Tissue distribution and tumor uptake of folate receptor-targeted epothilone folate conjugate, BMS-753493, in CD2F1 mice after systemic administration

Abstract

To assess targeting of an epothilone folate conjugate (BMS-753493) to the folate receptor (FR)-overexpressed tumor in mice bearing both FR+ 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 FR+ (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 over-expressing 98M109 tumors, thereby supporting targeted delivery of cytotoxics through the folate receptor.

Keywords: Epothilone folate conjugate; Folate receptor; Folate receptor–expressing tumor; Tissue distribution; Tumor selective targeting; Tumor uptake.

Graphical abstract

Figure 1

Chemical structures of [³H]BMS-753493 and [³H]BMS-748285.

Figure 2

Autoradiograms of selected sections of mice at 48 h after dosing with [³H]BMS-753493. The representative whole-body autoradiograms of tumor-bearing mice following i.v. dose (2.2 nmol/kg or 4 mg/kg) of [³H]BMS-753493 at 48 h. The sections were to compare radioactivity distribution in M109 (FR–, right side) and 98M109 (FR+, left side) tumors, and selected tissues. Details of whole-body autoradiography are described in the Section of Materials and methods.

Figure 3

Autoradiograms of tumors after dosing with [³H]BMS-753493. The representative autoradiograms of tumor following i.v. doses (2.2 nmol/kg or 4 mg/kg) of [³H]BMS-753493 to tumor-bearing mice at 24 and 48 h. The sections were to compare radioactivity distribution in M109 (FR–) and 98M109 (FR+) tumors. Details of whole-body autoradiography are described in the Section of Materials and methods.

Figure 4

Autoradiograms of selected sections of mice at 48 h after dosing with [³H]BMS-748285. The representative whole-body autoradiograms of tumor-bearing mice following i.v. dose (2.2 nmol/kg or 1.2 mg/kg) of [³H]BMS-748285 at 48 h. The sections were to compare radioactivity distribution in M109 (FR–, right side) and 98M109 (FR+, left side) tumors, and selected tissues. Details of whole-body autoradiography are described in the Section of Materials and methods.

Figure 5

Concentration versus time profile of BMS-748285 in mouse plasma after i.v. administration of 2.2 nmol/kg BMS-753493 or BMS-748285.

Figure 6

Concentrations of BMS-748285 in the kidney (A) and heart (B) after i.v. administration of 2.2 nmol/kg BMS-753493 or BMS-748285.