Safety and Efficacy of T-DM1 Plus Neratinib in Patients With Metastatic HER2-Positive Breast Cancer: NSABP Foundation Trial FB-10.

Purpose: Patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer eventually develop resistance to dual-antibody therapy with trastuzumab plus pertuzumab. Mechanisms of resistance have not been well elucidated. We evaluated the safety, tolerability, and efficacy of ado-trastuzumab emtansine (T-DM1) plus neratinib in patients who progressed on trastuzumab plus pertuzumab.

p95HER2-T cell bispecific antibody for breast cancer treatment.

T cell bispecific antibodies (TCBs) are engineered molecules that include, within a single entity, binding sites to the T cell receptor and to tumor-associated or tumor-specific antigens. The receptor tyrosine kinase HER2 is a tumor-associated antigen in ~25% of breast cancers. TCBs targeting HER2 may result in severe toxicities, likely due to the expression of HER2 in normal epithelia.

p95HER2 Methionine 611 Carboxy-Terminal Fragment Is Predictive of Trastuzumab Adjuvant Treatment Benefit in the FinHer Trial.

Expression of p95HER2 (p95), a truncated form of the HER2 receptor, which lacks the trastuzumab binding site but retains kinase activity, has been reported as a prognostic biomarker for poor outcomes in patients with trastuzumab-treated HER2-positive metastatic breast cancer. The impact of p95 expression on trastuzumab treatment efficacy in early HER2-positive breast cancer is less clear. In the current study, p95 was tested as a predictive marker of trastuzumab treatment benefit in the HER2-positive subset of the FinHer adjuvant phase III trial.

High p95HER2/HER2 Ratio Associated With Poor Outcome in Trastuzumab-Treated HER2-Positive Metastatic Breast Cancer NCCTG N0337 and NCCTG 98-32-52 (Alliance).

p95HER2 is a truncated form of HER2 that confers resistance to trastuzumab , but clinical results have been conflicting to date. Given that p95HER2 levels correlate with total HER2 expression levels, which confer better outcomes, we sought to evaluate the p95HER2/HER2 ratio in the North Central Cancer Treatment Group N0337 and N98-32-52 trials. The HERmark assay and VeraTag technology (Monogram Biosciences) were used to measure total HER2 and p95HER2 expression levels in 91 patient samples.

Predictive value of quantitative HER2, HER3 and p95HER2 levels in HER2-positive advanced breast cancer patients treated with lapatinib following progression on trastuzumab.

Lapatinib is a HER1 and HER2 tyrosine kinase inhibitor (TKI) approved in second line treatment of advanced or metastatic breast cancer following progression on trastuzumab-containing therapy. Biomarkers for activity of lapatinib and other TKIs are lacking. Formalin-fixed, paraffin-embedded primary tumor samples were obtained from 189 HER2-positive patients treated with lapatinib plus capecitabine following progression on trastuzumab.

Quantitative measurement of HER2 expression in breast cancers: comparison with 'real-world' routine HER2 testing in a multicenter Collaborative Biomarker Study and correlation with overall survival.

Introduction: Accurate assessment of HER2 status is critical in determining appropriate therapy for breast cancer patients but the best HER2 testing methodology has yet to be defined. In this study, we compared quantitative HER2 expression by the HERmark™ Breast Cancer Assay (HERmark) with routine HER2 testing by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), and correlated HER2 results with overall survival (OS) of breast cancer patients in a multicenter Collaborative Biomarker Study (CBS).

Methods: Two hundred and thirty-two formalin-fixed, paraffin-embedded breast cancer tissues and local laboratory HER2 testing results were provided by 11 CBS sites.

Quantitative HER2 and p95HER2 levels in primary breast cancers and matched brain metastases.

Background: Patients with advanced breast cancer positive for human epidermal growth factor receptor 2 (HER2) are at high risk for brain metastasis (BM). The prevalence and significance of expression of HER2 and its truncated form p95HER2 (p95) in BM is unknown.

Methods: Seventy-five pairs of formalin-fixed paraffin-embedded samples from matched primary breast cancers (PBCs) and BM were assayed for quantitative p95 and HER2-total (H2T) protein expression using the p95 VeraTag and HERmark assays, respectively.

