Tumour pharmacodynamics and circulating cell free DNA in patients with refractory colorectal carcinoma treated with regorafenib

Background

Regorafenib, a multi-kinase inhibitor, is used in the treatment of patients with metastatic colorectal cancer refractory to standard therapy. However, this benefit was limited to 1.4 months improvement in overall survival, with more than half of patients experiencing grade 3 to 4 adverse events. We aim to elucidate the pharmacodynamic effects of regorafenib in metastatic colorectal cancer and discover potential biomarkers that may predict clinical benefit.

Methods

Patients with metastatic colorectal adenocarcinoma refractory to standard therapy with tumours amenable to biopsy were eligible for the study. Regorafenib was administered orally at 160 mg daily for 3 out of 4 weeks with tumour assessment every 2 cycles. Metabolic response was assessed by FDG PET-CT scans (pre-treatment and day 15); paired tumour biopsies (pre-treatment and day 21 post-treatment) were sampled for immunohistochemistry and proteomic profiling analyses. Plasma circulating cell free DNA was quantified serially before and after treatment.

Results

There were 2(6%) partial responses out of 35 patients, and 8(23%) patients had stable disease for more than 7 months. Adverse event profile was similar to reported data. Recurrent somatic mutations in K-RAS, PIK3CA and BRAF were detected in plasma circulating cell free DNA in 14 patients; some mutations were not found in archival tumour. Total plasma circulating cell free DNA inversely correlated with progression free survival (PFS), and presence of KRAS mutations associated with shorter PFS. Immunohistochemistry of pre- and post- treatment biopsies showed majority of patients had downregulation of phosphorylated-VEGFR2, podoplanin, phosphorylated-AKT, Ki-67 and upregulation of the MEK-ERK axis, phosphorylated-C-MET, phosphorylated-SRC, phosphorylated-STAT3 and phosphorylated-JUN. Proteomic analysis of fine needle tumour aspirates showed down-regulation of PI3K was associated with longer PFS.

Conclusion

Plasma circulating cell free DNA may yield potential predictive biomarkers of regorafenib treatment. Downregulation of the PI3K-AKT axis may be an important predictor of clinical benefit.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0405-4) contains supplementary material, which is available to authorized users.

Capturing and molecular analysis of tumor cells isolated from ascites fluid to predict response to treatment

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Background: As access to tumor tissue if often limited in clinical studies, we are exploring technologies to capture tumor cells from body fluids with the aim to use the profile of pathway activation to predict response to treatment in early clinical trials. Methods: Tumor cells were captured from ascites fluid collected from an ovarian cancer patient via immunomagnetic enrichment. Isolated tumor cells were characterized for panel of signal transduction proteins at base line and after the treatment with PI3K inhibitor and/or MEK inhibitor alone or in combination. Comprehensive functional pathway modulation was determined using multiplexed Collaborative Enzyme Enhanced Reactive-immunoassay (CEER) to evaluate the treatment efficacy. Results: Sufficient numbers of tumor cells were present in ascites fluid for immunomagnetic enrichment and for subsequent functional pathway analysis. Comprehensive pathway modulations (HER1, HER2, HER3, cMET, IGF1R, PDK1, PI3K, AKT, PRAS40, RPS6, ERK, MEK and RSK) were determined with tumor cells using CEER. Pathway modulation upon in vitro drug treatment revealed insufficient targets as well as downstream signal protein inhibition against single agent PI3Ki or MEKi treatment. When these cells were treated with both compounds however, a dramatic target/pathway inhibition was observed. Conclusions: Viable, stimulatable tumor cells can be isolated in high number from ascites fluid and routine pathway analysis can be achieved in clinical setting. As pathway redundancy is a common feature in most solid tumor, a comprehensive in vitro analysis of pathway against various targeted drugs using tumor cells isolated from easily obtainable biological fluid (ascites, plural fluid, etc.) may guide clinicians in selecting the most effective targeted drug combination. Significant differences can be detected between single and combination treatment. Further studies need to be done to validate these findings.

