Overall survival with sacituzumab govitecan in hormone receptor-positive and human epidermal growth factor receptor 2-negative metastatic breast cancer (TROPiCS-02): a randomised, open-label, multicentre, phase 3 trial

BACKGROUND

Sacituzumab govitecan demonstrated significant progression-free survival benefit over chemotherapy in the phase 3 TROPiCS-02 trial in patients with pretreated, endocrine-resistant hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+ and HER2-) metastatic breast cancer with limited treatment options. Here, we report the protocol-specified final analysis of overall survival and endpoints by trophoblast cell-surface antigen 2 (Trop-2) expression and other variables.

METHODS

In this randomised, open-label, multicentre, phase 3 trial, which took place in 91 centres across North America (the USA and Canada) and Europe (Belgium, France, Germany, Italy, the Netherlands, Spain, and the UK), patients were randomly assigned (1:1) to receive sacituzumab govitecan or chemotherapy (eribulin, vinorelbine, capecitabine, or gemcitabine). Patients had confirmed HR+ and HER2- locally recurrent inoperable or metastatic breast cancer and had received at least one previous endocrine therapy, a taxane, and a CDK4/6 inhibitor in any setting and two to four previous chemotherapy regimens for metastatic disease. The primary endpoint was progression-free survival (previously reported and not included in this analysis), and secondary endpoints included overall survival, objective response rate (ORR), and patient-reported outcomes. Overall survival was assessed using stratified log-rank tests and Cox regression. Trop-2 expression was assessed in tumour tissue by immunohistochemistry. In the statistical testing hierarchy, ORR and patient-reported outcomes were tested sequentially if overall survival was significant. This study is registered with ClinicalTrials.gov, NCT03901339.

FINDINGS

At the data cutoff date of July 1, 2022, 543 of 776 screened patients were randomly assigned between May 30, 2019, and April 5, 2021, with 272 patients in the sacituzumab govitecan group and 271 patients in the chemotherapy group. With a 12·5-month (IQR 6·4-18·8) median follow-up, 390 deaths occurred among 543 patients. Overall survival was significantly improved with sacituzumab govitecan versus chemotherapy (median 14·4 months [95% CI 13·0-15·7] vs 11·2 months [10·1-12·7]; hazard ratio [HR] 0·79, 95% CI 0·65-0·96; p=0·020); survival benefit was consistent across Trop-2 expression-level subgroups. ORR was significantly improved with sacituzumab govitecan compared with chemotherapy (57 [21%] patients vs 38 [14%]; odds ratio 1·63 [95% CI 1·03-2·56]; p=0·035), as was time to deterioration of global health status and quality of life (median 4·3 months vs 3·0 months; HR 0·75 [0·61-0·92]; p=0·0059) and fatigue (median 2·2 months vs 1·4 months; HR 0·73 [0·60-0·89]; p=0·0021). The safety profile of sacituzumab govitecan was consistent with previous studies (including the TROPiCS-02 primary analysis and the ASCENT trial). One fatal adverse event (septic shock caused by neutropenic colitis) was determined to be related to sacituzumab govitecan treatment.

INTERPRETATION

Sacituzumab govitecan demonstrated statistically significant and clinically meaningful benefit over chemotherapy, with a 3·2-month median overall survival improvement and a manageable safety profile. These data support sacituzumab govitecan as a new treatment option for patients with pretreated, endocrine-resistant HR+ and HER2- metastatic breast cancer.

FUNDING

Gilead Sciences.

Activity of eftozanermin alfa plus venetoclax in preclinical models and patients with acute myeloid leukemia

Activation of apoptosis in malignant cells is an established strategy for controlling cancer and is potentially curative. To assess the impact of concurrently inducing the extrinsic and intrinsic apoptosis-signaling pathways in acute myeloid leukemia (AML), we evaluated activity of the TRAIL receptor agonistic fusion protein eftozanermin alfa (eftoza; ABBV-621) in combination with the B-cell lymphoma protein-2 selective inhibitor venetoclax in preclinical models and human patients. Simultaneously stimulating intrinsic and extrinsic apoptosis-signaling pathways with venetoclax and eftoza, respectively, enhanced their activities in AML cell lines and patient-derived ex vivo/in vivo models. Eftoza activity alone or plus venetoclax required death receptor 4/5 (DR4/DR5) expression on the plasma membrane but was independent of TP53 or FLT3-ITD status. The safety/tolerability of eftoza as monotherapy and in combination with venetoclax was demonstrated in patients with relapsed/refractory AML in a phase 1 clinical trial. Treatment-related adverse events were reported in 2 of 4 (50%) patients treated with eftoza monotherapy and 18 of 23 (78%) treated with eftoza plus venetoclax. An overall response rate of 30% (7/23; 4 complete responses [CRs], 2 CRs with incomplete hematologic recovery, and 1 morphologic leukemia-free state) was reported in patients who received treatment with eftoza plus venetoclax and 67% (4/6) in patients with myoblasts positive for DR4/DR5 expression; no tumor responses were observed with eftoza monotherapy. These data indicate that combination therapy with eftoza plus venetoclax to simultaneously activate the extrinsic and intrinsic apoptosis-signaling pathways may improve clinical benefit compared with venetoclax monotherapy in relapsed/refractory AML with an acceptable toxicity profile. This trial was registered at www.clinicaltrials.gov as #NCT03082209.

Abstract 4392: Expression landscape of trophoblast cell surface antigen 2 (Trop-2) in breast cancer

Background: Antibody-drug conjugates (ADCs) are novel agents linking potent payloads to antibodies targeting antigen-expressing tumors. Sacituzumab govitecan (SG), a Trop-2-directed ADC, is approved for patients with metastatic triple-negative breast cancer (mTNBC) with ≥2 prior therapies (≥1 in metastatic setting). SG is also being investigated in other breast cancer subtypes, including hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) metastatic breast cancer and in earlier lines of treatment. To understand the landscape of Trop-2 expression and potential clinical actionability of Trop-2 and other antigens, we evaluated RNA expression data in breast cancer from The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC).

Methods: TCGA and METABRIC datasets were assessed for Trop-2, HER2, and programmed death ligand 1 (PD-L1) expression via processed RNA sequencing (RNA-seq) and microarray data of the corresponding genes TACSTD2, ERBB2, and CD274. Gene expression across clinical parameters was assessed via one-way ANOVA, t-test, or Spearman correlation. HER2 status was classified as HER2 immunohistochemistry (IHC) 0 or HER2-low (IHC1+, or IHC2+ and in situ hybridization-negative). Survival was estimated via Kaplan-Meier method. Neoadjuvant therapy datasets were assessed for effects of aromatase inhibitors on Trop-2 expression.

