Abstract 848: In vitro and in vivo evaluation of the beta-emitting lutetium-177 labeled anti-CD37 antibody radionuclide conjugate 177Lu-NNV003 in DLBCL, CLL and MCL models
Authors: Maaland Astri F. , Heyerdahl Helen , O'Shea Adam , Eiriksdottir Bergthora , Dahle Jostein 
Published: August 2018

The aim of this study was to evaluate the cytotoxic and anti-tumor efficacy of the beta-emitting lutetium labelled NNV003 antibody (177Lu-NNV003) in non-Hodgkin lymphoma (NHL) and Chronic Lymphocytic Leukemia (CLL) models.

Antibody-Dependent Cellular Cytotoxicity (ADCC) and Complement-Dependent Cytotoxicity (CDC) were measured in REC-1 (MCL), MEC-2 (CLL) and DOHH-2 (DLBCL) cells using FcRγIIIa immortalized NK92 cells as effector cells. Antibody-Dependent Cellular Phagocytosis (ADCP) was measured using a commercially available FcRγIIa-H reporter kit. Binding and internalization of 177Lu-NNV003 after up to 18 hours incubation were measured by a stripping buffer method. Cytotoxicity effects were evaluated by incubating cells with increasing concentrations of 177Lu-NNV003 and measuring cell proliferation. Biodistribution of 177Lu-NNV003 was measured in CB17 SCID and NSG mice with DLBCL and CLL xenografts, respectively. Therapeutic and toxic effects of 177Lu-NNV003 were measured in different strains of immunocompromised mice bearing systemic DLBCL (in RAG-2), CLL (in RAG-1) or MCL (in NOD SCID) xenografts, and compared with NaCl and unspecific 177Lu-labelled isotype control groups.

NNV003 elicited ADCC lysis in all cell lines and induced ADCP in MEC-2 and DOHH-2. Minimal CDC activation was observed. 177Lu-NNV003 showed activity dependent antiproliferative effect in all cell lines. Maximum tumor uptake in vivo was 45% IA/g in MEC-2 tumors and 15% IA/g in DOHH-2 tumors. Survival was significantly extended in DOHH-2 xenograft-bearing mice treated with NNV003 (2-30 mg/kg) and 177Lu-NNV003 (200-400 MBq/kg) compared to control groups (p&lt;0.0001). In the MEC-2 model, 200 MBq/kg 177Lu-NNV003 extended survival compared to the NNV003 and the 177Lu-isotype treatment (p&lt;0.025). In mice bearing REC-1 xenografts, both 50 and 100 MBq/kg 177Lu-NNV003 improved survival compared to control groups (p&lt;0.02). Transient hematological toxicity was observed in all groups treated with radioactivity, and one mouse treated with 200 MBq/kg in the MEC-2 study died of radiation toxicity. 177Lu-NNV003 showed best anti-tumor effect in the two NHL models, and less effect in the CLL model despite the high tumor uptake, which might be explained by the very aggressive growth of the MEC-2 cells in vivo.

In conclusion, in vitro studies have shown that the unlabelled NNV003 antibody have an immunological cytotoxicity effect on tumor cells, mainly through ADCC, and that 177Lu-NNV003 inhibits cell growth. 177Lu-NNV003 has shown significant tumor uptake and therapeutic effect in vivo in all three models tested. The results warrant clinical testing in patients suffering from CD37-expressing B-cell malignancies.

Citation Format: Astri F. Maaland, Helen Heyerdahl, Adam O'Shea, Bergthora Eiriksdottir, Jostein Dahle. In vitro and in vivo evaluation of the beta-emitting lutetium-177 labeled anti-CD37 antibody radionuclide conjugate 177Lu-NNV003 in DLBCL, CLL and MCL models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 848.