Natural History and Characteristics of ERBB2-mutated Hormone Receptor-positive Metastatic Breast Cancer: A Multi-institutional Retrospective Case-control Study from AACR Project GENIE.

PURPOSE: We wanted to determine the prognosis and the phenotypic characteristics of hormone receptor-positive advanced breast cancer tumors harboring an ERBB2 mutation in the absence of a HER2 amplification. EXPERIMENTAL DESIGN: We retrospectively collected information from the American Association of Cancer Research-Genomics Evidence Neoplasia Information Exchange registry database from patients with hormone receptor-positive, HER2-negative, ERBB2-mutated advanced breast cancer. Phenotypic and co-mutational features, as well as response to treatment and outcome were compared with matched control cases ERBB2 wild type. RESULTS: A total of 45 ERBB2-mutant cases were identified for 90 matched controls. The presence of an ERBB2 mutation was not associated with worse outcome determined by overall survival (OS) from first metastatic relapse. No significant differences were observed in phenotypic characteristics apart from higher lobular infiltrating subtype in the ERBB2-mutated group. ERBB2 mutation did not seem to have an impact in response to treatment or time-to-progression (TTP) to endocrine therapy compared with ERBB2 wild type. In the co-mutational analyses, CDH1 mutation was more frequent in the ERBB2-mutated group (FDR < 1). Although not significant, fewer co-occurring ESR1 mutations and more KRAS mutations were identified in the ERBB2-mutated group. CONCLUSIONS: ERBB2-activating mutation was not associated with a worse OS from time of first metastatic relapse, or differences in TTP on treatment as compared with a series of matched controls. Although not significant, differences in coexisting mutations (CDH1, ESR1, and KRAS) were noted between the ERBB2-mutated and the control group.

The Phase II MutHER Study of Neratinib Alone and in Combination with Fulvestrant in HER2-Mutated, Non-amplified Metastatic Breast Cancer.

PURPOSE: HER2 mutations (HER2mut) induce endocrine resistance in estrogen receptor-positive (ER+) breast cancer. PATIENTS AND METHODS: In this single-arm multi-cohort phase II trial, we evaluated the efficacy of neratinib plus fulvestrant in patients with ER+/HER2mut, HER2 non-amplified metastatic breast cancer (MBC) in the fulvestrant-treated (n = 24) or fulvestrant-naïve cohort (n = 11). Patients with ER-negative (ER-)/HER2mut MBC received neratinib monotherapy in an exploratory ER- cohort (n = 5). RESULTS: The clinical benefit rate [CBR (95% confidence interval)] was 38% (18%-62%), 30% (7%-65%), and 25% (1%-81%) in the fulvestrant-treated, fulvestrant-naïve, and ER- cohorts, respectively. Adding trastuzumab at progression in 5 patients resulted in three partial responses and one stable disease ≥24 weeks. CBR appeared positively associated with lobular histology and negatively associated with HER2 L755 alterations. Acquired HER2mut were detected in 5 of 23 patients at progression. CONCLUSIONS: Neratinib and fulvestrant are active for ER+/HER2mut MBC. Our data support further evaluation of dual HER2 blockade for the treatment of HER2mut MBC.

GCN2 kinase activation by ATP-competitive kinase inhibitors.

Small-molecule kinase inhibitors represent a major group of cancer therapeutics, but tumor responses are often incomplete. To identify pathways that modulate kinase inhibitor response, we conducted a genome-wide knockout (KO) screen in glioblastoma cells treated with the pan-ErbB inhibitor neratinib. Loss of general control nonderepressible 2 (GCN2) kinase rendered cells resistant to neratinib, whereas depletion of the GADD34 phosphatase increased neratinib sensitivity. Loss of GCN2 conferred neratinib resistance by preventing binding and activation of GCN2 by neratinib. Several other Food and Drug Administration (FDA)-approved inhibitors, such erlotinib and sunitinib, also bound and activated GCN2. Our results highlight the utility of genome-wide functional screens to uncover novel mechanisms of drug action and document the role of the integrated stress response (ISR) in modulating the response to inhibitors of oncogenic kinases.

Biomarker Analysis of the Phase III NALA Study of Neratinib + Capecitabine versus Lapatinib + Capecitabine in Patients with Previously Treated Metastatic Breast Cancer.

