Treatment by mycophenolate mofetil of advanced graft vascular disease in non-human primate recipients of orthotopic aortic allografts

Nanodelivery of Mycophenolate Mofetil to the Organ Improves Transplant Vasculopathy

Inflammation occurring within the transplanted organ from the time of harvest is an important stimulus of early alloimmune reactivity and promotes chronic allograft rejection. Chronic immune-mediated injury remains the primary obstacle to the long-term success of organ transplantation. However, organ transplantation represents a rare clinical setting in which the organ is accessible ex vivo, providing an opportunity to use nanotechnology to deliver therapeutics directly to the graft. This approach facilitates the directed delivery of immunosuppressive agents (ISA) to target local pathogenic immune responses prior to the transplantation. Here, we have developed a system of direct delivery and sustained release of mycophenolate mofetil (MMF) to treat the donor organ prior to transplantation. Perfusion of a donor mouse heart with MMF-loaded PEG-PLGA nanoparticles (MMF-NPs) prior to transplantation abrogated cardiac transplant vasculopathy by suppressing intragraft pro-inflammatory cytokines and chemokines. Our findings demonstrate that ex vivo delivery of an ISA to donor organs using a nanocarrier can serve as a clinically feasible approach to reduce transplant immunity.

Mechanisms of action of mycophenolate mofetil

Mycophenolate mofetil (MMF, CellCept®) is a prodrug of mycophenolic acid (MPA), an inhibitor of inosine-5′‘monophosphate dehydrogenase. MPA depletes guanosine nucleotides preferentially in T and B lymphocytes and inhibits their proliferation, thereby suppressing cell-mediated immune responses and antibody formation. MPA also inhibits the glycosylation and expression of adhesion molecules, and the recruitment of lymphocytes and monocytes into sites of inflammation. MPA depletes tetrahydrobiopterin and decreases the production of nitric oxide by inducible NO synthase without affecting the activity of constitutive NO synthases. Activated macrophages produce NO and superoxide, which combine to generate tissue-damaging peroxynitrite. By these two mechanisms MMF exerts anti-inflammatory activity. Unlike calcineurin inhibitors, MMF is not nephrotoxic and does not induce the production of TGF β, which is fibrogenic. MMF does not increase blood pressure, cholesterol levels or triglyceride levels in recipients. MMF reduces acute and chronic rejection in allograft recipients and is efficacious in some nephropathies. Evidence is accumulating that MMF may have clinical utility in some autoimmune disorders.

Mycophenolate mofetil and animal models

Mycophenolate mofetil (MMF), is the morpholinoethyl ester of mycophenolic acid (MPA). Though initially developed as an anti-rejection treatment, MMF is beginning to find application in more common immune-mediated diseases. MMF has been shown to be effective against transplant-associated vascular disease, lupus and other inflammatory diseases via multiple mechanisms in several animal models. MMF treatment blocks the proliferation of T cells and B cells, attenuates the production of autoreactive IgG and IgM, diminishes complement deposition, and reduces the production of multiple proinflammatory cytokines including TNF-α, IFN-γ, IL-2, IL-3, IL-4, IL-5, IL-6 and IL-12. It also increases production of the anti-inflammatory mediator IL-10. In addition, MMF reduces the infiltration of immune cells into sites of inflammation by interfering with the expression of cell-surface molecules critical for this process, including MHC class II, CD40, CD80, CD86, I-A, and ICAM-1. Additional mechanisms involving mannosylation and N-linked glycosylation of cell-surface molecules are only beginning to be investigated. This article will focus on the contribution of animal models of disease as investigational tools in the development of MMF as an immunomodulatory drug. The use of mice, rats, rabbits, monkeys, baboons and interspecific xenografts will be discussed.

Measuring T-cell responses against LCV and CMV in cynomolgus macaques using ELISPOT: potential application to non-clinical testing of immunomodulatory therapeutics