Mutational analysis of plasma DNA from patients (pts) in the phase III GRID study of regorafenib (REG) versus placebo (PL) in tyrosine kinase inhibitor (TKI)-refractory GIST: Correlating genotype with clinical outcomes

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Background: The phase III GRID study showed that REG provides a significant improvement in progression-free survival (PFS) compared with PL in pts with advanced gastrointestinal stromal tumors (GIST) following failure of at least imatinib (IM) and sunitinib (SU; HR 0.27, p<0.0001). Determining GIST genotype in TKI-refractory disease has proven challenging due to inter-tumoral heterogeneity and pt preference to avoid serial biopsies. To overcome this, we analysed circulating DNA in plasma as a source of tumor DNA and studied the correlation between mutational status and clinical outcome. Methods: DNA was isolated from both archival tumor tissue (n=102) and plasma at baseline (n=163) and analyzed for mutations via Sanger sequencing (tissue) or BEAMing (plasma). Results: Mutational frequencies for tumor tissue samples were: KIT, 66%; PDGFRA, 3%; KRAS, 1%; BRAF, 0%. For plasma, frequencies were: KIT, 58%; PDGFRA, 1%; KRAS, 1 out of 2 samples, BRAF, 0%. Detection of primary KIT mutations showed 84% concordance between tissue and plasma. Secondary KIT mutations were more commonly detected in plasma (47%) than in tissue (12%). Subgroup analysis based on mutational status showed an improved PFS in REG-treated pts vs PL in all subgroups by both central and local review of imaging studies. The presence of a secondary KIT mutation in plasma was associated with shorter PFS in pts receiving PL (HR 1.82, p=0.05). Pts with a KIT-exon 9 mutation received IM for a shorter period of time, and SU for a longer period of time, relative to other GIST genotypes. Pts with a PDGFRA mutation showed variable clinical responses, while 1/1 KRAS-mutant GIST did not respond well to IM, SU, or REG. Conclusions: KIT mutational status correlated to IM and SU treatment duration. While consistent with prior reports using tissue sampling, this validates the utility of plasma-based circulating DNA analysis of target oncogenes. Secondary KIT mutations appear to have a negative prognostic impact in GIST, while the clinical benefit of REG vs PL was not influenced by KIT mutational status. Clinical trial information: NCT01271712.

Analysis of plasma protein biomarkers from the CORRECT phase III study of regorafenib for metastatic colorectal cancer

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Background: In the CORRECT phase III trial, the multikinase inhibitor regorafenib (REG) demonstrated significant improvement in overall survival (OS) and progression-free survival (PFS) vs placebo (Pla) in patients with metastatic colorectal cancer (mCRC) whose disease had progressed on other standard therapies. An exploratory biomarker subanalysis was conducted to identify protein biomarkers with potential predictive or prognostic value. Methods: Fifteen proteins of interest, many of which are involved in angiogenesis, were quantified by multiplex immunoassay or ELISA in baseline plasma samples collected at study entry from 80% (611/760) of patients. Potential predictive and prognostic effects were evaluated. Results: The biomarker subpopulation was representative of the overall study population in terms of OS and PFS. Using OS as the clinical endpoint, Tie-1 was the only protein whose level demonstrated significant correlation with efficacy (low protein group: REG/Pla, HR 0.87; high protein group, HR 0.56; interaction, p=0.035). Using PFS as the clinical endpoint, von Willebrand factor (VWF) was the only protein whose level demonstrated significant correlation with efficacy (low protein group: REG/Pla, HR 0.39; high protein group, HR 0.60; interaction, p=0.02). Following correction for multiple testing, neither Tie-1 nor VWF data retained statistical significance. Baseline levels of IL-8 and placental growth factor (PlGF) were found to have prognostic value for OS (IL-8: high/low protein levels, HR 3.48, p<0.001; PIGF: HR 1.81, p=0.002). IL-8 was also prognostic for PFS (high/low protein levels: HR 1.63, p<0.001). Conclusions: None of the plasma proteins examined showed significant predictive value for REG efficacy after multiple testing correction. The association between baseline levels of Tie-1/VWF and REG efficacy may be a hypothesis to be tested in further trials. Clinical trial information: NCT01103323.