PURPOSE: Neratinib plus capecitabine (N+C) demonstrated significant progression-free survival (PFS) benefit in NALA (NCT01808573), a randomized phase III trial comparing N+C with lapatinib + capecitabine (L+C) in 621 patients with HER2-positive (HER2+) metastatic breast cancer (MBC) who had received ≥2 prior HER2-directed regimens in the metastatic setting. We evaluated correlations between exploratory biomarkers and PFS. PATIENTS AND METHODS: Somatic mutations were evaluated by next-generation sequencing on primary or metastatic samples. HER2 protein expression was evaluated by central IHC, H-score, and VeraTag/HERmark. p95 expression (truncated HER2) was measured by VeraTag. HRs were estimated using unstratified Cox proportional hazards models. RESULTS: Four hundred and twenty samples had successful sequencing: 34.0% had PIK3CA mutations and 5.5% had HER2 (ERBB2) mutations. In the combined patient populations, PIK3CA mutations trended toward shorter PFS [wild-type vs. mutant, HR = 0.81; 95% confidence interval (CI), 0.64-1.03], whereas HER2 mutations trended toward longer PFS [HR = 1.69 (95% CI, 0.97-3.29)]. Higher HER2 protein expression was associated with longer PFS [IHC 3+ vs. 2+, HR = 0.67 (0.54-0.82); H-score ≥240 versus <240, HR = 0.77 (0.63-0.93); HERmark positive vs. negative, HR = 0.76 (0.59-0.98)]. Patients whose tumors had higher HER2 protein expression (any method) derived an increased benefit from N+C compared with L+C [IHC 3+, HR = 0.64 (0.51-0.81); H-score ≥ 240, HR = 0.54 (0.41-0.72); HERmark positive, HR = 0.65 (0.50-0.84)], as did patients with high p95 [p95 ≥2.8 relative fluorescence (RF)/mm2, HR = 0.66 (0.50-0.86) vs. p95 < 2.8 RF/mm2, HR = 0.91 (0.61-1.36)]. CONCLUSIONS: PIK3CA mutations were associated with shorter PFS whereas higher HER2 expression was associated with longer PFS. Higher HER2 protein expression was also associated with a greater benefit for N+C compared with L+C.

PI3K and MAPK Pathways as Targets for Combination with the Pan-HER Irreversible Inhibitor Neratinib in HER2-Positive Breast Cancer and TNBC by Kinome RNAi Screening.

Human epidermal growth factor receptor (EGFR) 2 (HER2) is overexpressed/amplified in about 25% of all breast cancers, and EGFR is overexpressed in up to 76% and amplified in up to 24% of triple-negative breast cancers (TNBC). Here, we aimed to identify inhibitors that may enhance the anti-tumor activity of neratinib for HER2+ breast cancer and TNBC. By conducting a non-biased high-throughput RNA interference screening, we identified PI3K/AKT/mTOR and MAPK as two potential inhibitory synergistic canonical pathways. We confirmed that everolimus (mTOR inhibitor) and trametinib (MEK inhibitor) enhances combinatorial anti-proliferative effects with neratinib under anchorage-independent growth conditions (p < 0.05). Compared to single agent neratinib, the combination therapies significantly enhanced tumor growth inhibition in both SUM190 HER2+ breast cancer (neratinib plus everolimus, 77%; neratinib plus trametinib, 77%; p < 0.0001) and SUM149 TNBC (neratinib plus everolimus, 71%; neratinib plus trametinib, 81%; p < 0.0001) xenograft models. Compared to single-agent neratinib, everolimus, or trametinib, both everolimus plus neratinib and trametinib plus neratinib significantly suppressed proliferation marker Ki67 and enhanced antitumor efficacy by activating the apoptosis pathway shown by increased Bim and cleaved-PARP expression. Taken together, our data justify new neratinib-based combinations for both HER2+ breast cancer and TNBC.

Co-occurring gain-of-function mutations in HER2 and HER3 modulate HER2/HER3 activation, oncogenesis, and HER2 inhibitor sensitivity.

