Place of mycophenolate mofetil in renal transplantation

Production of 5-hydroxy-7-methoxy-4-methylphthalide in a culture of Penicillium crustosum

The chemical reactions carried out by microorganisms have been used as a tool in modern chemistry. This paper reports the production of mycophenolic acid and a new phthalide by the endophytic fungus Penicillium crustosum obtained from coffee seeds. The fungus was cultivated in a liquid medium for a period of seven days and after that the culture medium was divided into four treatments: A, B, C and D, to which different organic substances were added. Treatment A was maintained as the control to evaluate the occurrence of biotransformation. Organic acids were added to the culture media of treatments B (ferulic and quinic acids) and C [cinnamic and 3,4-(methylenedioxy) cinnamic acids], and caffeine was added in the treatment D. All these organic compounds were dissolved in DMSO, and the fermentation was maintained for more 13 days, totalizing 20 days. Mycophenolic acid was isolated from the culture with no added acids (treatment A). Mycophenolic acid and a new phthalide, 5-hydroxy-7-methoxy-4-methylphthalide were isolated from treatments B and C, and mycophenolic acid and caffeine (added to the culture medium) were isolated from treatment D. The structures were determined by NMR techniques and confirmed by MS and MS/MS techniques.

Does mycophenolate mofetil decrease the recurrent acute rejection in renal transplant recipients

PURPOSE

Mycophenolate mofetil (MMF) has emerged as a valuable immunosuppression in renal transplant patients. However, it is expensive and cannot be used routinely in our population.

MATERIAL AND METHODS

In a retrospective study, 60 renal transplant patients on MMF based triple immunosuppression were analysed. The indication for MMF was as rescue therapy after treatment of acute vascular rejection (Banff type-4, grade IIA, IIB and III) in all patients. However, 20 such patients also had associated chronic liver diseases. The patients were given 1.5-2.0 g MMF in two divided doses at least for 6 months, depending upon the tolerability, adverse effects and affordability, and followed-up at least for 1 year. The control group consisted of 60 cases of acute vascular rejection (Banff type-4, grade IIA, IIB and III) who were placed on cyclosporine, azathioprine and steroid based maintenance immunosuppressive regimen in same time frame.

RESULTS

The incidence recurrent acute rejections in MMF group was 18% and 42% in control group (P < 0.005). The serum transaminases in all patients of the liver diseases became normal in 3-6 months. The incidence of opportunistic infections in MMF and control group were 22% and 11% respectively (P < 0.05). The MMF based regimen was two times more expensive. The 1 year patient and graft survivals between two groups were not statistically significantly different.

CONCLUSION

The MMF based regimen significantly decreases the recurrent acute rejections. However, it is expensive and cannot be used routinely in all patients in Indian scenario.

Mycophenolate mofetil, an inhibitor of inosine monophosphate dehydrogenase, causes a paradoxical elevation of GTP in erythrocytes of renal transplant patients

The immunosuppressant MMF (mycophenolate mofetil) has increasingly replaced AZA (azathioprine) in renal transplantation. MMF is a prodrug of MPA (mycophenolic acid), which inhibits lymphocyte IMPDH (inosine monophosphate dehydrogenase), thereby drastically decreasing GTP concentrations essential to lymphocyte proliferation in vitro and in vivo. Erythrocyte GTP concentrations are commonly elevated in severe renal disease, but normalize following successful engraftment. Consequently, elevated GTP in renal transplant recipients might signal impending loss of immunosuppression and graft failure. In the present study, we compared erythrocyte nucleotides and plasma metabolites in two groups of 25 patients after renal transplantation, both receiving prednisolone and cyclosporin A, but one group receiving MMF and the other AZA. No patients had recent allograft biopsy evidence of rejection. Erythrocyte GTP concentrations at MMF commencement were 50.4+/-23.4 micromol/l. An increase occurred during the first 3 months after transplant when MMF was used de novo, stabilizing at 146.7+/-62.9 micromol/l after 4 months. This was significantly higher (P=2.5 x 10(-6)) than erythrocyte GTP (40.4+/-15.9 micromol/l) in the AZA group, which was essentially unchanged from values immediately after successful transplantation. The effect of MMF on erythrocyte GTP levels was reversible, since GTP levels fell when MMF therapy was terminated. The results demonstrate paradoxically high GTP concentrations in erythrocytes of renal transplant patients receiving MMF. MPA may stabilize reticulocyte IMPDH, allowing the protein to persist during erythropoiesis. This behaviour is in marked contrast with the decrease in GTP levels seen in white blood cells of patients on chronic MMF therapy.

Comparison of two drug regimens upon clinical outcome among renal transplant recipients with positive flow cytometric crossmatches

Renal transplant recipients with positive flow cytometric crossmatches (FCXM) face greater risk of early rejection and graft failure. It is clear that the pharmacologic needs of this high risk group have not been identified. We retrospectively compared the impact of two drug regimens upon early rejection and 5 yr actuarial survival among 324 primary cadaveric transplant recipients with positive and negative FCXM. Patients received either Regimen I (OKT3 induction, cyclosporine and steroids) or Regimen II (mycophenolate mofetil with cyclosporine or Prograf). Recipient gender, age, disease etiology, ethnic distribution and cytotoxic panel reactive antibody (PRA) were equivalent between regimens (p=ns). With Regimen I, the incidence of rejection was greater for FCXM positive vs. FCXM negative patients (51 vs. 21%, p=0.001). In contrast, with Regimen II the incidence of rejection for FCXM positive and FCXM negative patients was equivalent (18 vs. 12%, p=ns) and lower than patients treated with Regimen I (p < 0.01). Ethnic variation was only observed with Regimen I in which African Americans with positive FCXM had more rejections than Caucasians (60 vs. 45%, p < 0.05). Five-year actuarial survival was lower for FCXM positive vs. FCXM negative patients treated with Regimen I (40 vs. 75%, p=0.0006) or Regimen 2 (60 vs. 90%, p=0.001). Allograft survival was equivalent (p=ns) among FCXM positive individuals receiving Regimen I or II. However, allograft survival among FCXM negative individuals improved with Regimen II (p < 0.05). Ethnic variation in survival was not observed with either regimen (p=ns).