A number of immunomodulatory therapeutics increase the risk of disease associated with latent herpesviruses such as cytomegalovirus (CMV) and Epstein-Barr virus (EBV), a member of the lymphocryptovirus (LCV) family that infects humans. The diseases associated with loss of immunity to these viruses can have major impacts on patients as well as on the commercial viability of the immunomodulatory therapeutics. In an effort to develop non-clinical methods for measuring effects on anti-viral immunity, we have developed an interferon (IFN)-γ enzyme-linked immunosorbent spot (ELISPOT) assay to quantify the number of CMV or LCV-reactive T-cells in peripheral blood of cynomolgus macaques. After optimization of various parameters, the IFN-γ ELISPOT assay was characterized for specificity, intra-assay, monkey-to-monkey, and longitudinal variability and sensitivity to immunosuppression. The results show that nearly all animals have detectable responses against both CMV and LCV and responses were derived from T-cells specific to the virus of interest. Analyses of variability show assay reproducibility (≤23% CV), and that variability over time in anti-viral responses in individual animals (larger for LCV than for CMV) was ∼2-fold in most animals over a 3-month time period, which is predicted to allow for detection of drug-induced changes when using group sizes typical of non-clinical studies. In addition, the IFN-γ ELISPOT assay was capable of detecting decreases in the numbers of CMV and LCV reactive T-cells induced by immunosuppressive drugs in vitro. This assay may allow for non-clinical assessment of the effects of immunomodulatory therapeutics on anti-viral T-cell immunity in monkeys, and may help determine if therapeutics increase the risk of reactivating latent viral infections.

Mycophenolate Mofetil and Atherosclerosis: Results of Animal and Human Studies

The immunosuppressive agent mycophenolate mofetil (MMF) has beneficial effects in cardiac transplant patients beyond the suppression of tissue rejection. Patients with regimens containing MMF experience diminished intimal thickening and cardiac allograft vasculopathy compared to patients treated with azathioprine. Studies have shown that diet-induced atherosclerosis (a related vasculopathy) is a chronic inflammatory process, and so MMF has also been used to reduce atherosclerosis in a rabbit model of hyperlipidemia. These data hold out the intriguing possibility that MMF might be a viable primary or secondary preventive agent in people at significant risk for atherosclerosis.

Modulation of tolerance to the transgene product in a nonhuman primate model of AAV-mediated gene transfer to liver

Adeno-associated virus (AAV)-mediated gene transfer of factor IX (F.IX) to the liver results in long-term expression of transgene in experimental animals, but only short-term expression in humans. Loss of F.IX expression is likely due to a cytotoxic immune response to the AAV capsid, which results in clearance of transduced hepatocytes. We used a nonhuman primate model to assess the safety of AAV gene transfer coupled with an anti-T-cell regimen designed to block this immune response. Administration of a 3-drug regimen consisting of mycophenolate mofetil (MMF), sirolimus, and the anti-IL-2 receptor antibody daclizumab consistently resulted in formation of inhibitory antibodies to human F.IX following hepatic artery administration of an AAV-hF.IX vector, whereas a 2-drug regimen consisting only of MMF and sirolimus did not. Administration of daclizumab was accompanied by a dramatic drop in the population of CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs). We conclude that choice of immunosuppression (IS) regimen can modulate immune responses to the transgene product upon hepatic gene transfer in subjects not fully tolerant; and that induction of transgene tolerance may depend on a population of antigen-specific Tregs.

Validation of Immunological Biomarkers for the Pharmacodynamic Monitoring of Immunosuppressive Drugs in Humans

Pharmacodynamic monitoring (PD) can evaluate the efficacy of immunosuppressive drug therapies. In this study, the expressions of PD biomarkers [lymphocyte proliferation, CD25 and CD71 expression, interleukin-2 (IL-2), and tumor necrosis factor-alpha (TNF-alpha) synthesis] were determined in whole-blood assays and were validated for their application in PD of immune modulators in future clinical trials. Initially, the assay conditions were re-evaluated. The measurement of T-lymphocyte proliferation and activation marker expression in whole-blood cultures resulted in optimized stimulation for 72 hours with 7.5 microg/mL concavalin A. Intracellular cytokine expression of CD3+ T-cells received optimized stimulation for 4 hours with 15 ng/mL phorbol 12-myristate 13-acetate and 0.75 microg/mL ionomycin. Statistical assay parameters (intra-assay, intra-individual, and interindividual variabilities) were determined. It was found that blood storage for up to 24 hours is possible without any change in biomarker expression. Dosage effects of immunosuppressive drugs (tacrolimus, cyclosporin A, sirolimus, mycophenolic acid, and methylprednisolone) were evaluated in vitro and the assay was applied successfully to dialysis, renal transplant, and liver transplant patients. We conclude that these biomarkers used in whole-blood assays are suitable for PD of immune modulators in clinical trials.