Activating mutations in HER2 (ERBB2) drive the growth of a subset of breast and other cancers and tend to co-occur with HER3 (ERBB3) missense mutations. The HER2 tyrosine kinase inhibitor neratinib has shown clinical activity against HER2-mutant tumors. To characterize the role of HER3 mutations in HER2-mutant tumors, we integrate computational structural modeling with biochemical and cell biological analyses. Computational modeling predicts that the frequent HER3E928G kinase domain mutation enhances the affinity of HER2/HER3 and reduces binding of HER2 to its inhibitor neratinib. Co-expression of mutant HER2/HER3 enhances HER2/HER3 co-immunoprecipitation and ligand-independent activation of HER2/HER3 and PI3K/AKT, resulting in enhanced growth, invasiveness, and resistance to HER2-targeted therapies, which can be reversed by combined treatment with PI3Kα inhibitors. Our results provide a mechanistic rationale for the evolutionary selection of co-occurring HER2/HER3 mutations and the recent clinical observations that HER3 mutations are associated with a poor response to neratinib in HER2-mutant cancers.

Neratinib plus trastuzumab is superior to pertuzumab plus trastuzumab in HER2-positive breast cancer xenograft models.

Lapatinib (L) plus trastuzumab (T), with endocrine therapy for estrogen receptor (ER)+ tumors, but without chemotherapy, yielded meaningful response in HER2+ breast cancer (BC) neoadjuvant trials. The irreversible/pan-HER inhibitor neratinib (N) has proven more potent than L. However, the efficacy of N+T in comparison to pertuzumab (P) + T or L + T (without chemotherapy) remains less studied. To address this, mice bearing HER2+ BT474-AZ (ER+) cell and BCM-3963 patient-derived BC xenografts were randomized to vehicle, N, T, P, N+T, or P+T, with simultaneous estrogen deprivation for BT474-AZ. Time to tumor regression/progression and incidence/time to complete response (CR) were determined. Changes in key HER pathway and proliferative markers were assessed by immunohistochemistry and western blot of short-term-treated tumors. In the BT474-AZ model, while all N, P, T, N + T, and P + T treated tumors regressed, N + T-treated tumors regressed faster than P, T, and P + T. Further, N + T was superior to N and T alone in accelerating CR. In the BCM-3963 model, which was refractory to T, P, and P + T, while N and N + T yielded 100% CR, N + T accelerated the CR compared to N. Ki67, phosphorylated (p) AKT, pS6, and pERK levels were largely inhibited by N and N + T, but not by T, P, or P + T. Phosphorylated HER receptor levels were also markedly inhibited by N and N + T, but not by P + T or L + T. Our findings establish the efficacy of combining N with T and support clinical testing to investigate the efficacy of N + T with or without chemotherapy in the neoadjuvant setting for HER2+ BC.

Comparative analysis of drug response and gene profiling of HER2-targeted tyrosine kinase inhibitors.

BACKGROUND: Human epidermal growth factor 2 (HER2/ERBB2) is frequently amplified/mutated in cancer. The tyrosine kinase inhibitors (TKIs) lapatinib, neratinib, and tucatinib are FDA-approved for the treatment of HER2-positive breast cancer. Direct comparisons of the preclinical efficacy of the TKIs have been limited to small-scale studies. Novel biomarkers are required to define beneficial patient populations. METHODS: In this study, the anti-proliferative effects of the three TKIs were directly compared using a 115 cancer cell line panel. Novel TKI response/resistance markers were identified through cross-analysis of drug response profiles with mutation, gene copy number and expression data. RESULTS: All three TKIs were effective against HER2-amplified breast cancer models; neratinib showing the most potent activity, followed by tucatinib then lapatinib. Neratinib displayed the greatest activity in HER2-mutant and EGFR-mutant cells. High expression of HER2, VTCN1, CDK12, and RAC1 correlated with response to all three TKIs. DNA damage repair genes were associated with TKI resistance. BRCA2 mutations were correlated with neratinib and tucatinib response, and high expression of ATM, BRCA2, and BRCA1 were associated with neratinib resistance. CONCLUSIONS: Neratinib was the most effective HER2-targeted TKI against HER2-amplified, -mutant, and EGFR-mutant cell lines. This analysis revealed novel resistance mechanisms that may be exploited using combinatorial strategies.

Combining Neratinib with CDK4/6, mTOR, and MEK Inhibitors in Models of HER2-positive Cancer.

