Abstract CT007: PETRA: First in class, first in human trial of the next generation PARP1-selective inhibitor AZD5305 in patients (pts) with BRCA1/2, PALB2 or RAD51C/D mutations

Background: AZD5305 is a potent, highly selective PARP1 inhibitor and trapper with superior preclinical tolerability, target engagement and efficacy vs 1st generation dual PARP1/2 inhibitors (PARPi). This is the first report of the ongoing Phase 1/2a PETRA (NCT04644068) trial.

Methods: Pts with advanced breast, ovarian, prostate or pancreatic cancer bearing germline or somatic BRCA1/2, PALB2 or RAD51C/D mutations received AZD5305 QD PO until disease progression. ECOG PS 0-2 and Hb ≥9.0 g/dL were required. Prior PARPi and platinum therapy were permitted. The primary objective was safety; secondary objectives included pharmacokinetics (PK) and pharmacodynamics in tumor and/or blood samples and response by RECIST v1.1, CA125 or PSA. Exploratory genomic analyses included zygosity evaluation and ctDNA response monitoring.

Results: At data cutoff (Nov 17, 2021), 46 pts received AZD5305 10-90 mg QD (43.5% had prior PARPi; median 3.5 prior lines of therapy). AZD5305 was well tolerated across all doses without DLTs (Table). PK exposures were dose-proportional. Steady-state Ctrough was higher than 1st generation PARPi: specifically 6.3 and 31.9 fold above target effective concentration at 10 and 90 mg, respectively. PARylation inhibition was ≥90% at 10-40 mg QD (PBMCs) confirming target engagement. 7/25 (28%) pts had objective responses: 5 RECIST PRs (3 confirmed) and 2 additional pts with PSA50 responses (1 confirmed), including platinum- and PARPi-resistant pts. 13/22 (59%) RECIST-measurable pts had SD or PR up to 51+ weeks. ctDNA declined on treatment in 7/13 (54%) evaluable pts (3 complete, 4 >50% reductions) across doses.

Conclusions: AZD5305 is a highly selective PARP1 inhibitor and trapper with excellent physiochemical properties and a wide therapeutic index. It led to maximal target engagement and showed promising clinical activity with favorable tolerability at exposures surpassing those of 1st generation PARPi.

AZD5305 10 mg/d (n=8) AZD5305 20 mg/d (n=19) AZD5305 40 mg/d (n=13) AZD5305 60 mg/d (n=3) AZD5305 90 mg/d (n=3) Total (N=46) Most common (>10%) TRAEs, n (%) Any grade Any grade Any grade Any grade Any grade Grade ≥3 Any grade Nausea 3 (37.5) 5 (26.3) 1 (7.7) 1 (33.3) 0 0 10 (21.7) Anemia* 2 (25.0) 4 (21.1) 1 (7.7) 0 0 6 (13.0) 7 (15.2) Neutropenia* 3 (37.5) 2 (10.5) 1 (7.7) 0 1 (33.3) 2 (4.3) 7 (15.2) Thrombocytopenia* 1 (12.5) 2 (10.5) 2 (15.4) 0 0 1 (2.2) 5 (10.9) Fatigue and asthenia* 2 (25.0) 2 (10.5) 0 1 (33.3) 0 0 5 (10.9) Any TRAE leading to dose reduction 1 (12.5) 0 0 0 0 1 (2.2) Any TRAE leading to discontinuation 0 0 0 0 0 0 AE, adverse event; TRAE, treatment-related adverse event *Grouped Terms

Citation Format: Timothy A. Yap, Seock-Ah Im, Alison M. Schram, Adam Sharp, Judith Balmana, Richard D. Baird, Jessica S. Brown, Maria Schwaederle, Elizabeth A. Pilling, Ganesh Moorthy, Spiros Linardopoulos, Adam Dowson, Carol Pound, Edit Lukacs, Sabina Cosulich, Stephen J. Luen. PETRA: First in class, first in human trial of the next generation PARP1-selective inhibitor AZD5305 in patients (pts) with BRCA1/2, PALB2 or RAD51C/D mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT007.

Abstract CT244: A phase 1 study of IV MEDI5395, an oncolytic virus, in combination with durvalumab in patients with advanced solid tumors

Background: Oncolytic viruses selectively infect tumors and activate antitumor immune responses via innate and adaptive pathways, which may potentiate the efficacy of immune checkpoint inhibitors. MEDI5395 is a recombinant Newcastle disease virus incorporating a granulocyte macrophage colony-stimulating factor (GM-CSF) transgene that exhibits tumor cell-specific viral replication, stimulates PD-L1 expression, and induces tumor regression in murine and patient-derived xenograft models. Increased T cell recruitment and expression of IFNγ-inducible genes observed in vitro suggest immune activation in the tumor microenvironment (TME). Antitumor activity is enhanced by concurrent PD-L1 blockade. This clinical study is evaluating IV MEDI5395 in combination with the anti-PD-L1 antibody durvalumab in patients with advanced solid tumors. Methods: This is a Phase 1, first-in-human, multicenter, open-label trial (NCT03889275) enrolling patients with breast cancer, colorectal cancer, hepatocellular carcinoma, head and neck squamous cell carcinoma, renal cell carcinoma, non-small-cell lung cancer or melanoma. Eligibility criteria include relapsed/refractory disease or intolerance to standard therapy after ≥1 prior line of treatment for recurrent/metastatic disease, and ≥1 tumor measurable by RECIST v1.1. Exclusion criteria include rapidly progressing disease precluding a break of ≥8 weeks from systemic therapy, life expectancy ≥12 weeks by GRIm Score, uncontrolled metastatic central nervous system disease, and concomitant immunosuppressive therapy. The initial dose escalation phase will enroll up to 84 patients across all eligible tumor types. Three sequentially ascending dose levels of MEDI5395 will be evaluated. Durvalumab is administered either sequentially or concurrently with MEDI5395, for up to 2 years or until radiologically confirmed disease progression, clinical deterioration, withdrawal of consent, or unacceptable toxicity. The subsequent dose expansion phase will include 2 cohorts of ~40 patients, each enrolling a single tumor type. The tumor types, MEDI5395 dose level and schedule will be selected based on dose escalation data. On-treatment biopsies of the primary tumor or a metastatic site are required in the dose escalation phase and optional in the dose expansion phase. Primary objectives are evaluating the safety, tolerability and incidence of dose-limiting toxicities of MEDI5395, and identifying the optimal dose/schedule in combination with durvalumab. Secondary objectives include assessing MEDI5395 pharmacokinetics (viremia and GM-CSF transgene expression), pharmacodynamics in the TME, immunogenicity, and initial efficacy in combination with durvalumab. The trial is actively accruing.

