Burington, Bart

11063 Background: Dacetuzumab (SGN-40) is a humanized IgG1 monoclonal antibody that binds to CD40, mediates effector cell functions, and activates downstream apoptosis signaling pathways. Dacetuzumab has shown single-agent activity in relapsed/refractory DLBCL in phase I and phase II trials, with multiple objective responses and 1/3 of patients demonstrating tumor shrinkage, defined as a decrease in tumor volume (SPD) of at least 10%. We previously reported a 14-gene signature (ASH 2008 #1593) that was strongly associated with dacetuzumab sensitivity in DLBCL cell lines. Here, we report an initial evaluation of the gene signature as a classifier of patients likely to demonstrate tumor shrinkage after dacetuzumab therapy. Methods: The original 14 microarray probes were chosen for high correlation with in vitro dacetuzumab sensitivity (IC25) in 31 NHL cell line models. Matching qRT-PCR probes were developed and confirmed to correlate with the microarray probes in paired cell line samples. In this retrospective analysis, archived paraffin blocks from a 26 patient subset of the phase I and II trials, with a diagnosis of DLBCL and available tumor measurements, were assayed by qRT-PCR. Results: Overall, 42% of patients (11/26) exhibited decreased SPD of at least 10%. Of those who were marker +, 10 out of 13 (78%) had 10% or better decreases in SPD, whereas only 1 of 13 patients who were marker - demonstrated tumor shrinkage (8%). The overall accuracy for predicting tumor shrinkage was 85% (one-sided P=0.002, by permutation test). Among the 14 genes contributing to the multivariate signature, CD22 and VNN2 were the most strongly down-regulated in specimens from patients without at least a 10% decrease in SPD (P=0.14 and P=0.10, respectively), while IGF1R and CTSC were the most strongly up-regulated (P=0.05 and P=0.08, respectively). Conclusions: A 14-gene signature appears to predict tumor shrinkage in DLBCL patients receiving dacetuzumab in single-agent clinical trials (P=0.002). A larger clinical data set will be analyzed to further evaluate the correlation of this gene signature with objective clinical response rates.. [Table: see text]

Abstract Abstract 2721 Poster Board II-697 The role of the CD40 pathway in B-cell cancers is rather enigmatic due to having polar opposite roles in tumor biology. Stimulation of the CD40 receptor can reduce cell viability of NHL cell lines and xenograft tumor models, whereas, in sharp contrast, constitutive CD40 stimulation can actually promote proliferation of NHL cell lines, as well as drive lymphomagenesis and transformation of primary B-cells. Therefore, targeting the CD40 pathway has been challenging due to a knowledge gap in understanding the factors that may dictate a pro- or anti-tumor role. To address this directly, we employed a large panel of NHL cell lines and xenografts models to simulate a patient population and to define the molecular parameters to test in the context of clinical trials. Using baseline gene expression profiling, we found that the in vitro activity of an antibody that stimulates the CD40 pathway, Dacetuzumab (SGN-40), correlated strikingly with a transcriptional profile that was representative of an inactive CD40 pathway. Resistant cells, on the other hand, displayed a transcriptional profile indicative of an activated CD40 pathway. Consistent with these observations, constitutive phosphorylation of ERK, a node downstream of CD40 signaling, was present predominantly in cell lines that were resistant to Dacetuzumab. Fifteen genes, based on their association with in vitro activity and their biology as components of the CD40 network, were selected as a classifier from these pre-clinical data and independently tested in a panel of cell lines and xenografts models. Testing the selected gene classifier by qRT-PCR from baseline fixed tumor tissue of 39 patients treated with Dacetuzumab in phase I and II clinical trials revealed the ability to predict sensitivity in patients, as determined by tumor shrinkage >10%, with an overall accuracy of 80%. Consistent with the observed tumor shrinkage, the classifier positive, predicted to respond to Dacetuzumab, patients also exhibited a prolonged progression free survival (PFS) compared to classifier negative patients, predicted not to respond to Dacetuzumab (HR = 0.23, p = 0.001). Finally, using a novel microarray approach to genome-wide expression profiling on fixed tumor tissue revealed that CD40 pathway activation was indeed an important predictor of response. Overall, these data suggest that sensitivity to Dacetuzumab can be predicted by pre-determining the CD40 pathway activation status of tumors. Disclosures: Dornan: Genentech, Inc.: Employment, Equity Ownership. Burington:Genentech, Inc.: Employment, Equity Ownership. Yue:Genentech, Inc.: Employment, Equity Ownership. Shi:Genentech, Inc.: Employment, Equity Ownership. Advani:Seattle Genetics, Inc.: Research Funding. Yu:Genentech, Inc.: Employment, Equity Ownership. Lau:Genentech, Inc.: Employment, Equity Ownership. Yu:Genentech, Inc.: Employment, Equity Ownership. De Vos:Seattle Genetics, Inc.: Research Funding. Forero-Torres:Seattle Genetics, Inc.: Research Funding. Modrusan:Genentech, Inc.: Employment, Equity Ownership. Koeppen:Genentech, Inc.: Employment, Equity Ownership. Yang:Genentech, Inc.: Employment, Equity Ownership. Du:Genentech, Inc.: Employment, Equity Ownership. Elkins:Genentech, Inc.: Employment, Equity Ownership. Polson:Genentech, Inc.: Employment, Equity Ownership. Offringa:Genentech, Inc.: Employment, Equity Ownership. Whiting:Seattle Genetics, Inc.: Employment, Equity Ownership. Ebens:Genentech, Inc.: Employment, Equity Ownership.

A 15-gene expression signature predicts whether a patient with diffuse large B cell lymphoma will respond to dacetuzumab, a therapeutic antibody.