PURPOSE: Neratinib is an irreversible, pan-HER tyrosine kinase inhibitor that is FDA approved for HER2-overexpressing/amplified (HER2+) breast cancer. In this preclinical study, we explored the efficacy of neratinib in combination with inhibitors of downstream signaling in HER2+ cancers in vitro and in vivo. EXPERIMENTAL DESIGN: Cell viability, colony formation assays, and Western blotting were used to determine the effect of neratinib in vitro. In vivo efficacy was assessed with patient-derived xenografts (PDX): two breast, two colorectal, and one esophageal cancer (with HER2 mutations). Four PDXs were derived from patients who received previous HER2-targeted therapy. Proteomics were assessed through reverse phase protein arrays and network-level adaptive responses were assessed through Target Score algorithm. RESULTS: In HER2+ breast cancer cells, neratinib was synergistic with multiple agents, including mTOR inhibitors everolimus and sapanisertib, MEK inhibitor trametinib, CDK4/6 inhibitor palbociclib, and PI3Kα inhibitor alpelisib. We tested efficacy of neratinib with everolimus, trametinib, or palbociclib in five HER2+ PDXs. Neratinib combined with everolimus or trametinib led to a 100% increase in median event-free survival (EFS; tumor doubling time) in 25% (1/4) and 60% (3/5) of models, respectively, while neratinib with palbociclib increased EFS in all five models. Network analysis of adaptive responses demonstrated upregulation of EGFR and HER2 signaling in response to CDK4/6, mTOR, and MEK inhibition, possibly providing an explanation for the observed synergies with neratinib. CONCLUSIONS: Taken together, our results provide strong preclinical evidence for combining neratinib with CDK4/6, mTOR, and MEK inhibitors for the treatment of HER2+ cancer.

Neratinib in patients with HER2-mutant, metastatic cervical cancer: Findings from the phase 2 SUMMIT basket trial.

OBJECTIVE: Somatic HER2 mutations occur in ~5% of cervical cancers and are considered oncogenic and associated with poor prognosis. Neratinib, an irreversible pan-HER tyrosine kinase inhibitor, is active in multiple HER2-mutant cancers. SUMMIT is a phase II basket trial investigating the efficacy and safety of neratinib in solid tumors. METHODS: Patients with HER2-mutant, persistent, metastatic/recurrent cervical cancer with disease progression after platinum-based treatment for advanced/recurrent disease received oral neratinib 240 mg/day with mandatory loperamide prophylaxis during cycle 1. The primary endpoint was confirmed objective response rate (ORR). Secondary endpoints included: response duration (DOR); clinical benefit rate (CBR); progression-free survival (PFS); overall survival (OS); safety. RESULTS: Sixteen eligible patients were enrolled; 10 (62.5%) had endocervical adenocarcinoma. The most common HER2 mutation was S310F (63% of patients). Three of 12 RECIST-measurable patients had confirmed partial responses (ORR 25%; 95%CI 5.5-57.2%); 3 had stable disease ≥16 weeks (CBR 50%; 95%CI 21.1-78.9%). DOR for responders were 5.6, 5.9, and 12.3 months. Median PFS was 7.0 months (95%CI 0.7-18.3 months); median OS was 16.8 months (95%CI 4.1-NE months). Diarrhea (75%), nausea (44%), and decreased appetite (38%) were the most common adverse events. One patient (6%) reported grade 3 diarrhea. There were no grade 4 events, and no diarrhea-related treatment discontinuations. CONCLUSIONS: Neratinib monotherapy showed evidence of activity in heavily pretreated patients with HER2-mutant cervical cancer, with no new safety signals. Given the few effective options for cervical cancer after platinum-based therapy failure, neratinib warrants further investigation in this molecularly defined patient population. TRIAL REGISTRATION NUMBER: NCT01953926 (ClinicalTrials.gov), 2013-002872-42 (EudraCT).

HER2-Mediated Internalization of Cytotoxic Agents in ERBB2 Amplified or Mutant Lung Cancers.

Amplification of and oncogenic mutations in ERBB2, the gene encoding the HER2 receptor tyrosine kinase, promote receptor hyperactivation and tumor growth. Here we demonstrate that HER2 ubiquitination and internalization, rather than its overexpression, are key mechanisms underlying endocytosis and consequent efficacy of the anti-HER2 antibody-drug conjugates (ADC) ado-trastuzumab emtansine (T-DM1) and trastuzumab deruxtecan (T-DXd) in lung cancer cell lines and patient-derived xenograft models. These data translated into a 51% response rate in a clinical trial of T-DM1 in 49 patients with ERBB2-amplified or -mutant lung cancers. We show that cotreatment with irreversible pan-HER inhibitors enhances receptor ubiquitination and consequent ADC internalization and efficacy. We also demonstrate that ADC switching to T-DXd, which harbors a different cytotoxic payload, achieves durable responses in a patient with lung cancer and corresponding xenograft model developing resistance to T-DM1. Our findings may help guide future clinical trials and expand the field of ADC as cancer therapy. SIGNIFICANCE: T-DM1 is clinically effective in lung cancers with amplification of or mutations in ERBB2. This activity is enhanced by cotreatment with irreversible pan-HER inhibitors, or ADC switching to T-DXd. These results may help address unmet needs of patients with HER2-activated tumors and no approved targeted therapy.See related commentary by Rolfo and Russo, p. 643.This article is highlighted in the In This Issue feature, p. 627.

