Abstract 4430: Combination of IGF1R/InsR and proteasome inhibition shows strong antitumor activity in proteasome inhibitor resistant multiple myeloma

Background: Overcoming proteasome inhibitor (PI) resistance remains an unmet medical need in multiple myeloma (MM) therapy. Anaplastic Lymphoma Kinase (ALK) inhibitors co-target related tyrosine-kinases, such as InsR and IGF1R. Ceritinib, a second-generation ALK inhibitor, has anti-MM activity in monotherapy or in combination with PI carfilzomib (CFZ). MM cells do not express ALK, but are dependent on InsR/IGF1R to sustain their high metabolic demand. Here, we aimed to identify the mechanism of action of ceritinib and the mechanism of synergy between ceritinib and CFZ in MM cells in vitro, in vivo, and ex vivo. Methods: PI-naïve and PI-resistant MM cell lines and primary cells were used. Genome-wide CRISPR/Cas9-based screening was performed to identify ceritinib resistance candidate genes. A pam-kinase screening, RNA sequencing and untargeted LC-MS/MS were used to elucidate mechanism of action of treatment combination. RNA-seq data from patients included in the CoMMpass study and from patients treated at the Wurzburg University Hospital were analyzed for InsR and IGF1R expression. An orthotopic in vivo mouse model with PI-resistant cells was used to determine the effect of the drug combination in vivo. Results: Among several approved ALK inhibitors tested, ceritinib shows the highest synergistic cytotoxicity in combination with CFZ in MM cell lines and primary cells. The combination of ceritinib and CFZ is active in PI-resistant MM in vivo. MM cell lines and primary cells are negative for ALK but positive for InsR and IGF1R expression, which is increased in the relapsed/refractory MM cohort. Kinase screening identified InsR and IGF1R as major kinases inhibited by ceritinib in MM. CRISPR/Cas9-screening identified transcription factor FOXO1, a downstream target of InsR/IGF1R/Akt, as the top resistance candidate to ceritinib. Subsequently, FOXO1 inhibition protected MM cells from ceritinib-induced cytotoxicity. Ceritinib in combination with CFZ caused rapid translocation of FOXO1 to the nucleus, suggesting its activation. Consistently, ceritinib induced the expression of genes related to cell cycle arrest, which are regulated by FOXO1. Ceritinib, by targeting the InsR/IGF1R, impaired glycolysis and amino acid homeostasis, observed as an accumulation of aromatic amino acids. Collectively, ceritinib decreases Akt activity via InsR/IGF1R inhibition, leading to metabolic and proliferative shut-down. In combination with proteasome inhibition, this has a detrimental effect, impairing protein homeostasis and inducing starvation in MM cells. Conclusion: Ceritinib in combination with carfilzomib represents a promising treatment option for MM to be tested in the clinic. Support: Supported by the project National Institute for Cancer Research (Programme EXCELES, ID Project No. LX22NPO5102) - Funded by the European Union - Next Generation EU. Citation Format: Andrej Besse, Tiberiu Totu, Marianne Kraus, Max Mendez Lopez, Jana Veprkova, Ondrej Slaby, Marija Buljan, Leo Rasche, K. Martin Kortum, Christoph Driessen, Lenka Besse. Combination of IGF1R/InsR and proteasome inhibition shows strong antitumor activity in proteasome inhibitor resistant multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4430.