Cure of Micrometastatic B-Cell Lymphoma in a SCID Mouse Model Using 213Bi-Anti-CD20 Monoclonal Antibody.

We studied the feasibility of using the α-emitting 213Bi-anti-CD20 therapy with direct bioluminescent tracking of micrometastatic human B-cell lymphoma in a SCID mouse model. Methods: A highly lethal SCID mouse model of minimal-tumor-burden disseminated non-Hodgkin lymphoma (NHL) was established using human Raji lymphoma cells transfected to express the luciferase reporter. In vitro and in vivo radioimmunotherapy experiments were conducted. Single- and multiple-dose regimens were explored, and results with 213Bi-rituximab were compared with various controls, including no treatment, free 213Bi radiometal, unlabeled rituximab, and 213Bi-labeled anti-HER2/neu (non-CD20-specific antibody). 213Bi-rituximab was also compared in vivo with the low-energy ß-emitter 131I-tositumomab and the high-energy ß-emitter 90Y-rituximab. Results: In vitro studies showed dose-dependent target-specific killing of lymphoma cells with 213Bi-rituximab. Multiple in vivo studies showed significant and specific tumor growth delays with 213Bi-rituximab versus free 213Bi, 213Bi-labeled control antibody, or unlabeled rituximab. Redosing of 213Bi-rituximab was more effective than single dosing. With a single dose of therapy given 4 d after intravenous tumor inoculation, disease in all untreated controls, and in all mice in the 925-kBq 90Y-rituximab group, progressed. With 3,700 kBq of 213Bi-rituximab, 75% of the mice survived and all but 1 survivor was cured. With 2,035 kBq of 131I-tositumomab, 75% of the mice were tumor-free by bioluminescent imaging and 62.5% survived. Conclusion: Cure of micrometastatic NHL is achieved in most animals treated 4 d after intravenous tumor inoculation using either 213Bi-rituximab or 131I-tositumomab, in contrast to the lack of cures with unlabeled rituximab or 90Y-rituximab or if there was a high tumor burden before radioimmunotherapy. α-emitter-labeled anti-CD20 antibodies are promising therapeutics for NHL, although a longer-lived α-emitter may be of greater efficacy.

Relationship of BMPR2 mutations to vasoreactivity in pulmonary arterial hypertension.

BACKGROUND: Vasoreactivity tests are fundamental in evaluating pulmonary arterial hypertension (PAH). Mutations of the transforming growth factor-beta type II receptor gene, BMPR2, predispose to the development of pulmonary hypertension and may alter the response to vasodilators. Previous investigations have not examined the relationship of BMPR2 mutations to vasoreactivity. METHODS AND RESULTS: We identified 133 consecutive unrelated patients with either idiopathic or familial PAH. Sixty-six patients were excluded because we lacked either DNA samples (n=18) or complete data from a vasoreactivity test (n=48). The remaining 67 patients were screened for BMPR2 DNA sequence variations, and specific variations were confirmed by gene sequencing. The vasoreactivity of patients with nonsynonymous BMPR2 variations was compared with that of patients without nonsynonymous BMPR2 variations. We found nonsynonymous BMPR2 variations in 27 of 67 patients with idiopathic (n=16 of 52) or familial (n=11 of 15) PAH. Vasoreactivity was identified in 3.7% of 27 patients with nonsynonymous BMPR2 variations and in 35% of 40 patients without nonsynonymous BMPR2 variations (P=0.003). Five of the 27 nonsynonymous variations occur commonly in healthy individuals. None of the remaining 22 patients with BMPR2 variations demonstrated vasoreactivity, and the analysis remained unchanged when we assumed that nonsynonymous BMPR2 variations were present in all 15 patients with familial PAH. CONCLUSIONS: Patients with familial or idiopathic PAH and nonsynonymous BMPR2 variations are unlikely to demonstrate vasoreactivity. Further trials are required to determine whether long-term therapy can be directed by tests for BMPR2 variations.