[24] Development of a novel Ikaros/Aiolos transcriptional signature and correlation with patient response in multiple myeloma patients treated with CELMoDs

Multiple myeloma (MM) is a neoplasm characterized by the clonal proliferation of malignant plasma cells in the bone marrow. CELMoD™ agents—including iberdomide (IBER) and mezigdomide (MEZI)—modulate Cereblon to induce the degradation of the hematologic transcription factors Ikaros (Ik) and Aiolos (Ai), exerting anti-proliferative and pro-apoptotic effects on MM cells. While Ik/Ai protein degradation can be semi-quantified by immunohistochemistry (IHC), clinical responses are not always correlated with IHC readouts, motivating a more quantitative genomic approach.

We performed CUT&RUN and ChIP-seq on the H929 MM cell line to map Ik binding targets genome-wide. By intersecting these targets with differential expression analysis (DESeq2) across multiple CELMoD treatments (LEN, POM, MEZI, IBER) at multiple timepoints, we compiled a high-confidence Ik regulon consisting of 115 up-regulated and 95 down-regulated target genes.

Gene Set Variation Analysis (GSVA) was then applied to this regulon to derive a sample-level Ik activity score. Key findings include:

• On-treatment decrease: RNA-seq paired samples from MEZI-treated (N=7) and IBER-treated (N=41) patients showed significantly lower Ik activity scores at cycle 2 day 15 compared to screening.
• Association with survival: Using an optimal cutpoint, greater on-treatment reduction in Ik activity score was significantly associated with longer progression-free survival (PFS) in IBER-treated patients.
• Concordance with IHC: The RNA-seq based score showed significant agreement with IHC-based Ik degradation scores in a validation cohort (N=22), supporting its use as a complementary or standalone biomarker.

This work establishes a robust transcriptomic framework for monitoring Ik/Ai target engagement and predicting clinical outcomes in MM patients receiving CELMoD therapy.