Pharmacodynamic effects of regorafenib in metastatic colorectal carcinoma (mCRC)

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Background: Regorafenib, an oral multikinase inhibitor of VEGFR2/3, PDGFRb, KIT, FGFR, RET, RAF and TIE2, is efficacious in refractory mCRC but its mechanism of action is unclear and predictive biomarkers are lacking. Methods: We assessed tumor and circulatory biomarkers in a phase 2 study of regorafenib in refractory mCRC patients. Regorafenib was administered orally at 160mg/d for 3 out of 4 weeks. Post cycle 2 response was assessed by RECIST 1.1. Subjects were scheduled for FDG PET-CT scans (pre + D15) and paired core needle tumor biopsies for IHC analysis (pre + D21) in cycle 1. Archival tumor mutations were evaluated using Sequenom MassARRAY OncoCarta Panel V1.0 assay. Results: 35 patients were treated; 49% received > 4 prior therapies and 43% had prior bevacizumab. Median PFS was 3.45 mths (95% CI: 3.40-3.49), ORR was 3% and disease control rate [DCR] (PR + SD at 8 wks) was 57%. Early PET responses (EORTC criteria) were seen in 49%, but did not predict for DCR (p=1.0). Fatigue, hand foot skin reaction (HFSR), voice change and diarrhea occurred in > 30% of subjects. Grade 3-5 toxicities occurred in 46%, the commonest being HFSR and rash (17% each). Median relative dose intensity was 92%; 43% required > 1 dose reduction, 60% required > 1 dose interruption. KRAS (29%), BRAF (9%), EGFR (9%), NRAS (6%) KIT (3%), PIK3CA (3%), PDGFRA (3%) and CDK (3%) mutations were detected in archival tumors. None predicted for ORR or DCR; PFS was identical in KRAS mutant vs wt patients (3.45 mths, p=0.39) and similar in BRAF mutant vs wt patients (3.48 vs 3.45 mths, p=0.10). The patient with the longest PFS (12.6 mths) had a BRAF mutation. Amongst the 10 paired tumor samples available, IHC markers upregulated in >50% cases were pMEK, pERK, pJun and pJNK, whilst those downregulated/ unchanged in >50% were pKIT, pVEGFR2, CD31 [vascular endothelial cells (ECs)] and podoplanin (lymphatic ECs). The greatest change was observed in podoplanin expression, corresponding to a 60% reduction in lymphatic vessel density. Conclusions: FDG-PET responses in cycle 1 did not predict for regorafenib clinical benefit in mCRC patients. Targeting lymphatic/vascular ECs in the tumor microenvironment may be a more significant antitumor mechanism of regorafenib than MAP kinase pathway inhibition. Clinical trial information: NCT01189903.

Abstract LB-295: Detection of oncogenic kinase mutations in circulating plasma DNA and correlation with clinical benefit in the phase III GRID study of regorafenib vs placebo in TKI-refractory metastatic GIST

Background: GRID is a phase III study for patients with advanced gastrointestinal stromal tumors (GIST) following failure of imatinib (I) and sunitinib (S) who were randomized to receive either the multikinase inhibitor regorafenib (R) or placebo (P). R demonstrated a highly significant improvement in progression-free survival compared with P (HR 0.27, p&lt;0.0001). A preplanned retrospective biomarker analysis was conducted to assess GIST genotypes in GRID patients and to explore the possible impact of different driver oncogene mutations on clinical outcomes.

Methods: DNA was isolated from archival tumor tissue and analyzed for KIT mutations via Sanger sequencing. The expectation was that primary KIT mutations would be detectable in archival tissue but that secondary KIT mutations may be undetectable in tissues obtained before treatment with I or S. To overcome this potential limitation, plasma samples drawn at GRID study entry, post I and S failure, were used as a source of circulating DNA for evaluation of GIST oncogenic mutations (KIT, PDGFRA, BRAF) via BEAMing technology.

Results: KIT mutations were detected in 83 of 138 (60%) plasma samples and 64 of 99 (65%) tumor tissue samples analyzed. Primary KIT exon 11 and 9 mutations were identified in approximately 42% and 18% of the tissue samples, respectively. The frequency of the canonical exon 9 mutations was similar for plasma and tissue samples, showing consistency between mutation-detection technologies. With limitations of tumor-based assays, a lower incidence of secondary KIT resistance mutations was detected in patient-matched archival tumor tissue compared with plasma samples: resistance mutations were detected in 12% of tissue samples vs 48% of plasma samples. Most (76%) secondary KIT mutations detected in plasma DNA were located in the KIT activation loop encoding structural alterations known to mediate resistance to I and S. Nearly half of the plasma samples in which secondary KIT mutations were identified harbored multiple secondary mutations, consistent with the results of previous studies on fresh tumor biopsies taken following resistance to both I and S. R was clinically active compared with P in all KIT mutational subgroups evaluated (HR 0.27 in patients with KIT exon 9 mutations; HR 0.25 in patients with secondary KIT mutations identified via plasma DNA).

