Clinical benefit of lapatinib-based therapy in patients with HER2-positive breast tumors expressing p95HER2

1048

Background: Approximately 25% of HER2 overexpressing breast tumors express a truncated form of the receptor (p95HER2) that lacks the extracellular domain but retains kinase activity. p95HER2-positive tumors are associated with a worse prognosis and resistant to trastuzumab therapy. In preclinical models, lapatinib (L), a tyrosine kinase inhibitor of EGFR and HER2, is active in p95HER2 expressing tumors. The aim of this analysis was to test the hypothesis that benefit from L-based therapy is independent of p95HER2 expression in 2 clinical trials in patients (pts) with HER2-positive tumors treated with either L monotherapy (Study EGF20009 ) or L in combination with capecitabine (Study EGF100151). Methods: Pre-treatment tumor tissue from both trials (N=201) was analyzed for p95HER2 expression by immunofluorescence as previously described (Scaltriti M. et al, JNCI 2007). Expression of p95HER2 was correlated with clinical benefit rate (CBR: complete response [CR] + partial response [PR] + stable disease [SD] ≥ 24 weeks) and progression-free survival (PFS) using logistic regression and Cox-proportional hazard models. Results: 68/105 and an initial 72/96 tissue samples were evaluable for p95HER2 expression from studies EGF20009 and EGF100151, respectively. The Table summarizes the results from the L treated pts. The CBR and PFS in L treated pts were not significantly different between the p95HER2 subgroups. Expanded data for p95HER2 expression in additional EGF100151 tumor samples will be presented. Conclusions: L as a monotherapy or in combination with capecitabine has similar response activity in pts with p95HER2-positive and p95HER2-negative HER2-positive breast tumors.

[Table: see text]

[Table: see text]

A 6 gene molecular predictor of lapatinib related benefit: from cell line models to clinical trials

Abstract #58

Background: Identification of molecular predictors of response is an important aspect of individualized cancer treatment. Responses to lapatinib (L), an oral inhibitor of HER2 and EGFR, approved in combination with capecitabine for HER2+ metastatic breast cancer (MBC), were evaluated in a panel of BC cell lines. Computational approaches were used to identify transcripts that quantitatively associate with response to L in the cell line panel that were then tested in 2 clinical trials.
 Methods: The clinical utility of a 6-gene predictor was tested retrospectively using a branched-chain DNA assay in paraffin-embedded archival tumor tissue from patients (pts) with HER2 negative or untested MBC tumors enrolled in a phase III trial of paclitaxel (P) vs. P+L, and from pts with HER2 positive MBC enrolled in a L monotherapy trial. Expression of HER2 transcript using the branched-chain assay was compared with HER2 fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) status; discordant cases were analyzed. Response patterns for pts with HER2+ tumors and a computational model that predicts L sensitivity or resistance is described.
 Results: Ingenuity analysis of the mRNA predictors of response to L identified in the BC cell line panel revealed saturated gene networks with HER2 as a major node. The 6-gene predictor of response was comprised of 2 genes associated with sensitivity to L: HER2 and GRB7; 4 genes associated with resistance to L: CRK, ACOT9, FLJ31079, and DDX5. Expression results for the 6 genes and progression-free survival (PFS) data were available for 159 pts on L+P. Median PFS in the branched-chain HER2+ group was 32.9 wks vs. 22.4 wks in the HER2-negative group. The 6-gene predictor was used to predict response to L in the HER2+ pts. Comparison of PFS in the 24 “L sensitive” tumors vs. 25 “L resistant” tumors indicated that the predictor, derived from cell-line analyses, had the potential to predict clinical response to L in pts treated with L+P (HR=0.58; 95% CI=0.30-1.11; p=0.07). The 6-gene predictor was further tested in an independent L monotherapy study in pts with HER2 FISH+ MBC. Comparison of PFS in the 24 “L sensitive” tumors vs. 28 “ L resistant” tumors reconfirmed the potential of the 6-gene predictor to enrich for HER2+ pts most likely to experience clinical benefit from L (HR=0.40; 95% CI=0.19-0.84; p=0.015). Further testing is ongoing.
 Conclusions: This study suggests that molecular predictors of clinical response can be developed through an analysis of response from a collection of 50 BC cell lines. The identification of a L specific 6-gene assay is promising as a clinical predictor of benefit from L in pts with HER2+ BC.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 58.

Comprehensive analysis of tagging sequence variants in DTNBP1 shows no association with schizophrenia or with its composite neurocognitive endophenotypes

In a previous study we identified a relatively homogeneous subtype of schizophrenia characterized by pervasive cognitive deficit, which was the exclusive contributor to our findings of linkage to 6p25-p24. The 6p region contains Dysbindin (DTNBP1), considered to be one of the major schizophrenia candidate genes. While multiple studies have reported association between genetic variation in DTNBP1 and schizophrenia, the findings have been inconsistent and controversial, leading to recent calls for systematic re-examination and unambiguous evidence of association. To address this, we have undertaken a comprehensive survey of common genetic variation within DTNBP1 and its association with schizophrenia, using a HapMap-based gene-tagging approach. We genotyped 39 tSNPs in a sample of 336 cases and 172 controls of Anglo-Irish ancestry, with the phenotype defined as clinical schizophrenia, and as composite neurocognitive endophenotypes. Allele and haplotype frequencies, and LD structure in our control sample were similar to those in other European populations. Using multivariate generalized linear modeling, we observed no significant association between any tSNP and any outcome variable. Association with haplotypes was examined across the gene and in the previously associated 5' region. Neither global haplotype tests, nor specific analysis of the "risk" haplotype previously reported in an ethnically related population, the Irish high-density schizophrenia families, showed significant evidence of association with schizophrenia or with the neurocognitive endophenotypes in our sample. The framework and results of this study should facilitate further attempts at re-analysis of DTNBP1, in terms of standardized approaches to both phenotype definition and analysis of genetic variation.