Citation Format: Grace K. Dy, Diwakar Davar, Evanthia Galanis, Danielle Townsley, Djuro Karanovic, Maria Schwaederle, Beth Kelly, Dmitriy Zamarin, Mitesh Borad, Kevin Harrington. A phase 1 study of IV MEDI5395, an oncolytic virus, in combination with durvalumab in patients with advanced solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT244.

MET alterations detected in blood-derived circulating tumor DNA correlate with bone metastases and poor prognosis

Background

We analyzed clinical associations of MET alterations in the plasma of patients with diverse malignancies.

Methods

Digital sequencing of circulating tumor DNA (ctDNA) (54–70 genes) was performed in 438 patients; 263 patients also had tissue sequencing (182–315 genes). The most represented tumor types were gastrointestinal (28.1%), brain (24.9%), and lung (23.2%). Most patients (71.2%) had recurrent/metastatic disease.

Results

MET alterations were observed in 31 patients (7.1%) and correlated with bone metastasis (P = 0.007), with TP53 (P = 0.001) and PTEN (P = 0.003) abnormalities, and with an increased number of alterations (median, 4 vs 1, P = 0.001) (all multivariable analyses). Patients with MET alterations demonstrated a significantly shorter median time to metastasis/recurrence (1.0 vs 10.4 months, P = 0.044, multivariable) and a poorer survival (30.6 vs 58.4 months, P = 0.013, univariate only). Of the 31 patients with MET alterations, 18 also had tissue testing; only two also had tissue MET alterations (11.1%); MET alterations were detected at a lower frequency in tissue (1.14%) compared to ctDNA (7.1%), with P = 0.0002.

Conclusions

In conclusion, the detection of MET alterations by liquid biopsy is feasible. MET ctDNA alterations were associated with a poorer prognosis, higher numbers of genomic abnormalities, and bone metastases. The correlation with bone metastases may explain the higher frequency of MET alterations in blood ctDNA than in tissue (since bones are rarely biopsied) and the previous observations of bone-predominant responses to MET inhibitors. The high number of co-altered genes suggests that MET inhibitors may need to be combined with other agents to induce/optimize responses.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0610-8) contains supplementary material, which is available to authorized users.

TP53 mutations and number of alterations correlate with maximum standardized uptake value (SUVmax) determined by positron emission tomography/computed tomography (PET/CT) [18F] fluorodeoxyglucose (18F-FDG PET)

Background

Our study explored the relationship between the molecular changes in cancer and the maximum standardized uptake value (SUVmax) determined by positron emission tomography/computed tomography (PET/CT) with [¹⁸F] fluorodeoxyglucose (¹⁸F-FDG).

Results

A higher SUVmax correlated with TP53 alterations, but not with histologic diagnosis or other gene/pathway mutations or copy number alterations. In data from breast, lung and colon cancer, patients with the highest SUVmax show more genomic anomalies compared to those with the lowest SUVmax (P < 0.005).

Conclusions

A higher SUVmax on ¹⁸F-FDG PET/CT is associated with TP53 tumor suppressor gene anomalies and the presence of more genomic anomalies. Since TP53 alterations and high SUVmax both correlate with a poor prognosis, the underlying mechanism/implications of this association merit further study.

Methods

Overall, 176 patients with diverse cancers had a tumor biopsy within 6 months after a PET/CT image for SUVmax measurement. The biopsy was interrogated by next generation sequencing (182 to 315 genes). TP53, EGFR, ALK, MYC, MET and FGF/FGFR genes and DNA repair, PI3K/Akt/mTOR (PAM), MEK, CYCLIN, and WNT pathway genes were analyzed.

An appraisal of drug development timelines in the Era of precision oncology

The effects of incorporating a biomarker-based (personalized or precision) selection strategy on drug development timelines for new oncology drugs merit investigation. Here we accessed documents from the Food and Drug Administration (FDA) database for anticancer agents approved between 09/1998 and 07/2014 to compare drugs developed with and without a personalized strategy. Sixty-three drugs were included (28 [44%] personalized and 35 [56%] non-personalized). No differences in access to FDA-expedited programs were observed between personalized and non-personalized drugs. A personalized approach for drug development was associated with faster clinical development (Investigational New Drug [IND] to New Drug Application [NDA] submission; median = 58.8 months [95% CI 53.8-81.8] vs. 93.5 months [95% CI 73.9-112.9], P =.001), but a similar approval time (NDA submission to approval; median=6.0 months [95% CI 5.5-8.4] vs. 6.1 months [95% CI 5.9-8.3], P = .756) compared to a non-personalized strategy. In the multivariate model, class of drug stratified by personalized status (targeted personalized vs. targeted non-personalized vs. cytotoxic) was the only independent factor associated with faster total time of clinical drug development (clinical plus approval phase, median = 64.6 vs 87.1 vs. 112.7 months [cytotoxic], P = .038). Response rates (RR) in early trials were positively correlated with RR in registration trials (r = 0.63, P = <.001), and inversely associated with total time of drug development (r = -0.29, P = .049). In conclusion, targeted agents were developed faster than cytotoxic agents. Shorter times to approval were associated, in multivariate analysis, with a biomarker-based clinical development strategy.

Telomerase reverse transcriptase promoter alterations across cancer types as detected by next-generation sequencing: A clinical and molecular analysis of 423 patients

BACKGROUND

Telomerase reverse transcriptase (TERT) promoter mutations that may affect telomerase activity have recently been described in human malignancies. The purpose of this study was to investigate the clinical correlates of TERT promoter abnormalities in a large cohort of patients with diverse cancers.

METHODS

This study analyzed TERT promoter alterations and clinical characteristics of 423 consecutive patients for whom molecular testing by next-generation sequencing was performed between August 2014 and July 2015.

RESULTS

Of the 423 patients, 61 (14.4%) had TERT promoter mutations, and this placed TERT promoter alterations among the most prevalent aberrations after tumor protein 53 (TP53; 39%) and KRAS and cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) alterations (15% each) in this population. TERT promoter alterations were more frequent in men (P = .031) and were associated with brain cancers (P = .001), skin cancers/melanoma (P = .001), and a higher number of aberrations (P = .0001). A co-alteration analysis found that TERT promoter alterations were significantly correlated with CDKN2A/B (P = .001) and BRAF abnormalities (P = .0003). Patients harboring TERT promoter alterations or TP53 or CDKN2A/B alterations and those with 4 or more alterations demonstrated shorter survival (hazard ratio for normal TERT promoters vs aberrant ones, 0.44; P = .017). However, only a higher number of alterations remained significant in the multivariate analysis.

