Impact of EML4-ALK Variants and Co-Occurring TP53 Mutations on Duration of First-Line ALK Tyrosine Kinase Inhibitor Treatment and Overall Survival in ALK Fusion-Positive NSCLC: Real-World Outcomes From the GuardantINFORM database.

INTRODUCTION: Tyrosine kinase inhibitors (TKIs) are first-line treatment options for ALK-positive (ALK+) NSCLC. Factors such as variant allele frequencies (VAFs), EML4-ALK fusion variant, and concurrent TP53 mutations (TP53mt) in circulating tumor DNA (ctDNA) may affect treatment outcomes. We evaluated their effects on time to discontinuation (TTD) of first-line treatment with next-generation ALK TKIs in a real-world setting. METHODS: Adults with advanced or metastatic NSCLC and ctDNA-detected ALK fusion who received first-line next-generation ALK TKI monotherapy were identified in GuardantINFORM. Effects of ALK fusion VAF, EML4-ALK variants, and TP53mt detection on TTD were evaluated. RESULTS: A total of 307 patients with ALK fusion in baseline ctDNA received first-line alectinib (n = 280), brigatinib (n = 15), lorlatinib (n = 9), or ceritinib (n = 3); 150 patients (49%) had ALK-fusion VAF greater than or equal to 1%. Among 232 patients with EML4-ALK fusions (v1, 50%; v3, 36%), TP53mt co-occurred with v1 in 42 (18%) and v3 in 32 (14%). Patients with VAF less than 1% versus greater than or equal to 1% had a median TTD of 32.2 (95% confidence interval [CI]: 20.7-not estimable [NE]) versus 14.7 months (10.4-19.9; hazard ratio [HR] = 1.57 [95% CI: 1.09-2.26]; p = 0.0146). Median TTD was 13.1 (9.5-19.9) versus 27.6 months (17.3-NE) in patients with versus without TP53mt detected (HR = 1.53 [1.07-2.19]; p = 0.0202) and 20.3 (14.4-NE) versus 11.5 months (7.4-31.1) in patients with v1 versus v3 (HR = 1.29 [0.83-2.01]; p = 0.2641). Patients with TP53mt and v3 had a median TTD of 7.4 months (95% CI: 4.2-31.1). CONCLUSION: High ctDNA VAF, EML4-ALK v3, and TP53mt were associated with early discontinuation of first-line ALK TKIs.

A randomized phase 2 study of sapanisertib in combination with paclitaxel versus paclitaxel alone in women with advanced, recurrent, or persistent endometrial cancer.

OBJECTIVE: This phase 2 study investigated sapanisertib (selective dual inhibitor of mTORC1/2) alone, or in combination with paclitaxel or TAK-117 (a selective small molecule inhibitor of PI3K), versus paclitaxel alone in advanced, recurrent, or persistent endometrial cancer. METHODS: Patients with histologic diagnosis of endometrial cancer (1-2 prior regimens) were randomized to 28-day cycles on four treatment arms: 1) weekly paclitaxel 80 mg/m2 (days 1, 8, and 15); 2) weekly paclitaxel 80 mg/m2 + oral sapanisertib 4 mg on days 2-4, 9-11, 16-18, and 23-25; 3) weekly sapanisertib 30 mg, or 4) sapanisertib 4 mg + TAK-117 200 mg on days 1-3, 8-10, 15-17, and 22-24. RESULTS: Of 241 patients randomized, 234 received treatment (paclitaxel, n = 87 [3 ongoing]; paclitaxel+sapanisertib, n = 86 [3 ongoing]; sapanisertib, n = 41; sapanisertib+TAK-117, n = 20). The sapanisertib and sapanisertib+TAK-117 arms were closed to enrollment after futility analyses. After a median follow-up of 14.4 (paclitaxel) versus 17.2 (paclitaxel+sapanisertib) months, median progression-free survival (PFS; primary endpoint) was 3.7 versus 5.6 months (hazard ratio [HR] 0.82; 95% confidence interval [CI] 0.58-1.15; p = 0.139); in patients with endometrioid histology (n = 116), median PFS was 3.3 versus 5.7 months (HR 0.66; 95% CI 0.43-1.03). Grade ≥ 3 treatment-emergent adverse event rates were 54.0% with paclitaxel versus 89.5% paclitaxel+sapanisertib. CONCLUSIONS: Our findings support inclusion of chemotherapy combinations with investigational agents for advanced or metastatic disease. The primary endpoint was not met and toxicity was manageable. TRIAL REGISTRATION: ClinicalTrials.gov number, NCT02725268.