Results: RNA-Seq data was available from 1030 and 2136 breast cancer patients in TCGA and METABRIC datasets, respectively. Most patients (96%) had high TACSTD2 expression (>100 transcripts per million [TPM]). TACSTD2 expression was comparable by breast cancer histology (median log2TPM 6.8-7.5), by disease stages I-IV (median log2TPM 7.0-7.5), or by subtypes (median log2TPM 7.1-7.3). TACSTD2 expression was not correlated with ERBB2 (Spearman rho=0.06) or CD274 (Spearman rho=-0.13) expression. No difference in TACSTD2 expression was noted between HER2 IHC0 or HER2-low subtypes. TACSTD2 expression was not associated with survival, though low tertile TACSTD2 groups had better prognosis in the basal subtype; treatments were heterogeneous. Changes in TACSTD2 gene expression were not observed post-aromatase inhibitors.

Conclusions: While SG is approved for use in mTNBC, TACSTD2 is stably expressed across all breast cancer stages and subtypes, including HER2 IHC0 and HER2-low, and across all ranges of PD-L1 expression, suggesting a broad patient population may benefit from Trop-2-directed ADCs.

Citation Format: Kai Song, Oh Kyu Yoon, Luting Zhuo, Emon Elboudwarej, Biao Li, Jillian Boice, Yang Pan, See Phan, Monica Motwani. Expression landscape of trophoblast cell surface antigen 2 (Trop-2) in breast cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4392.

Abstract GS1-11: Sacituzumab Govitecan (SG) vs Treatment of Physician’s Choice (TPC): Efficacy by Trop-2 Expression in the TROPiCS-02 Study of Patients (Pts) With HR+/HER2– Metastatic Breast Cancer (mBC)

Background: HR+/HER2– mBC, the most common subset of breast cancer, is treated with sequential endocrine therapy + targeted agents followed by sequential single-agent chemotherapy (CT), with increasingly shorter benefit duration with each subsequent treatment. High Trop-2 expression is observed in breast cancer regardless of subtype. SG is a Trop-2-directed antibody-drug conjugate approved for pre-treated metastatic triple-negative breast cancer. In the phase 3 TROPiCS-02 study, SG showed both significant progression-free survival (PFS) benefit (HR, 0.66; P<0.001; median 5.5 vs 4.0 mo; JCO 2022) at the primary analysis and overall survival (OS) benefit (median 14.4 vs 11.2 mo; HR, 0.79; P=0.02; ESMO 2022) at the 2nd planned interim OS analysis vs TPC in pretreated HR+/HER2- mBC. Here we compare efficacy outcomes for SG and TPC by Trop-2 expression. Methods: Eligible pts had HR+/HER2- locally recurrent inoperable or mBC; received ≥1 prior taxane, endocrine therapy, a CDK4/6 inhibitor; and received 2-4 prior CT regimens for mBC. Pts were randomized 1:1 to receive SG (10 mg/kg IV on d 1 and 8, every 21 d) or TPC (eribulin, gemcitabine, capecitabine, or vinorelbine) until disease progression or unacceptable toxicity. The primary endpoint was PFS by independent review per RECIST v1.1; OS and objective response rate (ORR) were key secondary endpoints. ORR was assessed by blinded independent central review per RECIST v1.1. Membrane Trop-2 expression on archival tumor tissue was assessed by immunohistochemistry and expressed as a histochemical score (H-score; range, 0-300); efficacy outcomes were assessed in H-score <100 and ≥100 groups. The H-score <100 group was further divided into H-score ≤10 and >10- <100 subgroups to assess the activity of SG in pts with very low Trop-2 expression. Results: Data cut-off was January 3, 2022 for PFS (median follow-up, 10.2 mo) and July 1, 2022 for OS (median follow-up, 12.5 mo). In total, 543 pts were randomized to receive SG (n=272) vs TPC (n=271). Pts had a median of 3 prior CT regimens for mBC; 95% had visceral metastases. There were 238 (88%) vs 224 (83%) Trop-2-evaluable pts in the SG vs TPC groups, respectively; of these, 95% had tumors with Trop-2 H-score >0. Of Trop-2-evaluable pts, 192 (42%) and 270 (58%) had H-scores <100 and ≥100, respectively. Demographics and baseline characteristics were generally consistent across H-score groups. PFS and OS benefit was observed for SG vs TPC across both Trop-2 groups (Table). Median PFS was 5.3 vs 4.0 mo (HR, 0.77; 95% CI, 0.54-1.09) and 6.4 vs 4.1 mo (HR, 0.60; 95% CI, 0.44-0.81) in the H-score <100 and ≥100 groups; median OS was 14.6 vs 11.3 mo (HR, 0.75; 95% CI, 0.54-1.04) and 14.4 vs 11.2 mo (HR, 0.83; 95% CI, 0.62-1.11), respectively. Disease response was observed in the 34 pts with H-score ≤10 who received SG. In pts who received SG, those with H-score ≤10, >10- <100, and ≥100 had ORRs of 24%, 18%, and 23%, respectively. The safety profile for SG by Trop-2 H-score was consistent with previous reports. Conclusions: In this TROPiCS-02 post-hoc analysis, improved efficacy with SG vs TPC was observed regardless of Trop-2 expression, and there was no clear level of Trop-2 expression at which a better treatment effect for SG was observed. These results support SG as an effective novel treatment option for patients with pretreated, endocrine-resistant HR+/HER2- mBC, and reinforce that Trop-2 testing is not required for SG treatment.

Table

Citation Format: Hope Rugo, Aditya Bardia, Frederik Marmé, Javier Cortés, Peter Schmid, Delphine Loirat, Olivier Trédan, Eva Ciruelos, Florence Dalenc, Patricia Gómez Pardo, Komal Jhaveri, Monica Motwani, Oh Kyu Yoon, Hao Wang, Wendy Verret, Sara Tolaney. Sacituzumab Govitecan (SG) vs Treatment of Physician’s Choice (TPC): Efficacy by Trop-2 Expression in the TROPiCS-02 Study of Patients (Pts) With HR+/HER2– Metastatic Breast Cancer (mBC) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr GS1-11.

Phase Ib Study of Telisotuzumab Vedotin in Combination With Erlotinib in Patients With c-Met Protein-Expressing Non-Small-Cell Lung Cancer

PURPOSE

Overexpression of c-Met protein and epidermal growth factor receptor (EGFR) mutations can co-occur in non-small-cell lung cancer (NSCLC), providing strong rationale for dual targeting. Telisotuzumab vedotin (Teliso-V), a first-in-class antibody-drug conjugate targeting c-Met, has shown a tolerable safety profile and antitumor activity as monotherapy. Herein, we report the results of a phase Ib study (ClinicalTrials.gov identifier: NCT02099058) evaluating Teliso-V plus erlotinib, an EGFR tyrosine kinase inhibitor (TKI), in patients with c-Met-positive (+) NSCLC.

PATIENTS AND METHODS

This study evaluated Teliso-V (2.7 mg/kg once every 21 days) plus erlotinib (150 mg once daily) in adult patients (age ≥ 18 years) with c-Met+ NSCLC. Later enrollment required presence of an EGFR-activating mutation (EGFR-M+) and progression on a prior EGFR TKI. End points included safety, pharmacokinetics, objective response rate (ORR), and progression-free survival (PFS). The efficacy-evaluable population consisted of c-Met+ patients (confirmed histology [H]-score ≥ 150) who had at least one postbaseline scan; c-Met+ patients with H-scores ≥ 225 were classified as c-Met high.

