Figure S1, Figure S2, Table S1, Table S2, Table S3, Table S4

We present a rigorous validation strategy to evaluate the performance of Ultivue multiplex immunofluorescence panels. We have quantified the accuracy and precision of four different multiplex panels (three human and one mouse) in tumor specimens with varying levels of T cell density. Our results show that Ultivue panels are typically accurate wherein the relative difference in cell proportion between a multiplex image and a 1-plex image is less than 20% for a given biomarker. Ultivue panels exhibited relatively high intra-run precision (CV ≤ 25%) and relatively low inter-run precision (CV >> 25%) which can be remedied by using local intensity thresholding to gate biomarker positivity. We also evaluated the reproducibility of cell–cell distance estimates measured from multiplex images which show high intra- and inter-run precision. We introduce a new metric, multiplex labeling efficiency, which can be used to benchmark the overall fidelity of the multiplex data across multiple batch runs. Taken together our results provide a comprehensive characterization of Ultivue panels and offer practical guidelines for analyzing multiplex images.

Cyclin-dependent kinase 4/6 inhibitor (CDK4/6) therapy plus endocrine therapy (ET) is an effective treatment for patients with hormone receptor-positive/human epidermal receptor 2-negative metastatic breast cancer (HR+/HER2− MBC); however, resistance is common and poorly understood. A comprehensive genomic and transcriptomic analysis of pretreatment and post-treatment tumors from patients receiving palbociclib plus ET was performed to delineate molecular mechanisms of drug resistance. Tissue was collected from 89 patients with HR+/HER2− MBC, including those with recurrent and/or metastatic disease, receiving palbociclib plus an aromatase inhibitor or fulvestrant at Samsung Medical Center and Seoul National University Hospital from 2017 to 2020. Tumor biopsy and blood samples obtained at pretreatment, on-treatment (6 weeks and/or 12 weeks), and post-progression underwent RNA sequencing and whole-exome sequencing. Cox regression analysis was performed to identify the clinical and genomic variables associated with progression-free survival. Novel markers associated with poor prognosis, including genomic scar features caused by homologous repair deficiency (HRD), estrogen response signatures, and four prognostic clusters with distinct molecular features were identified. Tumors with TP53 mutations co-occurring with a unique HRD-high cluster responded poorly to palbociclib plus ET. Comparisons of paired pre- and post-treatment samples revealed that tumors became enriched in APOBEC mutation signatures, and many switched to aggressive molecular subtypes with estrogen-independent characteristics. We identified frequent genomic alterations upon disease progression in RB1, ESR1, PTEN, and KMT2C. We identified novel molecular features associated with poor prognosis and molecular mechanisms that could be targeted to overcome resistance to CKD4/6 plus ET. ClinicalTrials.gov, NCT03401359. The trial was posted on 18 January 2018 and registered prospectively.

CDK4/6 inhibitors such as palbociclib in combination with endocrine therapy (ET) have remarkablyimproved the outcome of patients with ER+/HER2- metastatic breast cancer (MBC). However, manypatients are intrinsically resistant to CDK4/6i therapy, and those who respond eventually acquireresistance. Although high baseline CCNE1 expression and rare alterations in RB1 and FAT1 geneshave been shown to be associated with CDK4/6i resistance, the molecular mechanisms of CDK4/6iresistance are complex and remain poorly understood. To better understand and overcome CDK4/6iresistance, we performed multi-omics profiling of paired tumor biopsies from ER+/HER2- MBCpatients treated with palbociclib combined with ET. Tumor biopsies taken at pre-treatment, on-treatment, and progressive disease (PD) from 71 patients were profiled using whole-exomesequencing (WES), whole-transcriptome sequencing (RNA-Seq) and IHC analysis. Ourcomprehensive analysis identified several tumor intrinsic molecular markers associated with worsePFS, including the Luminal B subtype (p=0.012, HR=2.593), BRCA1/2 pathogenic mutation (p=0.012,HR=2.67) and mutation signatures linked to APOBEC enzymatic activity (p=0.002, HR=3.19).Conversely, the estrogen response signature (p=0.006, HR=0.43) was associated with favorableprognosis. Unsupervised analysis revealed a cluster of tumors enriched in homologousrecombination deficiency (HRD) linked genomic scars that was associated with poor prognosis(p=0.005, HR=2.49). Of note, these HRD-high tumors responded even more poorly to treatment whenco-occurring with TP53 somatic mutations. Integrative analysis further identified three poorprognosis clusters (IC2-4) enriched in Luminal B, proliferative and HRD features when compared tothe favorable prognosis cluster (IC1).Comparing baseline vs. PD samples, we observed a pattern of post-treatment enrichment for the poorprognosis markers. In addition, breast cancer-associated genes such as BRCA1/2, TP53 and PTENharbored a higher prevalence of genomic alterations including somatic mutation, amplification,. deletion and gene fusion at PD. Cell cycle gene expression and signatures also markedly increased atPD compared to baseline whereas estrogen response signatures decreased. Upon diseaseprogression, tumors had frequently switched to molecular subtypes with aggressive and estrogenindependent characteristics, demonstrating high plasticity in response to CDK4/6i and ET treatment.These patterns of acquired resistance were validated by IHC analysis of cyclins E1 and E2, Ki67 andpRb. To investigate the genomic alterations responsible for acquired resistance, we compared 21paired baseline and PD samples. We observed that PD-specific RB1 loss-of-function events occurredwith higher prevalence than previously reported, underscoring a major role of cell cycle de-regulation in conferring resistance to CDK4/6 inhibition. In this prospective longitudinal multi-omicsstudy, we identified novel candidate biomarkers that can be used to improve prediction of responseto CDK4/6i. In addition, we derived new insights into the molecular mechanisms of drug resistanceto palbociclib plus ET that will help guide therapeutic strategies and drug development inHR+/HER2− MBC. Citation Format: Zhengyan Kan, Seock-Ah Im, Kyunghee Park, Ji Wen, Kyung-Hun Lee, Yoon-La Choi, Won-Chul Lee, Ahrum Min, Vinicius Bonato, Seri Park, Sripad Ram, Dae-Won Lee, Ji-Yeon Kim, Su Kyeong Lee, Won-Woo Lee, Jisook Lee, Miso Kim, Scott L. Weinrich, Han Suk Ryu, Tae Yong Kim, Stephen Dann, Diane Fernandez, Jiwon Koh, Song Yi Park, Shibing Deng, Eric Powell, Rupesh Kanchi Ravi, Jadwiga Bienkowska, Paul A. Rejto, Woong-Yang Park, Yeon Hee Park. Serial genomic profiling reveals molecular mechanisms of breast cancer resistance to palbociclib [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD2-08.