HER2 over-expressing high grade endometrial cancer expresses high levels of p95HER2 variant.

Background: Subsets of high grade endometrial cancer (EnCa) over-express HER2 (ERBB2), yet clinical trials have failed to demonstrate any anti-tumor activity utilizing trastuzumab, an approved platform for HER2 positive breast cancer (BrCa). A truncated p95HER2 variant lacking the trastuzumab binding site may confer resistance. The objective of this investigation was to characterize the expression of the p95HER2 truncated variant in EnCa.

High HER2 expression correlates with response to the combination of lapatinib and trastuzumab.

Purpose: Expression of p95HER2 has been associated with resistance to trastuzumab-based therapy in patients with metastatic breast cancer. Conversely, high levels of HER2 have been linked with increased clinical benefit from anti-HER2 therapy. In this work, we aimed to investigate whether the levels of p95HER2 and HER2 can predict response to anti-HER2 therapy in patients with breast cancer.

Quantitative measurements of tumoral p95HER2 protein expression in metastatic breast cancer patients treated with trastuzumab: independent validation of the p95HER2 clinical cutoff.

Purpose: P95HER2 (p95) is a truncated form of the HER2, which lacks the trastuzumab-binding site and contains a hyperactive kinase domain. Previously, an optimal clinical cutoff of p95 expression for progression-free survival (PFS) and overall survival (OS) was defined using a quantitative VeraTag assay (Monogram Biosciences) in a training set of trastuzumab-treated metastatic breast cancer (MBC) patients.

Experimental Design: In the current study, the predictive value of the p95 VeraTag assay cutoff established in the training set was retrospectively validated for PFS and OS in an independent series of 240 trastuzumab-treated MBC patients from multiple institutions.

Potential biomarkers of long-term benefit from single-agent trastuzumab or lapatinib in HER2-positive metastatic breast cancer.

In 2009 a prospective, randomized Phase II trial (NCT00842998) was initiated to evaluate the activity of HER2-targeting agents without chemotherapy (CT) in HER2-positive metastatic breast cancer (MBC) patients. The primary tumors of the patients enrolled in this study offered a unique opportunity to identify biomarkers that could predict durable clinical benefit from CT-free anti-HER2 therapy. Patients with HER2-positive MBC were randomized to trastuzumab or lapatinib as first-line therapy.

HER3, p95HER2, and HER2 protein expression levels define multiple subtypes of HER2-positive metastatic breast cancer.

Trastuzumab is effective in the treatment of HER2/neu over-expressing breast cancer, but not all patients benefit from it. In vitro data suggest a role for HER3 in the initiation of signaling activity involving the AKT–mTOR pathway leading to trastuzumab insensitivity. We sought to investigate the potential of HER3 alone and in the context of p95HER2 (p95), a trastuzumab resistance marker, as biomarkers of trastuzumab escape.

Correlation between quantitative HER-2 protein expression and risk for brain metastases in HER-2+ advanced breast cancer patients receiving trastuzumab-containing therapy.

Background: Patients with human epidermal growth factor receptor (HER)-2+ breast cancer are at particularly high risk for brain metastases; however, the biological basis is not fully understood. Using a novel HER-2 assay, we investigated the correlation between quantitative HER-2 expression in primary breast cancers and the time to brain metastasis (TTBM) in HER-2+ advanced breast cancer patients treated with trastuzumab.

Methods: The study group included 142 consecutive patients who were administered trastuzumab-based therapy for HER-2+ metastatic breast cancer.

Trastuzumab has preferential activity against breast cancers driven by HER2 homodimers.

In breast cancer cells with HER2 gene amplification, HER2 receptors exist on the cell surface as monomers, homodimers, and heterodimers with EGFR/HER3. The therapeutic antibody trastuzumab, an approved therapy for HER2(+) breast cancer, cannot block ligand-induced HER2 heterodimers, suggesting it cannot effectively inhibit HER2 signaling. Hence, HER2 oligomeric states may predict the odds of a clinical response to trastuzumab in HER2-driven tumors.

Quantitation of p95HER2 in paraffin sections by using a p95-specific antibody and correlation with outcome in a cohort of trastuzumab-treated breast cancer patients.