Conclusions: In GIST patients from the GRID trial, driver oncogenic mutations and secondary oncogenic mutations leading to I and S resistance are readily detectable via BEAMing of circulating DNA from plasma. BEAMing may provide a real-time assessment of tumor genotype in GIST and other cancers using blood-derived circulating DNA, that may be more comprehensive than tumor sampling. GIST patients with a wide spectrum of primary and secondary mutations in oncogenic kinases benefit from treatment with R.

Citation Format: George D. Demetri, Michael Jeffers, Peter Reichardt, Yoon-Koo Kang, Jean-Yves Blay, Piotr Rutkowski, Hans Gelderblom, Peter Hohenberger, Michael Leahy, Margaret von Mehren, Heikki Joensuu, Giuseppe Badalamenti, Martin Blackstein, Axel Le Cesne, Patrick Schöffski, Robert G Maki, Sebastian Bauer, Binh Bui Nguyen, Jianming Xu, Toshirou Nishida, John Chung, Chetan D. Lathia, Christian Kappeler, Iris Kuss, Dirk Laurent, Paolo G Casali. Detection of oncogenic kinase mutations in circulating plasma DNA and correlation with clinical benefit in the phase III GRID study of regorafenib vs placebo in TKI-refractory metastatic GIST. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-295. doi:10.1158/1538-7445.AM2013-LB-295

Abstract SY11-02: Detection of tumor-associated mutations in circulating DNA: clinical applications and experiences

The detection of tumor-associated mutations is of paramount importance in the era of personalized medicine. Mutational testing is now a prerequisite for the use of some approved therapies (e.g., KRAS for cetuximab in colorectal cancer [CRC]; BRAF for vemurafenib in melanoma), and these clearly established correlations between tumor mutational status and drug response elevate the importance and urgency of evaluating such associations in clinical trials of investigational drugs.

While archival primary tumor tissue is often used for mutational evaluation, such material has inherent limitations, which may be overcome by recent technological developments enabling the detection of tumor-associated mutations using plasma-derived DNA. For example, when a tumor tissue specimen is unavailable, use of plasma DNA would allow mutational status to be ascertained without the need for an invasive procedure to obtain a new tumor sample. In addition, it is now apparent that most patients treated with targeted therapies will eventually develop drug resistance, often via the acquisition of new tumor-associated mutations; these mutations may vary not only between patients but also between metastases within an individual patient. As such, the mutational status of an archival primary tumor specimen may not be relevant to guide the selection of subsequent therapies, and obtaining fresh tumor tissue from each metastasis that arises following the development of drug resistance is impractical. In such instances, mutational analysis of DNA derived from a real-time plasma sample obtained after the onset of drug resistance may offer advantages in terms of both availability and biological relevance, since new mutations acquired in response to a particular targeted therapy may be detectable in plasma DNA. Finally, mutational analysis of plasma DNA may be useful in clinical trials to evaluate potential correlations between mutational status and clinical outcome. For such exploratory analyses, the collection of archival tumor specimens from a high proportion of enrolled patients can be logistically and ethically difficult to achieve, not to mention of questionable relevance given that acquired mutations would not be detectable in these specimens. Collection of fresh tumor tissue samples at study entry would provide biologically relevant material, but can be problematic and costly to obtain in large, global clinical trials. Thus, the utility of plasma DNA for real-time mutational analysis in the clinical-trial setting offers several distinct advantages.

Since DNA derived from both normal and tumor cells exists in the circulation, the detection of tumor-associated mutations in plasma DNA requires the ability to identify a relatively small number of mutant alleles among an excess of wild-type alleles. With the goal of identifying the most suitable technology for this purpose, we conducted a comparison of available methodologies and found that BEAMing technology (Beads, Emulsions, Amplification, and Magnetics) offered very sensitive detection of known tumor-associated mutations using plasma DNA, although this technique is not well suited for the discovery of previously unknown mutations. We have now used BEAMing to analyze more than 2,000 patient samples collected from oncology clinical trials, allowing us to evaluate a number of genes (e.g., KRAS, NRAS, HRAS, BRAF, PIK3CA, AKT1, EGFR, KIT, and PDGFRA) in different cancer types (e.g., CRC, gastrointestinal stromal tumors, hepatocellular carcinoma, non-small-cell lung cancer, and breast cancer). We have used BEAMing of plasma DNA both prospectively, to enroll patients into a phase I trial based on a molecular profile of interest, and retrospectively, to evaluate potential associations between mutational status and clinical outcome in phase II and III trials. In many of these trials, collection of both fresh plasma and archival tumor tissue from a subset of patients has enabled us to compare mutational status in patient-matched plasma and tumor samples. Our experiences with BEAMing of plasma DNA to determine tumor-associated mutational status will be discussed.

