Immunosuppressants tacrolimus

Discovery and development of a novel immunosuppressant. Tacrolimus hydrate (FK-506), macrolide antibiotic with piperidine and tetrahydrofuran fragments 97YZ542. 

Lampen, A., Christians, U., Guengerich, F. P., Watkins, P. B., Koiars, J. C., Bader, A., Dralle, H., Hackbarth, I., Sewing, K. F., Metabolism of the immunosuppressant tacrolimus in the small intestine cytochrome P450 drug interactions, and interindividual variability, Drug Metab. Disp. 1995, 23, 1315-1324. 

Lampen A, Christians U, Guengerich FP, et al. Metabolism of the immunosuppressant tacrolimus in the small intestine cytochrome P450, drug interactions, and interindividual variability. Drug Metab Dispos 1995 23 1315-1324. 

Diltiazem can increase the blood concentration of the macrolide immunosuppressant tacrolimus (38). 

An interaction of nelfinavir with the macrolide immunosuppressant tacrolimus has been reported in a patient co-infected with HIV and hepatitis C virus who had undergone orthotopic liver transplantation (18). The dose of tacrolimus had to be reduced to a 70th of the normal dose to avoid adverse effects. Nelfinavir serum concentrations were not affected by tacrolimus. The authors suggested that this effect had resulted from inhibition of the metabolism of tacrolimus, because both compounds are substrates of CYP3A4. 

Microsomal incubations coupled with mass spectral analysis of products has also been conducted for the H2-receptor antagonist mifentidine (104), the immunosuppressant tacrolimus (169), the antipsychotic drug tiospirone (170),... 

Ali SM, Ahmad A, Sheikh S, Ahmad MU, Rane RC, Kale P, Paithankar M, Saptarishi D, Sehgal A, Maheshwari K, Ahmad I. Polyoxyl 60 hydrogenated castor oil free nanosomal formulation of immunosuppressant tacrolimus pharmacokinetics, safety, and tolerability in rodents and humans. Lit Lmnunophaima-col 2010 10(3) 325-30. 

Amongst the —> immunosuppressive agents besides the —> glucocorticoids the modern nontoxic drugs have become drugs of choice including ciclosporin, tacrolimus or ascomycin. 

FKBP12 is a member of immunophilin family that has prolyl isomerase activity and is related to the cyclophi-lins in function. FKBP12 binds immunosuppressant molecule FK506 (tacrolimus). The FBKP-FK506 complex inhibits calcineurin, a protein phosphatase, thus blocking signal transduction in the T-lymphocyte... 

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). 

The introduction of PP2B (calcinemin) inhibitors revolutionized kidney transplantation. Cyclosporine A and tacrolimus (FK506) are the principal immunosuppressants prescribed for adult and pediatric renal transplantation. Cyclosporine A was in use clinically long before its mechanism of action was elucidated. 

Cyclosporine and tacrolimus are calcineurin inhibitors that are administered as part of immunosuppressive regimens in kidney, liver, heart, lung, and bone marrow transplant recipients. In addition, they are used in autoimmune disorders such as psoriasis and multiple sclerosis. The pathophysiologic mechanism for ARF is renal vascular vasoconstriction.41 It often occurs within the first 6 to 12 months of treatment, and can be reversible with dose reduction or drug discontinuation. Risk factors include high dose, elevated trough blood concentrations, increased age, and concomitant therapy with other nephrotoxic drugs.41 Cyclosporine and tacrolimus are extensively metabolized by... 

Cyclosporine and tacrolimus belong to a class of immunosuppressants called the calcineurin inhibitors. These agents are considered by many to be the cornerstone of medical immunosuppression. The calcineurin inhibitors work by complexingwith cytoplasmic proteins (cyclosporine with cyclophylin and tacrolimus with FK binding protein 12). These complexes then inhibit calcineurin phosphatase, which results in reduced IL-2 gene transcription. The final outcome is a decrease in IL-2 synthesis and a subsequent reduction in T cell activation.7 11 20 21... 

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. 

Tacrolimus has shown the propensity to cause less severe hyperlipidemia when compared with cyclosporine. Thus conversion from cyclosporine-based immunosuppression to tacrolimus-based immunosuppression may be one way to counteract this disease in transplant recipients.66 Studies demonstrate that steroid withdrawal in renal transplant patients lowered total cholesterol by 17% and LDL-C by 16% unfortunately, an 18% decrease in high-density lipoprotein (HDL) levels also was noted in these patients.66... 

Immunosuppressive medications. Steroid minimization and possibly withdrawal are effective strategies for the prevention of NODAT. Also, patients with worsening blood glucose levels after transplantation who are receiving tacrolimus may benefit from conversion to cyclosporine.74... 

Tacrolimus, an immunosuppressant that inhibits T-cell activation, is a useful alternative in severe recalcitrant psoriasis. Although it is not FDA approved for this indication, patients have received oral doses of 0.05 mg/kg daily, with increases up to 0.15 mg/kg daily, depending on results. Adverse effects include diarrhea, nausea, paresthesias, hypertension, tremor, and insomnia. 

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. 

The expression level of intestinal MDR1 mRNA has been utilized to the personalized immunosuppressant therapy with tacrolimus in cases of living-donor liver transplantation (LDLT) [84], Tacrolimus shows wide... 

Figure 23.3 Drug transporters in the intestinal epithelial cells. PEPT1 is the most characterized transporter for intestinal drug absorption. The basolateral peptide transporter, which is not identified at the molecular level, also plays important roles. OATP-B, OCTN2 and MRP3 may be responsible for the intestinal absorption of some drugs. On the contrary, ABC transporters such as P-gp located at brush-border membranes mediated the efflux of drugs from intestinal epithelial cells, contributing to the low bioavailabihty of drugs such as the immunosuppressive agent, tacrolimus.

Immunosuppressants Cyclosporine (i) Tacrolimus Dexamethasone Rapamycin Valspodar (PSC833) (i)... 

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