RESULTS

As of January 2020, 42 patients were enrolled (N = 36 efficacy-evaluable). Neuropathies were the most common any-grade adverse events reported, with 24 of 42 patients (57%) experiencing at least one event. The pharmacokinetic profile of Teliso-V plus erlotinib was similar to Teliso-V monotherapy. Median PFS for all efficacy-evaluable patients was 5.9 months (95% CI, 2.8 to not reached). ORR for EGFR-M+ patients (n = 28) was 32.1%. Of EGFR-M+ patients, those who were c-Met high (n = 15) had an ORR of 52.6%. Median PFS was 6.8 months for non-T790M+ and for those whose T790M status was unknown, versus 3.7 months for T790M+.

CONCLUSION

Teliso-V plus erlotinib showed encouraging antitumor activity and acceptable toxicity in EGFR TKI-pretreated patients with EGFR-M+, c-Met+ NSCLC.

Eftozanermin alfa (ABBV-621) monotherapy in patients with previously treated solid tumors: findings of a phase 1, first-in-human study

Eftozanermin alfa (eftoza), a second-generation tumor necrosis factor-related apoptosis-inducing ligand receptor (TRAIL-R) agonist, induces apoptosis in tumor cells by activation of death receptors 4/5. This phase 1 dose-escalation/dose-optimization study evaluated the safety, pharmacokinetics, pharmacodynamics, and preliminary activity of eftoza in patients with advanced solid tumors. Patients received eftoza 2.5-15 mg/kg intravenously on day 1 or day 1/day 8 every 21 days in the dose-escalation phase, and 1.25-7.5 mg/kg once-weekly (QW) in the dose-optimization phase. Dose-limiting toxicities (DLTs) were evaluated during the first treatment cycle to determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D). Pharmacodynamic effects were evaluated in circulation and tumor tissue. A total of 105 patients were enrolled in the study (dose-escalation cohort, n = 57; dose-optimization cohort, n = 48 patients [n = 24, colorectal cancer (CRC); n = 24, pancreatic cancer (PaCA)]). In the dose-escalation cohort, seven patients experienced DLTs. MTD and RP2D were not determined. Most common treatment-related adverse events were increased alanine aminotransferase and aspartate aminotransferase levels, nausea, and fatigue. The one treatment-related death occurred due to respiratory failure. In the dose-optimization cohort, three patients (CRC, n = 2; PaCA, n = 1) had a partial response. Target engagement with regard to receptor saturation, and downstream apoptotic pathway activation in circulation and tumor were observed. Eftoza had acceptable safety, evidence of pharmacodynamic effects, and preliminary anticancer activity. The 7.5-mg/kg QW regimen was selected for future studies on the basis of safety findings, pharmacodynamic effects, and biomarker modulations. (Trial registration number: NCT03082209 (registered: March 17, 2017)).

A Phase 1b Study of Telisotuzumab Vedotin in Combination With Nivolumab in Patients With NSCLC

Introduction

Telisotuzumab vedotin (Teliso-V) is an anti-c-Met-directed antibody-drug conjugate that has exhibited antitumor activity as monotherapy in NSCLC. Its potential activity combined with programmed cell death protein-1 inhibitors has not been previously evaluated.

Methods

In a phase 1b study (NCT02099058), adult patients (≥18 y) with advanced NSCLC received combination therapy with Teliso-V (1.6, 1.9, or 2.2 mg/kg, every 2 wk) plus nivolumab (3 mg/kg, 240 mg, or per locally approved label). The primary objective was to assess safety and tolerability; secondary objectives included the evaluation of antitumor activity.

Results

As of January 2020, a total of 37 patients received treatment with Teliso-V (safety population) in combination with nivolumab; 27 patients (efficacy population) were c-Met immunohistochemistry-positive. Programmed death-ligand 1 (PD-L1) status was evaluated in the efficacy population (PD-L1-positive [PD-L1+]: n = 15; PD-L1-negative [PD-L1-]: n = 9; PD-L1-unknown: n = 3). The median age was 67 years and 74% (20 of 27) of patients were naive to immune checkpoint inhibitors. The most common any-grade treatment-related adverse events were fatigue (27%) and peripheral sensory neuropathy (19%). The pharmacokinetic profile of Teliso-V plus nivolumab was similar to Teliso-V monotherapy. The objective response rate was 7.4%, with two patients (PD-L1+, c-Met immunohistochemistry H-score 190, n = 1; PD-L1-, c-Met H-score 290, n = 1) having a confirmed partial response. Overall median progression-free survival was 7.2 months (PD-L1+: 7.2 mo; PD-L1-: 4.5 mo; PD-L1-unknown: not reached).

Conclusions

Combination therapy with Teliso-V plus nivolumab was well tolerated in patients with c-Met+ NSCLC with limited antitumor activity.

Phase I Study of 2- or 3-Week Dosing of Telisotuzumab Vedotin, an Antibody-Drug Conjugate Targeting c-Met, Monotherapy in Patients with Advanced Non-Small Cell Lung Carcinoma

PURPOSE

Telisotuzumab vedotin (Teliso-V) is an anti-c-Met-directed antibody-drug conjugate. Here, we present safety and efficacy data from a phase I/Ib study of Teliso-V monotherapy evaluated in once every 2 weeks/once every 3 weeks schedules in patients with non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

During dose escalation, patients received Teliso-V monotherapy intravenously once every 3 weeks (0.15-3.3 mg/kg) or once every 2 weeks (1.6-2.2 mg/kg). The dose-expansion phase enrolled patients with NSCLC and c-Met H-score ≥150 (c-Met+) or MET amplification/exon 14 skipping mutations. Safety, pharmacokinetics, and efficacy were assessed. Herein, the analysis of patients receiving ≥1.6 mg/kg once every 2 weeks or ≥2.4 mg/kg once every 3 weeks Teliso-V is reported.

RESULTS

Fifty-two patients with NSCLC were enrolled and received ≥1.6 mg/kg Teliso-V once every 2 weeks (n = 28) or ≥2.4 mg/kg Teliso-V once every 3 weeks (n = 24). The most common adverse events were fatigue (54%), peripheral neuropathy (42%), and nausea (38%). No dose-limiting toxicities were observed for Teliso-V once every 2 weeks and once every 3 weeks up to 2.2 and 2.7 mg/kg, respectively. The recommended phase II dose was established at 1.9 mg/kg once every 2 weeks and 2.7 mg/kg once every 3 weeks on the basis of overall safety and pharmacokinetics. Forty of 52 patients were c-Met+ (33 nonsquamous, 6 squamous, 1 mixed histology) and were included in the efficacy-evaluable population. Of those, 9 (23%) had objective responses with median duration of response of 8.7 months; median progression-free survival was 5.2 months.

CONCLUSIONS

Teliso-V monotherapy was tolerated and showed antitumor activity in c-Met+ NSCLC. On the basis of overall safety, pharmacokinetics, and efficacy outcomes, 1.9 mg/kg Teliso-V once every 2 weeks and 2.7 mg/kg once every 3 weeks schedules were selected for further clinical development.