Brigatinib Versus Alectinib in ALK-Positive NSCLC After Disease Progression on Crizotinib: Results of Phase 3 ALTA-3 Trial.

INTRODUCTION: This open-label, phase 3 trial (ALTA-3; NCT03596866) compared efficacy and safety of brigatinib versus alectinib for ALK+ NSCLC after disease progression on crizotinib. METHODS: Patients with advanced ALK+ NSCLC that progressed on crizotinib were randomized 1:1 to brigatinib 180 mg once daily (7-d lead-in, 90 mg) or alectinib 600 mg twice daily, aiming to test superiority. The primary end point was blinded independent review committee-assessed progression-free survival (PFS). Interim analysis for efficacy and futility was planned at approximately 70% of 164 expected PFS events. RESULTS: The population (N = 248; brigatinib, n = 125; alectinib, n = 123) was notable for long median duration of prior crizotinib (16.0-16.8 mo) and low rate of ALK fusion in baseline circulating tumor DNA (ctDNA; 78 of 232 [34%]). Median blinded independent review committee-assessed PFS was 19.3 months with brigatinib and 19.2 months with alectinib (hazard ratio = 0.97 [95% confidence interval: 0.66-1.42], p = 0.8672]). The study met futility criterion. Overall survival was immature (41 events [17%]). Exploratory analyses pooled across the treatment groups revealed median PFS of 11.1 versus 22.5 months in patients with versus without ctDNA-detectable ALK fusion at baseline (hazard ratio: 0.48 [95% confidence interval: 0.32-0.71]). Treatment-related adverse events in more than 30% of patients (brigatinib, alectinib) were elevated levels of blood creatine phosphokinase (70%, 29%), aspartate aminotransferase (53%, 38%), and alanine aminotransferase (40%, 36%). CONCLUSIONS: Brigatinib was not superior to alectinib for PFS in crizotinib-pretreated ALK+ NSCLC. Safety was consistent with the well-established and unique profiles of each drug. The low proportion of patients with ctDNA-detectable ALK fusion may account for prolonged PFS with both drugs in ALTA-3.

Distribution and Detectability of EGFR Exon 20 Insertion Variants in NSCLC.

INTRODUCTION: EGFR exon 20 insertion (ex20ins) mutations represent 5% to 10% of EGFR mutations in NSCLC. Identifying patients with EGFR ex20ins is challenging owing to the limited coverage of polymerase chain reaction (PCR) assays and the relatively recent use of next-generation sequencing (NGS). This study analyzes the spectrum of EGFR ex20ins variants in a large patient population from a global clinical trial and several real-world cohorts and the ability of PCR kits to identify these alterations. METHODS: We conducted this retrospective analysis in patients with NSCLC who underwent NGS or other sequencing testing and had a known EGFR ex20ins mutation. Patients were gathered from a clinical trial (NCT02716116), a chart review study in Germany, and the LC-SCRUM-Japan, GENIE, and U.S. COTA databases. Proportions of patients with ex20ins variants that could have been detected by six commercially available and widely used PCR kits were calculated in each data set. RESULTS: Overall, 636 patients with NSCLC harboring EGFR ex20ins mutations were included in this analysis and 104 unique EGFR ex20ins variants were identified across the data sources. The proportion of patients whose ex20ins could have been detected by any PCR test alone ranged from 11.8% to 58.9% across the data sources. CONCLUSIONS: Our findings suggest that the PCR tests evaluated would have missed more than 40% of patients with NSCLC harboring EGFR ex20ins mutations. NGS-based genetic testing is preferable than standard PCR assays and can substantially improve the identification of the diverse profile of EGFR ex20ins variants in NSCLC.

Survival Outcomes and Treatment Patterns in Patients With NFE2L2 and/or KEAP1 Mutation-Positive Advanced Squamous Cell NSCLC Using a Real-World Clinico-Genomic Database.