Mycophenolate mofetil and sirolimus combination in renal transplantation

Mycophenolate mofetil (MMF) and sirolimus (SRL) are potent non-nephrotoxic xenobiotic immunosuppressants. Their complementary properties may provide the rationale for their combination in induction and maintenance regimens. MMF, a reversible inhibitor of inosin monophosphate dehydrogenase (IMPDH) acts as an antiproliferative drug; and SRL, an mTOR (mammalian target of rapamycin) inhibitor, inhibits cell proliferation driven by growth factors. Early experiences with the use of the SRL, MMF and steroid combination yielded insufficient prophylaxis of acute rejection. However, the introduction of induction therapy with mono- or polyclonal antilymphocyte antibodies to the SRL-MMF and steroid combination brings an efficient acute rejection prophylaxis, while improving renal function and/or reducing of chronic allograft nephropathy (CAN). However, adverse events related to the use of this drug combination (mainly haematological and surgery-related) result in a high rate of discontinuations in some trials, which may hamper the potential benefits of this calcineurin-inhibitor (CNI)-free strategy. Also, currently under investigation is whether in long-term immunosuppression, in MMF-treated patients, CNIs can be replaced by SRL to avoid and/or halt progression of chronic nephropathy and to improve graft survival. However, some authors reported a high proportion of patients with oral ulcers and proteinuria after switching to SRL. In short, refining the use of MMF and SRL may provide a better risk/benefit ratio to pave the way towards non-nephrotoxic immunosuppression.

Activation of the purine salvage pathway in mononuclear cells of cardiac recipients treated with mycophenolate mofetil

BACKGROUND

The objective of this study was to investigate purine nucleotide metabolism in peripheral blood mononuclear cells (PBMC) of cardiac transplant recipients switched from azathioprine to mycophenolate mofetil (MMF).

METHODS

Concentrations of guanosine 5'triphosphate (GTP) and adenosine 5'triphosphate (ATP), the activities of inosine monophosphate dehydrogenase (IMPDH), guanine phosphoribosyltransferase (GPRT), and hypoxanthine phosphoribosyltransferase (HPRT) were determined in PBMC of 27 cardiac transplant recipients before switch to MMF and 3, 6, and 12 months thereafter.

RESULTS

There was no difference in the activities of IMPDH and salvage pathway enzymes GPRT and HRPT as well as in intracellular GTP and ATP concentrations between the patients before switch to MMF and healthy controls. The GTP and ATP concentrations in PBMC of cardiac recipients did not change during the entire observation period. Although the MPA trough level remained similar, IMPDH activity declined from 897 to 316 pmol/10(6)PBMC/h 3 months after MMF onset, was almost completely inhibited after 6 months, and partially restored to 143 pmol/10(6)PBMC/h 12 months after switch to MMF. In contrast, GPRT activity increased after 3, 6, and 12 months of MMF therapy and HPRT activity 3 and 6 months after switch to MMF.

CONCLUSIONS

We demonstrated for the first time an induction of salvage pathway enzyme activities in PBMC under MMF therapy. This probably accounts for the maintenance of intracellular purine nucleotide pools and prevents the GTP depletion.

Simultaneous corticosteroid avoidance and calcineurin inhibitor minimization in renal transplantation

Steroids and calcineurin inhibitors (CNI) have been mainstays of immunosuppression but both have numerous side effects that are associated with substantial morbidity and mortality. This study was carried out to determine if steroids can be eliminated with early discontinuation of cyclosporine A (CsA) and later discontinuation of mycophenolate mofetil (MMF). Ninety-six patients with kidney transplants were entered into four subgroups of two pilot studies. All patients received Thymoglobulin induction, rapamycin (RAPA), and the immunonutrients arginine and an oil containing omega-3 fatty acids. Mycophenolate mofetil was started in standard doses and discontinued by 2 years. CsA was given in reduced doses for either 4, 6, or 12 months. Follow-up was 12-36 months. Thirteen first rejection episodes occurred during the first year (14%). Combining all patients, 86% were rejection-free at 1 year, 80% at 2 years and 79% at 3 years. No kidney has been lost to acute rejection. Ninety percent of the 84 patients at risk at the end of the study were steroid-free and 87% were off CNI. Fifty-seven percent of 54 patients with a functioning kidney at 3 years were receiving monotherapy with RAPA. We conclude that this therapeutic strategy is worthy of a prospective multi-center clinical trial.

Mechanisms of action of mycophenolate mofetil in preventing acute and chronic allograft rejection

Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), an inhibitor of inosine-5'-monophosphate dehydrogenase, has several immunosuppressant actions. MPA depletes guanosine and deoxyguanosine nucleotides preferentially in T and B lymphocytes, inhibiting proliferation and suppressing cell-mediated immune responses and antibody formation, major factors in acute and chronic rejection. MPA also can induce T-lymphocyte apoptosis. MPA suppresses dendritic cell maturation and can induce human monocyte-macrophage cell line differentiation, decreasing the expression of interleukin (IL)-1 and enhancing expression of the IL-1 receptor antagonist. In addition, MPA inhibits adhesion molecule glycosylation and expression and lymphocyte and monocyte recruitment. Activated macrophages produce nitric oxide (NO) and superoxide, which combine to generate tissue-damaging peroxynitrite. MPA depletes tetrahydrobiopterin and decreases NO production by inducible NO synthase without affecting constitutive NO synthase activity. By these mechanisms, MMF exerts anti-inflammatory activity, which could attenuate both acute and chronic rejection. Unlike calcineurin inhibitors, MMF is nonnephrotoxic and does not induce transforming growth factor-beta production, which is fibrogenic. MMF inhibits arterial smooth muscle cell proliferation, a contributor to graft proliferative arteriopathy, and does not increase blood pressure, cholesterol, or triglyceride levels. By decreasing high-density lipoprotein oxidation and macrophage recruitment, MMF also may delay onset/progression of graft atherosclerosis. Thus, MMF may prevent chronic rejection by several mechanisms. MMF activity is synergistic with that of other agents such as valganciclovir for treating cytomegalovirus infection. MMF also has synergistic activity with angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists in the treatment of some nephropathies in experimental animals. This combination may prevent progression toward end-stage renal disease in humans with chronic allograft, lupus, and diabetic nephropathies.

Combined Use of the JAK3 Inhibitor CP-690,550 with Mycophenolate Mofetil to Prevent Kidney Allograft Rejection in Nonhuman Primates

BACKGROUND

Immunosuppression via Janus kinase (JAK) 3 inhibition affords significant prolongation of allograft survival. We investigated the effects of an immunosuppressive regimen combining the JAK3 inhibitor CP-690,550 with mycophenolate mofetil (MMF) in nonhuman primates (NHPs).

METHODS

Life-supporting kidney transplantations were performed between ABO-compatible, MLR-mismatched NHPs. Animals were treated orally twice a day with CP-690,550 and MMF (n=8) or MMF alone (n=2) and were euthanized at day 90 or earlier due to allograft rejection.

RESULTS

Mean survival time (+/-SEM) in animals treated with MMF alone (23+/-1 days) was significantly extended in animals that concurrently received CP-690,550 (59.5+/-9.8 days, P=0.02). Combination animals exposed to higher levels of CP-690,550 had a significantly better survival (75.2+/-8.7 days) than animals that received less CP-690,550 (33.3+/-12.6 days, P=0.02). Three combination therapy animals were euthanized at day 90 with a subnormal renal function and early-stage acute graft rejection. Rejection, delayed by treatment, ultimately developed in other animals. Anemia and gastrointestinal intolerance was seen in combination therapy animals that otherwise did not show evidence of viral or bacterial infection besides signs consistent with subclinical pyelonephritis (n=3). One incidental lymphosarcoma was noted.

CONCLUSIONS

Addition of CP-690,550 to MMF significantly improved allograft survival. The observed side effects appear amenable to improvements upon alteration of dosing strategies. Efficacy of this combination regimen suggests that it could become the backbone of calcineurin inhibitor-free regimens.

Three-year results of a randomized, double-blind, controlled trial of mycophenolate mofetil versus azathioprine in cardiac transplant recipients

BACKGROUND

This study reports the 36-month results of a randomized, double-blind, active-controlled trial of mycophenolate mofetil (MMF) vs azathioprine (AZA) in heart transplant patients.

METHODS

Patients were randomized at the time of transplant to receive MMF (1,500 mg twice a day, N = 327) or AZA (1.5 to 3 mg/kg in 4 daily doses, N = 323) in addition to cyclosporine and corticosteroids; 289 patients in each group received study drug. Data were analyzed in all randomized patients (enrolled) and in patients who received study medications (treated). Clinical and graft assessments continued for 36 months.

RESULTS

For the co-primary end-point, 53 of 289 (18.3%) AZA-treated patients either died or received another transplant compared with 34 of 289 (11.8%) MMF-treated patients (p < 0.01). Time to re-transplantation or patient death was significantly shorter for AZA- than MMF-treated patients (p = 0.029). In patients undergoing intravascular ultrasound, the change in mean maximal intimal thickness was less for the MMF group than for the AZA group (0.06 +/- 0.03 mm vs 0.13 +/- 0.03 mm, respectively; p = 0.056). No significant differences between treatments were observed in quantitative coronary angiographic measurements of transplant coronary vasculopathy. Congestive heart failure, atrial arrhythmia and leukopenia were more common in the AZA group, whereas diarrhea, esophagitis, Herpes simplex, Herpes zoster and cytomegalovirus (CMV) tissue invasion were more common in MMF-treated patients.

CONCLUSION

MMF reduces mortality and graft loss up to 36 months after transplantation.