Citation Format: Michael Jeffers, Chetan D. Lathia, Scott M. Wilhelm, Dimitris Voliotis, Dirk Laurent, Carol E. Pena. Detection of tumor-associated mutations in circulating DNA: clinical applications and experiences. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr SY11-02. doi:10.1158/1538-7445.AM2013-SY11-02

Multicenter phase I trial of the mitogen-activated protein kinase 1/2 inhibitor BAY 86-9766 in patients with advanced cancer

PURPOSE

To evaluate the safety, pharmacokinetics, and pharmacodynamics of BAY 86-9766, a selective, potent, orally available, small-molecule allosteric inhibitor of mitogen-activated protein kinase 1/2 in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

BAY 86-9766 was administered orally daily in 28-day courses, with doses escalated to establish the maximum-tolerated dose (MTD). An expanded cohort was evaluated at the MTD. Pharmacokinetic and pharmacodynamic parameters were assessed, with extracellular signal-regulated kinase (ERK) phosphorylation evaluated in paired biopsies from a subset of the expanded MTD cohort. Tumor specimens were evaluated for mutations in select genes.

RESULTS

Sixty-nine patients were enrolled, including 20 patients at the MTD. The MTD was 100 mg given once-daily or in two divided doses. BAY 86-9766 was well-tolerated. The most common treatment-related toxicities were acneiform rash and gastrointestinal toxicity. BAY 86-9766 was well-absorbed after oral administration (plasma half-life ~12 hours), and displayed dose proportional pharmacokinetics throughout the tested dose range. Continuous daily dosing resulted in moderate accumulation at most dose levels. BAY 86-9766 suppressed ERK phosphorylation in biopsied tissue and tetradecanoylphorbol acetate-stimulated peripheral blood leukocytes. Of 53 evaluable patients, one patient with colorectal cancer achieved a partial response and 11 patients had stable disease for 4 or more courses. An ocular melanoma specimen harbored a GNAQ-activating mutation and exhibited reduced ERK phosphorylation in response to therapy.

CONCLUSION

This phase I study showed that BAY 86-9766 was well-tolerated, with good oral absorption, dose proportional pharmacokinetics, target inhibition at the MTD, and some evidence of clinical benefit across a range of tumor types.

Mutational analysis of biomarker samples from the CORRECT study: Correlating mutation status with clinical response to regorafenib

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Background: In the CORRECT Ph3 trial, regorafenib demonstrated significant improvement in OS and PFS vs. placebo in subjects with metastatic colorectal cancer (mCRC) who had progressed on standard therapies. An exploratory biomarker substudy was conducted on samples collected from subjects enrolled in CORRECT. Methods: DNA was isolated from archival tumor tissue and fresh baseline plasma samples that were available from 239 (31%) and 503 (66%) subjects enrolled in CORRECT, respectively. Mutations in KRAS, PIK3CA and BRAF were evaluated via BEAMing technology. Results: Mutations were readily detected in DNA isolated from both tumor and plasma samples: KRAS: 59/69%; PIK3CA: 12/17% and BRAF: 1.5/3.4%. The frequency of KRAS mutation detected in tumor samples via BEAMing (59%) was identical to the frequency determined from pre-existing “historical” KRAS mutation data that was available from 96% of the subjects enrolled in the study. Concordance among the mutations detected via BEAMing in tumor vs. plasma was 76% (KRAS), 88% (PIK3CA), and 97% (BRAF). A subset of CRC which was found to be KRAS-wildtype in DNA from archival tumor, but KRAS-mutant in DNA from fresh plasma was identified and may represent subjects whose KRAS mutational status had changed during prior therapy. Correlative subgroup analyses demonstrated that regorafenib mediated a trend for clinical benefit vs. placebo in both KRAS wildtype and mutant subgroups identified by plasma BEAMing (OS: KRAS WT, HR: 0.67, 95% CI: 0.41–1.08; KRAS mutant, HR: 0.81, 95% CI: 0.61–1.09; interaction p=0.561). Similar results were noted for PIK3CA WT/mutant subgroups (OS: WT, HR: 0.75, 95% CI: 0.57–0.99; mutant, HR: 0.84, 95% CI: 0.47–1.50; interaction p=0.723). BRAF was not analysed due to the small number of BRAF-mutant samples. Conclusions: The mutational analysis of DNA isolated from fresh plasma is feasible and robust using the BEAMing platform and may better represent the mutational status of the tumor(s) that a mCRC patient harbors at the time of enrollment than does the mutational analysis of archival primary tumor tissue. Regorafenib was associated with clinical benefit (vs. placebo) in all mutational subgroups evaluated. Clinical trial information: NCT01103323.