BACKGROUND: NFE2L2 and/or KEAP1 mutations are associated with worse prognosis in all non-small cell lung cancer (NSCLC). We determined real-world survival outcomes and treatment patterns among patients with advanced squamous cell NSCLC by NFE2L2 and KEAP1 mutation status. PATIENTS AND METHODS: A retrospective study (January 2011-December 2018) was conducted using a de-identified US-based clinico-genomic database. Adult patients with advanced squamous cell NSCLC with ≥ 2 in-network visits and comprehensive genomic profiling during the study period were included. Outcomes included real-world progression free survival (rwPFS) by line of therapy and overall survival (OS). The real-world effectiveness of anti-PD-1/PD-L1 first-line therapy was also evaluated in patients with a NFE2L2 and/or KEAP1 mutation. RESULTS: Of 703 patients included (median age: 70.0 years), 31.6% had a NFE2L2 and/or KEAP1 mutation. The most common first- and second-line treatments regardless of mutation status were platinum-based chemotherapies and anti-PD-1/PD-L1 therapies. The most common third-line treatment was anti-PD-1/PD-L1 therapy in patients with a NFE2L2 and/or KEAP1 mutation and single-agent chemotherapy in patients with wild-type disease. Patients with a NFE2L2 and/or KEAP1 mutation versus wild-type disease had significantly shorter rwPFS (4.54 vs. 6.25 months; P = .003) following first- but not second- or third-line therapy and shorter median OS (13.59 vs. 17.37 months; P  =  .4105). No survival differences were observed in patients with a NFE2L2 and/or KEAP1 mutation receiving first-line anti-PD-1/PD-L1 therapies versus other therapies. CONCLUSIONS: Patients with advanced squamous cell NSCLC with a NFE2L2 and/or KEAP1 mutation have poor real-world survival, highlighting the need for a genotype-directed therapeutic strategy in this population.

Sapanisertib plus Fulvestrant in Postmenopausal Women with Estrogen Receptor-Positive/HER2-Negative Advanced Breast Cancer after Progression on Aromatase Inhibitor.

PURPOSE: This phase II study investigated daily or weekly sapanisertib (a selective dual inhibitor of mTOR complexes 1 and 2) in combination with fulvestrant. PATIENTS AND METHODS: Postmenopausal women with estrogen receptor-positive (ER+)/HER2-negative (HER2-) advanced or metastatic breast cancer following progression during/after aromatase inhibitor treatment were randomized to receive fulvestrant 500 mg (28-day treatment cycles), fulvestrant plus sapanisertib 4 mg daily, or fulvestrant plus sapanisertib 30 mg weekly, until progressive disease, unacceptable toxicity, consent withdrawal, or study completion. RESULTS: Among 141 enrolled patients, baseline characteristics were balanced among treatment arms, including prior cyclin-dependent kinase-4/6 (CDK4/6) inhibitor treatment in 33% to 35% of patients. Median progression-free survival (PFS; primary endpoint) was 3.5 months in the single-agent fulvestrant arm, compared with 7.2 months for fulvestrant plus sapanisertib daily [HR, 0.77; 95% confidence interval (CI), 0.47-1.26] and 5.6 months for fulvestrant plus sapanisertib weekly (HR, 0.88; 95% CI, 0.53-1.45). The greatest PFS benefits were seen in patients who had previously received CDK4/6 inhibitors. The most common adverse events were nausea, vomiting, and hyperglycemia, all occurring more frequently in the combination therapy arms. Treatment discontinuation due to adverse events occurred more frequently in the two combination therapy arms than with single-agent fulvestrant (32% and 36% vs. 4%, respectively). CONCLUSIONS: Fulvestrant plus sapanisertib daily/weekly resulted in numerically longer PFS in patients with ER+/HER2- advanced or metastatic breast cancer, compared with single-agent fulvestrant. The combination was associated with increased toxicity. Further development of sapanisertib using these dosing schedules in this setting is not supported by these data.

Treatment Outcomes and Safety of Mobocertinib in Platinum-Pretreated Patients With EGFR Exon 20 Insertion-Positive Metastatic Non-Small Cell Lung Cancer: A Phase 1/2 Open-label Nonrandomized Clinical Trial.