Appraisal of the extent of chronic allograft vasculopathy in animal models: Proposition of a standardized micromorphometric method

Arterial obstruction due to intimal myproliferation is an outcome used for investigating chronic allograft vasculopathy in animal models. Since harvested tissue may be distorted while processing, discrepancy may happen in the measure of the obstruction. We propose a standardized micromorphometric method for calculating the percentage of obstruction with eliminating the variability in the shape of the vessel cross-section. The mathematical adjustment avoids the overestimation of the percentage of obstruction and improves accuracy.

Mechanisms of action of mycophenolate mofetil

Mycophenolate mofetil (MMF, CellCept) is a prodrug of mycophenolic acid (MPA), an inhibitor of inosine-5'-monophosphate dehydrogenase. MPA depletes guanosine nucleotides preferentially in T and B lymphocytes and inhibits their proliferation, thereby suppressing cell-mediated immune responses and antibody formation. MPA also inhibits the glycosylation and expression of adhesion molecules, and the recruitment of lymphocytes and monocytes into sites of inflammation. MPA depletes tetrahydrobiopterin and decreases the production of nitric oxide by inducible NO synthase without affecting the activity of constitutive NO synthases. Activated macrophages produce NO and superoxide, which combine to generate tissue-damaging peroxynitrite. By these two mechanisms MMF exerts anti-inflammatory activity. Unlike calcineurin inhibitors, MMF is not nephrotoxic and does not induce the production of TGFbeta, which is fibrogenic. MMF does not increase blood pressure, cholesterol levels or triglyceride levels in recipients. MMF reduces acute and chronic rejection in allograft recipients and is efficacious in some nephropathies. Evidence is accumulating that MMF may have clinical utility in some autoimmune disorders.

Mycophenolate mofetil substitution for cyclosporine a in renal transplant recipients with chronic progressive allograft dysfunction: the "creeping creatinine" study

BACKGROUND

This study determined whether cyclosporine A (CsA)-treated renal allograft recipients with deteriorating renal function ("creeping creatinine") secondary to chronic allograft nephropathy (CAN) benefit from the addition of mycophenolate mofetil (MMF) to their immunosuppressive regimen, followed by withdrawal of CsA.

METHODS

In a controlled, open, multicenter study, CsA-treated renal allograft recipients with progressively deteriorating renal function were randomized to have their CsA discontinued with the concomitant addition of MMF to their regimen (group A) or to continue treatment with CsA (group B). The primary endpoint was the response rate over the 6-month period after withdrawal of CsA in group A or the equivalent time in group B. Response was defined as a stabilization or reduction of serum creatinine (SCr), as evidenced by a flattening or positive slope of the 1/SCr plot and no graft loss. Secondary endpoints included the incidence of acute rejection, graft and patient survival, and changes in selected metabolic parameters.

RESULTS

The response rate in the primary intent-to-treat population (n=122) was 58% (36/62) in group A versus 32% (19/60) in group B (P=0.0060). The corresponding percentages of responders in the per-protocol population (n=107) were 60% (36/60) and 26% (12/47), respectively (P=0.0008). There were no acute rejections in group A during the study period. Patients in this group also experienced a significant decrease in total cholesterol.

CONCLUSIONS

In patients with progressively deteriorating renal function secondary to CAN, addition of MMF followed by withdrawal of CsA results in a significant improvement in transplant function without the risk of acute rejection.

Withdrawal of cyclosporine or tacrolimus after addition of mycophenolate mofetil in patients with chronic allograft nephropathy

There has been a need for a prospective, randomized, controlled trial to determine whether the addition of mycophenolate mofetil (MMF) to a calcineurin inhibitor (CNI)-based regimen or MMF addition followed by CNI withdrawal is an effective treatment for chronic allograft nephropathy (CAN). We conducted the first randomized, prospective study to compare the introduction of MMF with or without CNI withdrawal in long-term transplant recipients with histologically proven CAN and deteriorating renal function. The primary endpoint was renal function as indicated by the slope of the inverse serum creatinine vs. time at 32 weeks after randomization. After an interim analysis found a greater-than-expected difference between groups in the slopes of the inverse serum-creatinine, the study was stopped for ethical reasons. There were 20 patients in the MMF/CNI continuation and 19 patients in the MMF/CNI withdrawal groups (mean time post-transplant 7 years). Renal function improved in the dual-therapy compared with the triple-therapy group (p=0.002). Blood pressure decreased in the dual-therapy group with a significant difference between groups at 35 weeks (p=0.04). No acute rejections occurred. Long-term patients with CAN experience a significant improvement in renal function and blood pressure when CNIs are replaced by MMF.