sirolimus and brequinar

Maintenance immunosuppressive drugs act by partially blocking rate-limiting steps in the immune response. The new maintenance immunosuppressive drugs are either inhibitors of de novo synthesis of nucleotides (purines or pyrimidines), or are immunophilin-binding drugs that inhibit signal transduction in lymphocytes. The new inhibitors of de novo nucleotide synthesis include mycophenolate mofetil (MMF), mizoribine (MZ), brequinar (BQR), and leflunomide (LEF). MMF and MZ act to inhibit de novo purine synthesis, by inhibition of inosine monophosphate dehydrogenase (IMPDH). They create a selective immunodeficiency in T and B lymphocytes. MMF is hydrolyzed to mycophenolic acid (MPA), an uncompetitive inhibitor of IMPDH. MPA reduces the pools of guanine nucleotides, and increases some adenine nucleotides, inhibiting the cell cycle. Thus the number of specific effector T and B lymphocytes is reduced by limiting clonal expansion. MZ is a competitive inhibitor of IMPDH, which creates a similar defect. The relative clinical effectiveness of MMF versus MZ is not known. MMF has been approved in a number of countries; MZ has been approved in Japan. The inhibitors of de novo pyrimidine synthesis (BQR, LEF) act on the enzyme dehydroorotate dehydrogenase. Neither is currently in clinical trials in transplantation. The new immunophilin-binding drugs inhibit either the calcium-dependent phosphatase calcineurin (CN) [tacrolimus (or FK-506) and the microemulsion form of cyclosporine (CsA)] or signaling from growth factor receptors [rapamycin (sirolimus)]. Tacrolimus binds to FK binding protein-12 (FKBP-12) to create a complex that inhibits CN. CsA binds to cyclophilin to create a complex that inhibits CN. Inhibition of CN prevents activation of cytokine genes in T cells. The relative clinic effectiveness of tacrolimus versus microemulsion CsA is unknown. Rapamycin inhibits signaling from growth factor receptors, such as IL-2R. Rapamycin binds to FKBP to create a complex that engages proteins called TOR (target of rapamycin), or RAFT (rapamycin and FKBP target), which may be kinases. The result is a block in the ability of cytokine receptors to activate cell cycling, interfering with clonal expression. Deoxyspergualin, a parenteral drug in development for induction or antirejection therapy, may inhibit intracellular chaperoning by Hsc70, a member of the heat shock protein family. It may have its principal effect by inhibiting the activation of transcription factor NF-kappa B i

Topics: Amino Acid Isomerases; B-Lymphocytes; Biphenyl Compounds; Calcineurin; Calmodulin-Binding Proteins; Carrier Proteins; Cyclosporine; Enzyme Inhibitors; Humans; Immunosuppressive Agents; IMP Dehydrogenase; Isoxazoles; Leflunomide; Mycophenolic Acid; Oxidoreductases; Peptidylprolyl Isomerase; Phosphoprotein Phosphatases; Polyenes; Purines; Pyrimidines; Receptors, Cytokine; Ribonucleosides; Signal Transduction; Sirolimus; T-Lymphocytes; Tacrolimus

Topics: Biphenyl Compounds; Cyclosporine; Dose-Response Relationship, Drug; Drug Interactions; Drug Therapy, Combination; Humans; Immunosuppressive Agents; Kidney Transplantation; Models, Theoretical; Polyenes; Sirolimus

Topics: Biphenyl Compounds; Cyclosporine; Guanidines; Humans; Immunosuppressive Agents; Mycophenolic Acid; Polyenes; Ribonucleosides; Sirolimus; Spiro Compounds; Tacrolimus; Transplantation Immunology

Topics: Animals; Antimetabolites; Azathioprine; Biphenyl Compounds; Cell Differentiation; Cyclosporine; Guanidines; Humans; Immunosuppressive Agents; Isoxazoles; Leflunomide; Lymphocytes; Lymphokines; Oligonucleotides, Antisense; Polyenes; Receptors, Cytokine; Ribonucleosides; Signal Transduction; Sirolimus; Tacrolimus

