Targeting HER2 with multiple HER2-directed therapies represents a promising area of treatment for HER2-positive cancers. We investigated combining the HER2-directed antibody-drug conjugate trastuzumab emtansine (T-DM1) with the HER2 dimerization inhibitor pertuzumab (Perjeta).Drug combination studies with T-DM1 and pertuzumab were performed on cultured tumor cells and in mouse xenograft models of HER2-amplified cancer. In patients with HER2-positive locally advanced or metastatic breast cancer (mBC), T-DM1 was dose-escalated with a fixed standard pertuzumab dose in a 3+3 phase Ib/II study design.Treatment of HER2-overexpressing tumor cells in vitro with T-DM1 plus pertuzumab resulted in synergistic inhibition of cell proliferation and induction of apoptotic cell death. The presence of the HER3 ligand, heregulin (NRG-1β), reduced the cytotoxic activity of T-DM1 in a subset of breast cancer lines; this effect was reversed by the addition of pertuzumab. Results from mouse xenograft models showed enhanced antitumor efficacy with T-DM1 and pertuzumab resulting from the unique antitumor activities of each agent. In patients with mBC previously treated with trastuzumab, lapatinib, and chemotherapy, T-DM1 could be dosed at the maximum tolerated dose (MTD; 3.6 mg/kg every 3 weeks) with standard dose pertuzumab. Adverse events were mostly grade 1 and 2, with indications of clinical activity.Dual targeting of HER2 with the combination of T-DM1 and pertuzumab in cell culture and mouse xenograft models resulted in enhanced antitumor activity. In patients, this combination showed an encouraging safety and tolerability profile with preliminary evidence of efficacy.
Abstract Background This phase 1b study (ClinicalTrials.gov identifier NCT03695380) evaluated regimens combining PARP and MEK inhibition, with or without PD‐L1 inhibition, for BRCA wild‐type, platinum‐sensitive, recurrent ovarian cancer (PSROC). Methods Patients with PSROC who had received one or two prior treatment lines were treated with 28‐day cycles of cobimetinib 60 mg daily (days 1–21) plus niraparib 200 mg daily (days 1–28) with or without atezolizumab 840 mg (days 1 and 15). Stage 1 assessed safety before expansion to stage 2, which randomized patients who had BRCA wild‐type PSROC to receive either doublet or triplet therapy, stratified by genome‐wide loss of heterozygosity status (<16% vs. ≥16%; FoundationOne CDx assay) and platinum‐free interval (≥6 to <12 vs. ≥12 months). Coprimary end points were safety and the investigator‐determined objective response rate (ORR) according to Response Evaluation Criteria in Solid Tumors (RECIST). Potential associations between genetic parameters and efficacy were explored, and biomarker profiles of super‐responders (complete response or those with progression‐free survival [PFS] >15 months) and progressors (disease progression as the best response) were characterized. Results The ORR in patients who had BRCA wild‐type PSROC was 35% (95% confidence interval, 20%–53%) with the doublet regimen ( n = 37) and 27% (95% confidence interval, 14%–44%) with the triplet regimen ( n = 37), and the median PFS was 6.0 and 7.4 months, respectively. Post‐hoc analyses indicated more favorable ORR and PFS in the homologous recombination‐deficiency‐signature (HRDsig)‐positive subgroup than in the HRDsig‐negative subgroup. Tolerability was consistent with the known profiles of individual agents. NF1 and MKNK1 mutations were associated with sustained benefit from the doublet and triplet regimens, respectively. Conclusions Chemotherapy‐free doublet and triplet therapy demonstrated encouraging activity, including among patients who had BRCA wild‐type, HRDsig‐positive or HRDsig‐negative PSROC harboring NF1 or MKNK1 mutations.
Squamous cell carcinomas (SCCs) account for the majority of cancer mortalities. Although TP63 is an established lineage-survival oncogene in SCCs, therapeutic strategies have not been developed to target TP63 or it's downstream effectors. In this study we demonstrate that TP63 directly regulates NRG1 expression in human SCC cell lines and that NRG1 is a critical component of the TP63 transcriptional program. Notably, we show that squamous tumors are dependent NRG1 signaling in vivo, in both genetically engineered mouse models and human xenograft models, and demonstrate that inhibition of NRG1 induces keratinization and terminal squamous differentiation of tumor cells, blocking proliferation and inhibiting tumor growth. Together, our findings identify a lineage-specific function of NRG1 in SCCs of diverse anatomic origin.
ABSTRACT While epidermal growth factor receptor (EGFR) has been shown to be important in the entry process for multiple viruses, including hepatitis C virus (HCV), the molecular mechanisms by which EGFR facilitates HCV entry are not well understood. Using the infectious cell culture HCV model (HCVcc), we demonstrate that the binding of HCVcc particles to human hepatocyte cells induces EGFR activation that is dependent on interactions between HCV and CD81 but not claudin 1. EGFR activation can also be induced by antibody mediated cross-linking of CD81. In addition, EGFR ligands that enhance the kinetics of HCV entry induce EGFR internalization and colocalization with CD81. While EGFR kinase inhibitors inhibit HCV infection primarily by preventing EGFR endocytosis, antibodies that block EGFR ligand binding or inhibitors of EGFR downstream signaling have no effect on HCV entry. These data demonstrate that EGFR internalization is critical for HCV entry and identify a hitherto-unknown association between CD81 and EGFR.
Breast cancers (BC) with HER2 overexpression (referred to as HER2 positive) progress more aggressively than those with normal expression. Targeted therapies against HER2 can successfully delay the progression of HER2-positive BC, but details of how this overexpression drives the disease are not fully understood. Using single-molecule biophysical approaches, we discovered a new effect of HER2 overexpression on disease-relevant cell biological changes in these BC. We found HER2 overexpression causes deformation of the cell membranes, and this in turn disrupts epithelial features by perturbing cell-substrate and cell-cell contacts. This membrane deformation does not require receptor signalling activities, but results from the high levels of HER2 on the cell surface. Our finding suggests that early-stage morphological alterations of HER2-positive BC cells during cancer progression can occur in a physical and signalling-independent manner.
