YounJeong Choi

Upregulation of Periostin and Reactive Stroma Is Associated with Primary Chemoresistance and Predicts Clinical Outcomes in Epithelial Ovarian Cancer

Purpose: Up to one third of ovarian cancer patients are intrinsically resistant to platinum-based treatment. However, predictive and therapeutic strategies are lacking due to a poor understanding of the underlying molecular mechanisms. This study aimed to identify key molecular characteristics that are associated with primary chemoresistance in epithelial ovarian cancers. Experimental Design: Gene expression profiling was performed on a discovery set of 85 ovarian tumors with clinically well-defined response to chemotherapies as well as on an independent validation dataset containing 138 ovarian patients from the chemotreatment arm of the ICON7 trial. Results: We identified a distinct “reactive stroma” gene signature that is specifically associated with primary chemoresistant tumors and was further upregulated in posttreatment recurrent tumors. Immunohistochemistry (IHC) and RNA in situ hybridization (RNA ISH) analyses on three of the highest-ranked signature genes (POSTN, LOX, and FAP) confirmed that modulation of the reactive stroma signature genes within the peritumoral stromal compartments was specifically associated with the clinical chemoresistance. Consistent with these findings, chemosensitive ovarian cells grown in the presence of recombinant POSTN promoted resistance to carboplatin and paclitaxel treatment in vitro. Finally, we validated the reactive stroma signature in an independent dataset and demonstrated that a high POSTN expression level predicts shorter progression-free survival following first-line chemotherapy. Conclusions: Our findings highlight the important interplay between cancer and the tumor microenvironment in ovarian cancer biology and treatment. The identified reactive stromal components in this study provide a molecular basis to the further development of novel diagnostic and therapeutic strategies for overcoming chemoresistance in ovarian cancer. Clin Cancer Res; 21(13); 2941–51. ©2015 AACR.

Abstract LB-64: GDC-0032, a beta isoform-sparing PI3K inhibitor: Results of a first-in-human phase Ia dose escalation study.

Background: GDC-0032 is an orally bioavailable, potent, and selective inhibitor of Class I PI3Kα, δ, and γ isoforms, with 30 fold less inhibition of the PI3K β isoform relative to the PI3Kα isoform. Preclinical data show that GDC-0032 has increased activity against PI3Kα isoform (PIK3CA) mutant and HER2-amplified cancer cell lines. Methods: A Phase Ia, multicenter, open-label study was conducted to evaluate the safety and pharmacokinetics (PK) of GDC-0032 administered once daily in patients with locally advanced or metastatic solid tumors. Preliminary assessment of the anti-tumor activity of GDC-0032 was also performed. The study consisted of 3+3 dose-escalation cohorts with a 35-day window to evaluate dose-limiting toxicity (DLT). Results: As of August 1, 2012, 34 patients were enrolled in this study. Five dosing cohorts ranging from 3 to 16 mg QD were tested (3, 5, 8, 12, and 16 mg), and dose escalation has been completed. Two DLTs (Grade 4 hyperglycemia and Grade 3 fatigue) were observed in two patients from the 16 mg cohort. Adverse events (AEs) assessed by the investigator as related to GDC-0032 in ≥10% of patients, were diarrhea, hyperglycemia, fatigue, nausea, decreased appetite, and vomiting. The only Grade 4 treatment-related AE (hyperglycemia) occurred in the 16 mg cohort. GDC-0032 PK was approximately dose proportional and time independent with a mean t1/2 of 40 hours. Paired pre-treatment and on-treatment tumor biopsies of a patient in the 3 mg cohort showed pharmacodynamic inhibition of the PI3K pathway as assessed by reverse phase protein array. Metabolic partial responses via FDG-PET (≥ 20% decrease in mSUVmax) were observed in 7 out of 13 patients assessed (54%). Clinical partial responses (PRs) were observed in 5 patients treated at doses of GDC-0032 ranging from 3-12 mg QD. Consistent with GDC-0032 preclinical data, 3 PRs (2 confirmed) were observed out of 5 patients with PIK3CA mutant breast cancer (RECIST -30% to -70%). One cPR has been observed in a patient with PIK3CA mutant NSCLC, and 1 uPR in a patient with HER2-positive, PIK3CA wildtype, breast cancer. Conclusion: GDC-0032 is a PI3K inhibitor with dose-linear PK and expected in-class toxicities. Pharmacodynamic inhibition of the PI3K pathway has been observed in tumor biopsies and FDG-PET imaging. Clinical partial responses observed in patients with PIK3CA mutant and HER2+ tumors suggest that GDC-0032 may have increased anti-tumor activity in diagnostically defined subpopulations. Citation Format: Dejan Juric, Ian Krop, Ramesh K. Ramanathan, Jim Xiao, Sandra Sanabria, Timothy R. Wilson, YounJeong Choi, Hema Parmar, Jerry Hsu, Jose Baselga, Daniel D. Von Hoff. GDC-0032, a beta isoform-sparing PI3K inhibitor: Results of a first-in-human phase Ia dose escalation study. [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-64. doi:10.1158/1538-7445.AM2013-LB-64

