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EANM OP-069
Sunday, October 14, 11:30 - 12:45
11:30
Therapeutic efficacy of 177Lu-lilotomab satetraxetan in non-Hodgkin B-cell Lymphoma is controlled by G2/M cell cycle progression
A. Pichard1, S. Marcatili2, I. Navarro-Teulon1, H. Heyerdahl3, S. Patzke3, V. Stenberg3, M. Bardiès2, J. Dahle3, J. Pouget1; ; 1IRCM/INSERMU1194, Montpellier, FRANCE, 2CRCT Toulouse, Toulouse, FRANCE, 3Nordic Nanovector ASA, Oslo, NORWAY.
Abstract
We aimed at determining the molecular mechanisms involved in the therapeutic efficacy of 177Lu-labeled lilotomab satetraxetan (Betalutin®) directed against the CD37 receptor expressed by non-Hodgkin lymphoma (NHL) B-cells. Materials and methods. In vitro , Ramos, Raji and rituximab resistant Raji (Raji2R, all Burkitt lymphoma), DOHH2 (transformed follicular), Rec-1 (mantle), U2932 and OCILy8 (diffuse large B-cell) lymphoma cell lines were exposed for 18 hours to increasing activities (0-6 MBq/mL) of 177Lu-lilotomab, of the non-specific 177Lu-cetuximab or to unlabelled mAbs (0-40µg/mL). Clonogenic survival, proliferation, expression level of phosphorylated CDK1, cell cycle progression and apoptosis were investigated. In vivo , mice bearing subcutaneous Ramos, DOHH2, Raji, Raji2R or OCILy8 tumour xenografts, were treated with 177Lu-mAbs, with rituximab or lilotomab and tumour growth was monitored. Results. We showed in all lymphoma cell lines that unlabelled rituximab was more cytotoxic than lilotomab. When lilotomab was radiolabeled, 177Lu-lilotomab was more cytotoxic than rituximab in the so determined radiosensitive DOHH2 cells while its cytotoxicity in Ramos cells was less pronounced. The higher response to 177Lu-lilotomab in DOHH2 cells than in Ramos cells was mainly mediated by lack of G2/M cell cycle arrest in DOHH2 cells followed by strong induction of apoptosis. Inhibition of CDK1 Tyr15 phosphorylation using MK1775 or PD166285 drugs radiosensitized Ramos cells. These results were supported by in vivo data. In Ramos tumour xenograft models, 250 MBq/kg (1.25 mg/kg) 177Lu-lilotomab and 10 mg/kg rituximab could not delay tumor growth compared with untreated mice. 177Lu-lilotomab significantly delayed tumour growth compared with rituximab (used at the same concentration) only if injected activity was increased up to 500 MBq/kg. Conversely, in DOHH2 tumour xenografts, 100 MBq/kg (0.5 mg/kg) 177Lu-lilotomab was more efficient than rituximab. The in vivo use of MK1775 was shown to radiosensitize Ramos tumour xenografts to 177Lu-lilotomab. Experiments analysis is ongoing for OCILy8, Raji and Raji2R cell lines.
Conclusion: These results indicate that 177Lu-lilotomab is an efficient therapeutic tool for NHL, particularly for tumors showing reduced inhibitory CDK1 phosphorylation.
EANM OP-252
Monday, October 15, 08:00 - 09:30
08:54
Tumor Absorbed Dose and Changes in FDG PET Parameters in Non-Hodgkin Lymphoma Patients Treated With 177Lu-Lilotomab Satetraxetan
A. Løndalen1,2, J. Blakkisrud1,3, J. Dahle4, M. E. Revheim1,2, H. Holte5, A. Kolstad5, C. Stokke1,6; ; 1Division of Radiology and Nuclear Medicine, Oslo University Hospital, Oslo, NORWAY, 2Faculty of Medicine, University of Oslo, Oslo, NORWAY, 3Dept. of Physics, University of Oslo, Oslo, NORWAY, 4Nordic Nanovector ASA, Oslo, NORWAY, 5Dept. of Oncology, Radiumhospitalet, Oslo University Hospital, Oslo, NORWAY, 6Dept. of Life Sciences and Health, Oslo Metropolitan University, Oslo, NORWAY.
Abstract
Introduction: 177Lu-lilotomab satetraxetan is a novel anti-CD37 antibody-radionuclide conjugate for treatment of non-Hodgkin lymphoma (NHL) patients. Patients from four treatment arms with different pre-treatment and pre-dosing regimens in the phase 1 part of the LYMRIT-37-01 trial were included. Patients were injected with 10, 15 or 20 MBq/kg of 177Lu-lilotomab satetraxetan. The aim of this work was to calculate changes in FDG-PET parameters at a lesion level and investigate correlations with tumor absorbed doses. Subjects and Methods: A total of 40 tumours from 15 patients (1-5 tumours per patient) were included, based on eligibility for dosimetry. Tumour absorbed doses were calculated from post therapy SPECT/CT-images as previously described (Blakkisrud et. al, JNM 58(1) 2017). FDG PET/CT was performed at baseline and three months after treatment. The following PET parameters were measured: Standardized uptake value (SUV) max, SUVpeak, metabolic tumour volume (MTV) and total lesion glycolysis (TLG). MTV and TLG were calculated according to EANM guidelines for tumour imaging v2. The relative change at three months compared to baseline was calculated for each parameter. Results: Mean baseline values (range) for SUVmax, SUVpeak, MTV and TLG were 9.5 (4.6 - 19.4), 8.0 (3.5 - 16.8), 13.0 (1.9 - 112.8) ml and 91.2 (7.6 - 1071.1). A full reduction in SUVmax, SUVpeak, MTV and TLG was observed in 18, 25, 26 and 26 tumours, respectively. Average change in FDG PET-parameters for SUVmax, SUVpeak, MTV and TLG were 56, 64, 78 and 75 %, respectively. The tumour absorbed doses ranged from 35 to 859 cGy, with a mean value of 299 cGy. No significant linear correlation was found between tumour absorbed dose and the relative change in PET-parameters. However, when inspecting each patient individually (excluding patients that had a complete reduction in all included tumours), higher tumour absorbed doses resulted in more reductions in SUVmax for 6 of 8 patients. Conclusion: Using a generalized linear model, no clear overall correlation between tumour absorbed dose and relative change in the FDG PET parameters were observed. This could possibly be attributed to the fit model and individual differences, as most lesions demonstrated either a complete reduction in SUVmax or an intra-patient increased reduction for higher absorbed doses.