Machine learning from quantitative coronary computed tomography angiography predicts ischemia and impaired myocardial blood flow

Background

Atherosclerotic plaque characteristics influence the hemodynamic consequences of coronary lesions. This study sought to assess the performance of a machine learning (ML) score integrating coronary computed tomography angiography (CCTA)-based quantitative plaque features for the prediction of ischemia by invasive fractional flow reserve (FFR) and impaired myocardial blood flow (MBF) by [15O]H2O positron emission tomography (PET).

Methods

This post-hoc analysis of the PACIFIC (Prospective Comparison of Cardiac PET/CT, SPECT/CT Perfusion Imaging and CT Coronary Angiography With Invasive Coronary Angiography) trial included 208 patients with suspected coronary artery disease who underwent CCTA, [15O]H2O PET, and 3-vessel invasive FFR. Plaque quantification from CCTA was performed using semiautomated software. A boosted ensemble ML algorithm (XGBoost) trained on data from the NXT (Analysis of Coronary Blood Flow using CT Angiography: Next Steps) trial was used to develop a ML score for the prediction of per-vessel ischemia (invasive FFR ≤0.80). The performance of the ML score was evaluated in 551 vessels from the PACIFIC trial for external validation. Thereafter, we assessed the discriminative ability of the ML score for per-vessel impaired hyperemic MBF (≤2.30 mL/min/g).

Results

In total, 138 (25.0%) vessels had ischemia and 195 (35.4%) vessels had impaired hyperemic MBF. CCTA-derived quantitative percent diameter stenosis and low-density noncalcified plaque (LDNCP) volume were higher in ischemic vessels compared with non-ischemic vessels (60.8% vs. 19.9%; and 42.3 mm3 vs. 9.1 mm3; both p<0.001). The ML score demonstrated a significantly higher area under the receiver-operating characteristic curve (AUC) for predicting ischemia (0.92, 95% confidence interval [CI] 0.89–0.94) compared with visual stenosis grade (0.84, 95% CI 0.80–0.87; p<0.001). Overall, quantitative percent diameter stenosis and LDNCP volume had greatest feature importance for ML, followed by percent area stenosis, minimum luminal diameter, and contrast density drop (Figure 1). An individualized explanation of ML ischemia prediction is shown in Figure 2. When applied for impaired MBF discrimination, the ML score exhibited an AUC of 0.82 (95% CI 0.78–0.85) and was superior to visual stenosis grade (AUC 0.76, 95% CI 0.72–0.80; p=0.03).

Conclusions

An externally validated ML score integrating CCTA-based quantitative plaque features accurately predicts FFR-defined ischemia and abnormal MBF by PET, outperforming standard visual CCTA interpretation.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Heart, Lung, and Blood Institute, United States Performance of the ML scoreIndividual explanation of ML prediction

Phase I Open-Label Study Evaluating the Safety, Pharmacokinetics, and Preliminary Efficacy of Dilpacimab in Patients with Advanced Solid Tumors

Dilpacimab (formerly ABT-165), a novel dual-variable domain immunoglobulin, targets both delta-like ligand 4 (DLL4) and VEGF pathways. Here, we present safety, pharmacokinetic (PK), pharmacodynamic (PD), and preliminary efficacy data from a phase I study (trial registration ID: NCT01946074) of dilpacimab in patients with advanced solid tumors. Eligible patients (≥18 years) received dilpacimab intravenously on days 1 and 15 in 28-day cycles at escalating dose levels (range, 1.25-7.5 mg/kg) until progressive disease or unacceptable toxicity. As of August 2018, 55 patients with solid tumors were enrolled in the dilpacimab monotherapy dose-escalation and dose-expansion cohorts. The most common treatment-related adverse events (TRAE) included hypertension (60.0%), headache (30.9%), and fatigue (21.8%). A TRAE of special interest was gastrointestinal perforation, occurring in 2 patients (3.6%; 1 with ovarian and 1 with prostate cancer) and resulting in 1 death. The PK of dilpacimab showed a half-life ranging from 4.9 to 9.5 days, and biomarker analysis demonstrated that the drug bound to both VEGF and DLL4 targets. The recommended phase II dose for dilpacimab monotherapy was established as 3.75 mg/kg, primarily on the basis of tolerability through multiple cycles. A partial response was achieved in 10.9% of patients (including 4 of 16 patients with ovarian cancer). The remaining patients had either stable disease (52.7%), progressive disease (23.6%), or were deemed unevaluable (12.7%). These results demonstrate that dilpacimab monotherapy has an acceptable safety profile, with clinical activity observed in patients with advanced solid tumors.

P323Triage-HF Plus: identification of heart failure and non-heart failure events in an ambulatory population using remote monitoring and the triage heart failure risk score Algorithm

Background/introduction

Previous studies examining the utility of cardiac implantable electronic devices (CIEDs) to remotely monitor heart failure patients for decompensation have not demonstrated an impact on hard end-points. However, a key limitation of these prior studies (REM-HF and MORE-CARE) has been the failure to stratify patients according to their risk of worsening heart failure (WHF) prior to randomization (usual care vs active monitoring). We examined a different approach, using a single manufacturer’s remote monitoring platform, whereby only patients with CIED-derived data indicating the highest risk of WHF are contacted for assessment. The validated ‘Triage Heart Failure Risk Score’ (Triage-HFRS) is a medical algorithm within Medtronic CIEDs that can risk-stratify patients as low-, medium- or high-risk of WHF in the next 30 days based on integrated monitoring of physiological parameters.

Purpose

 This study is the largest prospective evaluation of the Triage-HFRS, and examines the additional role of contacting those patients with a ‘High-Risk’ Triage-HFRS alert by telephone (Triage-HF Plus pathway).

Methods

 Prospective, real-world evaluation of the Triage-HF Plus pathway undertaken between June 2016 and September 2019. 326 high-risk Triage-HFRS transmissions were contacted for telephone triage assessment. Screening questions were designed to identify episodes of WHF and non-heart failure events. Interventions were at the discretion of the clinical practitioner and in line with guideline-directed practice. An additional 3-month consecutive sample of low and medium Triage-HFRS transmissions (control group) were also contacted for telephone triage assessment (n= 98).

Results

Successful telephone contact was made following 245 high-risk Triage-HFRS alerts. Following contact, 194 (79.1%) patients reported an acute medical issue: 137 (70.6%) reported symptoms consistent with worsening heart failure (WHF) requiring intervention; and 57 (29.4%) had an alternative acute medical problem. 51 (26.2%) had no apparent reason for the high score. The sensitivity and specificity of CIED-based remote monitoring to identify any HF and non-HF events requiring intervention was 99.5% (97.2-99.9%) and 65.5% (57.3-73.2%) respectively; positive predictive value was 79.2%. The negative predictive value of a non-high risk score to rule out an acute event was 98.9%. Overall accuracy of the pathway to identify an acute issue (HF or non-HF related) was 84.8%.