Phase I Study of DMOT4039A, an Antibody-Drug Conjugate Targeting Mesothelin, in Patients with Unresectable Pancreatic or Platinum-Resistant Ovarian Cancer

DMOT4039A, a humanized anti-mesothelin mAb conjugated to the antimitotic agent monomethyl auristatin E (MMAE), was given to patients with pancreatic and ovarian cancer every 3 weeks (0.2–2.8 mg/kg; q3w) or weekly (0.8–1.2 mg/kg). A 3+3 design was used for dose escalation followed by expansion at the recommended phase II dose (RP2D) to evaluate safety and pharmacokinetics. Antitumor response was evaluated per RECIST 1.1 and serum CA19-9 or CA125 declines. Tumor mesothelin expression was determined by IHC. Seventy-one patients (40 pancreatic cancer; 31 ovarian cancer) were treated with DMOT4039A. For the q3w schedule (n = 54), the MTD and RP2D was 2.4 mg/kg, with dose-limiting toxicities of grade 3 hyperglycemia and grade 3 hypophosphatemia at 2.8 mg/kg. For the weekly schedule (n = 17), the maximum assessed dose was 1.2 mg/kg, with further dose escalations deferred because of toxicities limiting scheduled retreatment in later cycles, and therefore the RP2D level for the weekly regimen was determined to be 1 mg/kg. Across both schedules, the most common toxicities were gastrointestinal and constitutional. Treatment-related serious adverse events occurred in 6 patients; 4 patients continued treatment following dose reductions. Drug exposure as measured by antibody-conjugated MMAE and total antibody was generally dose proportional over all dose levels on both schedules. A total of 6 patients had confirmed partial responses (4 ovarian; 2 pancreatic) with DMOT4039A at 2.4 to 2.8 mg/kg i.v. q3w. DMOT4039A administered at doses up to 2.4 mg/kg q3w and 1.0 mg/kg weekly has a tolerable safety profile and antitumor activity in both pancreatic and ovarian cancer. Mol Cancer Ther; 15(3); 439–47. ©2016 AACR.