Purpose: p95HER2 is an NH(2)-terminally truncated form of HER2 that lacks the trastuzumab binding site and is therefore thought to confer resistance to trastuzumab treatment. In this report, we introduce a new antibody that has enabled the first direct quantitative measurement of p95HER2 in formalin-fixed paraffin-embedded (FFPE) breast cancer tissues. We sought to show that quantitative p95HER2 levels would correlate with outcome in trastuzumab-treated HER2-positive metastatic breast cancer.

Quantitative HER2 protein levels predict outcome in fluorescence in situ hybridization-positive patients with metastatic breast cancer treated with trastuzumab.

Background: Only a portion of breast cancer patients currently selected for trastuzumab therapy respond.

Methods: Using a novel assay (HERmark) to quantify total human epidermal growth factor receptor 2 (HER2) expression, the authors examined outcomes in 102 trastuzumab-treated metastatic breast cancer patients previously assessed as immunohistochemistry (IHC) 3+ by local but not central IHC, or fluorescence in situ hybridization (FISH) positive, and then retested by central FISH.

Results: Of 102 MBC patients previously scored as IHC 3+ or 2+/FISH-positive and treated with trastuzumab-containing regimens, 98 had both central FISH and HER2 total expression values.

Anti-tumor effect of CT-322 as an adnectin inhibitor of vascular endothelial growth factor receptor-2.

CT-322 is a new anti-angiogenic therapeutic agent based on an engineered variant of the tenth type III domain of human fibronectin, i.e., an Adnectin™, designed to inhibit vascular endothelial growth factor receptor (VEGFR)-2.

Differential survival following trastuzumab treatment based on quantitative HER2 expression and HER2 homodimers in a clinic-based cohort of patients with metastatic breast cancer.

Background: We have recently described the correlation between quantitative measures of HER2 expression or HER2 homodimers by the HERmark assay and objective response (RR), time-to progression (TTP), and overall survival (OS) in an expanded access cohort of trastuzumab-treated HER2-positive patients with metastatic breast cancer (MBC) who were stringently selected by fluorescence in situ hybridization (FISH). Multivariate analyses suggested a continuum of HER2 expression that correlated with outcome following trastuzumab. Here we investigate the relationship between HER2 expression or HER2 homodimers and OS in a clinic-based population of patients with MBC selected primarily by IHC.

A novel proximity assay for the detection of proteins and protein complexes: quantitation of HER1 and HER2 total protein expression and homodimerization in formalin-fixed, paraffin-embedded cell lines and breast cancer tissue.

The availability of drugs targeting the EGFR/HER/erbB signaling pathway has created a need for diagnostics that accurately predict treatment responses. We have developed and characterized a novel assay to provide sensitive and quantitative measures of HER proteins and homodimers in formalin-fixed, paraffin-embedded (FFPE) cell lines and breast tumor tissues, to test these variables. In the VeraTag assay, HER proteins and homodimers are detected through the release of fluorescent tags conjugated to specific HER antibodies, requiring proximity to a second HER antibody.

Quantitation of HER2 expression or HER2:HER2 dimers and differential survival in a cohort of metastatic breast cancer patients carefully selected for trastuzumab treatment primarily by FISH.

The selection of patients with HER2-positive breast cancer for treatment with trastuzumab is based on the measurement of HER2 protein expression by immunohistochemistry, or the presence of HER2 gene amplification by fluorescence in situ hybridization (FISH). By using multivariate analyses, we investigate the relationship between quantitative measurements of HER2 expression or HER2:HER2 dimers and objective response (Response Evaluation Criteria in Solid Tumors), time to progression, and breast cancer survival after trastuzumab treatment in a cohort of patients with metastatic breast cancer who were primarily selected for treatment by FISH. The VeraTag assay, a proximity-based assay designed to quantitate protein expression and dimerization in formalin-fixed, paraffin-embedded tissue specimens, was used to measure HER2 protein expression and HER2:HER2 dimer levels.

Exosome nanovesicles displaying G protein-coupled receptors for drug discovery.

Exosomes are naturally occurring nanovesicles that can be tailored to display a broad range of drug targets, including G protein-coupled receptors. Such vesicles provide a new source of complex membrane proteins that are maintained in their native conformation. Given the difficulties to isolate receptors for drug target validation and discovery, receptor presentation on exosome emerges as a promising new tool for drug screening.