Abolition of the effect of cyclosporine on rat cardiac allograft rejection by the new immunomodulator LS-2616 (Linomide).

ABSTRACT

The effect of the quinoline-3-carboxamide LS-2616 (Linomide), given alone or together with cyclosporine, was studied in the first set cardiac allograft transplantation model in the rat. PVG rat hearts were transplanted heterotopically to Wistar/Kyoto rat recipients on day 0. The recipients were given LS-2616 orally on day -1 to rejection and/or CsA orally on days 0-9. In untreated animals rejection occurred on days 8-9, as judged by the absence of palpable pulsations. Treatment with CsA (5 or 10 mg/kg) resulted in prolongation of graft survival to days 17-21, i.e., the rejection occurred 8-10 days after cessation of treatment. LS-2616 in a dose of 160 mg/kg did not in itself have any impact on graft survival, but when given in doses of 40 or 160 mg/kg simultaneously with CsA (10 mg/kg), the effect of CsA was totally abolished. Animals treated with LS-2616 together with CsA had slightly lower trough blood levels than those treated with CsA alone. This interaction with CsA pharmacokinetics does not explain the results, as doubling of the CsA dose to 20 mg/kg, which well compensated for the difference in blood levels, was not sufficient to reverse the effect of LS-2616. To our knowledge this is the first compound known to abolish the effect of CsA. The mechanism is unknown, but is is possible that studies on the interaction between these two drugs will shed further light on the molecular basis of their modes of action.