Topics: Animals; Biphenyl Compounds; Cyclosporine; Cyclosporins; Drug Synergism; Humans; Immunosuppressive Agents; Lymphocyte Activation; Models, Biological; Polyenes; Sirolimus; Transplantation Immunology

In summary, many new modalities of immunosuppression after transplantation are being investigated (Fig. 1). These approaches include various new drugs or monoclonal antibodies that target different cell subsets, cellular activation pathways, cellular effector function or mediators (such as cytokines) of effector function, ligands that stabilize cellular interactions, or antimetabolites that preferentially affect lymphocytes (Tables 4 and 5). Because of the excellent early graft and patient survival results after liver transplantation under various current immunosuppressive protocols, future clinical trials using these various new modalities will require large numbers of patients to show statistically significant differences in graft or patient survival. Therefore, other criteria in addition to graft and patient survival must be analyzed to evaluate the importance of new immunosuppressive therapies. These criteria may include incidence of acute or chronic rejection, long-term graft function, incidence of infectious complications, length of hospitalization, drug toxicity, and patient tolerance and compliance with new therapies.

Topics: Alprostadil; Animals; Antibodies, Monoclonal; Biphenyl Compounds; Child; Disease Models, Animal; Dogs; Guanidines; Humans; Immunosuppressive Agents; Liver Transplantation; Mycophenolic Acid; Polyenes; Rats; Sirolimus; Tacrolimus

Topics: Biphenyl Compounds; Cyclosporins; Guanidines; Humans; Immunosuppressive Agents; Kidney; Mycophenolic Acid; Polyenes; Sirolimus; T-Lymphocytes; Tacrolimus; Transplantation Immunology

Topics: Animals; Biphenyl Compounds; Cyclosporine; Guanidines; Humans; Immunosuppressive Agents; Polyenes; Sirolimus; Tacrolimus

Topics: Animals; Biphenyl Compounds; Cyclosporine; Graft Rejection; Guanidines; Humans; Immunosuppressive Agents; Mycophenolic Acid; Polyenes; Ribonucleosides; Sirolimus; Tacrolimus; Xenobiotics

We sought to examine the impact of the preferential activation of Th2 cells on the induction and maintenance of a tolerant state in heart allograft rat recipients treated with a short course of cyclosporine (CsA), sirolimus (SRL) or brequinar (BQR). A quantitative polymerase chain reaction (PCR) method was used to measure the levels of cytokine mRNAs, namely interferon (IFN)-gamma and interleukin (IL)-2 in T helper 1 (Th1) cells and IL-4, IL-5 and IL-10 in Th2 cells. Our main findings were that on day 5 postgrafting allografts from untreated recipients had increased levels of IFN-gamma (216 +/- 119 fg), IL-2 (449 +/- 75 fg), IL-4 (6.2 +/- 1.3 fg), IL-5 (34.8 +/- 9.3 fg) and IL-10 (1554 +/- 184 fg) mRNAs compared with normal hearts. CsA reduced the levels of IFN-gamma, IL-2, IL-5 and IL-10, but not IL-4, mRNAs. SRL did not affect the expression of cytokine mRNAs. BQR decreased the levels of IFN-gamma, IL-2 and IL-10, but not IL-5 or IL-4 mRNAs. Compared with grafts from untreated recipients, those from CsA- or BQR-treated tolerant hosts (day 100) displayed undetectable IL-2 mRNA levels, and reduced levels of IFN-gamma, IL-4 and IL-10 mRNAs. In fact, the patterns of cytokine mRNA expression in grafts from CsA- and BQR-treated tolerant hosts were similar to those of normal hearts. Grafts from SRL-treated tolerant hosts merely showed slightly increased Th2 cell activity. In conclusion the selective activation of Th2 cells is not absolutely required for induction or maintenance of tolerance.