CONCLUSIONS

Overall, TERT promoter alterations were among the most prevalent aberrations in this population, with very high rates in brain cancers (48% of patients) and melanomas (56% of patients). These aberrations frequently coexist with a high number of other aberrations, with the latter feature also significantly associated with poorer overall survival. Therapeutic options for targeting tumors with TERT promoter mutations are currently limited, although a variety of novel approaches are under development. Cancer 2018;124:1288-96. © 2017 American Cancer Society.

Genomic Alterations in Circulating Tumor DNA from Diverse Cancer Patients Identified by Next-Generation Sequencing

Noninvasive genomic profiling of tumors may be possible with next-generation sequencing (NGS) of blood-derived circulating tumor DNA (ctDNA), but proof of concept in a large cohort of patients with diverse cancers has yet to be reported. Here we report the results of an analysis of plasma-derived ctDNA from 670 patients with diverse cancers. The tumors represented in the patient cohort were mainly gastrointestinal (31.8%), brain (22.7%), or lung (20.7%). ctDNA obtained from most patients [N = 423 (63%)] displayed at least one alteration. The most frequent alterations seen, as characterized mutations or variants of unknown significance, occurred in TP53 (32.5% of patients), EGFR (13%), KRAS (12.5%), and PIK3CA (9.1%); for characterized alterations, 30.7% (TP53), 7.6% (EGFR), 12.2% (KRAS), and 7.7% (PIK3CA). We found that 32% of brain tumors had at least one ctDNA alteration. Head and neck tumors were independently associated with a higher number of alterations in a multivariable analysis (P = 0.019). Notably, 320/670 (48%) of patients displayed potentially actionable alterations, with 241 patients possible candidates for on-label or off-label treatment with an FDA-approved drug. Several illustrations of the clinical utility of the information obtained for improving treatment of specific patients is provided. Our findings demonstrate the feasibility and impact of genomic profiling of tumors by ctDNA NGS, greatly encouraging broader investigations of the application of this technology for precision medicine in cancer management. Cancer Res; 77(19); 5419-27. ©2017 AACR.

Topoisomerase expression and amplification in solid tumours: Analysis of 24,262 patients

Background

Topoisomerase I (TOPO1) and topoisomerase IIα (TOP2A) are specific targets of multiple chemotherapy drugs. Increased expression of TOPO1 protein and amplification of the TOP2A gene have been associated with treatment response in colorectal and breast cancers, respectively. TOPO1 and TOP2A may be potential therapeutic targets in other malignancies as well.

Summary of methods

We analysed TOPO1 protein expression and TOP2A gene amplification in patients (n = 24,262 specimens) with diverse cancers. Since HER2 and TOP2A co-amplification have been investigated for predictive value regarding anthracycline benefit, we analysed specimens for HER2 amplification as well.

Results

Overexpressed TOPO1 protein was present in 51% of the tumours. Four percent of the tumours had TOP2A amplification, with gallbladder tumours and gastroesophageal/oesophageal tumours having rates over 10%. Overall, 4903 specimens were assessed for both TOP2A and HER2 amplification; 129 (2.6%) had co-amplification. High rates (>40%) of HER2 amplification were seen in patients with TOP2A amplification in breast, ovarian, gastroesophageal/oesophageal and pancreatic cancer.

Conclusion

Our data indicate that increased TOPO1 expression and TOP2A amplification, as well as HER2 co-alterations, are present in multiple malignancies. The implications of these observations regarding sensitivity to chemotherapy not traditionally administered to these tumour types merits investigation.

Association of Biomarker-Based Treatment Strategies With Response Rates and Progression-Free Survival in Refractory Malignant Neoplasms: A Meta-analysis

Importance

The impact of a biomarker-based (personalized) cancer treatment strategy in the setting of phase 1 clinical trials was analyzed.

Objective

To compare patient outcomes in phase 1 studies that used a biomarker selection strategy with those that did not.

Data Sources

PubMed search of phase 1 cancer drug trials (January 1, 2011, through December 31, 2013).

Study Selection

Studies included trials that evaluated single agents, and reported efficacy end points (at least response rate [RR]).

Data Extraction and Synthesis

Data were extracted independently by 2 investigators.

Main Outcomes and Measures

Response rate and progression-free survival (PFS) were compared for arms that used a personalized strategy (biomarker selection) vs those that did not. Overall survival was not analyzed owing to insufficient data.

Results

A total of 346 studies published in the designated 3-year time period were included in the analysis. Multivariable analysis (meta-regression and weighted multiple regression models) demonstrated that the personalized approach independently correlated with a significantly higher median RR (30.6% [95% CI, 25.0%-36.9%] vs 4.9% [95% CI, 4.2%-5.7%]; P < .001) and a longer median PFS (5.7 [95% CI, 2.6-13.8] vs 2.95 [95% CI, 2.3-3.7] months; P < .001). Targeted therapy arms that used a biomarker-based selection strategy (n = 57 trials) were associated with statistically improved RR compared with targeted therapy arms (n = 177 arms) that did not (31.1% [95% CI, 25.4%-37.4%] vs 5.1% [95% CI, 4.3%-6.0%]; P < .001). Nonpersonalized targeted arms had outcomes comparable with those that tested a cytotoxic agent (median RR, 5.1% [95% CI, 4.3%-6.0%] vs 4.7% [95% CI, 3.6%-6.2%]; P = .63; respectively; median PFS, 3.3 [95% CI, 2.6-4.0] months vs 2.5 [95% CI, 2.0-3.7] months; P = .22). Personalized arms using a "genomic (DNA) biomarker" had higher median RR than those using a "protein biomarker" (42.0% [95% CI, 33.7%-50.9%] vs 22.4% [95% CI, 15.6%-30.9%]; P = .001). The median treatment-related mortality was not statistically different for arms that used a personalized strategy vs not (1.89% [95% CI, 1.36%-2.61%] vs 2.27% [95% CI, 1.97%-2.62%]; P = .31).

