednisolone prior to, during, or immediately following the transplant operation. The patient then will begin the maintenance immunosuppressive regimen. The center-specific protocol will specify which calcineurin inhibitor (cyclosporine or tacrolimus) is used in combination with mycophenolate mofetil or sirolimus with or without steroids. Patients then are monitored for signs and symptoms of rejection. 

Sirolimus is currently the only FDA-approved ToR inhibitor. One of its derivatives, everolimus, is in phase III clinical trials and has been approved for use in some European countries.30 Sirolimus is a macrolide antibiotic that has no effect on cal-cineurin phosphatase.11,31,32 Sirolimus inhibits T cell activation and proliferation by binding to and inhibiting the activation of the mammalian ToR, which suppresses cellular response to IL-2 and other cytokines (i.e., IL-4 and IL-15J.11,31 Studies have shown that sirolimus may be used safely and effectively with either cyclosporine or tacrolimus as a replacement for either azathioprine or mycophenolate mofetil.33 However, when using both sirolimus and cyclosporine as part of a patient s immunosuppressant therapy, because of a drug interaction between the two resulting in a marked increase in sirolimus concentrations, it is recommended to separate the sirolimus and cyclosporine doses by at least 4 hours. Sirolimus also can be used as an alternative agent for patients who do not tolerate calcineurin inhibitors due to nephrotoxicity or other adverse events.34... 

Although tacrolimus therapy is associated with increasing blood pressure, studies have found that tacrolimus has less dramatic effects on GFR and RBF than cyclosporine. In some clinical trials, tacrolimus caused less severe HTN and required significantly fewer antihypertensive medications at both 24 and 60 months after transplantation than cyclosporine.61-63 Thus conversion from cyclosporine-based immunosuppression to tacrolimus-based immunosuppression may be one way to minimize blood pressure increases in transplant recipients. Conversion to sirolimus also may be an alternative to the calcineurin inhibitors in patients with difficult-to-treat HTN because sirolimus therapy is less associated with increased blood pressure. Additionally, withdrawal or tapering of steroid therapy may be an effective strategy for lowering blood pressure. 

Koal et al. (2004) measured four immunosuppressants (cyclosporine A, tacrolimus, sirolimus, and everolimus) in whole blood samples from transplant recipients. The samples were treated first with a protein precipitation step. The supernatant was extracted with a Poros Rl/20 perfusion column (30 x 2.1 mm, 20 tm, Applied Biosystems, Darmstadt, Germany) online. A Luna phenyl hexyl column (2 x 50 mm, Phenomenex, Schaffenburg, Germany) was used for separation. The total run time was 2.5 min. The lower limit of quantitation was 10 ng/mL for cyclosporine A and 1 ng/mL for the other three analytes. 

Sirolimus is a potent immunosuppressive agent. To prevent thrombocytopenia and hypercholesterolemia, optimize efficacy, and reduce organ rejection, assays were developed to monitor concentrations of sirolimus in the whole blood of patients under treatment.40"12 Wallemacq et al.43 developed and validated a simple high-throughput HPLC-MS/MS method to routinely monitor sirolimus... 

Everolimus, a derivative of sirolimus, is a novel macrocyclic immunosuppressant. Risk of acute rejection increases when the everolimus trough level falls below 3 fig/L in renal transplant patients.46... 

Sirolimus is a calcineurin inhibitor that acts as an immunosuppressant. It is administered systemically in the prophylaxis of organ rejection in kidney allograft recipients. It may be used in combination with ciclosporin, particularly initially. However since ciclosporin is markedly nephrotoxic, when sirolimus is used with ciclosporin, monitoring of kidney function is essential. 

Everolimus (40 Afinitor Novartis, 2009), a rapamycin analog, is the 42-0-(2-hydroxyethyl) derivative of sirolimus (34), and is marketed as an immunosuppressant by Novartis under the tradename Afinitor for use in advanced renal cell carcinoma.In March 2009, the FDA approved everolimus (40) for use against advanced renal cell carcinoma after failure of treatment with sunitinib or sorafenib. The drug works similarly to sirolimus as an inhibitor of mTOR (mammalian target of rapamycin), a serine-threonine kinase, downstream of the PI3K/AKT pathway. Everolimus (40) binds to an intracellular protein, EKBP-12, resulting in an inhibitory... 