IMPORTANCE: Metastatic non-small cell lung cancer (mNSCLC) with EGFR exon 20 insertion (EGFRex20ins) mutations is associated with a poor prognosis. Mobocertinib is an oral tyrosine kinase inhibitor designed to selectively target EGFRex20ins mutations. OBJECTIVE: To evaluate treatment outcomes and safety of mobocertinib in patients with previously treated EGFRex20ins-positive mNSCLC. DESIGN, SETTING, AND PARTICIPANTS: This 3-part, open-label, phase 1/2 nonrandomized clinical trial with dose-escalation/dose-expansion cohorts (28 sites in the US) and a single-arm extension cohort (EXCLAIM; 40 sites in Asia, Europe, and North America) was conducted between June 2016 and November 2020 (data cutoff date). The primary analysis populations were the platinum-pretreated patients (PPP) cohort and the EXCLAIM cohort. The PPP cohort included 114 patients with platinum-pretreated EGFRex20ins-positive mNSCLC who received mobocertinib 160 mg once daily from the dose-escalation (n = 6), dose-expansion (n = 22), and EXCLAIM (n = 86) cohorts. The EXCLAIM cohort included 96 patients with previously treated EGFRex20ins-positive mNSCLC (10 were not platinum pretreated and thus were excluded from the PPP cohort). INTERVENTIONS: Mobocertinib 160 mg once daily. MAIN OUTCOMES AND MEASURES: The primary end point of the PPP and EXCLAIM cohorts was confirmed objective response rate (ORR) assessed by independent review committee (IRC). Secondary end points included confirmed ORR by investigator, duration of response, progression-free survival, overall survival, and safety. RESULTS: Among the PPP (n = 114) and EXCLAIM (n = 96) cohorts, the median (range) age was 60 (27-84) and 59 (27-80) years, respectively; most patients were women (75 [66%] and 62 [65%], respectively) and of Asian race (68 [60%] and 66 [69%], respectively). At data cutoff, median follow-up was 14.2 months in the PPP cohort (median 2 prior anticancer regimens; 40 [35%] had baseline brain metastases), with confirmed ORR of 28% (95% CI, 20%-37%) by IRC assessment and 35% (95% CI, 26%-45%) by investigator assessment; median duration of response by IRC assessment was 17.5 months (95% CI, 7.4-20.3). Median progression-free survival by IRC assessment was 7.3 months (95% CI, 5.5-9.2). Median overall survival was 24.0 months (95% CI, 14.6-28.8). In the EXCLAIM cohort, median follow-up was 13.0 months, with confirmed ORR by IRC assessment of 25% (95% CI, 17%-35%) and by investigator assessment of 32% (95% CI, 23%-43%). The most common treatment-related adverse events were diarrhea and rash. CONCLUSIONS AND RELEVANCE: In this open-label, phase 1/2 nonrandomized clinical trial, mobocertinib was associated with clinically meaningful benefit in patients with previously treated EGFRex20ins-positive mNSCLC, with a manageable safety profile. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02716116.

Targeting HER2 Exon 20 Insertion-Mutant Lung Adenocarcinoma with a Novel Tyrosine Kinase Inhibitor Mobocertinib.

