Differential Effects of Iberdomide Versus Revlimid on Leukocyte Trafficking, Immune Activation and DLBCL Tumor Cell Killing

Introduction: Revlimid (Rev), binds to CRL4 ^CRBN E3 ligase leading to recruitment and proteasomal degradation of transcription factors Aiolos and Ikaros. This inhibits proliferation of malignant B cells and stimulates activity of T, NK and macrophage cells, thereby providing clinical activity of Rev as a single agent and in combination with CD19/CD20 antibodies in DLBCL and FL. Iberdomide (Iber), a new CELMoD with enhanced substrate degradation compared to Rev, is currently being studied in clinical trials for B-NHL and MM. Presented here is extensive in vitro and in vivo characterization of immune enhancement and antitumor effects of Iber with direct comparison to Rev.

Results: In a panel of DLBCL cell lines, comprising ABC and GCB-DLBCL models, Iber degraded Aiolos/Ikaros with faster kinetics and to a greater depth than Rev, which led to enhanced antiproliferative and cytotoxic effects. Iber acted in a cell of origin independent manner, whereas Rev is preferentially active in ABC-DLBCL. To examine the molecular effects of Iber and Rev in immune cells, we performed RNAseq and proteomic based analyses on Iber and Rev treated T, NK and monocyte cell populations. These experiments revealed a complex series of immunomodulatory activities including promotion of pro-inflammatory cytokine production, activation marker expressions and migratory machinery with a trend of Iber exhibiting greater enhancements. We confirmed these findings by demonstrating that secretion of chemoattractants for T cells, NK cells and monocytes including CXCL9, 10 and 11 (10-90% increase) and CCL8 (30% increase, p<0.01) were higher in PBMCs treated with Iber compared to Rev. Additionally, functional chemotaxis assays demonstrated that Iber and Rev increased the trafficking capacity of T-cells compared to DMSO alone, with Iber demonstrating a greater increase than Rev (46% vs 21%, p<0.01). Furthermore, Iber increased the proliferative capacity of CD8+ T and NK cells compared to Rev (10 and 3.6-fold vs 4 and 2.8-fold, respectively). Functional co-culture assays with DLBCL cells showed that Iber induced NK cell mediated killing of DLBCL cells to a greater extent than Rev and each molecule enhanced ADCC with Rituximab compared to vehicle controls. Translational data from clinical trials of a related CELMoD, Avadomide, revealed significant trafficking of immune cells such a T cells, NK cells and monocytes to the tumor microenvironment (TME). To examine the effects of Rev and Iber in an in vivo DLBCL GEMM model, we developed a humanized CRBN (hCRBN) mouse capable of facilitating proteasomal degradation of target substrates upon treatment with a CELMoD. The hCRBN mouse was then crossed with the Eμ-Myc DLBCL mouse model resulting in Eμ-Myc/hCRBN progeny that then developed disease. Splenocytes were collected and transplanted to recipient hCRBN mice. The tumor cells were allowed to engraft for 5 days upon which 3 daily doses of vehicle, Rev and Iber were given prior to the mice being sacrificed. Non-transplanted hCRBN mice served as controls. Similar to human disease, DLBCL cells remodeled the myofibroblast-immune network within lymph node and the splenic tissues including activated podoplanin (PDPN)-expressing fibroblastic reticular cells (FRCs) and diminished CD8+ T cells and CD11c+ DCs within the lymphoid TMEs. Treatment with Iber resulted in significantly enhanced infiltration of DCs and notably, cytolytic granzyme B positive T cells into the TME compared to Rev or vehicle treated mice (Figure 1). Additional characterization of the immune (T cell, NK and monocyte)-stroma TME is on-going and will be presented.

Conclusion: Our data demonstrate that Iber is more potent in substrate degradation and functionality in anti-proliferative activity against DLBCL cell line models and at triggering immunostimulatory activities in multiple lymphoid and myeloid populations. Additionally, we generated a humanized CRBN mouse model that revealed the ability of CELMoDs in inducing immune-rich TMEs supporting rational combination strategies with immune focused agents being explored in lymphoma such as SIRPα blockade, CAR T and CD3xCD20 bispecifics.

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