OP0119 The CRL4 Cereblon E3 Ubiquitin Ligase Modulator CC-220 Induces Degradation of the Transcription Factors Aiolos and Ikaros: Immunomodulation in Healthy Volunteers and Relevance to Systemic Lupus Erythematosus
Authors: P. Schafer, Y. Ye, L. Wu, J. Kosek, Z. Yang, L. Liu, M. Thomas, M. Palmisano, R. Chopra
Journal: Annals of the Rheumatic Diseases (2015)

<h3>Background</h3> CC-220 is an immunomodulatory compound that binds to cereblon (CRBN), part of the CRL4<sup>CRBN</sup> E3 ubiquitin ligase complex, which has been shown to ubiquitinate the transcription factors Ikaros (IKZF1) and Aiolos (IKZF3). Polymorphisms at the IKZF1 and IKZF3 loci have been associated with risk of systemic lupus erythematosus (SLE). <h3>Objectives</h3> We explored CRBN, IKZF1, and IKZF3 gene expression in peripheral blood mononuclear cells (PBMC) from SLE patients; the effect of CC-220 on Ikaros and Aiolos protein levels and SLE autoantibody production in vitro; and the impact of CC-220 on immunological parameters in a double-blinded, placebo-controlled, single-ascending dose, healthy volunteer phase 1 clinical trial. <h3>Methods</h3> CRBN, IKZF1, and IKZF3 gene expression were measured by qRT-PCR. Ikaros and Aiolos protein levels were measured by western blot and flow cytometry. Anti-dsDNA and anti-phospholipid autoantibodies were measured from SLE PBMC cultures treated for 7 days with CC-220. In the phase 1 healthy volunteer study, 56 subjects were randomized and enrolled in 7 cohorts, with 6 subjects per cohort receiving a single oral dose of CC-220 (0.03-6 mg) and 2 subjects per cohort receiving placebo. CD19+ B cells, CD3+ T cells, and intracellular Aiolos were measured by flow cytometry. IL-2 and IL-1β production were stimulated with anti-CD3 or LPS, respectively, in the TruCulture ex vivo whole blood assay system. <h3>Results</h3> Compared to normal PBMC, SLE PBMC expressed significantly higher levels of CRBN (1.5-fold), IKZF1 (2.1-fold), and IKZF3 (4.1-fold). CC-220 treatment of whole blood significantly reduced Aiolos and Ikaros protein levels in B cells, T cells, and monocytes, but not in granulocytes. In cultures of SLE PBMC, CC-220 inhibited anti-dsDNA and anti-phospholipid autoantibody production with an IC<sub>50</sub> of $≈ $10 nM. Following administration of single doses of CC-220 to healthy volunteers, there was a treatment-related decrease in intracellular Aiolos, with minimum mean percent of baseline values of $≈ $12%&gt;28% in B cells and 0%&gt;33% in T cells, for 0.3-6 mg. There was also a treatment-related decrease in absolute CD19+ B cells and CD3+ T cells, with minimum mean percent of baseline values of $≈ $41%&gt;67% for B cells and 66%&gt;73% for T cells, for 2-6 mg. CC-220 administration also resulted in increased IL-2 (maximum mean percent of baseline values ranging from 247%&gt;1896% for 0.1-6 mg), and a decrease in IL-1β (minimum mean percent of baseline values of $≈ $11% at 6 mg). <h3>Conclusions</h3> These results demonstrate that CRBN, IKZF1, and IKZF3 mRNA are overexpressed in PBMC of SLE patients. Targeting the CRL4<sup>CRBN</sup> E3 ubiquitin ligase with CC-220 resulted in a potent reduction in Aiolos and Ikaros protein levels in B cells, T cells, and monocytes, and inhibited autoantibody production. Administration of single doses of CC-220 (0.3-6 mg) reduced intracellular Aiolos protein expression in B cells and T cells, reduced absolute B-cell and T-cell counts in peripheral blood, and increased T-cell-derived IL-2 production and decreased LPS-induced IL-1β production in whole blood ex vivo. These findings support the further development of CC-220 for the treatment of SLE and other autoimmune diseases. <h3>Disclosure of Interest</h3> P. Schafer Employee of: Celgene Corporation, Y. Ye Employee of: Celgene Corporation, L. Wu Employee of: Celgene Corporation, J. Kosek Employee of: Celgene Corporation, Z. Yang Employee of: Celgene Corporation, L. Liu Employee of: Celgene Corporation, M. Thomas Employee of: Celgene Corporation, M. Palmisano Employee of: Celgene Corporation, R. Chopra Employee of: Celgene Corporation