Conclusion

The Triage-HF Plus clinical pathway is a potentially useful remote monitoring tool for patients with heart failure. The pathway has high diagnostic accuracy to identify patients with WHF and a wide range of non-HF issues which are just as relevant in a population who often have multiple complex co-morbidities and are known for their high health care utilisation.

Pharmacodynamic effects in blood and tumor tissue of eftozanermin alfa, a tumor necrosis factor-related apoptosis-inducing ligand receptor agonist

e15668

Background: Eftozanermin alfa (eftoza; formerly known as ABBV-621), a 2nd-generation tumor necrosis factor-related apoptosis-inducing ligand receptor agonist, is being evaluated in previously treated solid and hematologic malignancies (NCT03082209). In a dose-expansion cohort, patients (pts) with KRAS-mutant colorectal cancer (n = 24) and pancreatic cancer (n = 24) were evaluated at 3 dose levels with 12 mandatory paired biopsies per tumor type (pretreatment [Tx] and on-Tx collection). Following eftoza dosing, RNA and protein expression including posttranslational modifications were assessed in tumor biopsies to understand the target engagement and downstream pathway activation. Plasma was evaluated for changes in somatic mutant allele frequency and M30, M65 (circulating apoptotic markers). Methods: Biopsies were collected anytime during the screening period (pre-Tx) and 24±4 h following 2nd or 3rd infusion (on-Tx). Of the requested 4–6 fresh biopsy cores, 1–2 cores were collected as formalin fixed paraffin embedded (FFPE) and the rest were frozen tissue. FFPE tissue was analyzed by multiplex immunohistochemistry (IHC) and RNAseq; reverse phase protein array was used for frozen cores. Plasma was collected at cycle 1 predose and 2, 8, 24, 48, and 168 h postdose and analyzed for M30, M65 (by ELISA) and circulating tumor DNA (64-gene PlasmaSELECT assay). Results: Twenty-five pts consented to biopsies; paired biopsies were obtained from 16 pts at a 64% success rate: FFPE (n = 15) and frozen cores (n = 12). Tumor cells were detected in 11/15 (73%) FFPE and 4/12 (33%) frozen cores. Increase in M30, activated caspases, and cleaved PARP levels was observed in on-Tx biopsy samples compared with pre-Tx, thus serving as evidence for apoptosis induction in tumors following eftoza dosing. Changes in the tumor microenvironment were observed post-Tx by RNAseq and multiplex IHC (eg, CD68 level). Downregulation of prosurvival signaling pathways (eg, AKT/MEK) was also observed following eftoza dosing. Thirteen out of 16 pts showed transient increase in mutant allele fractions post eftoza Tx that correlated with increased plasma circulating tumor markers M30 and M65 at similar time points, suggesting activation of apoptosis pathway. Increase in M30, M65 levels also preceded increase in liver enzymes (ALT/AST) at 2, 48 hr post-Tx. Conclusions: Pharmacodynamic effect of eftoza was successfully demonstrated in blood and tumor tissue, including induction of apoptosis and modulation of PI3K and MEK signaling pathways. Clinical trial information: NCT03082209.

Phase I Dose-Escalation and -Expansion Study of Telisotuzumab (ABT-700), an Anti-c-Met Antibody, in Patients with Advanced Solid Tumors

This first-in-human phase I study evaluated the pharmacokinetics, safety, and preliminary efficacy of telisotuzumab, formerly called ABT-700, an antagonistic antibody directed against c-Met. For dose escalation (3+3 design), 3 to 6 patients with advanced solid tumors were enrolled into four dose cohorts (5-25 mg/kg). In the dose-expansion phase, a subset of patients was prospectively selected for MET amplification (FISH screening). Patients received telisotuzumab intravenously on day 1 every 21 days. For dose expansion, 15 mg/kg was chosen as the dose on the basis of safety, pharmacokinetics, and other data from the escalation cohorts. Forty-five patients were enrolled and received at least one dose of telisotuzumab (dose escalation, n = 15; dose expansion, n = 30). Telisotuzumab showed a linear pharmacokinetics profile; peak plasma concentration was proportional to dose level. There were no acute infusion reactions and no dose-limiting toxicities were observed. The most common treatment-related adverse events included hypoalbuminemia (n = 9, 20.0%) and fatigue (n = 5, 11.1%). By Response Evaluation Criteria In Solid Tumors (RECIST), 4 of 10 (40.0%) patients with MET-amplified tumors had confirmed partial response in target lesions (one ovarian, two gastric, and one esophageal), two (20.0%) had stable disease, three (30.0%) had progressive disease; one patient was unable to be evaluated. Among patients with nonamplified tumors (n = 35), no objective responses were observed; however, 11 patients had stable disease per RECIST criteria. In conclusion, telisotuzumab has an acceptable safety profile with clinical activity observed in patients with MET-amplified advanced solid tumors.

Results of the phase 1b study of ABBV-399 (telisotuzumab vedotin; teliso-v) in combination with erlotinib in patients with c-Met+ non-small cell lung cancer by EGFR mutation status

3011

Background: Telisotuzumab vedotin (ABBV-399; teliso-v [T]) is a c-Met–targeted antibody and MMAE drug conjugate. Activity of T was shown in late-line c-Met+ non-small cell lung cancer (NSCLC) irrespective of EGFR mutation (M+) status. We present mature data from the T+ erlotinib (E) cohort of a phase 1b study (NCT02099058) by EGFR M+ status. Methods: T was administered at 2.4 mg/kg (dose-escalation phase) or 2.7 mg/kg IV Q3W, and E at 150 mg PO QD/prior tolerated dose in adult patients (pts) with advanced NSCLC. Efficacy-evaluable pts were c-Met+ (central lab IHC H-score ≥150 or local lab MET amplification/Ex 14 skipping) and had ≥1 postbaseline scan or discontinued study. EGFR M+ was defined as del19 or L858R by local lab. PK was assessed. Results: As of Dec 2018, 42 NSCLC pts received T+E; 37 were c-MET+ (36 evaluable; 35 H-score≥150, 1 MET amplified). Median age was 65 years, 25 pts (69%) had ECOG PS 1, 29 (81%) were EGFR M+ (97% had prior EGFR TKI, 55% 3rd-generation TKI, 69% TKI as last prior therapy, and 62% platinum doublet). All-grade (Gr; ≥20%) adverse events (AEs) were dermatitis acneiform (38%), diarrhea (36%), peripheral motor/sensory neuropathy (52%; 7% Gr 3), dyspnea, fatigue, hypoalbuminemia (31% each), decreased appetite, nausea (24% each), asthenia, vomiting (21% each). Gr ≥3 (≥10%) AE: pulmonary embolism (14%). PK of T+E was similar to single-agent T. The table presents efficacy data. Conclusions: These data suggest acceptable safety and promising activity of T+E and support further study in EGFR M+ c-Met+ NSCLC pts for whom frontline EGFR TKI failed. Clinical trial information: NCT02099058. [Table: see text]

