Abstract 2215: Pharmacogenomic investigation of Bruton's tyrosine kinase (BTK) inhibitor ibrutinib (PCI-32765): drug sensitivity in diffuse large B-cell lymphoma (DLBCL) within a tumor microenvironment-aligned high-throughput screen.

Ibrutinib (PCI-32765) is an orally administered small molecule that covalently binds to Cys-481 of Bruton9s tyrosine kinase (BTK). Ibrutinib has demonstrated promise across several types of B-cell malignancies and is currently in Phase 2/3 clinical testing. Preclinical studies have established three key mechanisms following blunting of proximal B cell receptor (BCR) signaling through BTK inhibition: (1) suppression of pro-survival pathways, (2) diminished integrin activation and (3) attenuation of chemotactic response. Single agent ibrutinib Phase 1/2 clinical trials have revealed high clinical response rates in both naive and relapsed or refractory chronic lymphocytic leukemia (CLL), as well as, relapsed or refractory mantle cell lymphoma (MCL) patients (Byrd, et al. 2012 ASH; Wang, et al. 2012 ASH; Advani, et al. 2010 JCO). Response rates in a phase 2 diffuse large B cell lymphoma (DLBCL) clinical trial appeared to be more prevalent in “activated B-cell” (ABC) over “germinal center B-cell like” (GCB) DLBCL patients (Staudt et al., ASH 2012). To gain a further understanding of ibrutinib response and inform optimal therapeutic combinations in DLBCL, we established a combination high throughput pharmacology screen (cHTS) with ibrutinib. Ibrutinib was evaluated alone and in combination with 99 targeted compounds, across 17 (12 GCB; 5 ABC) DLBCL cell lines. To better align with human biology, DLBCL cell lines were screened in the presence of human marrow stromal cell conditioned media (hMSC-CM) and B-cell receptor stimulation via anti-IgG/anti-IgM antibodies. Interestingly, 8/17 (47%) DLBCL cell lines were intolerant to any external BCR stimulation, so those lines were screened in hMSC-CM without exogenous BCR stimulation. Under our experimental conditions, 11/17 (65%) cell lines displayed some sensitivity (IC 50 TM measurements [breakdown: 4/17 (24%) highly sensitive (IC 50 50 200 nM 50 1 M 50 > 10 M)]. Consistent with DLBCL clinical responses, the highly sensitive (IC 50 Citation Format: Cuc Davis, Tineke Casneuf, Willem Lightenberg, Richard Rickles, Winnie Tam, Matthias Versele, Steven McClue, Sriram Balasubramanian, Joseph Buggy, Kate Sasser, Brett Hall. Pharmacogenomic investigation of Bruton9s tyrosine kinase (BTK) inhibitor ibrutinib (PCI-32765): drug sensitivity in diffuse large B-cell lymphoma (DLBCL) within a tumor microenvironment-aligned high-throughput screen. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2215. doi:10.1158/1538-7445.AM2013-2215