No targeted treatments are currently approved for HER2 exon 20 insertion-mutant lung adenocarcinoma patients. Mobocertinib (TAK-788) is a potent irreversible tyrosine kinase inhibitor (TKI) designed to target human epidermal growth factor receptor 2 (HER2/ERBB2) exon 20 insertion mutations. However, the function of mobocertinib on HER2 exon 20 insertion-mutant lung cancer is still unclear. Here we conducted systematic characterization of preclinical models to understand the activity profile of mobocertinib against HER2 exon 20 insertions. In HER2 exon 20 insertion-mutant cell lines, the IC50 of mobocertinib was higher than poziotinib and comparable with or slightly lower than afatinib, neratinib, and pyrotinib. Mobocertinib had the lowest HER2 exon 20 insertion IC50/wild-type (WT) EGFR IC50 ratio, indicating that mobocertinib displayed the best selectivity profile in these models. Also, mobocertinib showed strong inhibitory activity in HER2 exon 20YVMA allograft and patient-derived xenograft models. In genetically engineered mouse models, HER2 exon 20G776>VC lung tumors exhibited a sustained complete response to mobocertinib, whereas HER2 exon 20YVMA tumors showed only partial and transient response. Combined treatment with a second antibody-drug conjugate (ADC) against HER2, ado-trastuzumab emtansine (T-DM1), synergized with mobocertinib in HER2 exon 20YVMA tumors. In addition to the tumor cell autonomous effect, sustained tumor growth control derived from M1 macrophage infiltration and CD4+ T-cell activation. These findings support the ongoing clinical development of mobocertinib (NCT02716116) and provide a rationale for future clinical evaluation of T-DM1 combinational therapy in HER2 exon 20YVMA insertion-mutant lung adenocarcinoma patients. SIGNIFICANCE: This study elucidates the potent inhibitory activity of mobocertinib against HER2 exon 20 insertion-mutant lung cancer and the synergic effect of combined mobocertinib and T-DM1, providing a strong rationale for clinical investigation.

Sapanisertib Plus Exemestane or Fulvestrant in Women with Hormone Receptor-Positive/HER2-Negative Advanced or Metastatic Breast Cancer.

PURPOSE: This open-label, multicenter, phase IB/II study evaluated sapanisertib, a dual inhibitor of mTOR kinase complexes 1/2, plus exemestane or fulvestrant in postmenopausal women with hormone receptor-positive (HR+)/HER2-negative (HER2-) advanced/metastatic breast cancer. PATIENTS AND METHODS: Eligible patients had previously progressed on everolimus with exemestane/fulvestrant and received ≤3 (phase IB) or ≤1 (phase II) prior chemotherapy regimens. Patients received sapanisertib 3 to 5 mg every day (phase IB), or 4 mg every day (phase II) with exemestane 25 mg every day or fulvestrant 500 mg monthly in 28-day cycles. Phase II enrolled parallel cohorts based on prior response to everolimus. The primary objective of phase II was to evaluate antitumor activity by clinical benefit rate at 16 weeks (CBR-16). RESULTS: Overall, 118 patients enrolled in phase IB (n = 24) and II (n = 94). Five patients in phase IB experienced dose-limiting toxicities, at sapanisertib doses of 5 mg every day (n = 4) and 4 mg every day (n = 1); sapanisertib 4 mg every day was the MTD in combination with exemestane or fulvestrant. In phase II, in everolimus-sensitive versus everolimus-resistant cohorts, CBR-16 was 45% versus 23%, and overall response rate was 8% versus 2%, respectively. The most common adverse events were nausea (52%), fatigue (47%), diarrhea (37%), and hyperglycemia (33%); rash occurred in 17% of patients. Molecular analysis suggested positive association between AKT1 mutation status and best treatment response (complete + partial response; P = 0.0262). CONCLUSIONS: Sapanisertib plus exemestane or fulvestrant was well tolerated and exhibited clinical benefit in postmenopausal women with pretreated everolimus-sensitive or everolimus-resistant breast cancer.

Mobocertinib (TAK-788): A Targeted Inhibitor of EGFR Exon 20 Insertion Mutants in Non-Small Cell Lung Cancer.

Most EGFR exon 20 insertion (EGFRex20ins) driver mutations in non-small cell lung cancer (NSCLC) are insensitive to approved EGFR tyrosine kinase inhibitors (TKI). To address the limitations of existing therapies targeting EGFR-mutated NSCLC, mobocertinib (TAK-788), a novel irreversible EGFR TKI, was specifically designed to potently inhibit oncogenic variants containing activating EGFRex20ins mutations with selectivity over wild-type EGFR. The in vitro and in vivo activity of mobocertinib was evaluated in engineered and patient-derived models harboring diverse EGFRex20ins mutations. Mobocertinib inhibited viability of various EGFRex20ins-driven cell lines more potently than approved EGFR TKIs and demonstrated in vivo antitumor efficacy in patient-derived xenografts and murine orthotopic models. These findings support the ongoing clinical development of mobocertinib for the treatment of EGFRex20ins-mutated NSCLC. SIGNIFICANCE: No oral EGFR-targeted therapies are approved for EGFR exon 20 insertion (EGFRex20ins) mutation-driven NSCLC. Mobocertinib is a novel small-molecule EGFR inhibitor specifically designed to target EGFRex20ins mutants. Preclinical data reported here support the clinical development of mobocertinib in patients with NSCLC with EGFR exon 20 insertion mutations.See related commentary by Pacheco, p. 1617.This article is highlighted in the In This Issue feature, p. 1601.