Phase 1, first-in-human study of TRAIL receptor agonist fusion protein ABBV-621

3013

Background: ABBV-621 is a potent tumor-necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor agonist fusion protein that induces apoptotic cell death, particularly in DR4/5 expressing tumor models. Methods: Patients (pts) with previously treated solid tumors and ECOG 0–2 were administered ABBV-621 (2.5–15 mg/kg IV) on day (D) 1 (dose level [DL] 1) or D1D8 (DL2 and beyond) of each 21-day cycle. Dose escalation (DE) was guided by a Bayesian continual reassessment method. In addition to PK studies, blood-based PD markers of apoptosis (M30, M65) and drug binding were assessed. Results: As of 14 December 2018, 57 pts were enrolled in the DE portion, of which 30% had pancreatic, 23% colorectal cancer, and 47% other tumor types; 13 were KRAS mutant. Median age was 61 yrs. 60% were male; pts had a median of 4 prior regimens (range 1–10). Pts per DL: 2.5 (5 on D1, 16 on D1D8), 3.75 (12), 5 (6), 6.5 (6), 8.5 (4), 11 (4), and 15 mg/kg (4). Median duration of ABBV-621 exposure was 2 cycles (range 1–11). Seven pts had dose-limiting toxicities: respiratory failure (5 mg/kg; Grade 5, the only treatment-related death), blood bilirubin increased (3.75, 6.5 mg/kg), nausea (3.75 mg/kg), fatigue (3.75 mg/kg), increased ALT (2.5, 3.75, 6.5, 15 mg/kg), and increased AST (6.5 mg/kg). Summary of AEs is shown in Table. Clinical trial information: NCT03082209. A partial response (duration 20 weeks) was observed in a pt with pancreatic cancer (2.5 mg/kg D1D8). 27 pts had stable disease (6 pts for > 12 weeks). ABBV-621 PK was linear (mean ± SD clearance was 1.79 mL/h/kg ± 0.44) with a terminal half-life of 36.7 ± 5.55 h (n = 49). ABBV-621 bound to decoy receptors on neutrophils for up to 168 h; the duration of binding was dose-dependent. M30 and M65 increased at 8, 24, and 48 h following ABBV-621, but effect was independent of dose. Conclusions: ABBV-621 shows evidence of antitumor activity and effect on blood-based markers of apoptosis, with acceptable toxicity (MTD not reached). NCT03082209.[Table: see text]

c-Met expression and response to telisotuzumab vedotin (teliso-v) in patients with non-small cell lung cancer

9023

Background: c-Met overexpression (OE) and MET amplification (amp) are prognostic of poor outcome for non-small cell lung cancer (NSCLC). Telisotuzumab vedotin (ABBV-399; teliso-v [T]), an anti–c-Met Ab and monomethyl auristatin E drug conjugate, showed efficacy as monotherapy (mono) and combined with erlotinib (T+Er) in a phase 1/1b trial (NCT02099058) in NSCLC patients (pts) with c-Met OE. Here, c-Met OE (by immunohistochemistry [IHC]) and its association with T efficacy were explored. IHC, mRNA, and amp platforms for MET were also compared. Methods: Archival tissue from pts with NSCLC in the phase 1/1b trial was examined. c-Met was assessed centrally by IHC with SP44 Ab (Ventana Medical Systems) and pts with c-Met OE (membrane H-score [H-S] of ≥150) were enrolled. MET mRNA expression was analyzed from total RNA and sequenced on HiSeq 3000 (Illumina). MET amp was analyzed by FISH ( MET/ CEP7 ratio of ≥2) or whole-exome sequencing (copy number ≥2). Efficacy in the T mono every 2 (TQ2W) or 3 (TQ3W) weeks and the T+Er EGFR mutant cohorts was assessed for IHC H-S ≥150 and ≥225. Results: As of Dec 2018, 238 pts with NSCLC were screened centrally for c-Met OE. Of these, 118 pts were enrolled. For screened pts, 76%/37% of nonsquamous (NSQ, n = 201) and 58%/16% of squamous (SQ, n = 32) pts had H-S ≥150/≥225; 75%/41% of NSQ and 55%/16% of SQ NSCLC pts had ≥50% cells with 2+/3+ staining intensity. MET amp was reported for 5 pts, all with high H-S (≥270); there was an association between MET amp and MET RNA levels (n = 4) (t-test p value: 0.0002). See Table for ORR and median PFS by H-S and T treatment. Conclusions: c-Met expression prevalence in NSCLC showed a similar trend as in previous reports. In T+Er-treated pts, ORR was higher for those with c-Met H-S ≥225 than ≥150– < 225, suggesting that biomarker expression may act as an effect size multiplier. Optimization of the c-Met IHC cutoff warrants further investigation. Clinical trial information: NCT02099058. [Table: see text]

ABT-165 plus FOLFIRI versus bevacizumab plus FOLFIRI in patients with metastatic colorectal cancer (mCRC) previously treated with fluoropyrimidine/oxaliplatin and bevacizumab

TPS720

Background: Dual variable domain immunoglobulin ABT-165 targets human vascular endothelial growth factor (VEGF) and delta-like ligand 4 (DLL4). Combined VEGF and DLL4 blockade increased inhibition of subcutaneous xenograft growth of human colon cancer-derived cell lines versus blockade of either axis alone. In vivo, ABT-165 plus chemotherapy (CT) induced tumor regression with improved efficacy, vs anti-VEGF monoclonal antibody plus CT. In a phase 1 study, tolerable recommended phase 2 dose was identified for ABT-165 plus FOLFIRI and showed promising efficacy. This phase 2 trial in progress assesses efficacy/safety of ABT-165 plus FOLFIRI vs bevacizumab (bev) plus FOLFIRI in patients with second-line mCRC. Methods: This is an open-label, multicenter, phase 2 randomized (1:1) trial (NCT03368859) in patients (≥ 18 years; Eastern Cooperative performance status: 0–1) with histologically/cytologically confirmed mCRC who progressed after fluoropyrimidine/oxaliplatin and bev. ABT-165 (2.5 mg/kg) plus FOLFIRI (irinotecan: 180 mg/m2; leucovorin: 400 mg/m2; fluorouracil bolus: 400 mg/m2, infusion: 2400 mg/m2) or bev (5 mg/kg) plus FOLFIRI are given intravenously on day 1 of each 14-day cycle, until disease progression/intolerable toxicity. Primary endpoint is progression-free survival (PFS). Secondary endpoints include overall survival (OS), objective response rate (ORR), and safety. Exploratory endpoints include biomarkers predictive for efficacy/safety, correlation of DLL4 levels with PFS, OS, and ORR, pharmacodynamic effects, and efficacy/safety-exposure relationships in ABT-165 arm. Hazard ratios of PFS and OS comparing the 2 groups are estimated using Cox proportional hazard model. Kaplan-Meier methodology is used to estimate PFS and OS curves, median PFS and OS, and their 90% confidence intervals. Safety is assessed by ABT-165 exposure, adverse events (AEs), serious AEs, all deaths, and changes in laboratory data and vital signs. Archival tissue is collected and evaluated for DLL4 expression and angiogenesis signature. Approximately 100 patients are planned to be enrolled, with recruitment initiated January 2018. Clinical trial information: NCT03368859.

