Published in:
01-03-2016 | Original Article
High treatment efficacy by dual targeting of Burkitt’s lymphoma xenografted mice with a 177Lu-based CD22-specific radioimmunoconjugate and rituximab
Published in: European Journal of Nuclear Medicine and Molecular Imaging | Issue 3/2016
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Purpose
Dual-targeted therapy has been shown to be a promising treatment option in recurrent and/or refractory B-cell non-Hodgkin’s lymphoma (B-NHL). We generated radioimmunoconjugates (RICs) comprising either a novel humanized anti-CD22 monoclonal antibody, huRFB4, or rituximab, and the low-energy β-emitter 177Lu. Both RICs were evaluated as single agents in a human Burkitt’s lymphoma xenograft mouse model. To increase the therapeutic efficacy of the anti-CD22 RIC, combination therapy with unlabelled anti-CD20 rituximab was explored.
Methods
The binding activity of CHX-A″-DTPA-conjugated antibodies to target cells was analysed by flow cytometry. To assess tumour targeting of 177Lu-labelled antibodies, in vivo biodistribution experiments were performed. For radioimmunotherapy (RIT) studies, non-obese diabetic recombination activating gene-1 (NOD-Rag1
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) interleukin-2 receptor common gamma chain (IL2rγ
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) null mice (NRG mice) were xenografted subcutaneously with Raji Burkitt’s lymphoma cells. 177Lu-conjugated antibodies were administered at a single dose of 9.5 MBq per mouse. For dual-targeted therapy, rituximab was injected at weekly intervals (0.5 – 1.0 mg). Tumour accumulation of RICs was monitored by planar scintigraphy.
Results
Conjugation of CHX-A”-DTPA resulted in highly stable RICs with excellent antigen-binding properties. Biodistribution experiments revealed higher tumour uptake of the 177Lu-labelled anti-CD22 IgG than of 177Lu-labelled rituximab. Treatment with 177Lu-conjugated huRFB4 resulted in increased tumour growth inhibition and significantly longer survival than treatment with 177Lu-conjugated rituximab. The therapeutic efficacy of the anti-CD22 RIC could be markedly enhanced by combination with unlabelled rituximab.
Conclusion
These findings suggest that dual targeting with 177Lu-based CD22-specific RIT in combination with rituximab is a promising new treatment option for refractory B-NHL.