Purpura fulminans in a patient with mixed connective tissue disease

A 43-year-old lady was admitted to the intensive care unit with sepsis. She had a history of mixed connective tissue disease, Raynaud's syndrome and hypothyroidism. 2 days later, she developed a purpuric rash on her face and extremities with a livedoid background. Few days later, her distal fingers and toes became gangrenous which then had to be amputated. Laboratory investigations showed that she was coagulopathic and had multiple organ dysfunctions. Antiphospholipid antibodies were negative; however, protein C and antithrombin III levels were low. A skin biopsy showed fibrinoid necrosis in the vessel wall with microthrombi and red-cell extravasation. A diagnosis of purpura fulminans was made.

Regorafenib (BAY 73-4506) in advanced colorectal cancer: a phase I study

BACKGROUND

In a phase I dose-escalation study, regorafenib demonstrated tolerability and antitumour activity in solid tumour patients. The study was expanded to focus on patients with metastatic colorectal cancer (CRC).

METHODS

Patients received oral regorafenib 60-220 mg daily (160 mg daily in the extension cohort) in cycles of 21 days on, 7 days off treatment. Assessments included toxicity, response, pharmacokinetics and pharmacodynamics.

RESULTS

Thirty-eight patients with heavily pretreated CRC (median 4 prior lines of therapy, range 0-7) were enrolled in the dose-escalation and extension phases; 26 patients received regorafenib 160 mg daily. Median treatment duration was 53 days (range 7-280 days). The most common treatment-related toxicities included hand-foot skin reaction, fatigue, voice change and rash. Twenty-seven patients were evaluable for response: 1 achieved partial response and 19 had stable disease. Median progression-free survival was 107 days (95% CI, 66-161). At steady state, regorafenib and its active metabolites had similar systemic exposure. Pharmacodynamic assessment indicated decreased tumour perfusion in most patients.

CONCLUSION

Regorafenib showed tolerability and antitumour activity in patients with metastatic CRC. This expanded-cohort phase I study provided the foundation for further clinical trials of regorafenib in this patient population.

Phase I study of intravenous PI3K inhibitor BAY 80-6946: Activity in patients (pts) with advanced solid tumors and non-Hodgkin lymphoma treated in MTD expansion cohorts

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Background: BAY 80-6946 (BAY) is a potent and highly selective reversible pan-Class I PI3K inhibitor, previously reported to be tolerated as a 1-hr infusion at a dose of 0.8 mg/kg on days 1, 8 and 15 every 28 days (MTD). Additional pts were treated in MTD expansion cohorts to assess safety, PK, biomarkers and clinical benefit in selected tumor types, as well as safety in Type 2 diabetics. Methods: To date, 23 nondiabetic pts with solid tumors and 5 with follicular lymphoma (FL) received BAY at the MTD, until disease progression or unacceptable toxicity. Tumor types were selected for high frequency of PIK3CA mutation, including breast cancer (BC; 16), endometrial (3), gastric (2), GU transitional cell (1) and ovarian clear cell (1). Partial enrichment for PIK3CA mutation was achieved by analysis of plasma DNA. 3 diabetic pts have been enrolled, at starting dose of 0.4 mg/kg. PK was done after the 1st and 3rd doses. FDG-PET/CT scans were done at baseline and 48 hrs after the 1st dose for pharmacodynamic assessment. Results: Safety and tolerability assessments confirmed MTD. There were no 1st cycle DLTs. Almost all nondiabetic pts had acute Grade 2/3 hyperglycemia (HG) following each dose; at least 10 of them received insulin for 1-3 days post dose. Hypertension (HTN) lasting < 24 hrs was common in pts with preexisting HTN, and manageable. 2 FL pts developed interstitial pneumonitis (IP) after cycles 2 and 3, both responsive to steroids. Diabetic pts tolerated 0.4 mg/kg. Tumor SUVmax consistently fell at 48 hrs. 3 of 4 FL pts had partial response (PR) after 2 cycles, with 2 confirmed PR pts on BAY for 10+ and 8+ mos. 2 BC pts showed PR , 1 confirmed. PIK3CA mutation (n=7) does not appear to correlate with response. Average T1/2 was 36 hrs. Observation of high Cmax in very obese pts led to recommended maximum dose of 65 mg. Conclusions: BAY induced PRs in pts with BC and FL. The acute toxicities of HG in most pts and HTN in some are manageable, and IP has been limited to 2 lymphoma pts and is responsive to steroids. The observed clinical activity of BAY, along with its acceptable safety profile, provide a rationale for the ongoing development of BAY in combination with cytotoxic and targeted agents.