First-in-Human Phase I, Dose-Escalation and -Expansion Study of Telisotuzumab Vedotin, an Antibody–Drug Conjugate Targeting c-Met, in Patients With Advanced Solid Tumors

Purpose

This first-in-human study evaluated telisotuzumab vedotin (Teliso-V), formerly called ABBV-399, an antibody–drug conjugate of the anti–c-Met monoclonal antibody ABT-700 and monomethyl auristatin E.

Materials and Methods

For dose escalation, three to six patients with advanced solid tumors were enrolled in eight cohorts (0.15 to 3.3 mg/kg). The dose-expansion phase enrolled patients with non–small-cell lung cancer (NSCLC) with c-Met–overexpressing tumors (c-Met positive; immunohistochemistry membrane H-score ≥ 150). Patients received Teliso-V monotherapy intravenously on day 1 once every 3 weeks. Safety, tolerability, pharmacokinetics, and maximum tolerated dose were determined.

Results

Forty-eight patients were enrolled (median age, 65 years; 35.4% NSCLC; median four prior therapies). One patient each in the 3.0-mg/kg (n = 9) and 3.3-mg/kg (n = 3) cohorts experienced dose-limiting toxicities. Although the maximum tolerated dose was not formally identified, the recommended phase II dose was defined as 2.7 mg/kg on the basis of overall safety and tolerability. The most frequent treatment-emergent adverse events (any grade) were fatigue (42%), nausea (27%), constipation (27%), decreased appetite (23%), vomiting (21%), dyspnea (21%), diarrhea (19%), peripheral edema (19%), and neuropathy (17%). The most frequent Teliso-V–related grade ≥ 3 adverse events were fatigue, anemia, neutropenia, and hypoalbuminemia (4% each). Teliso-V and total antibody pharmacokinetics were approximately dose proportional, with a mean harmonic half-life of 2 to 4 days each. Prospective screening identified 35 (60%) of 58 patients with c-Met–positive NSCLC. Of 16 patients with c-Met–positive NSCLC who were treated with Teliso-V 2.4 to 3.0 mg/kg, three (18.8%; 95% CI, 4.1% to 45.7%) achieved a partial response (median response duration, 4.8 months; median progression-free survival, 5.7 months; 95% CI, 1.2 months to 15.4 months). No other patients experienced a response.

Conclusion

Teliso-V monotherapy demonstrated favorable safety and tolerability profiles, with encouraging evidence of antitumor activity in patients with c-Met–positive NSCLC.

A First-Time-in-Human Study of GSK2636771, a Phosphoinositide 3 Kinase Beta-Selective Inhibitor, in Patients with Advanced Solid Tumors

Background: The PI3K/protein kinase B (AKT) pathway is commonly activated in several tumor types. Selective targeting of p110β could result in successful pathway inhibition while avoiding the on- and off-target effects of pan-PI3K inhibitors. GSK2636771 is a potent, orally bioavailable, adenosine triphosphate-competitive, selective inhibitor of PI3Kβ.Methods: We evaluated the safety, pharmacokinetics, pharmacodynamics and antitumor activity of GSK2636771 to define the recommended phase II dose (RP2D). During the dose-selection and dose-escalation stages (parts 1 and 2), patients with PTEN-deficient advanced solid tumors received escalating doses of GSK2636771 (25-500 mg once daily) using a modified 3+3 design to determine the RP2D; tumor type-specific expansion cohorts (part 3) were implemented to further assess tumor responses at the RP2D.Results: A total of 65 patients were enrolled; dose-limiting toxicities were hypophosphatemia and hypocalcemia. Adverse events included diarrhea (48%), nausea (40%), and vomiting (31%). Single- and repeat-dose exposure increased generally dose proportionally. GSK2636771 400 mg once daily was the RP2D. Phospho/total AKT ratio decreased with GSK2636771 in tumor and surrogate tissue. A castrate-resistant prostate cancer (CRPC) patient harboring PIK3CB amplification had a partial response for over a year; an additional 10 patients derived durable (≥24 weeks) clinical benefit, including two other patients with CRPC with PIK3CB alterations (≥34 weeks). GSK2636771 400 mg once daily orally induced sufficient exposure and target inhibition with a manageable safety profile.Conclusions: Genomic aberrations of PIK3CB may be associated with clinical benefit from GSK2636771. Clin Cancer Res; 23(19); 5981-92. ©2017 AACR.

Phase I study of ABBV-399, a c-Met antibody-drug conjugate (ADC), as monotherapy and in combination with erlotinib in patients (pts) with non-small cell lung cancer (NSCLC)

2509

Background: The c-Met receptor is overexpressed in ~50% of pts with NSCLC. ABBV-399 is a first-in-class ADC composed of ABT-700, an anti–c-Met antibody, conjugated to monomethyl auristatin E (a microtubule inhibitor). Preclinical data demonstrate that ABBV-399 can deliver a potent cytotoxin directly to c-Met+ tumor cells. Methods: ABBV-399 was administered at doses ranging from 2.4 to 3.0 mg/kg (dose expansion and combination cohorts at 2.7 mg/kg) once every 21 days to 29 pts with advanced c-Met+ (immunohistochemistry [IHC] H-score ≥150) NSCLC both as monotherapy (ABBV-399/monoT; 16 pts) and in combination with oral erlotinib 150 mg daily (ABBV-399/ERL; 13 pts) (NCT02099058). c-Met overexpression was assessed by IHC utilizing the SP44 antibody (Ventana; Tucson, AZ, USA). Results: As of January 9, 2017, 16 pts with c-Met+ NSCLC received ≥1 dose of ABBV-399/monoT. Monotherapy treatment-related adverse events (TRAEs) occurring in ≥10% of pts (all dose levels and all grades) were fatigue (43.8%), nausea (37.5%), neuropathy (25.0%), vomiting (18.8%), and anemia, constipation, and diarrhea (12.5% each). Three of 16 (19%) ABBV-399–treated c-Met+ NSCLC pts had a confirmed partial response (PR) with duration of response (DOR) 3, 4.5, and 10+ months. At week 12, 6 of 16 pts (37.5%) had disease control. TRAEs in ABBV-399/ERL occurring in ≥10% of pts (all grades) were neuropathy (30.8%), and acneiform rash, diarrhea, fatigue, nausea, and dry skin (15.4% each). Four of 13 (31%) evaluable ABBV-399/ERL–treated c-Met+ pts had a PR (3 confirmed, 1 unconfirmed) with DOR 1+, 2.7, 5.3+, and 11+ months. Three of the 4 pts with PR had EGFR-mutated tumor and recently progressed on TKI. At week 12, 8 of 13 pts (61.5%) had disease control. There were no treatment-related deaths as monotherapy or in combination with erlotinib. Responses were seen in both squamous and non-squamous histology. Conclusions: ABBV-399 is well tolerated at 2.7 mg/kg once every 21 days and has demonstrated antitumor activity in pts with c-Met+ NSCLC both as monotherapy and in combination with erlotinib. Updated efficacy/safety data and MET gene status will be presented. Clinical trial information: NCT02099058.