Conclusions and Relevance

In this meta-analysis, most phase 1 trials of targeted agents did not use a biomarker-based selection strategy. However, use of a biomarker-based approach was associated with significantly improved outcomes (RR and PFS). Response rates were significantly higher with genomic vs protein biomarkers. Studies that used targeted agents without a biomarker had negligible response rates.

Fibroblast growth factor receptor signaling in hereditary and neoplastic disease: biologic and clinical implications

Fibroblast growth factors (FGFs) and their receptors (FGFRs) are transmembrane growth factor receptors with wide tissue distribution. FGF/FGFR signaling is involved in neoplastic behavior and also development, differentiation, growth, and survival. FGFR germline mutations (activating) can cause skeletal disorders, primarily dwarfism (generally mutations in FGFR3), and craniofacial malformation syndromes (usually mutations in FGFR1 and FGFR2); intriguingly, some of these activating FGFR mutations are also seen in human cancers. FGF/FGFR aberrations reported in cancers are mainly thought to be gain-of-function changes, and several cancers have high frequencies of FGFR alterations, including breast, bladder, or squamous cell carcinomas (lung and head and neck). FGF ligand aberrations (predominantly gene amplifications) are also frequently seen in cancers, in contrast to hereditary syndromes. There are several pharmacologic agents that have been or are being developed for inhibition of FGFR/FGF signaling. These include both highly selective inhibitors as well as multi-kinase inhibitors. Of note, only four agents (ponatinib, pazopanib, regorafenib, and recently lenvatinib) are FDA-approved for use in cancer, although the approval was not based on their activity against FGFR. Perturbations in the FGFR/FGF signaling are present in both inherited and malignant diseases. The development of potent inhibitors targeting FGF/FGFR may provide new tools against disorders caused by FGF/FGFR alterations.

Cell-Cycle Gene Alterations in 4,864 Tumors Analyzed by Next-Generation Sequencing: Implications for Targeted Therapeutics

Alterations in the cyclin-dependent kinase (CDK)-retinoblastoma (RB) machinery disrupt cell-cycle regulation and are being targeted in drug development. To understand the cancer types impacted by this pathway, we analyzed frequency of abnormalities in key cell-cycle genes across 4,864 tumors using next-generation sequencing (182 or 236 genes; Clinical Laboratory Improvement Amendments laboratory). Aberrations in the cell-cycle pathway were identified in 39% of cancers, making this pathway one of the most commonly altered in cancer. The frequency of aberrations was as follows: CDKN2A/B (20.1% of all patients), RB1 (7.6%), CCND1 (6.1%), CCNE1 (3.6%), CDK4 (3.2%), CCND3 (1.8%), CCND2 (1.7%), and CDK6 (1.7%). Rates and types of aberrant cell-cycle pathway genes differed between cancer types and within histologies. Analysis of coexisting and mutually exclusive genetic aberrations showed that CCND1, CCND2, and CCND3 aberrations were all positively associated with CDK6 aberrations [OR and P values, multivariate analysis: CCND1 and CDK6 (OR = 3.5; P < 0.0001), CCND2 and CDK6 (OR = 4.3; P = 0.003), CCND3 and CDK6 (OR = 3.6; P = 0.007)]. In contrast, RB1 alterations were negatively associated with multiple gene anomalies in the cell-cycle pathway, including CCND1 (OR = 0.25; P = 0.003), CKD4 (OR = 0.10; P = 0.001), and CDKN2A/B (OR = 0.21; P < 0.0001). In conclusion, aberrations in the cell-cycle pathway were very common in diverse cancers (39% of 4,864 neoplasms). The frequencies and types of alterations differed between and within tumor types and will be informative for drug development strategies. Mol Cancer Ther; 15(7); 1682-90. ©2016 AACR.

Next generation sequencing demonstrates association between tumor suppressor gene aberrations and poor outcome in patients with cancer

Next generation sequencing is transforming patient care by allowing physicians to customize and match treatment to their patients’ tumor alterations. Our goal was to study the association between key molecular alterations and outcome parameters. We evaluated the characteristics and outcomes (overall survival (OS), time to metastasis/recurrence, and best progression-free survival (PFS)) of 392 patients for whom next generation sequencing (182 or 236 genes) had been performed. The Kaplan-Meier method and Cox regression models were used for our analysis, and results were subjected to internal validation using a resampling method (bootstrap analysis). In a multivariable analysis (Cox regression model), the parameters that were statistically associated with a poorer overall survival were the presence of metastases at diagnosis (P = 0.014), gastrointestinal histology (P < 0.0001), PTEN (P < 0.0001), and CDKN2A alterations (P = 0.0001). The variables associated with a shorter time to metastases/recurrence were gastrointestinal histology (P = 0.004), APC (P = 0.008), PTEN (P = 0.026) and TP53 (P = 0.044) alterations. TP53 (P = 0.003) and PTEN (P = 0.034) alterations were independent predictors of a shorter best PFS. A personalized treatment approach (matching the molecular aberration with a cognate targeted drug) also correlated with a longer best PFS (P = 0.046). Our study demonstrated that, across diverse cancers, anomalies in specific tumor suppressor genes (PTEN, CDKN2A, APC, and/or TP53) were independently associated with a worse outcome, as reflected by time to metastases/recurrence, best PFS on treatment, and/or overall survival. These observations suggest that molecular diagnostic tests may provide important prognostic information in patients with cancer.

Detection rate of actionable mutations in diverse cancers using a biopsy-free (blood) circulating tumor cell DNA assay

Analysis of cell-free DNA using next-generation sequencing (NGS) is a powerful tool for the detection/monitoring of alterations present in circulating tumor DNA (ctDNA). Plasma extracted from 171 patients with a variety of cancers was analyzed for ctDNA (54 genes and copy number variants (CNVs) in three genes (EGFR, ERBB2 and MET)). The most represented cancers were lung (23%), breast (23%), and glioblastoma (19%). Ninety-nine patients (58%) had at least one detectable alteration. The most frequent alterations were TP53 (29.8%), followed by EGFR (17.5%), MET (10.5%), PIK3CA (7%), and NOTCH1 (5.8%). In contrast, of 222 healthy volunteers, only one had an aberration (TP53). Ninety patients with non-brain tumors had a discernible aberration (65% of 138 patients; in 70% of non-brain tumor patients with an alteration, the anomaly was potentially actionable). Interestingly, nine of 33 patients (27%) with glioblastoma had an alteration (6/33 (18%) potentially actionable). Overall, sixty-nine patients had potentially actionable alterations (40% of total; 69.7% of patients (69/99) with alterations); 68 patients (40% of total; 69% of patients with alterations), by a Food and Drug Administration (FDA) approved drug. In summary, 65% of diverse cancers (as well as 27% of glioblastomas) had detectable ctDNA aberration(s), with the majority theoretically actionable by an approved agent.