1598PTRANSLATIONAL PKPD OF DNIB0600A, AN ANTI-NAPI2B-VC-MMAE ADC IN OVARIAN AND NSCLC CANCERS

ABSTRACT Aim: Antibody-drug conjugates (ADCs) represent an expanding class of therapeutic molecules in preclinical and clinical development for oncologic indications. Understanding the relationship between pre-clinical to clinical studies with strategic application of pharmacokinetic/pharmacodynamics modeling may allow for optimized dosing strategies for ADCs. NaPi2b is a multi-transmembrane, sodium-dependent phosphate transporter that is expressed in human lung, ovarian, and thyroid cancers. DNIB0600A, which consists of an anti-NaPi2b monoclonal antibody conjugated to the cytotoxic drug MMAE through a cleavable VC linker, is currently in Phase I/II clinical trials. The purpose of this study is to develop a PKPD model based on preclinical data and to utilize the preclinical exposure response relationships to predict clinical outcomes. Methods: DNIB0600A PK was evaluated in normal SCID mice. Dose ranging in-vivo efficacy studies were performed in NaPi2b-expressing xenograft mouse models of ovarian and lung cancers. A semi-mechanistic PKPD model was developed to describe exposure-efficacy relationships in both types of the tumor models. Human PK and PD data were collected from ongoing Phase I/II trials. Results: DNIB0600A demonstrated differential anti-tumor activities in the models, with the ovarian model being more responsive when compared with lung tumor model to NaPi2b ADC treatment. Human efficacious doses for treating ovarian cancer and NSCLC were predicted based on the pre-clinical PKPD relationships. Observed efficacy data from preliminary analysis of Phase I/II trials were in general agreements with model predictions. Conclusions: We built an integrated PKPD model to predict clinical outcome. This approach can be extended to other vc-MMAE based ADCs, and can help in preclinical model validation and ADC optimization. Disclosure: All authors have declared no conflicts of interest.

BRIM-P: A phase I, open-label, multicenter, dose-escalation study of vemurafenib in pediatric patients with surgically incurable, BRAF mutation-positive melanoma

Vemurafenib, a selective inhibitor of BRAF kinase, is approved for the treatment of adult stage IIIc/IV BRAF V600 mutation‐positive melanoma. We conducted a phase I, open‐label, dose‐escalation study in pediatric patients aged 12–17 years with this tumor type (NCT01519323).

Abstract POSTER-THER-1441: Biomarker evaluation of phase 1 clinical trials of antibody-drug conjugates (ADCs) in platinum resistant ovarian cancer

Purpose: DNIB0600A and DMUC5754A are two ADCs that conjugate the anti-mitotic agent MMAE with anti-NaPi2b and anti-MUC16 monoclonal antibodies, respectively. Both ADCs have shown promising anti-tumor activity in patients with platinum resistant ovarian cancer. Here we report biomarker analysis in patient samples collected from these phase 1 studies. The main goal of this study is to evaluate tissue-based biomarkers that can predict response or resistance to these ADCs. We also explored the utility of serum protein biomarkers and circulating tumor cells (CTCs) as potential surrogates for monitoring treatment response to ADCs and disease progression. Methods: Biomarker analysis was done on 55 ovarian cancer patients treated with clinically relevant doses (1.8-3.2mg/kg) from DNIB0600A and DMUC5754A Phase 1 studies. Protein and mRNA expression levels of NaPi2b and MUC16 targets were assessed in archival tumor specimen by immunohistochemistry (IHC) and qRT-PCR respectively. Serum collected at baseline and post-treatment were analyzed by CA125 and HE4 ELISA assays as well as by the OLINK 96-plex PEA protein biomarker panel. CTCs at baseline and post-treatment were analyzed using the Veridex CellSearch System. Results: Target expression in tumor tissues for both NaPi2b and MUC16 measured by IHC and qRT-PCR are concordant. High NaPi2b or MUC16 expression (IHC 2+/3+) was identified in all responders by RECIST criteria (11 from DNIB0600A and 5 from DMUC5754A) for respective target, while no patient from either study with IHC 0 showed RECIST response. In patients treated with DNIB0600A, longitudinal changes in serum CA125 level correlated with RECIST response. Additionally, CTC was detected in 60% of patients at baseline in the DNIB0600A trial, and decreased CTC counts was observed after 1-2 cycles of treatment for two-third of patients. In patients treated with DMUC5754A, circulating CA125 (i.e. extra-cellular domain of MUC16 shed in circulation) is cleared after initial dosing; therefore other ovarian cancer biomarkers including HE4 were assessed. Baseline serum HE4 level correlates well with the tumor burden at pre-treatment in DMUC5754A trial, and showed excellent correlation with RECIST response post-treatment. Conclusions: Target expression in archival tumor tissues is predictive to clinical response to ADCs. CTC enumeration as well as serum HE4 could be used as potential surrogate biomarkers for monitoring treatment response in ovarian cancer. Further validation of these findings is required. Citation Format: Yulei Wang, Ron Firestein, Lisa Ryner, Walter Darbonne, Yinghui Guan, Shan Lu, YJ Choi, Yuanyuan Xiao, Paul Polakis, Becky Suttmann, Rupal Desai, Ling Fu, Ola Saad, Kirsten Achilles Poon, Mitch Denker, Vincent Leveque, Teiko Sumiyoshi, Mark Lackner, David Shames, Eric Humke, Daniel Mayslar. Biomarker evaluation of phase 1 clinical trials of antibody-drug conjugates (ADCs) in platinum resistant ovarian cancer [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-THER-1441.