Use of Ex Vivo Patient-Derived Tumor Organotypic Spheroids to Identify Combination Therapies for HER2 Mutant Non-Small Cell Lung Cancer.

PURPOSE: Evaluating drug responses using primary patient-derived cells ex vivo represents a potentially rapid and efficient approach to screening for new treatment approaches. Here, we sought to identify neratinib combinations in HER2 mutant non-small cell lung cancer (NSCLC) patient xenograft-derived organotypic spheroids (XDOTS) using a short-term ex vivo system. EXPERIMENTAL DESIGN: We generated two HER2-mutant NSCLC PDX models [DFCI359 (HER2 exon19 755_757LREdelinsRP) and DFCI315 (HER2 exon20 V777_G778insGSP)] and used the PDX tumors to generate XDOTS. Tumor spheroids were grown in a microfluidic device and treated ex vivo with neratinib-based drug combinations. Live/dead quantification was performed by dual-labeling deconvolution fluorescence microscopy. The most efficacious ex vivo combination was subsequently validated in vivo using the DFCI359 and DFCI315 PDXs and a HER2 YVMA genetically engineered mouse model. RESULTS: Both neratinib and afatinib, but not gefitinib, induced cell death in DFCI359 XDOTS. The combinations of neratinib/trastuzumab and neratinib/temsirolimus enhanced the therapeutic benefit of neratinib alone in DFCI315 and DFCI359. The combination of neratinib and trastuzumab in vivo was more effective compared with single-agent neratinib or trastuzumab and was associated with more robust inhibition of HER2 and downstream signaling. CONCLUSIONS: The XDOTS platform can be used to evaluate therapies and therapeutic combinations ex vivo using PDX tumors. This approach may accelerate the identification and clinical development of therapies for targets with no or few existing models and/or therapies.

Hyperactivation of TORC1 Drives Resistance to the Pan-HER Tyrosine Kinase Inhibitor Neratinib in HER2-Mutant Cancers.

We developed neratinib-resistant HER2-mutant cancer cells by gradual dose escalation. RNA sequencing identified TORC1 signaling as an actionable mechanism of drug resistance. Primary and acquired neratinib resistance in HER2-mutant breast cancer patient-derived xenografts (PDXs) was also associated with TORC1 hyperactivity. Genetic suppression of RAPTOR or RHEB ablated P-S6 and restored sensitivity to the tyrosine kinase inhibitor. The combination of the TORC1 inhibitor everolimus and neratinib potently arrested the growth of neratinib-resistant xenografts and organoids established from neratinib-resistant PDXs. RNA and whole-exome sequencing revealed RAS-mediated TORC1 activation in a subset of neratinib-resistant models. DNA sequencing of HER2-mutant tumors clinically refractory to neratinib, as well as circulating tumor DNA profiling of patients who progressed on neratinib, showed enrichment of genomic alterations that converge to activate the mTOR pathway.

Efficacy and Determinants of Response to HER Kinase Inhibition in HER2-Mutant Metastatic Breast Cancer.

HER2 mutations define a subset of metastatic breast cancers with a unique mechanism of oncogenic addiction to HER2 signaling. We explored activity of the irreversible pan-HER kinase inhibitor neratinib, alone or with fulvestrant, in 81 patients with HER2-mutant metastatic breast cancer. Overall response rate was similar with or without estrogen receptor (ER) blockade. By comparison, progression-free survival and duration of response appeared longer in ER+ patients receiving combination therapy, although the study was not designed for direct comparison. Preexistent concurrent activating HER2 or HER3 alterations were associated with poor treatment outcome. Similarly, acquisition of multiple HER2-activating events, as well as gatekeeper alterations, were observed at disease progression in a high proportion of patients deriving clinical benefit from neratinib. Collectively, these data define HER2 mutations as a therapeutic target in breast cancer and suggest that coexistence of additional HER signaling alterations may promote both de novo and acquired resistance to neratinib. SIGNIFICANCE: HER2 mutations define a targetable breast cancer subset, although sensitivity to irreversible HER kinase inhibition appears to be modified by the presence of concurrent activating genomic events in the pathway. These findings have implications for potential future combinatorial approaches and broader therapeutic development for this genomically defined subset of breast cancer.This article is highlighted in the In This Issue feature, p. 161.

