Comparison of Immunoscintigraphy, Efficacy, and Toxicity of Conventional and Pretargeted Radioimmunotherapy in CD20-Expressing Human Lymphoma Xenografts

Comparison of Immunoscintigraphy, Efficacy, and Toxicity of Conventional and Pretargeted Radioimmunotherapy in CD20-Expressing Human Lymphoma Xenografts

Krishnan Subbiah, PhD¹, Don K. Hamlin, BS², John M. Pagel, MD, PhD¹, D. Scott Wilbur, PhD², Damon L. Meyer, PhD³, Don B. Axworthy, BS⁴, Robert W. Mallett, PhD⁴, Louis J. Theodore, PhD⁴, Pat S. Stayton, PhD⁵ and Oliver W. Press, MD, PhD¹^,3^,6

¹ Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington
² Department of Radiation Oncology, University of Washington, Seattle, Washington
³ Department of Medicine, University of Washington, Seattle, Washington
⁴ NeoRx Corporation, Seattle, Washington
⁵ Department of Bioengineering, University of Washington, Seattle, Washington
⁶ Department of Biological Structure, University of Washington, Seattle, Washington

View larger version (15K):

[in a new window]

FIGURE 1. Effects of CA on circulating 1F5-sAv conjugate. BALB/c mice (n = 4) were injected with 1.4 nmol of ¹²⁵I-1F5-sAv conjugate at time 0 and 24 h later with saline (•) or 5.8 nmol of CA ( ${square}$ ) or 11.6 nmol of CA ( ${blacktriangleup}$ ). Blood samples were collected at 6, 22, 25, 27, 29, and 44 h after ¹²⁵I-1F5-sAv injection and assayed in gamma counter. Data represent mean percentage injected dose per gram (%ID/g) ± SD.

View larger version (17K):

[in a new window]

Figure 2. Gamma-camera images of mice injected with 1.4 nmol of ¹³¹I-1F5-sAv at 24 h (just before CA injection) (A), 25 h (1 h after CA injection) (B), and 48 h (24 h after CA injection) (C). Images are shown at same camera intensity settings. CA was injected 24 h after ¹³¹I-1F5-sAv administration. Arrows indicate radioactivity in thyroid (Th), blood pool (B), and liver (L).

View larger version (28K):

[in a new window]

Figure 3. Gamma-camera images of Ramos xenograft-bearing athymic mice injected with either directly labeled ¹¹¹In-1F5 antibody (A and C) or pretargeted with 1F5-sAv conjugate followed 24 h later by CA and then by ¹¹¹In-DOTA-biotin (B and D). Images are shown at same camera intensity settings. Images of mice are shown 2 h after injection of radioactivity (A and B) and 24 h after injection of radioactivity (C and D). Arrows indicate radioactivity in tumor (T), blood pool (B), and urinary bladder (U).

View larger version (27K):

[in a new window]

Figure 4. Biodistributions of radioactivity (A) and tumor-to-normal organ ratios (B) of Ramos xenograft-bearing mice injected either with directly labeled ¹¹¹In-1F5 ( ${square}$ ) or with 1F5-sAv followed 24 h later by CA and then 1 h later with ¹¹¹In-DOTA-biotin ( ${blacksquare}$ ). Data in A were obtained 24 h after injection of radioactivity and are shown as %ID/g ± SD. Data represent the mean of 3 mice in each group.

View larger version (26K):

[in a new window]

Figure 5. Regression of lymphoma xenografts (A) and loss of body weight (B) after conventional or pretargeted RIT. BALB/c nude mice bearing Ramos lymphoma xenografts were injected with saline alone ( ${blacktriangleup}$ ), with control NR-LU-10-sAv followed by CA and later by 29.6 MBq (800 µCi) of ⁹⁰Y-DOTA-biotin ( ${triangleup}$ ), with 7.4 MBq (200 µCi) ( ${blacksquare}$ ) or 14.8 MBq (400 µCi) ( ${square}$ ) of directly labeled ⁹⁰Y-1F5, or with 1F5-sAv followed by CA and later by 14.8 MBq (400 µCi) (•) or 29.6 MBq (800 µCi) ( ${circ}$ ) of ⁹⁰Y-DOTA-biotin. Data represent mean percentage ± SD of initial values (n = 5).

View larger version (28K):

[in a new window]

Figure 6. Hematologic toxicity of mice as indicated by neutrophil counts (A), leukocyte counts (B), platelet counts (C), and hematocrit (D). BALB/c mice were injected with 7.4 MBq (200 µCi) ( ${blacksquare}$ ) or 14.8 MBq (400 µCi) ( ${square}$ ) of directly labeled ⁹⁰Y-1F5 or with 1F5-sAv followed by CA and later by 14.8 MBq (400 µCi) (•) or 29.6 MBq (800 µCi) ( ${circ}$ ) of ⁹⁰Y-DOTA-biotin. Data represent mean ± SD of 4 mice in each group.