Anti-NaPi2b antibody–drug conjugate lifastuzumab vedotin (DNIB0600A) compared with pegylated liposomal doxorubicin in patients with platinum-resistant ovarian cancer in a randomized, open-label, phase II study

Background Lifastuzumab vedotin (LIFA) is a humanized anti-NaPi2b monoclonal antibody conjugated to a potent antimitotic agent, monomethyl auristatin E, which inhibits cell division by blocking the polymerization of tubulin. This study is the first to compare an antibody-drug conjugate (ADC) to standard-of-care in ovarian cancer (OC) patients. Patients and methods Platinum-resistant OC patients were randomized to receive LIFA [2.4 mg/kg, intravenously, every 3 weeks (Q3W)] or pegylated liposomal doxorubicin (PLD) (40 mg/m2, intravenously, Q4W). NaPi2b expression and serum CA-125 and HE4 levels were assessed. The primary end point was progression-free survival (PFS) in intent-to-treat (ITT) and NaPi2b-high patients. Results Ninety-five patients were randomized (47 LIFA; 48 PLD). The stratified PFS hazard ratio was 0.78 [95% confidence interval (95% CI), 0.46-1.31; P = 0.34] with a median PFS of 5.3 versus 3.1 months (LIFA versus PLD arm, respectively) in the ITT population, and 0.71 (95% CI, 0.40-1.26; P = 0.24) with a median PFS of 5.3 months versus 3.4 months (LIFA versus PLD arm, respectively) in NaPi2b-high patients. The objective response rate was 34% (95% CI, 22% to 49%, LIFA) versus 15% (95% CI, 7% to 28%, PLD) in the ITT population (P = 0.03), and 36% (95% CI, 22% to 52%, LIFA) versus 14% (95% CI, 6% to 27%, PLD) in NaPi2b-high patients (P = 0.02). Toxicities included grade ≥3 adverse events (AEs) (46% LIFA; 51% PLD), serious AEs (30% both arms), and AEs leading to discontinuation of drug (9% LIFA; 8% PLD). Five (11%) LIFA versus 2 (4%) PLD patients had grade ≥2 neuropathy. Conclusion LIFA Q3W was well tolerated and improved objective response rate with a modest, nonstatistically significant improvement of PFS compared with PLD in platinum-resistant OC. While the response rate for the monomethyl auristatin E-containing ADC was promising, response durations were relatively short, thereby highlighting the importance of evaluating both response rates and duration of response when evaluating ADCs in OC. Clinical trials.gov NCT01991210.

High-Throughput and Sensitive Quantification of Circulating Tumor DNA by Microfluidic-Based Multiplex PCR and Next-Generation Sequencing

Circulating tumor DNA (ctDNA) has potential to serve as a biomarker for noninvasive monitoring of treatment response and disease progression. However, broad clinical applicability of ctDNA has been limited by the low sensitivity, throughput, and patient coverage offered by existing ctDNA detection methods. Herein, we report the adaptation and characterization of the microfluidics multiplex PCR sequencing technology for high-throughput and sensitive quantitation of ctDNA. A multiplex PCR preamplification step was developed and incorporated into the microfluidics multiplex PCR sequencing work flow to enable low-input ctDNA analysis with enhanced sensitivity. An empirical bayesian model was developed to characterize both position and substitution-associated system errors specific to this platform and provided a tailored approach to greatly enhance the confidence and accuracy of variant calling for ctDNA analysis. Clinical validation of this platform for ctDNA mutation detection demonstrated an overall sensitivity of 92% and specificity of 100% when using mutation calls in the matched tumor tissues as a benchmark. Finally, we established an early proof of concept of clinical utility of this ctDNA work flow for monitoring disease progression using clinical trial samples. Our novel ctDNA work flow provides a high-throughput and sensitive platform that can be implemented in clinical trials for mutation detection and disease monitoring from plasma ctDNA.