Evaluation of the PI3K inhibitor BAY 80-6946 in hematologic malignancies

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Background: BAY 80-6946 is a new investigational compound that potently inhibits all PI3K Class I isoforms. BAY 80-6946 is under phase 1 clinical evaluation and PRs have been observed in solid tumors (ST) and follicular lymphoma (FL). The present analysis was performed to gain mechanistic insights into the activity of this compound in FL and potentially other hematological malignancies. Methods: Preclinical: The growth-inhibitory activity of BAY 80-6946 on hematological cancer cell lines (n= 32) was determined by the CellTiterGlo assay. GS-1101 (formerly called CAL-101) and cisplatin (CP) were also tested. Clinical: Specimens from subjects enrolled in a BAY 80-6946 Phase 1 trial MTD expansion were used. Levels of various cytokines and chemokines were determined by ELISA or multiplex immunoassay in plasma samples (n= 27) obtained prior to and during BAY 80-6946 treatment of 6 subjects (3 FL + 3 ST). Proteins examined included CXCL13 (involved in B-cell homing) and BAFF (involved in B-cell survival). Tumor tissue was used to determine PTEN expression via IHC and the mutational status of PTEN via sequencing. PIK3CA mutational status was evaluated in tumor tissue and plasma via BEAMing. Results: Preclinical: BAY 80-6946 was more potent on B-cell lymphomas and other hematological cancer cell lines than GS-1101 or CP (median IC50 in μM: BAY 80-6946= 0.49; GS-1101= 37; CP= 2.9). Clinical: Plasma levels of CXCL13 decreased and BAFF increased following BAY 80-6946 administration in all subjects examined (CXCL13 mean change: -58%; p= 0.004; BAFF mean change: +67%; p= 0.042). PTEN expression was lower in FL compared to ST. No mutations in PTEN or PIK3CA were identified in FL. Mutations in PIK3CA were identified in some ST. Conclusions: These preclinical results indicate that the observed early clinical activity of BAY 80-6946 in FL may be due to a direct anti-proliferative effect on malignant B-cells. The plasma chemokine/cytokine results support the possibility that the modulation of factors involved in B-cell homing and survival may play a mechanistic role in mediating this activity. Overall these results support the continued clinical evaluation of BAY 80-6946 in FL and other hematological malignancies.

Abstract 742: Comparison of commercially available phosphorylated ERK antibodies for immunohistochemical biomarker analysis

