Suppression of acute rejection in allogeneic rat lung transplantation: A study of the efficacy and pharmacokinetics of rapamycin derivative (SDZ RAD)used alone and in combination with a microemulsion formulation of cyclosporine
B. Hausen et al., Suppression of acute rejection in allogeneic rat lung transplantation: A study of the efficacy and pharmacokinetics of rapamycin derivative (SDZ RAD)used alone and in combination with a microemulsion formulation of cyclosporine, J HEART LUN, 18(2), 1999, pp. 150-159
Background: The novel immunosuppressant SDZ RAD, 40-0 (2-hydroxyethyl)rapam
ycin, is an orally active rapamycin analogue developed for use in combinati
on with cyclosporine (Neoral(R)). The present study was designed to evaluat
e the efficacy of SDZ RAD, Neoral(R), or a combination of both drugs for su
ppression of acute rejection in an allogeneic, unilateral rat lung transpla
nt model.
Methods: Brown-Norway (RT1(n)) donor lungs were implanted into Lewis (RT1(1
)) recipients that were observed for 21 days. Postoperative evaluation incl
uded daily weights, serial chest radiographs, drug trough levels, and histo
logy scores of the transplanted lung on the day of sacrifice. Treatment gro
ups were comprised of rats treated orally with the RAD vehicle as controls
(n = 6); SDZ RAD 2.5 mg/kg/day (n 9); Neoral(R) 7.5 mg/kg/day (n = 8); Neor
al(R) 2.5 mg/kg/day (n = 6); SDZ RAD 2.5 mg/kg/day plus Neoral(R) 7.5 mg/kg
/day (n = 7); and Neoral(R) 2.5 mg/kg/day plus SDZ RAD 2.5 mg/kg/day (n = 6
).
Results: The results of this study showed that neither monotherapy with 2.5
mg/kg/day of Neoral(R), nor 2.5 mg/kg/day of SDZ RAD prevented severe acut
e rejection in unilateral lung transplant recipients. Furthermore, despite
high dose (7.5 mg/kg/day) Neoral(R) treatment, graft histology showed moder
ate rejection. However, addition of 2.5 mg/kg/day of SDZ RAD to 7.5 mg/kg/d
ay of Neoral(R) completely prevented histologic rejection in four of seven
grafts, although the remaining 3 grafts showed minimal rejection. This comb
ination resulted in significantly higher RAD trough levels when compared to
SDZ RAD treatment alone. Combining a lower dose of Neoral(R) (2.5 mg/kg/da
y) with 2.5 mg/kg/day of SDZ RAD resulted in less weight loss and improved
animal health; however, the histology of lung grafts in these rats showed m
ild rejection.
Conclusions: This is the first study on the efficacy of the novel rapamycin
derivative SDZ RAD for the control of acute lung allograft rejection. Resu
lts showed that acute. unilateral rat lung allograft rejection is refractor
y to monotherapy with either high dose Neoral(R) or SDZ RAD. The two regime
ns of combined treatment with Neoral(R) plus SDZ RAD used in these studies
produced either minimal rejection and reduced tolerability or mild rejectio
n and better tolerability and showed potentiation of immunosuppression when
both drugs were used together. Additional investigation of these two drugs
is needed, however, to devise regimens that produce both high immunosuppre
ssive efficacy and good tolerability.