Development and Application of a Microfluidics-Based Panel in the Basal/Luminal Transcriptional Characterization of Archival Bladder Cancers.

In the age of personalized medicine stratifying tumors into molecularly defined subtypes associated with distinctive clinical behaviors and predictable responses to therapies holds tremendous value. Towards this end, we developed a custom microfluidics-based bladder cancer gene expression panel for characterization of archival clinical samples. In silico analysis indicated that the content of our panel was capable of accurately segregating bladder cancers from several public datasets into the clinically relevant basal and luminal subtypes. On a technical level, our bladder cancer panel yielded robust and reproducible results when analyzing formalin-fixed, paraffin-embedded (FFPE) tissues. We applied our panel in the analysis of a novel set of 204 FFPE samples that included non-muscle invasive bladder cancers (NMIBCs), muscle invasive disease (MIBCs), and bladder cancer metastases (METs). We found NMIBCs to be mostly luminal-like, MIBCs to include both luminal- and basal-like types, and METs to be predominantly of a basal-like transcriptional profile. Mutational analysis confirmed the expected enrichment of FGFR3 mutations in luminal samples, and, consistently, FGFR3 IHC showed high protein expression levels of the receptor in these tumors. Our bladder cancer panel enables basal/luminal characterization of FFPE tissues and with further development could be used for stratification of bladder cancer samples in the clinic.

196PPREVALENCE, PROGNOSTIC SIGNIFICANCE, AND OVERLAP OF ACTIONABLE BIOMARKERS IN NSCLC

ABSTRACT Aim: Novel molecularly targeted agents such as small molecule kinase inhibitors and antibodies targeted against immune check-point inhibitors have begun to erode the dominant position held by platinum-based chemotherapy in the treatment of NSCLC. While in some cases, activating kinase mutations appear to be mutually exclusive (EGFR and KRAS), there are many overlapping molecular subsets within NSCLC. As we continue to develop novel drugs, it is important that we develop a greater understanding of the prevalence, overlap, and prognostic significance of drug targets including activating mutations, signaling pathways, and tumor immune markers, as this will aid in trial design and predictive biomarker development for drug combinations or sequential treatment regimens. Methods: Seven biomarkers - TTF1, p63, EGFR mutation, KRAS mutation, MET immunohistochemistry [IHC], PDL1 IHC, NaPI2B IHC- across two sample sets (Set 1, n = 561; Set 2, n = 310) were tested. Set 1 contained surgically resected cases obtained at MD Anderson Cancer Center (MDA) during 2003-2005. Samples from Set 2 were part of a collaboration between the University of Colorado Cancer Center (UofC), USA and The Norwegian Radium Hospital, and contained surgically-resected NSCLC tissues collected from 2006–2011. Results: The prevalence, overlap, and prognostic significance of each biomarker were compared between the two cohorts. Most endpoints were consistent between the cohorts. However, significant differences in prevalence were observed within adenocarcinomas for MET (50% vs. 34%, MDA vs. UofC; p 67% of patients in both cohorts were positive for more than one biomarker and >33% were positive for at least three biomarkers. Correlations with patient characteristics and outcomes will be described in further detail. Conclusions: These data suggest that the biomarker landscape in NSCLC is complex with most patients having multiple targetable alterations. Thus, the treatment landscape for NSCLC will become increasingly complex as more experimental agents approach pivotal testing. Disclosure: D. Shames, M. Kowanetz, Y. Xiao, Y. Choi, H. Koeppen, R. Firestein, Y. Wang, S. Mocci, C. Bowden and L.C. Amler all declare that: I am an employee of Genentech Inc. I own stock in Roche Holdings. All other authors have declared no conflicts of interest.