Topics: Animals; Biphenyl Compounds; Cyclosporine; Cytokines; Epitopes; Heart Transplantation; Immunosuppressive Agents; Interferon-gamma; Interleukins; Isoantigens; Lymphocyte Activation; Male; Polyenes; Polymerase Chain Reaction; Rats; Rats, Inbred Strains; RNA, Messenger; Sirolimus; Th1 Cells; Th2 Cells

In the present experiments, a multimodality regimen was developed that included an anti-T cell receptor R73 monoclonal antibody and the pharmacologic agents brequinar (BQR), cyclosporine (CsA), and sirolimus (rapamycin; RAPA) to prolong the survival of small bowel (SB) allografts. BQR was the most potent single drug: the 4.0 or 8.0 mg/kg/day BQR doses delivered every second day (q.o.d.) per gavage for 28 days prolonged the survival of Brown Norway (BN; RT1n) SB allografts in Lewis (LEW; RT1l) recipients from a mean survival time of 10.6 +/- 1.9 days in untreated controls to 29.2 +/- 5.8 days, respectively (both P < 0.001). When treatment was extended to 56 days, 8.0 mg/kg/q.o.d BQR produced a mean survival time of 83.8 +/0 33.8 days (P < 0.001), with 2/5 hosts surviving more than 100 days. In a host-versus-graft model, BQR (8.0 mg/kg/q.o.d) delivered for 28 days with CsA (2.0 mg/kg/day) and RAPA (0.04 mg/kg/day) delivered intravenously for 14 days prolonged the survival of BN SB grafts in LEW recipients to 54.4 +/- 21.0 days (P < 0.001). Extending triple-drug therapy to 42 days induced the prolongation of SB allograft survival to greater than 100 days in 5/7 recipients. Although pretransplant perfusion of the grafts with R73 mAb was ineffective alone, the combination of graft perfusion and a 28-day course of BQR (8.0 mg/kg/q.o.d) in the GVH model indefinitely prolonged LEW graft in F1 recipients. Alternatively, indefinite survival of SB allografts ( > 100 days; P < 0.001) was achieved by the combination of a 14-day course of a triple-drug regimen using each agent at subtherapeutic doses, namely BQR (2.0 mg/kg/q.o.d.), CsA (2.0 mg/kg/day), and RAPA (0.04 mg/kg/day). The state of transplantation tolerance is these hosts was documented by the acceptance of donor-type but not third-party heart allografts.

Topics: Animals; Antibodies, Monoclonal; Antilymphocyte Serum; Biphenyl Compounds; Cyclosporine; Graft Survival; Graft vs Host Disease; Graft vs Host Reaction; Host vs Graft Reaction; Immune Tolerance; Immunosuppressive Agents; Intestine, Small; Male; Perfusion; Polyenes; Rats; Rats, Inbred ACI; Rats, Inbred BN; Rats, Inbred Lew; Receptors, Antigen, T-Cell, alpha-beta; Sirolimus; Time Factors; Transplantation, Homologous

