Reported values are mean SEM. Open in a separate window FIGURE 2. Blood clearance of 225Ac-E4G10 and 225Ac-isotype control in glioblastoma-bearing (A) and na?ve Ntva Aldicarb sulfone (B) mice. assess overall survival alone and in combination with temozolomide, the standard-of-care chemotherapeutic agent. Results: 225Ac-E4G10 was found to accumulate in tissues expressing the target antigen. Antivascular -particle therapy of glioblastoma in the transgenic Ntva model resulted in significantly improved survival compared with controls and potent control of tumor Aldicarb sulfone growth. Adding the chemotherapeutic temozolomide to the treatment increased survival to 30 d (vs. 9 d for vehicle-treated animals). Histologic analyses showed a remodeled glioblastoma vascular microenvironment. Conclusion: Targeted -particle antivascular therapy is shown for the first time to be effective in increasing overall survival in a solid tumor in Aldicarb sulfone a clinically relevant transgenic glioblastoma mouse model. = 3); 40 na?ve Ntva mice were arranged into 8 groups (= 5). Each animal received a single intravenous dose of 11.1 kBq (300 nCi) of 225Ac-E4G10 or 225Ac-isotype. Mice were euthanized at 4, 12, 36, and 240 h, and tissue samples were harvested, weighed, and counted in a -counter using a 360- to 480-keV window at secular equilibrium. Aliquots (20 L) of the injected doses were used as decay-correction standards. The percentage injected doses per gram of tissue weight were calculated and plotted as means. Statistical analysis of data was performed using Prism software (GraphPad Software Inc.). Absorbed Dose Estimates The percentage injected dose per gram of tissue weight values were converted to percentage of injected activity (%IA) per gram of tissue weight. Thereafter, the areas under the activity concentrationCtime curves were estimated by trapezoidal integration with the contribution of the terminal portion calculated by extrapolation from the 240-h value using the faster of apparent terminal clearance rate or physical decay. Subsequently, absorbed doses, D (Gy/MBq), were calculated from the area under the curve (%IA h/g) values according to D = 10 area under the curve , where is the equilibrium dose constant for the total decay of 225Ac. The value used for (1.43 10?2 J/MBq h) includes the contributions of all the radioactive progeny of 225Ac and thus assumes no translocation of any progeny from the site of the original 225Ac decay. Histologic Analysis Glioblastoma-bearing Ntva mice (= 12) were placed into the following groups with an even distribution of tumor sizes: 225Ac-E4G10 (= 4), 225Ac-isotype (= 4), and 1% HSA vehicle (= 4). Anesthetized (1.5% isoflurane) mice received a single 7.4-kBq (200 nCi) SCDO3 dose (0.1 mL) via retroorbital venous plexus of 225Ac-E4G10, 225Ac-isotype control, or vehicle at day 0. Ten days after treatment, the tumor was harvested and analyzed. Briefly, mice were sacrificed and glioblastoma and brain were excised and fixed in 4% paraformaldehyde/phosphate-buffered saline for 2 d. Fixed tissue was paraffin-embedded and cut into 5-m sections. Sections were stained with hematoxylin and eosin or anti-CD31antibody for endothelium, respectively. Sections were scanned with the Mirax Digital Slide Scanner using a 20 lens (Carl Zeiss Microimaging). Analysis was performed on whole tumor sections with Pannoramic Viewer software (3DHISTECH). Survival Studies Therapy was conducted for all survival studies after the initial MR imaging 5 wk after induction. Tumor induction with the RCAS system resulted in a normal distribution of tumor sizes and disease progression in tumor-induced mice (60%C80% of tumors small/medium sized; 10%C20% very small/not visible in the initial MRI; 10%C20% were large tumors occupying up to 20% of cranial space). Mice with large tumor sizes exhibited glioblastoma symptoms such as hydrocephalus or hunched posture and were excluded from entering studies (as well as animals exhibiting very small/not-yet-visible tumors). However, these late-stage animals entered survival study II to investigate therapy results in a late-stage disease scenario. Survival outcomes were scored and plotted using KaplanCMeier survival analysis in Prism software. Survival Study I Mice were separated into a 225Ac-E4G10 treatment group (= 9) and a 1% HSA (vehicle) group (= 8) and treated with 0.46 kBq (12.5 nCi) of 225Ac-E4G10/g of body mass (7.4C11.1 kBq [200C300 nCi]/mouse). Tumor growth was followed in 4 representative mice per group using T2 MRI to measure tumor volume at baseline (day 0; 5 wk after tumor induction) and 10 d later. Survival Study II Mice treated in survival study II exhibited advanced glioblastoma with symptoms of hydrocephalus and hunched posture. Mice were separated into a specific 225Ac-E4G10 treatment group (= 4), a control 225Ac-isotype group (= 3), and a.