The calcium-sensing receptor: A novel target for treatment and prophylaxis of neratinib-induced diarrhea.

Diarrhea is one of the most commonly reported adverse effect of hemotherapy and targeted cancer therapies, such as tyrosine kinase inhibitors (TKI), which often significantly impact patient quality of life, morbidity, and mortality. Neratinib is an oral, irreversible pan-HER tyrosine kinase inhibitor, which is clinically active in HER2-positive breast cancer. Diarrhea is the most common side effect of this potent anticancer drug and the reasons for this adverse effect are still largely unclear. We have recently shown that activation of the calcium-sensing Receptor (CaSR) can inhibit secretagogue-induced diarrhea in the colon, therefore we hypothesized that CaSR activation may also mitigate neratinib-induced diarrhea. Using an established ex vivo model of isolated intestinal segments, we investigated neratinib-induced fluid secretion and the ability of CaSR activation to abate the secretion. In our study, individual segments of the rat intestine (proximal, middle, distal small intestine, and colon) were procured and perfused intraluminally with various concentrations of neratinib (10, 50, 100 nmol L-1). In a second set of comparison experiments, intraluminal calcium concentration was modulated (from 1.0 to 5.0 or 7.0 mmol L-1), both pre- and during neratinib exposure. In a separate series of experiments R-568, a known calcimimetic was used CaSR activation and effect was compared to elevated Ca2+ concentration (5.0 and 7.0 mmol L-1). As a result, CaSR activation with elevated Ca2+ concentration (5.0 and 7.0 mmol L-1) or R-568 markedly reduced neratinib-induced fluid secretion in a dose-dependent manner. Pre-exposure to elevated luminal calcium solutions (5.0 and 7.0 mmol L-1) also prevented neratinib-induced fluid secretion. In conclusion, exposure to luminal neratinib resulted in a pronounced elevation in fluid secretion in the rat intestine. Increasing luminal calcium inhibits the neratinib-associated fluid secretion in a dose-dependent manner. These results suggest that CaSR activation may be a potent therapeutic target to reduce chemotherapy-associated diarrhea.

Correction: HDAC inhibitors enhance neratinib activity and when combined enhance the actions of an anti-PD-1 immunomodulatory antibody in vivo.

[This corrects the article DOI: 10.18632/oncotarget.21660.].

Neratinib inhibits Hippo/YAP signaling, reduces mutant K-RAS expression, and kills pancreatic and blood cancer cells.

Prior studies demonstrated that the irreversible ERBB1/2/4 inhibitor neratinib caused plasma membrane-associated mutant K-RAS to localize in intracellular vesicles, concomitant with its degradation. Herein, we discovered that neratinib interacted with the chemically distinct irreversible ERBB1/2/4 inhibitor afatinib to reduce expression of ERBB1, ERBB2, K-RAS and N-RAS; this was associated with greater-than-additive cell killing of pancreatic tumor cells. Knock down of Beclin1, ATG16L1, Rubicon or cathepsin B significantly lowered the ability of neratinib to reduce ERBB1 and K-RAS expression, and to cause tumor cell death. Knock down of ATM-AMPK suppressed vesicle formation and knock down of cathepsin B-AIF significantly reduced neratinib lethality. PKG phosphorylates K-RAS and HMG CoA reductase inhibitors reduce K-RAS farnesylation both of which remove K-RAS from the plasma membrane, abolishing its activity. Neratinib interacted with the PKG activator sildenafil and the HMG CoA reductase inhibitor atorvastatin to further reduce K-RAS expression, and to further enhance cell killing. Neratinib is also a Ste20 kinase family inhibitor and in carcinoma cells, and hematopoietic cancer cells lacking ERBB1/2/4, it reduced K-RAS expression and the phosphorylation of MST1/3/4/Ezrin by ~ 30%. Neratinib increased LATS1 phosphorylation as well as that of YAP and TAZ also by ~ 30%, caused the majority of YAP to translocate into the cytosol and reduced YAP/TAZ protein levels. Neratinib lethality was enhanced by knock down of YAP. Neratinib, in a Rubicon-dependent fashion, reduced PAK1 phosphorylation and that of its substrate Merlin. Our data demonstrate that neratinib coordinately suppresses both mutant K-RAS and YAP function to kill pancreatic tumor cells.

