Lopez‐Girona, Antonia

AbstractCancer treatment has been transformed by checkpoint blockade therapies, with the highest anti-tumor activity of anti-programmed death 1 (PD-1) antibody therapy seen in Hodgkin lymphoma. Disappointingly, response rates have been low in the non-Hodgkin lymphomas, with no activity seen in relapsed/refractory chronic lymphocytic leukemia (CLL) with PD-1 blockade. Thus, identifying more powerful combination therapy is required for these patients. Here, we preclinically demonstrate enhanced anti-CLL activity following combinational therapy with anti-PD-1 or anti-PD-1 ligand (PD-L1) and avadomide, a cereblon E3 ligase modulator (CELMoD). Avadomide induced type I and II interferon (IFN) signaling in patient T cells, triggering a feedforward cascade of reinvigorated T-cell responses. Immune modeling assays demonstrated that avadomide stimulated T-cell activation, chemokine expression, motility and lytic synapses with CLL cells, as well as IFN-inducible feedback inhibition through upregulation of PD-L1. Patient-derived xenograft tumors treated with avadomide were converted to CD8+ T cell-inflamed tumor microenvironments that responded to anti-PD-L1/PD-1-based combination therapy. Notably, clinical analyses showed increased PD-L1 expression on T cells, as well as intratumoral expression of chemokine signaling genes in B-cell malignancy patients receiving avadomide-based therapy. These data illustrate the importance of overcoming a low inflammatory T-cell state to successfully sensitize CLL to checkpoint blockade-based combination therapy.

Abstract Abstract 1793 Thalidomide (THAL) and IMID® immunomodulary drugs lenalidomide (LEN) and (POM) have proven beneficial in the treatment of a variety of hematological malignancies. Pre-clinical studies demonstrate multiple direct and indirect anti-tumor activities including anti-angiogeneic, proapoptotic, anti-proliferative and immunomodulatory effects. Recent studies have identified cerebron (CRBN) as a potential direct physical target of THAL and IMiD compounds and CRBN expression is reportedly required for IMiD compound activity. However, the precise link between CRBN and IMiD compound mechanism of action (MOA) have not been clearly defined. We applied Drosophila as a drug discovery platform to assess the MOA of THAL and IMiD compounds in vivo. THAL or POM fed Drosophila demonstrate morphological phenotypes that replicate wingless (wg) mutants indicating that drugs are inhibitors of Wg/Wnt signaling. In this model system, THAL and IMiD compounds disrupt membrane localization of GSK-3 indicating that the bioactivity of IMiD compounds is achieved through spatial regulation and potentiation of Sgg/GSK-3 in Drosophila. Using epistasis analysis we show that Drosophila expressing genetic mutants lacking GSK-3 activity and myeloma cells in which GSK-3a and GSK-3b have been knocked down by siRNA fail to respond to POM. In both Drosophila and myeloma cells therefore it appears that GSK-3 activity is required for biological responses. To test the clinical validity of GSK-3 as a biomarker, we obtained patient tumor samples from a Phase II clinical trial of single agent LEN for previously untreated CLL (Chen CI et al., J Clin Oncol, 2011; 29:1175). Twenty five patients were enrolled onto this study and received LEN at a starting dose of 2.5 mg days 1–21 of a 28 day cycle with monthly escalation to a target dose of 10 mg. The primary clinical endpoint for the trial was objective response to lenalidomide (complete response (CR) and partial response (PR)) evaluated as defined in the revised 1996 NCI Working Group guidelines. Peripheral blood samples for correlative studies were collected on days 1 (pre-dosing) and 8 of cycles 1 and 2. CRBN expression was evaluated by gene expression profiling and Western blot and found to be uniformly expressed in all 19 evaluable day 1 patient samples regardless of LEN response. Thus CRBN expression does not appear to be a useful predictive biomarker of response in this population of previously untreated patients. However, GSK-3 localization was correlated with response. Paired analysis of CD19 selected CLL cells comparing day 1 vs day 8 revealed focal membrane localization of GSK-3 on day 1 and subcellular redistribution on day 8 in 11 out of 12 evaluable responders (PR or better). By contrast, in the CLL cells from all 6 evaluable non-responders, GSK-3 expression appeared diffusely distributed before and after treatment. In preliminary studies using confocal immunofluorescence microscopy we determined that CRBN and GSK-3 co-localize in day 1 CLL samples of responders but not in those of non-responders. In summary, our results indicate that THAL and the IMiD compounds target GSK-3 function by spatial regulation and identify GSK-3 localization as a potential clinical biomarker of IMiD response. Disclosures: Trudel: Celgene: Honoraria; GlaxoSmithKline: Research Funding; Janssen: Honoraria. Mercurio:Celgene: Equity Ownership, Research Funding. Lopez-Girona:Celgene Corp: Employment, Equity Ownership. Gaidarova:Celgene Corp: Employment, Equity Ownership. Webb:Celgene: Employment, Equity Ownership. Chen:Johnson & Johnson: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; GlaxoSmithKline: Research Funding; Lundbeck: Consultancy. Stewart:Millenium: Consultancy, Honoraria, Research Funding; Onyx: Consultancy; Celgene: Consultancy. Manoukian:Celgene: Research Funding.