Cure of human carcinoma xenografts by a single dose of pretargeted yttrium-90 with negligible toxicity

Abstract

A covalent conjugate (NR-LU-10/SA) was prepared between streptavidin (SA) and NR-LU-10, a mAb that binds an antigen expressed on the surface of most human carcinomas. NR-LU-10/SA was injected into nude mice bearing human tumor xenografts. Injection of biotinylated galactosyl-human serum albumin reduced the circulating levels of conjugate by 95%. Subsequent administration of (90)Y-1,4,7, 10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-biotin achieved peak uptake at the tumor within 2 hr while >80% of the radioactivity was eliminated in the urine. A single dose of 600-800 microCi of (90)Y-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-biotin produced cures in 10/10 mice with established (>200 mm(3)) s.c. human small cell lung or colon cancer xenografts and 8/10 cures in mice with human breast cancer xenografts without significant toxicity.

Figure 1

Effect of CA on blood disappearance in vivo. BALB/c mice (n = 3/group) were injected at t = 0 with 400 μg ¹²⁵I-NR-LU-10/SA conjugate. Blood samples (10 μl, n = 2/time point) were serially removed from the retroorbital plexus and assayed for radioactivity. At 28.5 hr, mice were injected with either saline (●) or 200 μg of CA (■). For the CA mice, blood was sampled at 28.5 (preinjection), 29, 29.5, 30.5, 32.5, 34.5, 35.5, 39.5, 50, and 114 hr. Control animals were sampled at t = 0.17, 0.5, 1.0, 2.0, 4.0, 28.5, 50.0, 72.0, 96.0, and 168 hr. Data are presented as the mean % i.d. in total blood +/− SD of each group.

Figure 2

Structure and biodistribution of ⁹⁰Y-DOTA-biotin (nonpretargeted). Male BALB/c mice (n = 3/time point) with externally ligated urinary bladders were injected with 5 μg (50 μC_i) ⁹⁰Y-DOTA-biotin. At 15, 30, and 120 min postinjection, blood samples were taken before sacrifice and dissection, and whole organs were assayed for radioactivity. Tissues sampled were (in order) blood, tail, lung, liver, spleen, stomach, kidneys, intestines, and urinary bladder. Data are presented as the mean % i.d. in total blood and each whole organ +/− SD.

Figure 3

Projected radioactivity concentrations resulting from either ⁹⁰Y-NR-LU-10 whole antibody or pretargeted ⁹⁰Y-DOTA-biotin. Tumor uptake (■) and blood clearance (●) data from Table 1 (mean %i.d./g of tissue) were used to calculate the decay-corrected radioactivity concentration after administration of either 200 μCi ⁹⁰Y-NR-LU-10 whole antibody (A) or 800 μCi pretargeted ⁹⁰Y-DOTA-biotin (B). Data are presented as μCi of ⁹⁰Y/g of tissue +/− SD at 2, 24, 48, and 120 hr postinjection. AUC values were calculated by using trapezoidal integration from 0 hr to 120 hr postinjection from the data in Table 1. T/B, tumor to blood.

Figure 4

Antitumor activity of pretargeted ⁹⁰Y-DOTA-biotin. Cure is defined as an established tumor that is not palpable for >300 days posttreatment. Data are presented as the average (10 animals/group) percent of initial tumor volume. (A) SHT-1 lung tumor xenografts (200–300 mm³ at the initiation of therapy). Controls included untreated animals (●), and those treated with only NR-LU-10/SA plus CA (■), or given 400 μCi of nonpretargeted ⁹⁰Y-DOTA-biotin. (B) SHT-1 lung tumor xenografts (200–300 mm³ at the initiation of therapy). Two hundred microcuries of ⁹⁰Y-NR-LU-10 whole antibody (100 μg) (●), 200 μCi (■), 400 μCi (▴), or 600 μCi (▾) of pretargeted ⁹⁰Y-DOTA-biotin. (C) MDA-MB-484 breast tumor xenografts 150–300 mm³ at the initiation of therapy. Control animals (●), 200 μCi of ⁹⁰Y-NR-LU-10 whole antibody (100 μg) (■), or 800 μCi (▴) of pretargeted ⁹⁰Y-DOTA-biotin. (D) SW-1222 colon tumor xenografts 100–300 mm³ at the initiation of therapy. Control animals (●), 800 μCi of nonpretargeted ⁹⁰Y-DOTA-biotin (■), and 800 μCi of pretargeted ⁹⁰Y-DOTA-biotin (▴).

Figure 5

Hematologic toxicity resulting from either ⁹⁰Y-NR-LU-10 whole antibody or pretargeted ⁹⁰Y-DOTA-biotin. Leukocyte toxicity was measured in separate groups of BALB/c female mice (n = 10) at weekly intervals postinjection. (A) On day −1, mice received (i.v.) either saline (●) or 100 μCi (■), 200 μCi (▴), or 300 μCi (▾) of ⁹⁰Y-NR-LU-10 whole antibody. (B) On day −1, mice received (i.v.) 400 μg NR-LU-10/SA, followed on day 0 by 200 μg of CA and either saline (●) or 200 μCi (■), 400 μCi (▴), or 800 μC_i (▾) of pretargeted ⁹⁰Y-DOTA-biotin. Specific activities of radiolabeled reagents were varied, with total mass dose held constant. Data are presented as the mean ± SD percent of initial leukocyte values.