Preclinical Characteristics of the Irreversible Pan-HER Kinase Inhibitor Neratinib Compared with Lapatinib: Implications for the Treatment of HER2-Positive and HER2-Mutated Breast Cancer.

An estimated 15-20% of breast cancers overexpress human epidermal growth factor receptor 2 (HER2/ERBB2/neu). Two small-molecule tyrosine kinase inhibitors (TKIs), lapatinib and neratinib, have been approved for the treatment of HER2-positive (HER2+) breast cancer. Lapatinib, a reversible epidermal growth factor receptor (EGFR/ERBB1/HER1) and HER2 TKI, is used for the treatment of advanced HER2+ breast cancer in combination with capecitabine, in combination with trastuzumab in patients with hormone receptor-negative metastatic breast cancer, and in combination with an aromatase inhibitor for the first-line treatment of HER2+ breast cancer. Neratinib, a next-generation, irreversible pan-HER TKI, is used in the US for extended adjuvant treatment of adult patients with early-stage HER2+ breast cancer following 1 year of trastuzumab. In Europe, neratinib is used in the extended adjuvant treatment of adult patients with early-stage hormone receptor-positive HER2+ breast cancer who are less than 1 year from the completion of prior adjuvant trastuzumab-based therapy. Preclinical studies have shown that these agents have distinct properties that may impact their clinical activity. This review describes the preclinical characterization of lapatinib and neratinib, with a focus on the differences between these two agents that may have implications for patient management.

PIK3CA alterations and benefit with neratinib: analysis from the randomized, double-blind, placebo-controlled, phase III ExteNET trial.

BACKGROUND: Neratinib is an irreversible pan-HER tyrosine kinase inhibitor that inhibits PI3K/Akt and MAPK signaling pathways after HER2 receptor activation. The ExteNET study showed that neratinib significantly improved 5-year invasive disease-free survival (iDFS) in women who completed trastuzumab-based adjuvant therapy for early breast cancer (EBC). We assessed the prognostic and predictive significance of PIK3CA alterations in patients in ExteNET. METHODS: Participants were women aged ≥ 18 years (≥ 20 years in Japan) with stage 1-3c (modified to stage 2-3c in February 2010) operable breast cancer, who had completed (neo)adjuvant chemotherapy plus trastuzumab ≤ 2 years before randomization, with no evidence of disease recurrence or metastatic disease at study entry. Patients were randomized to oral neratinib 240 mg/day or placebo for 1 year. Formalin-fixed, paraffin-embedded primary tumor specimens underwent polymerase chain reaction (PCR) PIK3CA testing for two hotspot mutations in exon 9, one hot-spot mutation in exon 20, and fluorescence in situ hybridization (FISH) analysis for PIK3CA amplification. The primary endpoint (iDFS) was tested with log-rank test and hazard ratios (HRs) estimated using Cox proportional-hazards models. RESULTS: Among the intent-to-treat population (n = 2840), tumor specimens were available for PCR testing (991 patients) and PIK3CA FISH (702 patients). Overall, 262 samples were PIK3CA altered: 201 were mutated (77%), 52 (20%) were amplified, and 9 (3%) were mutated and amplified. iDFS was non-significantly worse in placebo-treated patients with altered vs wild-type PIK3CA (HR 1.34; 95% CI 0.72-2.50; P = 0.357). Neratinib's effect over placebo was significant in patients with PIK3CA-altered tumors (HR 0.41; 95% CI 0.17-0.90, P = 0.028) but not PIK3CA wild-type tumors (HR 0.72; 95% CI 0.36-1.41; P = 0.34). The interaction test was non-significant (P = 0.309). CONCLUSIONS: Although there was a greater absolute risk reduction associated with neratinib treatment of patients with PIK3CA-altered tumors in ExteNET, current data do not support PIK3CA alteration as a predictive biomarker of response to neratinib in HER2-positive EBC. TRIAL REGISTRATION: ClinicalTrials.gov , NCT00878709 . Trial registered April 9, 2009.