Immunodepressive activity of FCE 23762 on humoral and cell-mediated immune responses in normal mice: comparison with doxorubicin.

FCE 23762 (3' desamino-3'[2(s)methoxyl-4-morpholinyl]doxorubicin) is a new doxorubicin (Dx) derivative that has been selected for clinical testing for its favourable antitumor characteristics, which include efficacy on Dx-resistant tumors. Immunosuppression is an undesirable side-effect of anti-cancer chemotherapy and the therapeutic efficacy of Dx is probably also related to its low immunotoxicity. It was, thus, of interest to compare the effects of FCE 23762 and its parental drug on the immune responses. Both compounds were injected i.v. into healthy mice at equitoxic doses and according to different treatment schedules. Single doses of FCE 23762 and Dx, given concomitant or after the antigen, suppressed at the same degree and dose-dependently the primary anti-SRBC antibody response. Following a multiple treatment schedule after the antigen, FCE 23762 was less suppressive than Dx on both primary and secondary antibody production. Differently from Dx, that was completely inactive, FCE 23762 moderately inhibited DTH reaction to SRBC, only at the highest single dose tested or for repeated administrations given simultaneously or after priming. Both drugs were totally ineffective in delaying skin allograft rejection. Since spleen cellularity and ex vivo lymphocyte proliferation to Con A and LPS were similarly impaired by the two drugs, the differentiated immunodepressive activity of FCE 23762 and Dx cannot be merely associated to their cytotoxic and antiproliferative action. The hypothesis of a selective effect on different regulatory cell subsets and/or immune mechanisms is discussed.