ORAL EFFICACY OF THE MACROLIDE IMMUNOSUPPRESSANT SDZ RAD AND OF CYCLOSPORINE MICROEMULSION IN CYNOMOLGUS MONKEY KIDNEY ALLOTRANSPLANTATION

Publisher Website
Google Scholar
Abstract
40-O-(2-Hydroxyethyl)-rapamycin (SDZ RAD) is a novel, potent, macrolide immunosuppressant. Its efficacy in rodent transplantation models provided the rationale for us to evaluate the compound in a more relevant, large animal transplantation model. Life-supporting kidney allotransplantation was performed in cynomolgus monkeys: rejection was inferred from a rise in serum creatinine or urea and was subsequently confirmed by histopathology. This model was validated with the microemulsion formulation of cyclosporine (i.e., Neoral). Two studies with a microemulsion formulation of SDZ RAD were performed. First, in a dose-finding study, the SDZ RAD dose was reduced in a stepwise fashion until rejection occurred, either with SDZ RAD as monotherapy, or in combination with a fixed, suboptimal dose of cyclosporine. Second, an efficacy study was performed in which two fixed SDZ RAD doses (0.75 and 1.50 mg/kg/day) were evaluated in monotherapy and compared with the same doses of rapamycin (sirolimus). All immunosuppressants were administered once daily by gastric gavage. Untreated control animals rejected their grafts between 4 and 8 days after transplantation. Cyclosporine (initially at 150 mg/kg/day, reduced to 100 mg/kg/day 2 weeks after transplantation) yielded long-term (>100 days) rejection-free allograft survival in four of five animals. A 10 mg/kg/day dose of cyclosporine led to rejection between 10 and 27 days after transplantation and was considered suboptimal. In the dose-finding study with SDZ RAD monotherapy, rejection occurred in most of the cases (four of six animals) when a dose level of 0.63 mg/kg/day had been reached. Combined with suboptimal cyclosporine, this threshold SDZ RAD dose was about 2-fold lower. In the efficacy study, median graft survival with histologically proven rejection was 32 days (range 8–91 days, n =6) for 0.75 mg/kg/day SDZ RAD and 59 days (range 28–85 days, n=6) for 1.50 mg/kg/day SDZ RAD. For sirolimus, median graft survival was 43 days (range 5–103 days, n=7) for the 0.75 mg/kg/day dose and 56 days (range 8–103 days, n=8) for the 1.50 mg/kg/day dose. There was no statistically significant difference in efficacy between SDZ RAD and sirolimus. SDZ RAD, in the absence of any other immunosuppressant and at doses that do not show any overt toxicity, considerably prolongs rejection-free survival of cynomolgus monkeys after life-supporting kidney allotransplantation.