Contributions
Abstract: PB2328
Type: Publication Only
Background
CD37 is an internalizing transmembrane glycoprotein widely expressed on mature B-cells and B-cell malignancies. The next generation anti-CD37 radioimmunoconjugate (RIC) 177Lu-lilotomab satetraxetan (Betalutin®), containing the beta-emitting radionuclide lutetium-177, is currently being tested as one-time injection therapy in a clinical phase 2b trial for follicular lymphoma (FL) and phase 1 trial for diffuse large B-cell (DLBCL) non-Hodgkin B-cell lymphomas.
Aims
The present work is to identify proliferation inhibiting drug combinations with 177Lu-lilotomab satetraxetan in radioimmunotherapy resistant DLBCL cell lines.
Methods
Cell cycle progression and DNA damage induction in response to 177Lu-lilotomab satetraxetan treatment was studied by flow cytometry in six human DLBCL cell lines. Two identified treatment resistant cell lines were treated for 18 hours with 177Lu-lilotomab satetraxetan (600 MBq/mg; 1 or 0.5 µg/ml), washed, and seeded on micro-well plates pre-printed with a drug library of 384 approved anti-cancer compounds at 10, 100, and 1000 nM f.c. (Selleck). Cell viability was monitored at days 3 to 6 post seeding using a RealTime-Glo™ MT Cell Viability Assay (Promega). Drug combinations were scored by effect size compared to drug or 177Lu-lilotomab satetraxetan treatment alone.Results
We identify two aggressive activated B-cell like DLBCL cell lines, U-2932 and RIVA, as resistant to treatment with 177Lu-lilotomab satetraxetan (1 µg/ml) in vitro. Both cell lines arrest in G2-phase with high amount of DNA damage (γH2AX staining) 18h after treatment, but display more than 80% viability six days post treatment. Two independent consecutive screens identify both cell line specific and shared compounds, which in combination with 177Lu-lilotomab satetraxetan result in growth inhibition greater than the additive effect of single treatments alone. Compounds scoring as hit in both investigated cell lines are considered candidates for combination therapy with 177Lu-lilotomab satetraxetan. Redundant hits are enriched in inhibitors targeting cell cycle kinases that regulate transition through mitosis, such as CDK1/2, AURKA, PLK1, as well as enzymes with important roles in DNA integrity surveillance and repair, such as Topoisomerases. Several identified compounds are in clinical trials for treatment of non-Hodgkin’s lymphomas. Selected hits, comprising antimitotic small molecule kinase inhibitors, are currently under further functional characterization.
Conclusion
177Lu-lilotomab satetraxetan shows promising activity against different DLBCL cell lines, but treatment resistance in an in vitro assay is evident for triple hit lymphoma cell lines U-2932 and RIVA. Combinatorial drug screening identifies 177Lu-lilotomab satetraxetan resistance reversing targets. Candidate compounds under clinical development for lymphoma treatment present particularly interesting leads for further functional characterization in mouse xenograft models of human lymphoma and new avenues for future radioimmuno-combination therapy.
Session topic: 19. Non-Hodgkin lymphoma Biology & Translational Research
Keyword(s): Cell line, Diffuse large B cell lymphoma, Non-Hodgkin's lymphoma, Radioimmunotherapy
Abstract: PB2328
Type: Publication Only
Background
CD37 is an internalizing transmembrane glycoprotein widely expressed on mature B-cells and B-cell malignancies. The next generation anti-CD37 radioimmunoconjugate (RIC) 177Lu-lilotomab satetraxetan (Betalutin®), containing the beta-emitting radionuclide lutetium-177, is currently being tested as one-time injection therapy in a clinical phase 2b trial for follicular lymphoma (FL) and phase 1 trial for diffuse large B-cell (DLBCL) non-Hodgkin B-cell lymphomas.
Aims
The present work is to identify proliferation inhibiting drug combinations with 177Lu-lilotomab satetraxetan in radioimmunotherapy resistant DLBCL cell lines.
Methods
Cell cycle progression and DNA damage induction in response to 177Lu-lilotomab satetraxetan treatment was studied by flow cytometry in six human DLBCL cell lines. Two identified treatment resistant cell lines were treated for 18 hours with 177Lu-lilotomab satetraxetan (600 MBq/mg; 1 or 0.5 µg/ml), washed, and seeded on micro-well plates pre-printed with a drug library of 384 approved anti-cancer compounds at 10, 100, and 1000 nM f.c. (Selleck). Cell viability was monitored at days 3 to 6 post seeding using a RealTime-Glo™ MT Cell Viability Assay (Promega). Drug combinations were scored by effect size compared to drug or 177Lu-lilotomab satetraxetan treatment alone.Results
We identify two aggressive activated B-cell like DLBCL cell lines, U-2932 and RIVA, as resistant to treatment with 177Lu-lilotomab satetraxetan (1 µg/ml) in vitro. Both cell lines arrest in G2-phase with high amount of DNA damage (γH2AX staining) 18h after treatment, but display more than 80% viability six days post treatment. Two independent consecutive screens identify both cell line specific and shared compounds, which in combination with 177Lu-lilotomab satetraxetan result in growth inhibition greater than the additive effect of single treatments alone. Compounds scoring as hit in both investigated cell lines are considered candidates for combination therapy with 177Lu-lilotomab satetraxetan. Redundant hits are enriched in inhibitors targeting cell cycle kinases that regulate transition through mitosis, such as CDK1/2, AURKA, PLK1, as well as enzymes with important roles in DNA integrity surveillance and repair, such as Topoisomerases. Several identified compounds are in clinical trials for treatment of non-Hodgkin’s lymphomas. Selected hits, comprising antimitotic small molecule kinase inhibitors, are currently under further functional characterization.
Conclusion
177Lu-lilotomab satetraxetan shows promising activity against different DLBCL cell lines, but treatment resistance in an in vitro assay is evident for triple hit lymphoma cell lines U-2932 and RIVA. Combinatorial drug screening identifies 177Lu-lilotomab satetraxetan resistance reversing targets. Candidate compounds under clinical development for lymphoma treatment present particularly interesting leads for further functional characterization in mouse xenograft models of human lymphoma and new avenues for future radioimmuno-combination therapy.
Session topic: 19. Non-Hodgkin lymphoma Biology & Translational Research
Keyword(s): Cell line, Diffuse large B cell lymphoma, Non-Hodgkin's lymphoma, Radioimmunotherapy