Increased susceptibility to infection and the possible development of lymphoma may result from immunosuppression. Only physicians experienced in immunosuppressive therapy and management of renal transplant patients should use sirolimus. Manage patients receiving the drug in facilities equipped and staffed with adequate laboratory and supportive medical resources. The physician responsible for maintenance therapy should have complete information needed for the follow-up of the patient. Liver transplantation-excess mortality, graft loss, and hepatic artery thrombosis (HAT) The use of sirolimus in combination with tacrolimus was associated with excess mortality and graft loss in a study in de novo liver transplant recipients. Many of these patients had evidence of infection at or near the time of death. 

Lung transplantation-bronchial anastomotic dehiscence Cases of bronchial anastomotic dehiscence, most fatal, have been reported in de novo lung transplant patients when sirolimus has been used as part of an immunosuppressive regimen. The safety and efficacy of sirolimus as immunosuppressive therapy have not been established in liver or lung transplant patients, and therefore, such use is not recommended. 

Pharmacology Sirolimus, a macrolide immunosuppressive agent, inhibits both T-lymphocyte activation and proliferation that occurs in response to antigenic and cytokine (interleukin-2, -4, and -15) stimulation and also inhibits antibody production. In cells, sirolimus binds to the immunophilin, FK binding protein-12 (FKBP-12), to generate an immunosuppressive complex. 

Some of these metabolites are also detectable in plasma, fecal, and urine samples. Glucuronide and sulfate conjugates are not present in any of the biologic matrices. Sirolimus is the major component in human whole blood and contributes to more than 90% of the immunosuppressive activity. 

Renal transplant patients have a higher prevalence of clinically significant hyperlipidemia. Accordingly, carefully consider the risk/benefit in patients with established hyperlipidemia before initiating an immunosuppressive regimen including sirolimus. 

Rapamycin (sirolimus), a macrolide antibiotic, has been used recently in organ transplantation for its potent immunosuppressive actions by inhibiting both cytokine mediated and growth factor mediated proliferation of smooth muscle cells and lymphocytes [55, 56]. In the RAVEL trial of non-acute single vessel lesions, the Sirolimus-eluting stent was compared to bare metal stent (BMS) in a 1 1 fashion [57]. One-year major adverse cardiovascular events and 6 month neointimal proliferation as assessed by late luminal loss (-0.01 0.33 mm in Sirolimus stent versus 0.80 0.53 mm in BMS) were improved. The Sirolimus-eluting stent thus virtually eliminated in-stent restenosis with no evidence of edge effect, dissection, or in-stent thrombosis. 

Webster AC, Lee VW, Chapman JR, Craig JC. Target of rapamycin inhibitors (sirolimus and everolimus) for primary immunosuppression of kidney transplant recipients a systematic review and meta-analysis of randomized trials. Transplantation 2006 81(9) 1234-48. 

Sirolimus (Rapamune) is structurally related to tacrolimus. It is approved for use as an adjunctive agent in combination with cyclosporine for prevention of acute renal allograft rejection. It blocks IL-2-dependent T-cell proliferation by inhibiting a cytoplasmic serine-threonine kinase. This mechanism of action is different from those of tacrolimus and cyclosporine. This allows sirolimus to augment the immunosuppressive effects of these drugs. 

Although it is not chemically related to cyclosporine, tacrolimus (6.7) has a similar mechanism of action. Tacrolimus is an immunosuppressant macrolide antibiotic derived from Streptomyces tsukubaenis. Like cyclosporine, tacrolimus inhibits the same cytoplasmic phosphatase, calcineurin, which catalyzes the activation of a T-cell-specific transcription factor (NF-AT) involved in the biosyntheses of interleukins such as IL-2. Sirolimus (6.8) is a natural product produced by Streptomyces hydroscopicus, it blocks the ability of T cells to respond to cytokines. 

Selective immunosuppressive agents mycophenolate mofetil sirolimus tacrolimus... 

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