To assess targeting of an epothilone folate conjugate(BMS-753493) to the folate receptor(FR)-overexpressed tumor in mice bearing both FRt and FR– tumors,a series of experiments were conducted by quantitative whole-body autoradiography(QWBA) and LC–MS/MS following i.v.administration of BMS-753493 or its active moiety,BMS-748285 in mice bearing FRt(98M109) and FR–(M109) tumors.QWBA showed [3H]BMS-753493–derived radioactivity was extensively distributed to various tissues.The FR over-expressing 98M109 tumors showed consistently higher level of radioactivity than FR-negative tumors(i.e.,M109 tumors) up to 48 h post dose of [3H]BMS-753493,despite the magnitude of difference between the tumors is relatively small(generally 3 5-fold).The radioactivity level in 98M109 tumors was 2 12-fold of normal tissues except intestine/content at 48 h post dose.No selective radioactivity uptake into 98M109 tumors over M109 or normal tissues was observed after i.v.administration of the active epothilone,[3H]BMS-748285.LC–MS/MS measurements demonstrated that the concentrations of BMS-748285,presumably from hydrolysis of the folate conjugate,in 98M109 tumors were greater than those in M109 tumors after i.v.administration of BMS-753493(2–3-fold) whereas no differential uptake in the tumors following BMS-748285 administration.Those data were consistent with radioactivity determinations.Those results demonstrated that the folate conjugation in BMS-753493 enabled moderately preferential distribution of the active epothilone to FR overexpressing 98M109 tumors,thereby supporting targeted delivery of cytotoxics through the folate receptor. To assess the targeting of an epothilone folate conjugate (BMS-753493) to the folate receptor (FR) -overexpressed tumor in mice bearing both FRt and FR-tumors, a series of experiments were conducted by quantitative whole-body autoradiography (QWBA) and LC -MS / MS following ivadministration of BMS-753493 or its active moiety, BMS-748285 in mice bearing FRt (98M109) and FR- (M109) tumors. QWBA showed [3H] BMS-753493-derived radioactivity was extensively distributed to various tissues. The FR over-expressing 98M109 tumors showed consistently higher level of radioactivity than FR-negative tumors (ie, M109 tumors) up to 48 h post dose of [3H] BMS-753493, despite the magnitude of difference between the tumors is relatively The radioactivity level in 98M109 tumors was 2 12-fold of normal tissues except intestine / content at 48 h post dose. No selective radioactivity uptake into 98M109 tumors over M109 or normal tissues was observed after ivadministration of the active epothi lone, [3H] BMS-748285.LC-MS / MS measurements of the concentration of BMS-748285, presumably from hydrolysis of the folate conjugate, in 98M109 tumors were greater than those in M109 tumors after ivadministration of BMS- 753493 ( 2-3-fold) no differential uptake in the tumors following BMS-748285 administration.Those data were consistent with radioactivity determinations. Those results demonstrated that the folate conjugation in BMS-753493 enabled moderately preferential distribution of the active epothilone to FR overexpressing 98M109 tumors, thereby supporting targeted delivery of cytotoxics through the folate receptor.