Activity and Safety of Mobocertinib (TAK-788) in Previously Treated Non-Small Cell Lung Cancer with EGFR Exon 20 Insertion Mutations from a Phase I/II Trial.

Mobocertinib, an oral epidermal growth factor receptor (EGFR) inhibitor targeting EGFR gene mutations, including exon 20 insertions (EGFRex20ins), in non-small cell lung cancer, was evaluated in a phase I/II dose-escalation/expansion trial (ClinicalTrials.gov NCT02716116). Dose escalation identified 160 mg/d as the recommended phase 2 dose and maximum tolerated dose. Among 136 patients treated with 160 mg/d, the most common any-grade treatment-related adverse events (TRAE; >25%) were diarrhea (83%), nausea (43%), rash (33%), and vomiting (26%), with diarrhea (21%) the only grade ≥3 TRAE >5%. Among 28 EGFRex20ins patients treated at 160 mg/d, the investigator-assessed confirmed response rate was 43% (12/28; 95% confidence interval, 24%-63%) with median duration of response of 14 months (5.0-not reached) and median progression-free survival of 7.3 months (4.4-15.6). Mobocertinib demonstrated antitumor activity in patients with diverse EGFRex20ins variants with a safety profile consistent with other EGFR inhibitors. SIGNIFICANCE: No oral EGFR-targeted therapies are currently approved for patients with EGFRex20ins NSCLC. Mobocertinib demonstrated antitumor activity with manageable toxicity in patients with advanced EGFRex20ins NSCLC in this study, supporting additional development of mobocertinib in this patient population.See related commentary by Pacheco, p. 1617.This article is highlighted in the In This Issue feature, p. 1601.

Translational strategy using multiple nuclear imaging biomarkers to evaluate target engagement and early therapeutic efficacy of SAR439859, a novel selective estrogen receptor degrader.

PURPOSE: Preclinical in vivo nuclear imaging of mice offers an enabling perspective to evaluate drug efficacy at optimal dose and schedule. In this study, we interrogated sufficient estrogen receptor occupancy and degradation for the selective estrogen receptor degrader (SERD) compound SAR439859 using molecular imaging and histological techniques. MATERIAL AND METHODS: [18F]FluoroEstradiol positron emission tomography (FES-PET), [18F]FluoroDeoxyGlucose (FDG) PET, and [18F]FluoroThymidine (FLT) PET were investigated as early pharmacodynamic, tumor metabolism, and tumor proliferation imaging biomarkers, respectively, in mice bearing subcutaneous MCF7-Y537S mutant ERα+ breast cancer model treated with the SERD agent SAR439859. ER expression and proliferation index Ki-67 were assessed by immunohistochemistry (IHC). The combination of palbociclib CDK 4/6 inhibitor with SAR439859 was tested for its potential synergistic effect on anti-tumor activity. RESULTS: After repeated SAR439859 oral administration over 4 days, FES tumoral uptake (SUVmean) decreases compared to baseline by 35, 57, and 55% for the 25 mg/kg qd, 12.5 mg/kg bid and 5 mg/kg bid treatment groups, respectively. FES tumor uptake following SAR439859 treatment at different doses correlates with immunohistochemical scoring for ERα expression. No significant difference in FDG uptake is observed after SAR439859 treatments over 3 days. FLT accumulation in tumor is significantly decreased when palbociclib is combined to SAR439859 (- 64%) but not different from the group dosed with palbociclib alone (- 46%). The impact on proliferation is corroborated by Ki-67 IHC data for both groups of treatment. CONCLUSIONS: In our preclinical studies, dose-dependent inhibition of FES tumoral uptake confirmed target engagement of SAR439859 to ERα. FES-PET thus appears as a relevant imaging biomarker for measuring non-invasively the impact of SAR439859 on tumor estrogen receptor occupancy. This study further validates the use of FLT-PET to directly visualize the anti-proliferative tumor effect of the palbociclib CDK 4/6 inhibitor alone and in combination with SAR439859.