Precision Oncology: The UC San Diego Moores Cancer Center PREDICT Experience

By profiling their patients' tumors, oncologists now have the option to use molecular results to match patients with drug(s) based on specific biomarkers. In this observational study, 347 patients with solid advanced cancers and next-generation sequencing (NGS) results were evaluated. Outcomes for patients who received a "matched" versus "unmatched" therapy following their NGS results were compared. Eighty-seven patients (25%) were treated with a "matched" therapy, 93 (26.8%) with an "unmatched" therapy. More patients in the matched group achieved stable disease (SD) ≥ 6 months/partial response (PR)/complete response (CR), 34.5% vs. 16.1%, (P ≤ 0.020 multivariable or propensity score methods). Matched patients had a longer median progression-free survival (PFS; 4.0 vs. 3.0 months, P = 0.039 in the Cox regression model). In analysis using PFS1 (PFS on the prior line of therapy) as a comparator to PFS after NGS, as expected, the unmatched group demonstrated a PFS2 significantly shorter than PFS1 (P = 0.009); however, this shortening was not observed in the matched patients (P = 0.595). Furthermore, 45.3% of the matched patients (24/53) had a PFS2/PFS1 ratio ≥1.3 compared with 19.3% of patients (11/57) in the unmatched group (P = 0.004 univariable and P ≥ 0.057 in multivariable/propensity score analysis). Patients with a "matching-score" (the number of matched drugs divided by the number of aberrations; unmatched patients had a score of zero) > 0.2 had a median overall survival (OS) of 15.7 months compared with 10.6 months when their matching-score was ≤ 0.2, (P = 0.040 in the Cox regression model). Matched versus unmatched patients had higher rates of SD ≥ 6 months/PR/CR and longer PFS, and improvement in OS correlated with a higher matching score in multivariable analysis. Mol Cancer Ther; 15(4); 743-52. ©2016 AACR.

Cyclin-dependent kinase pathway aberrations in diverse malignancies: clinical and molecular characteristics

Aberrations in the cyclin-dependent kinase (CDK) pathways that regulate the cell cycle restriction point contribute to genomic instability and tumor proliferation, and can be targeted by recently developed CDK inhibitors. We therefore investigated the clinical correlates of CDK4/6 and CDKN2A/B abnormalities in diverse malignancies. Patients with various cancers who underwent molecular profiling by targeted next generation sequencing (Foundation Medicine; 182 or 236 cancer-related genes) were reviewed. Of 347 patients analyzed, 79 (22.8%) had aberrant CDK 4/6 or CDKN2A/B. Only TP53 mutations occurred more frequently than those in CDK elements. Aberrations were most frequent in glioblastomas (21/26 patients; 81%) and least frequent in colorectal cancers (0/26 patients). Aberrant CDK elements were independently associated with EGFR and ARID1A gene abnormalities (P < 0.0001 and p = 0.01; multivariate analysis). CDK aberrations were associated with poor overall survival (univariate analysis; HR[95% CI] = 2.09 [1.35–4.70]; p = 0.004). In multivariate analysis, PTEN and TP53 aberrations were independently associated with poorer survival (HR = 4.83 and 1.92; P < 0.0001 and p = 0.01); CDK aberrations showed a trend toward worse survival (HR = 1.67; p = 0.09). There was also a trend toward worse progression-free survival (PFS) with platinum-containing regimens in patients with abnormal CDK elements (3.5 versus 5.0 months, p = 0.13). In conclusion, aberrations in the CDK pathway were some of the most common in cancer and independently associated with EGFR and ARID1A alterations. Patients with abnormal CDK pathway genes showed a trend toward poorer survival, as well as worse PFS on platinum-containing regimens. Further investigation of the prognostic and predictive impact of CDK alterations across cancers is warranted.

Molecular inimitability amongst tumors: implications for precision cancer medicine in the age of personalized oncology

Tumor sequencing has revolutionized oncology, allowing for detailed interrogation of the molecular underpinnings of cancer at an individual level. With this additional insight, it is increasingly apparent that not only do tumors vary within a sample (tumor heterogeneity), but also that each patient's individual tumor is a constellation of unique molecular aberrations that will require an equally unique personalized therapeutic regimen. We report here the results of 439 patients who underwent Clinical Laboratory Improvement Amendment (CLIA)-certified next generation sequencing (NGS) across histologies. Among these patients, 98.4% had a unique molecular profile, and aside from three primary brain tumor patients with a single genetic lesion (IDH1 R132H), no two patients within a given histology were molecularly identical. Additionally, two sets of patients had identical profiles consisting of two mutations in common and no other anomalies. However, these profiles did not segregate by histology (lung adenocarcinoma-appendiceal cancer (KRAS G12D and GNAS R201C), and lung adenocarcinoma-liposarcoma (CDK4 and MDM2 amplification pairs)). These findings suggest that most advanced tumors are molecular singletons within and between histologies, and that tumors that differ in histology may still nonetheless exhibit identical molecular portraits, albeit rarely.

Impact of a Biomarker-Based Strategy on Oncology Drug Development: A Meta-analysis of Clinical Trials Leading to FDA Approval

BACKGROUND

In order to ascertain the impact of a biomarker-based (personalized) strategy, we compared outcomes between US Food and Drug Administration (FDA)-approved cancer treatments that were studied with and without such a selection rationale.

METHODS

Anticancer agents newly approved (September 1998 to June 2013) were identified at the Drugs@FDA website. Efficacy, treatment-related mortality, and hazard ratios (HRs) for time-to-event endpoints were analyzed and compared in registration trials for these agents. All statistical tests were two-sided.