It is hypothesized that the mechanism, or mechanisms, responsible for donor-specific transfusion (DST)/cyclosporine (CsA) immunosuppression is generated by an active immune response that is most dynamic in the immediate peritransplant period and thus might be at the peak of vulnerability to the influences of added immunosuppression. To better define this concept, four immunosuppressive drugs were combined with a d-1 DST and 14-day course of CsA in the ACl-to-Lewis cardiac transplant model. A 5-day course of antithymocyte globulin (ATG) initiated at d-1 or d+4 with DST/CsA reduced survival vs. DST/CsA alone (27.0 +/- 2.6 days and 24.6 +/- 5.7 days vs. 95.3 +/- 16.3 days, P<.05). Delay of initiation to d+7 improved survival to 39.5 +/- 8.9 days. A 5-day course of methylprednisolone (MP) begun at d-1 with DST/CsA decreased survival vs. DST/CsA alone, 59.2 +/- l0.0 days vs. 95.3 +/- 16.3 days, but delay to d+4 improved survival to 110 +/- l8 days, P<.05 vs d-1. A 3-day course of brequinar (Breq) begun at d-1 with DST/CsA increased survival to 244 +/- 48.6 days, while delay to d+4 reduced survival to 49.0 +/- 6.7 days, P<.05 vs. d-1. Finally, a 5-day course of rapamycin (Rapa), was given with d-1 DST/CsA treatment beginning on d-1, d0, d+l, d+3, d+5, and d+7. In this instance, no significant differences in survival were found between timing groups or DST/CsA control. Together, these data support the hypothesis that DST/CsA treatment generates an active immune response that is inhibited by early initiation of ATG or MP, enhanced by early administration of Breq, and unchanged by early administration of Rapa.

Topics: Animals; Antilymphocyte Serum; Biphenyl Compounds; Blood Donors; Blood Transfusion; Cyclosporine; Drug Administration Schedule; Graft Rejection; Graft Survival; Heart Transplantation; Immunosuppressive Agents; Male; Methylprednisolone; Polyenes; Rats; Rats, Inbred ACI; Rats, Inbred Lew; Sirolimus; Time Factors

The effects of cyclosporine (CsA), sirolimus (RAPA), and/or brequinar (BQR) were examined in a vascularized heterotopic heart transplant model in mice. Untreated C3H (H-2k) recipients reject C57 BL/10 (H-2b) heart allografts at a mean survival time (MST) of 7.7 +/- 1.4 days. A 7-d intravenous (i.v.) infusion by osmotic pump of CsA at doses of 5.0, 10.0, or 20.0 mg/kg extended heart allograft survival to 9.8 +/- 1.3 d (NS), 15.0 +/- 5.1 d (P < 0.01) or 15.0 +/- 1.9 d (P < 0.01), respectively. RAPA delivered i.v. for 7 d at a dose of 0.1 mg/kg produced an MST of 13.0 +/- 7.5 d; 0.2 mg/kg, 20.0 +/- 10.9 d; and 0.4 mg/kg, 15.8 +/- 4.1 d (all P < 0.01). A 7-d alternate-day (q.o.d.) course of oral gavage with BQR (0.5, 1.0, or 2.0 mg/kg) produced survivals of 12.0 +/- 2.4 d, 17.6 +/- 3.4 d, and 20.0 +/- 4.1 d, respectively (all P < 0.01). The combination of 2.5 mg/kg CsA with 0.05 mg/kg RAPA extended graft survival to 18.2 +/- 2.9 d (P < 0.01), and 5.0 mg/kg CsA with 0.1 mg/kg RAPA prolonged survival to 23.0 +/- 9.0 d (P < 0.01). These combinations represent synergistic interactions based upon combination index (CI) values of 0.1-0.6. Although 7-d courses of 0.5 mg/kg CsA (7.3 +/- 1.0 d; NS), 0.01 mg/kg RAPA (7.6 +/- 0.9 d; NS), or 0.125 mg/kg BQR (7.6 +/- 0.9 d; NS) were individually ineffective, the triple-drug combination prolonged the MST to 64.6 +/- 32.7 d (P < 0.005; CI = 0.001), with 2/5 grafts beating for more than 100 d. Similar results were produced by 14-day therapy in the BALB/c (H-2d) to C3H combination.