Neuregulin 1 expression is a predictive biomarker for response to AV-203, an ERBB3 inhibitory antibody, in human tumor models.

PURPOSE: ERBB3 is overexpressed in a broad spectrum of human cancers, and its aberrant activation is associated with tumor pathogenesis and therapeutic resistance to various anticancer agents. Neuregulin 1 (NRG1) is the predominant ligand for ERBB3 and can promote the heterodimerization of ERBB3 with other ERBB family members, resulting in activation of multiple intracellular signaling pathways. AV-203 is a humanized IgG1/κ ERBB3 inhibitory antibody that completed a first-in-human phase I clinical trial in patients with advanced solid tumors. The purpose of this preclinical study was to identify potential biomarker(s) that may predict response to AV-203 treatment in the clinic. EXPERIMENTAL DESIGN: We conducted in vivo efficacy studies using a broad panel of xenograft models representing a wide variety of human cancers. To identify biomarkers that can predict response to AV-203, the relationship between tumor growth inhibition (TGI) by AV-203 and the expression levels of ERBB3 and NRG1 were evaluated in these tumor models. RESULTS: A significant correlation was observed between the levels of NRG1 expression and TGI by AV-203. In contrast, TGI was not correlated with ERBB3 expression. The correlation between the levels of NRG1 expression in tumors and their response to ERBB3 inhibition by AV-203 was further validated using patient-derived tumor explant models. CONCLUSIONS: NRG1 is a promising biomarker that can predict response to ERBB3 inhibition by AV-203 in preclinical human cancer models. NRG1 warrants further clinical evaluation and validation as a potential predictive biomarker of response to AV-203.

Dissecting genetic requirements of human breast tumorigenesis in a tissue transgenic model of human breast cancer in mice.

Breast cancer development is a complex pathobiological process involving sequential genetic alterations in normal epithelial cells that results in uncontrolled growth in a permissive microenvironment. Accordingly, physiologically relevant models of human breast cancer that recapitulate these events are needed to study cancer biology and evaluate therapeutic agents. Here, we report the generation and utilization of the human breast cancer in mouse (HIM) model, which is composed of genetically engineered primary human breast epithelial organoids and activated human breast stromal cells. By using this approach, we have defined key genetic events required to drive the development of human preneoplastic lesions as well as invasive adenocarcinomas that are histologically similar to those in patients. Tumor development in the HIM model proceeds through defined histological stages of hyperplasia, DCIS to invasive carcinoma. Moreover, HIM tumors display characteristic responses to targeted therapies, such as HER2 inhibitors, further validating the utility of these models in preclinical compound testing. The HIM model is an experimentally tractable human in vivo system that holds great potential for advancing our basic understanding of cancer biology and for the discovery and testing of targeted therapies.

Targeting of proteins to membranes through hedgehog auto-processing.

Hedgehog proteins use an auto-processing strategy to generate cholesterol-conjugated peptide products that act as extracellular ligands in a number of developmental signaling pathways. We describe an approach that takes advantage of the hedgehog auto-processing reaction to carry out intracellular modification of heterologous proteins, resulting in their localization to cell membranes. Such processing occurs spontaneously, without accessory proteins or modification by other enzymes. Using the green fluorescent protein (GFP) and the product of the Hras as model proteins, we demonstrate the use of hedgehog auto-processing to process heterologous N-terminal domains and direct the resulting biologically active products to cell membranes. This system represents a tool for targeting functional peptides and proteins to cell membranes, and may also offer a means of directing peptides or other small molecules to components of cholesterol metabolism or regulation.

Microphthalmia transcription factor analysis in posterior uveal melanomas.