RESULTS

Fifty-eight drugs were included (leading to 57 randomized [32% personalized] and 55 nonrandomized trials [47% personalized], n = 38 104 patients). Trials adopting a personalized strategy more often included targeted (100% vs 65%, P < .001), oral (68% vs 35%, P = .001), and single agents (89% vs 71%, P = .04) and more frequently permitted crossover to experimental treatment (67% vs 28%, P = .009). In randomized registration trials (using a random-effects meta-analysis), personalized therapy arms were associated with higher relative response rate ratios (RRRs, compared with their corresponding control arms) (RRRs = 3.82, 95% confidence interval [CI] = 2.51 to 5.82, vs RRRs = 2.08, 95% CI = 1.76 to 2.47, adjusted P = .03), longer PFS (hazard ratio [HR] = 0.41, 95% CI = 0.33 to 0.51, vs HR = 0.59, 95% CI = 0.53 to 0.65, adjusted P < .001) and a non-statistically significantly longer OS (HR = 0.71, 95% CI = 0.61 to 0.83, vs HR = 0.81, 95% CI = 0.77 to 0.85, adjusted P = .07) compared with nonpersonalized trials. Analysis of experimental arms in all 112 registration trials (randomized and nonrandomized) demonstrated that personalized therapy was associated with higher response rate (48%, 95% CI = 42% to 55%, vs 23%, 95% CI = 20% to 27%, P < .001) and longer PFS (median = 8.3, interquartile range [IQR] = 5 vs 5.5 months, IQR = 5, adjusted P = .002) and OS (median = 19.3, IQR = 17 vs 13.5 months, IQR = 8, Adjusted P = .04). A personalized strategy was an independent predictor of better RR, PFS, and OS, as demonstrated by multilinear regression analysis. Treatment-related mortality rate was similar for personalized and nonpersonalized trials.

CONCLUSIONS

A biomarker-based approach was safe and associated with improved efficacy outcomes in FDA-approved anticancer agents.

Impact of Precision Medicine in Diverse Cancers: A Meta-Analysis of Phase II Clinical Trials

PURPOSE

The impact of a personalized cancer treatment strategy (ie, matching patients with drugs based on specific biomarkers) is still a matter of debate.

METHODS

We reviewed phase II single-agent studies (570 studies; 32,149 patients) published between January 1, 2010, and December 31, 2012 (PubMed search). Response rate (RR), progression-free survival (PFS), and overall survival (OS) were compared for arms that used a personalized strategy versus those that did not.

RESULTS

Multivariable analysis (both weighted multiple linear regression and random effects meta-regression) demonstrated that the personalized approach, compared with a nonpersonalized approach, consistently and independently correlated with higher median RR (31% v 10.5%, respectively; P < .001) and prolonged median PFS (5.9 v 2.7 months, respectively; P < .001) and OS (13.7 v 8.9 months, respectively; P < .001). Nonpersonalized targeted arms had poorer outcomes compared with either personalized targeted therapy or cytotoxics, with median RR of 4%, 30%, and 11.9%, respectively; median PFS of 2.6, 6.9, and 3.3 months, respectively (all P < .001); and median OS of 8.7, 15.9, and 9.4 months, respectively (all P < .05). Personalized arms using a genomic biomarker had higher median RR and prolonged median PFS and OS (all P ≤ .05) compared with personalized arms using a protein biomarker. A personalized strategy was associated with a lower treatment-related death rate than a nonpersonalized strategy (median, 1.5% v 2.3%, respectively; P < .001).

CONCLUSION

Comprehensive analysis of phase II, single-agent arms revealed that, across malignancies, a personalized strategy was an independent predictor of better outcomes and fewer toxic deaths. In addition, nonpersonalized targeted therapies were associated with significantly poorer outcomes than cytotoxic agents, which in turn were worse than personalized targeted therapy.

Abstract 4957: Next generation sequencing demonstrates association between tumor suppressor gene aberrations and poor outcome in patients with cancer

Next generation sequencing is advancing at a breathtaking pace, and is transforming patient care by allowing physicians to customize and match treatment to their patients’ tumor alterations. Our goal was to study the association between key molecular alterations and outcome parameters. We retrospectively reviewed the clinicopathologic and clinical outcomes of 392 patients for whom molecular testing had been performed. Potential associations between clinical characteristics and outcome parameters (overall survival (OS), time to metastasis/recurrence, and best progression-free survival (PFS)) were examined. The Kaplan-Meier method and Cox regression models were used for our analysis, and results were subjected to internal validation using a resampling method (bootstrap analysis). In a multivariable analysis (Cox regression model), the parameters that were statistically associated with a poorer overall survival were the presence of metastases at diagnosis (P = 0.014), gastrointestinal histology (P&lt;0.0001), PTEN (P&lt;0.0001), and CDKN2A alterations (P = 0.0001). The variables associated with a shorter time to metastases/recurrence were gastrointestinal histology (P = 0.004), APC (P = 0.008), PTEN (P = 0.026) and TP53 (P = 0.044) alterations. TP53 (P = 0.003) and PTEN (P = 0.034) alterations were independent predictors of a shorter best PFS. A personalized treatment approach (matching the molecular aberration with a cognate targeted drug) also correlated with a longer best PFS (P = 0.046). Our study demonstrated that, across diverse cancers, anomalies in specific tumor suppressor genes (PTEN, CDKN2A, APC, and/or TP53) were independently associated with a worse outcome, as reflected by time to metastases/recurrence, best PFS on treatment, and/or overall survival. These observations suggest that molecular diagnostic tests may provide important prognostic information in patients with cancer.

Citation Format: Maria Schwaederle, Gregory A. Daniels, David E. Piccioni, Paul T. Fanta, Richard B. Schwab, Kelly A. Shimabukuro, Barbara A. Parker, Razelle Kurzrock. Next generation sequencing demonstrates association between tumor suppressor gene aberrations and poor outcome in patients with cancer. [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 4957. doi:10.1158/1538-7445.AM2015-4957

Squamousness: Next-generation sequencing reveals shared molecular features across squamous tumor types

In order to gain a better understanding of the underlying biology of squamous cell carcinoma (SCC), we tested the hypothesis that SCC originating from different organs may possess common molecular alterations. SCC samples (N = 361) were examined using clinical-grade targeted next-generation sequencing (NGS). The most frequent SCC tumor types were head and neck, lung, cutaneous, gastrointestinal and gynecologic cancers. The most common gene alterations were TP53 (64.5% of patients), PIK3CA (28.5%), CDKN2A (24.4%), SOX2 (17.7%), and CCND1 (15.8%). By comparing NGS results of our SCC cohort to a non-SCC cohort (N = 277), we found that CDKN2A, SOX2, NOTCH1, TP53, PIK3CA, CCND1, and FBXW7 were significantly more frequently altered, unlike KRAS, which was less frequently altered in SCC specimens (all P < 0.05; multivariable analysis). Therefore, we identified “squamousness” gene signatures (TP53, PIK3CA, CCND1, CDKN2A, SOX2, NOTCH 1, and FBXW7 aberrations, and absence of KRAS alterations) that were significantly more frequent in SCC versus non-SCC histologies. A multivariable co-alteration analysis established 2 SCC subgroups: (i) patients in whom TP53 and cyclin pathway (CDKN2A and CCND1) alterations strongly correlated but in whom PIK3CA aberrations were less frequent; and (ii) patients with PIK3CA alterations in whom TP53 mutations were less frequent (all P ≤ 0 .001, multivariable analysis). In conclusion, we identified a set of 8 genes altered with significantly different frequencies when SCC and non-SCC were compared, suggesting the existence of patterns for “squamousness.” Targeting the PI3K-AKT-mTOR and/or cyclin pathway components in SCC may be warranted.