Topics: Animals; Biphenyl Compounds; Cyclosporine; Dose-Response Relationship, Drug; Drug Synergism; Female; Graft Survival; Heart Transplantation; Immunosuppressive Agents; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Mice, Inbred C57BL; Models, Biological; Polyenes; Sirolimus

Topics: Animals; Biphenyl Compounds; Cyclosporine; Drug Synergism; Drug Therapy, Combination; Female; Graft Survival; Heart Transplantation; Immunosuppressive Agents; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Mice, Inbred C57BL; Polyenes; Sirolimus; Transplantation, Homologous

Topics: Animals; Biphenyl Compounds; Cyclosporine; Dogs; Drug Synergism; Drug Therapy, Combination; Female; Graft Survival; Immunosuppressive Agents; Kidney Transplantation; Male; Polyenes; Sirolimus; Transplantation, Homologous

Topics: Animals; Antibodies, Heterophile; Antibody Formation; B-Lymphocytes; Biphenyl Compounds; Cyclosporine; Graft Survival; Guinea Pigs; Immunosuppression Therapy; Immunosuppressive Agents; Mycophenolic Acid; Polyenes; Rats; Rats, Inbred Lew; Sirolimus; Splenectomy; Time Factors; Transplantation, Heterologous

Topics: Animals; Biphenyl Compounds; Cyclosporine; Dose-Response Relationship, Drug; Drug Administration Schedule; Graft Rejection; Heart Transplantation; Immunosuppressive Agents; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Models, Biological; Polyenes; Sirolimus; Tacrolimus; Transplantation, Homologous

Topics: Animals; Biphenyl Compounds; Cricetinae; Cyclosporine; Drug Evaluation, Preclinical; Drug Synergism; Drug Therapy, Combination; Graft Survival; Heart Transplantation; Immunosuppressive Agents; Male; Mesocricetus; Polyenes; Rats; Rats, Inbred Lew; Sirolimus; Transplantation, Heterologous

The rigorous median-effect analysis was used to assess the interactions between cyclosporine and drugs that inhibit nucleotide synthesis pathways. Using in vitro proliferation assays wherein human lymphocytes were triggered by phytohemagglutin, anti-CD3 monoclonal antibody, or mixed lymphocyte reactions, CsA was shown to display additive interactions with 6-mercaptopurine (6-MP), mizorbine (MZB), and mycophenolic acid (MPA), and a synergistic interaction with brequinar (BQR). In the in vitro assays, BQR contributed a further synergistic effect to the double-drug combination CsA/rapamycin (RAPA). Of the four inhibitors of nucleotide synthesis pathways, only BQR noncompetitively inhibited IL-2-stimulated proliferation of the CTLL-2 cell line. Using the in vivo assay of heterotopic Buffalo (BUF, RT-1b) cardiac allografts in Wistar-Furth (WFu, RT-1u) hosts, oral administration of BQR displayed about 100% bioavailability--which, like the bolus intravenous (i.v.) mode, was eight-fold more effective than continuous i.v. infusions. Furthermore median-effect analysis of serial amounts of orally administered BQR demonstrated that it contributes synergistically to the immunosuppressive effects of intravenously delivered CsA/RAPA (0.5/0.01 mg/kg/day). The degree of synergism was proportionate to the extent of the immunosuppression. These findings document the potency of the CsA/RAPA/BQR triple-drug combination and suggest that the synergistic effects may permit dose reductions of each component, thereby mitigating toxicities resulting from the large amounts of individual agents necessary to achieve allo-unresponsiveness.

Topics: Antibodies; Biphenyl Compounds; CD3 Complex; Cell Line; Cyclosporine; Dose-Response Relationship, Drug; Drug Synergism; Drug Therapy, Combination; Humans; Immunosuppressive Agents; Interleukin-2; Lymphocyte Culture Test, Mixed; Phytohemagglutinins; Polyenes; Sirolimus; T-Lymphocytes, Cytotoxic

Topics: Administration, Oral; Animals; Biphenyl Compounds; Cyclosporine; Dose-Response Relationship, Drug; Drug Synergism; Drug Therapy, Combination; Graft Survival; Heart Transplantation; Immunosuppressive Agents; Injections, Intravenous; Male; Polyenes; Rats; Rats, Inbred WF; Sirolimus; Transplantation, Homologous