PURPOSE: The protein encoded by the Microphthalmia gene (MITF) is a transcription factor essential for the development and survival of melanocytes. It serves as a master regulator in modulating extracellular signals. Because of its central role in melanocytes survival and to assess its potential use as a histopathological marker for melanoma, MITF expression was examined in human choroidal melanomas. METHODS: Fifty-seven paraffin-embedded sections of choroidal melanoma specimens and 1 choroidal melanoma cell line were analyzed using immunochemistry and RT-PCR. Normal choroids and normal choroidal melanocyte cells were used as control. RESULTS: Sixty-five percent of the tumoral specimens stained positively for MITF with a predominant nuclear pattern of reactivity. MITF-M and MITF-A isoforms were detected by RT-PCR in all specimens examined. Using a chimeric protein resulting from the fusion of each Mitf protein with the GFP, Mitf-M exhibited an exclusive nuclear staining whereas Mitf-A exhibited a mixed nuclear and cytoplasmic staining. No correlation between MITF-positivity and parameters such as cell type, largest tumor diameter, sclera invasion, mitotic figures was observed. In contrast, a significant negative association was found between MITF staining and the pigmentation (p=0.02) and a positive correlation between MITF staining and the proliferative marker Ki67 was found (p=0.02). CONCLUSION: MITF may be implicated in choroidal melanoma pigmentation and proliferation. Further analysis should provide new insights into the mechanisms underlying the molecular and cellular changes of choroidal melanomas.

Papillary tumor of the pineal region.

Primary papillary tumors of the central nervous system are rare. We have encountered a series of six papillary tumors of the pineal region with distinctive features that appear to represent a clinicopathologic entity. The tumors occurred in four women and two men, ranging in age from 19 to 53 years. Imaging studies showed a large well-circumscribed mass in the pineal region. The tumors were characterized by an epithelial-like growth pattern, in which the vessels were covered by a layer of tumoral cells. In papillary areas, the neoplastic cells were large, columnar or cuboidal, with a clear cytoplasm. Nuclei, round or infolded, were found generally at the basal pole of tumoral cells. Immunohistochemically, the tumor cells showed strong staining for cytokeratin, S-100 protein, neuron-specific enolase, and vimentin but only weak or no staining for epithelial membrane antigen and glial fibrillary acid protein. Ultrastructural examination of two cases revealed abundant rough endoplasmic reticulum with distended cisternae filled with secretory product, microvilli, and perinuclear intermediate filaments. The morphofunctional features of these papillary tumors of the pineal region, remarkably uniform within this series, are similar to those described for ependymal cells of the subcommissural organ, and the papillary tumors of the pineal region may be derived from these specialized ependymocytes.

Calbindin-d(28k): a marker of recurrence for medulloblastomas.

BACKGROUND: The expression of the Ca(2+)-binding protein calbindin-D(28k) was analyzed in medulloblastomas in relation to clinical features and other biologic markers related to cell proliferation, differentiation, p53, and cerebellar developmental regulated gene expression. METHODS: Immunohistochemistry was carried out on histologic slides from a first retrospective series of 29 nonmetastatic and 10 metastatic medulloblastoma formalin-fixed, paraffin-embedded tissues, using specific antibodies against calbindin-D(28k), calretinin, alpha-parvalbumin and beta-parvalbumin, and S100 proteins. Informed consent was obtained from the subjects and/or guardians. Other biologic markers for differentiation, cell proliferation, the expression of the p53 tumor suppressor gene protein, and cerebellar developmental regulated genes were similarly investigated. A second series of 16 medulloblastomas from young patients (younger than 15 years) was added in order to validate the results obtained in the first series. RESULTS: Of all the markers investigated, only calbindin-D(28k) was significantly associated with prognosis. Survival and remission (i.e. recurrence free) time analysis performed on all the cases (n = 55) confirmed a high risk of death (P = 0.004) and recurrence (P = 0.003) associated with calbindin-positivity. As calbindin-positivity was predominantly observed in tumors from young patients, the authors confirmed its prognostic value in the subgroup of patients younger than 15 years (n = 37). Cox regression analysis showed a significant and independent prognostic value for calbindin expression and, to a lesser extent, the type of surgery (total or subtotal). Three risk groups were thus identified, distinguishing among the cases characterized by a total resection and calbindin-negativity (good prognosis), by a subtotal resection and calbindin-negativity (intermediary), and by calbindin-positivity (bad prognosis). CONCLUSIONS: The current study suggests that calbindin-positive medulloblastomas represent a subclass of aggressive tumors more frequently seen in younger patients.