Fibroblast growth factor family aberrations in cancers: clinical and molecular characteristics

Fibroblast growth factor ligands and receptors (FGF and FGFR) play critical roles in tumorigenesis, and several drugs have been developed to target them. We report the biologic correlates of FGF/FGFR abnormalities in diverse malignancies. The medical records of patients with cancers that underwent targeted next generation sequencing (182 or 236 cancer-related genes) were reviewed. The following FGF/FGFR genes were tested: FGF3, 4, 6, 7, 10, 12, 14, 19, 23 and FGFR1, 2, 3, and 4. Of 391 patients, 56 (14.3%) had aberrant FGF (N = 38, all amplifications) and/or FGFR (N = 22 including 5 mutations and one FGFR3-TACC3 fusion). FGF/FGFR aberrations were most frequent in breast cancers (26/81, 32.1%, p = 0.0003). In multivariate analysis, FGF/FGFR abnormalities were independently associated with CCND1/2, RICTOR, ZNF703, RPTOR, AKT2, and CDK8 alterations (all P < 0.02), as well as with an increased median number of alterations (P < 0.0001). FGF3, FGF4, FGF19 and CCND1 were co-amplified in 22 of 391 patients (5.6%, P < 0.0001), most likely because they co-localize on the same chromosomal region (11q13). There was no significant difference in time to metastasis or overall survival when comparing patients harboring FGF/FGFR alterations versus those not. Overall, FGF/FGFR was one of the most frequently aberrant pathways in our population comprising patients with diverse malignancies. These aberrations frequently co-exist with anomalies in a variety of other genes, suggesting that tailored combination therapy may be necessary in these patients.

On the Road to Precision Cancer Medicine: Analysis of Genomic Biomarker Actionability in 439 Patients

Despite the increased use of molecular diagnostics, the extent to which patients who have these tests harbor potentially actionable aberrations is unclear. We retrospectively reviewed 439 patients with diverse cancers, for whom next-generation sequencing (mostly 236-gene panel) had been performed. Data pertaining to the molecular alterations identified, as well as associated treatment suggestions (on- or off-label, or experimental), were extracted from molecular diagnostic reports. Most patients (420/439; 96%) had at least one molecular alteration: 1,813 alterations (in 207 distinct genes) were identified [the majority being mutations (62%) or amplifications (29%)]. The three most common gene abnormalities were TP53 (44%), KRAS (16%), and PIK3CA (12%). The median number of alterations per patient was 3 (range, 0-16). Nineteen patients (4%) had no alterations; 48 patients (11%) had only one alteration; and 372 patients had two or more abnormalities (85%). The median number of potentially actionable anomalies per patient was 2 (range, 0-8). Most patients (393/439; 90%) had at least one potentially actionable alteration, and in all these cases the aberration could at least be targeted by an experimental drug in a clinical trial. A total of 307 patients (70%) had an alteration that was actionable with an approved drug, but in only 89 patients (20%) was the drug approved for their disease (on-label). Next-generation sequencing identified theoretically actionable aberrations in 90% of our patients. Many of the drugs are, however, experimental or would require off-label use. Strategies to address drug access for patients harboring potentially actionable mutations are needed.

HER2 expression status in diverse cancers: review of results from 37,992 patients

Human epidermal growth factor receptor 2 (HER2) amplification/overexpression is an effective therapeutic target in breast and gastric cancer. Although HER2 positivity has been reported in other malignancies, previous studies generally focused on one cancer type, making it challenging to compare HER2 positivity across studies/malignancies. Herein, we examined 37,992 patient samples for HER2 expression (+/- amplification) in a single laboratory. All 37,992 patients were tested by immunohistochemistry (IHC); 21,642 of them were also examined for HER2 amplification with either fluorescent in situ hybridization (FISH) (11,670 patients) or chromogenic in situ hybridization (CISH) (9,972 patients); 18,262 patients had tumors other than breast or gastric cancer. All tissues were analyzed in a Clinical Laboratory Improvement Amendments (CLIA) laboratory (Caris Life Sciences) at the request of referring physicians. HER2 protein overexpression was found in 2.7 % of samples. Over-expressed HER2 was detected predominantly in malignancies of epithelial origin; for cancers derived from mesenchyme, neuroendocrine tissue, central nervous system, and kidney, HER2 expression and amplification were remarkably rare or non-existent. Bladder carcinomas, gallbladder, extrahepatic cholangiocarcinomas, cervical, uterine, and testicular cancers showed HER2 positivity rates of 12.4, 9.8, 6.3, 3.9, 3.0, and 2.4 %, respectively. HER2 overexpression and/or amplification is frequently found across tumor types. These observations may have significant therapeutic implications in cancers not traditionally thought to benefit from anti-HER2 therapies.

Unique molecular signatures as a hallmark of patients with metastatic breast cancer: implications for current treatment paradigms

Our analysis of the tumors of 57 women with metastatic breast cancer with next generation sequencing (NGS) demonstrates that each patient's tumor is unique in its molecular fingerprint. We observed 216 somatic aberrations in 70 different genes, including 131 distinct aberrations. The most common gene alterations (in order of decreasing frequency) included: TP53, PIK3CA, CCND1, MYC, HER2 (ERBB2), MCL1, PTEN, FGFR1, GATA3, NF1, PIK3R1, BRCA2, EGFR, IRS2, CDH1, CDKN2A, FGF19, FGF3 and FGF4. Aberrations included mutations (46%), amplifications (45%), deletions (5%), splices (2%), truncations (1%), fusions (0.5%) and rearrangements (0.5%), with multiple distinct variants within the same gene. Many of these aberrations represent druggable targets, either through direct pathway inhibition or through an associated pathway (via ‘crosstalk’). The ‘molecular individuality’ of these tumors suggests that a customized strategy, using an “N-of-One” model of precision medicine, may represent an optimal approach for the treatment of patients with advanced tumors.