Modeling the initiation of Ewing sarcoma tumorigenesis in differentiating human embryonic stem cells

Oncogenic transformation in Ewing sarcoma tumors is driven by the fusion oncogene EWS-FLI1. However, despite the well-established role of EWS-FLI1 in tumor initiation, the development of models of Ewing sarcoma in human cells with defined genetic elements has been challenging. Here, we report a novel approach to model the initiation of Ewing sarcoma tumorigenesis that exploits the developmental and pluripotent potential of human embryonic stem cells. The inducible expression of EWS-FLI1 in embryoid bodies, or collections of differentiating stem cells, generates cells with properties of Ewing sarcoma tumors, including characteristics of transformation. These cell lines exhibit anchorage-independent growth, a lack of contact inhibition and a strong Ewing sarcoma gene expression signature. Furthermore, these cells also demonstrate a requirement for the persistent expression of EWS-FLI1 for cell survival and growth, which is a hallmark Ewing sarcoma tumors.

Combined BRAF and MEK Inhibition With Dabrafenib and Trametinib in BRAF V600-Mutant Colorectal Cancer

PURPOSE

To evaluate dabrafenib, a selective BRAF inhibitor, combined with trametinib, a selective MEK inhibitor, in patients with BRAF V600-mutant metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

A total of 43 patients with BRAF V600-mutant mCRC were treated with dabrafenib (150 mg twice daily) plus trametinib (2 mg daily), 17 of whom were enrolled onto a pharmacodynamic cohort undergoing mandatory biopsies before and during treatment. Archival tissues were analyzed for microsatellite instability, PTEN status, and 487-gene sequencing. Patient-derived xenografts were established from core biopsy samples.

RESULTS

Of 43 patients, five (12%) achieved a partial response or better, including one (2%) complete response, with duration of response > 36 months; 24 patients (56%) achieved stable disease as best confirmed response. Ten patients (23%) remained in the study > 6 months. All nine evaluable during-treatment biopsies had reduced levels of phosphorylated ERK relative to pretreatment biopsies (average decrease ± standard deviation, 47% ± 24%). Mutational analysis revealed that the patient achieving a complete response and two of three evaluable patients achieving a partial response had PIK3CA mutations. Neither PTEN loss nor microsatellite instability correlated with efficacy. Responses to dabrafenib plus trametinib were comparable in patient-derived xenograft-bearing mice and the biopsied lesions from each corresponding patient.

CONCLUSION

The combination of dabrafenib plus trametinib has activity in a subset of patients with BRAF V600-mutant mCRC. Mitogen-activated protein kinase signaling was inhibited in all patients evaluated, but to a lesser degree than observed in BRAF-mutant melanoma with dabrafenib alone. PIK3CA mutations were identified in responding patients and thus do not preclude response to this regimen. Additional studies targeting the mitogen-activated protein kinase pathway in this disease are warranted.

Abstract CT328: Exploratory genetic analysis of tumors from a phase I/II dose escalation study of GSK2636771 in patients (pts) with PTEN deficient advanced tumors

Background: GSK2636771 is a potent, orally bioavailable and selective inhibitor of PI3Kβ (apparent Ki = 0.89 nM), with &gt;900-fold selectivity over PI3Kα/PI3Kγ and 10-fold over PI3Kδ. It inhibits AKT phosphorylation and downstream signaling measured as decrease of PRAS40-, GSK3β-, and RPS6-phosphorylation in PTEN deficient cell lines.

Methods: An ongoing phase I/IIa FTIH, open label dose escalation study of GSK2636771, once daily (QD), is being conducted to evaluate safety, pharmacokinetics (PK), pharmacodynamics (PD) and efficacy in pts with advanced tumors deficient in PTEN. The study comprised 3 parts: starting-dose selection, 3+3 dose escalation, and phase II expansion. PD was assessed in tumor and platelet rich plasma samples. Archival tumor samples were analyzed for alterations in a custom panel of select oncogenes and tumor suppressors by next-generation sequencing and copy number analyses.

Results: As of Nov 2014, 62 pts (38 m: 24 f, mean 60 yrs) were enrolled and dosed at 7 dose levels (25 - 500 mg). In total 5 DLTs (3x hypophosphatemia/ 2x hypocalcemia G3) were observed in 3 pts at 500 mg, defining MTD. AEs ≥20% (all grades) included diarrhoea, nausea, vomiting, fatigue, abdominal pain, anemia, decreased appetite and headache. Cmax was reached 4-6 h after single and repeat dosing, with a mean t1/2 of 17.1-38.6 h across cohorts. Increases in mean Cmax and AUC(0-24 h) were dose-proportional up to 350 mg, but less than proportional at 400 and 500 mg. Phospho/total AKT ratio was decreased by &gt;50% in platelet-rich plasma in 21 of 23 pts across various doses. Similarly, phospho/total AKT ratio was decreased (median 35%) in post-treatment tumor biopsies compared to pre-treatment tumors in 4 of 5 pts treated at 400 mg dose. One pt (prostate) had a RECIST PR and 17 pts had SD, 8 of whom were on study for ≥6 months. Exploratory genomic analyses of tumor samples from 10 prostate cancer pts revealed a PIK3CB L1049R mutation in the tumor of one of the pts who remained on study for 33 weeks and an increased PIK3CB gene copy number in the tumor of a pt who achieved PR. Preclinical characterization of PIK3CB L1049R mutation is ongoing, as it is homologous to the oncogenic PIK3CA H1047R mutation. These data suggest potential clinical benefit with GSK2636771 in pts with tumors harboring genetic alterations in PIK3CB. Tumors from other histologies are being analyzed for alterations in key cancer-relevant genes, including PIK3CB.

Conclusions: MTD and recommended phase II dose of GSK2636771 is 400 mg QD. Pathway inhibition was observed with limited anti-tumor activity in pts with PTEN deficient tumors. Pts with tumors harboring concomitant genetic alterations in PIK3CB may benefit from GSK2636771 treatment. Recruitment into phase II expansion is ongoing.

Citation Format: Johann de Bono, Hendrik-Tobias Arkenau, Joaquin Mateo, Jeffrey R. Infante, Howard A. Burris, Yung-Jue Bang, Joseph Eder, Sunil Sharma, Hyun C. Chung, Shaun Decordova, Karen E. Swales, Michelle D. Garrett, Desamaparados Roda-Perez, Meichun Ding, Mark Russo, Li Yan, Ben Suttle, Jerry M. Tolson, Wendy S. Halsey, Ganji Gopi, Harjeet K. Van Der Keyl, Shanker Kalyana-Sundaram, Ganesh M. Sathe, Monica Motwani, Rakesh Kumar. Exploratory genetic analysis of tumors from a phase I/II dose escalation study of GSK2636771 in patients (pts) with PTEN deficient advanced tumors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT328. doi:10.1158/1538-7445.AM2015-CT328