Immunohistochemical (IHC) analysis of ERK phosphorylation is commonly performed on pre- and post-treatment cancer biopsies as part of pharmacodynamic biomarker assessments for targeted oncology therapeutics. The current study was performed to assess the specificity and sensitivity of four commercially-available pERK antibodies for IHC analysis, which included three monoclonal antibodies (clones 20G11, MAPK-YT, D13.14.4E) and one polyclonal antibody. To facilitate this analysis, the HEPG2 liver cancer cell line was grown in the presence or absence of inhibitors of the RAF/MEK/ERK pathway (U0126 or sorafenib). Cell lysates were prepared for analysis via Western blotting and formalin-fixed, paraffin-embedded cell pellets were prepared for analysis via IHC. All antibodies produced bands at 44 and 42 kDa, the expected molecular weights of ERK1/2, when used for Western analysis of untreated cells and demonstrated a reduction or ablation of these bands following treatment of cells with inhibitors of the RAF/MEK/ERK pathway. When examined via IHC, the monoclonals demonstrated nuclear and cytoplasmic staining in HEPG2 cells with increased sensitivity relative to the polyclonal antibody. The monoclonals also demonstrated greatly reduced staining in HEPG2 cells treated with inhibitors of the RAF/MEK/ERK pathway. These antibodies were further characterized for reactivity in human tumor specimens representing breast cancer, colon cancer, lung cancer, melanoma, and ovarian cancer. Melanoma tissues were stained with a red chromogen; all others were stained with DAB. Differences in the frequency of expression, percentage of expression, and protein localization were identified between the three monoclonals. In summary, this work has identified commercially-available antibodies that appear to be of suitable specificity and sensitivity for use in IHC assays.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 742. doi:1538-7445.AM2012-742

Abstract A88: Safety, pharmacokinetic, and pharmacodynamic results of BAY 86–9766, an oral MEK inhibitor, in combination with sorafenib, an oral multikinase inhibitor, in advanced cancer patients

Background: Preclinical data revealed a synergistic interaction between sorafenib (Nexavar®) and BAY 86-9766 (RDEA119). Sorafenib is an oral, small molecule, multikinase inhibitor that is approved for the treatment of unresectable hepatocellular carcinoma (HCC) and advanced renal cell carcinoma. BAY 86-9766 is an investigational, oral, potent, non-ATP competitive, highly selective inhibitor of MEK1/2. In a Phase 1 single-agent trial of BAY 86-9766 in advanced cancer patients, the maximum tolerated dose (MTD) was 100 mg daily, given as 50 mg twice daily (bid) or 100 mg once daily, with rash being the most common treatment-related adverse event (AE) and significant inhibition of tumor phosphorylated ERK (pERK) observed. This Phase 1 trial was conducted to determine the MTD, safety, pharmacokinetics (PK), pharmacodynamics (PD), and preliminary efficacy of BAY 86-9766 in combination with sorafenib. Data from the dose escalation cohorts and MTD expansion cohort are reported here. An additional cohort of patients with advanced HCC is ongoing in the MTD expansion phase and is not described here.

Materials and Methods: Key eligibility criteria included advanced metastatic or locally recurrent solid tumors, ECOG performance status of 0–1, acceptable organ function, and life expectancy of at least 3 months. Patients initially received BAY 86-9766 alone for up to 3 days to determine PK and then began a 28-day course of combination treatment with BAY 86-9766 and sorafenib. Dose escalation proceeded with increasing doses of BAY 86-9766 from 5 mg to 50 mg bid and either 200 mg or 400 mg bid of sorafenib. At least 3 patients were treated at each of 6 dose escalation levels. Safety was assessed by AEs, clinical laboratory tests, vital signs, ECGs, ECHO/MUGA scans, and physical exams. If benefiting from treatment, patients continued with subsequent 28-day courses and response was assessed every 2 courses. Tumor mutational status and PD effect on pERK in tumor biopsies were evaluated.

Results: Forty-three patients have been enrolled (32 in dose escalation and 11 in MTD expansion). Tumor types included 23 colorectal, 6 melanoma, 4 pancreatic, 3 head & neck, 2 esophageal, 2 ovarian, and 1 each of NSCLC, prostate, and small bowel adenocarcinoma. The MTD was determined to be the full doses of both drugs, 50 mg bid for BAY 86-9766 and 400 mg bid for sorafenib. The most common AEs were diarrhea (81%), rash (63%), fatigue (61%), nausea (49%), and vomiting (37%). Following single and multiple doses, mean Cmax and AUC0–12 of BAY 86-9766 increased nearly proportionally with dose, ranging between 5 mg bid and 50 mg bid. Plasma exposures of sorafenib at 200 mg bid and 400 mg bid were generally within the range reported from other studies. There was 1 confirmed partial response in a patient with colorectal cancer and 24 patients achieved a best overall response of stable disease. Tumor mutational analysis as well as PD data on tumor pERK suppression will be presented.

Conclusions: BAY 86-9766 in combination with sorafenib was well tolerated with diarrhea and rash being the most common AEs. Based on the results of this study, a Phase 2 study with BAY 86-9766 in combination with sorafenib is underway in HCC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A88.