Molecular tumor board: the University of California-San Diego Moores Cancer Center experience

OBJECTIVE

DNA sequencing tests are enabling physicians to interrogate the molecular profiles of patients' tumors, but most oncologists have not been trained in advanced genomics. We initiated a molecular tumor board to provide expert multidisciplinary input for these patients.

MATERIALS AND METHODS

A team that included clinicians, basic scientists, geneticists, and bioinformatics/pathway scientists with expertise in various cancer types attended. Molecular tests were performed in a Clinical Laboratory Improvement Amendments environment.

RESULTS

Patients (n = 34, since December 2012) had received a median of three prior therapies. The median time from physician order to receipt of molecular diagnostic test results was 27 days (range: 14-77 days). Patients had a median of 4 molecular abnormalities (range: 1-14 abnormalities) found by next-generation sequencing (182- or 236-gene panels). Seventy-four genes were involved, with 123 distinct abnormalities. Importantly, no two patients had the same aberrations, and 107 distinct abnormalities were seen only once. Among the 11 evaluable patients whose treatment had been informed by molecular diagnostics, 3 achieved partial responses (progression-free survival of 3.4 months, ≥6.5 months, and 7.6 months). The most common reasons for being unable to act on the molecular diagnostic results were that patients were ineligible for or could not travel to an appropriately targeted clinical trial and/or that insurance would not cover the cognate agents.

CONCLUSION

Genomic sequencing is revealing complex molecular profiles that differ by patient. Multidisciplinary molecular tumor boards may help optimize management. Barriers to personalized therapy include access to appropriately targeted drugs.

Abstract A212: Next generation sequencing (NGS) in 57 patients with advanced or metastatic breast cancer: Identification of unique genomic profiles and correlation with response

Background: Next generation sequencing (NGS) has revealed significant heterogeneity among patients’ tumors. Molecular aberrations may be both prognostic and predictive.

Methods: We retrospectively analyzed 57 patients with advanced or metastatic breast cancer, with NGS profiling of their tumors, treated on Phase I trials at MD Anderson Cancer Center and UCSD-Moores Cancer Center. The objectives of this study were to: 1) characterize molecular aberrations and, 2) correlate molecular aberrations with response to targeted therapies.

Results: Fifty-seven patients with advanced or metastatic breast cancer with NGS profiling of their tumors were included. Fifty-six of 57 patients (98%) with NGS analysis of their tumors demonstrated at least one molecular aberration. A total of 216 somatic aberrations in 71 different genes were identified including variants in the same gene. There were 99 mutations, 97 amplifications, 11 deletions, 5 splices, 2 truncations, 1 fusion and 1 rearrangement. The most commonly mutated genes were: TP53 (26 patients, 46%); PIK3CA (18 patients, 32%); PIK3R1, GATA3 (5 patients, 9% each); BRCA2, CDH1, and NF1 (3 patients, 5% each). The most common amplifications occurred at: CCND1, MYC (12 patients, 21% each); HER2 (official gene name ERBB2), MCL1 (7 patients, 12% each); and FGFR1 (6 patients, 11%). In addition, PTEN deletion and CDKN2 deletion were found in 6 (11%) and 3 (5%) patients, respectively. Among those genes with the highest number of gene variants included: TP53 (26 variants); PIK3CA (7 variants); GATA (5 variants); PIK3R1 (4 variants); and BRCA 2 (4 variants). No two patients demonstrated the same spectrum of molecular aberrations. Forty-four of 57 patients were evaluable for response on targeted therapies excluding single-agent hormone therapy (13 patients did not receive targeted therapy). Thirty-seven patients received therapies that were either directly or indirectly matched to NGS aberrations resulting in 2 patients with complete responses (CR), 5 with partial response (PR), 10 with stable disease ≥ 6 months (SD) and, 20 with progressive disease (PD). Seven patients who did receive matched therapy demonstrated SD (3 patients) and PD (4 patients) 3 SD (Fisher's exact test, p=0.88).

Conclusion: Unique profiles of genomic aberrations in patients with breast cancer were demonstrated. Further evaluation NGS in larger patient cohorts is warranted including studies that prospectively match aberrations to targeted therapies.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A212.

Citation Format: Jennifer J. Wheler, Barbara A. Parker, Jack Lee, Roman Yelensky, Stacy Moulder, Apostolia M. Tsimberidou, Filip Janku, Johnique T. Atkins, Ralph Zinner, Richard Q. Schwab, Maria Schwaederle, Vivek Subbiah, Siqing Fu, Philip J. Stephens, Razelle Kurzrock. Next generation sequencing (NGS) in 57 patients with advanced or metastatic breast cancer: Identification of unique genomic profiles and correlation with response. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A212.

K-RAS mutant pancreatic tumors show higher sensitivity to MEK than to PI3K inhibition in vivo

Activating K-RAS mutations occur at a frequency of 90% in pancreatic cancer, and to date no therapies exist targeting this oncogene. K-RAS signals via downstream effector pathways such as the MAPK and the PI3K signaling pathways, and much effort has been focused on developing drugs targeting components of these pathways. To better understand the requirements for K-RAS and its downstream signaling pathways MAPK and PI3K in pancreatic tumor maintenance, we established an inducible K-RAS knock down system that allowed us to ablate K-RAS in established tumors. Knock down of K-RAS resulted in impaired tumor growth in all pancreatic xenograft models tested, demonstrating that K-RAS expression is indeed required for tumor maintenance of K-RAS mutant pancreatic tumors. We further examined signaling downstream of K-RAS, and detected a robust reduction of pERK levels upon K-RAS knock down. In contrast, no effect on pAKT levels could be observed due to almost undetectable basal expression levels. To investigate the requirement of the MAPK and the PI3K pathways on tumor maintenance, three selected pancreatic xenograft models were tested for their response to MEK or PI3K inhibition. Tumors of all three models regressed upon MEK inhibition, but showed less pronounced response to PI3K inhibition. The effect of MEK inhibition on pancreatic xenografts could be enhanced further by combined application of a PI3K inhibitor. These data provide further rationale for testing combinations of MEK and PI3K inhibitors in clinical trials comprising a patient population with pancreatic cancer harboring mutations in K-RAS.