BackgroundMultiplex immunofluorescence assays represent an essential tool in immuno-oncology research. The recent past has witnessed the introduction of several multiplexing methodologies to detect multiple biomarkers on a single tissue section. The quantitative assessment of the accuracy and precision of multiplex panels is of paramount importance for their widespread use in clinical samples. While there have been numerous reports providing qualitative characterization of multiplex panels, there is a paucity of data concerning the quantitative validation of these panels.MethodsUltivue Insituplex® T-act, PD-L1 and APC panels, which are 4-plex assays, were evaluated using breast tumor resections with varying levels of T-cell infiltration. For each panel, accuracy and precision was evaluated through a concordance and a reproducibility test, respectively. In the concordance test, five serial sections from each tumor specimen were cut and the 3rd (middle) serial section was immunolabeled with the 4-plex assay whereas the remaining sections were immunolabeled for the individual biomarkers (1-plex) that comprised the 4-plex assay. In the reproducibility test, five serial sections from each tumor specimen were immunolabeled with the 4-plex assay in separate, independent runs. The coefficient of variation (CV) of the density of different cell phenotypes was quantified from the serial sections and was used to assess the precision of that multiplex panel. All whole-slide image analysis was performed in QuPath software (version 0.2.3).ResultsThe results of the concordance test revealed that the relative difference in the single-biomarker cell density between 1-plex and 4-plex assays for the biomarkers in the 3 panels was typically less than 25%. Results of the precision test revealed that the CV for most cell phenotypes was typically less than 30%. We also identified special phenotypes such as CD3+PanCK+ cells and CD3+CD68+ cells, which exhibited unexpected combinations of biomarkers. Additional analysis revealed that these special phenotypes were in fact pairs of touching cells that were positive for the corresponding individual biomarkers (e.g., CD3+ cell touching a PanCK+ cell), and that this was due to limitations in the image analysis software package to segment the touching nuclei as two separate entities.ConclusionsOur results demonstrated that the Ultivue panels evaluated here had satisfactory accuracy and precision in breast tumor resections. The identification of special cell phenotypes in our data revealed the potential shortcomings of image analysis software and underscored the importance of performing a comprehensive evaluation of the multiplex assay as well as the image analysis workflow.Ethics ApprovalThe biospecimens used in the study were anonymized specimens which were collected with written patient consent, processed and distributed in full ethical and regulatory compliance with the Sites from which they were collected. This includes independent ethical review, Institutional Review Board approval (where appropriate), and independent regulatory review.

Immunohistochemistry (IHC) assays play a central role in evaluating biomarker expression in tissue sections for diagnostic and research applications. Manual scoring of IHC images, which is the current standard of practice, is known to have several shortcomings in terms of reproducibility and scalability to large scale studies. Here, by using a digital image analysis-based approach, we introduce a new metric called the pixelwise H-score (pix H-score) that quantifies biomarker expression from whole-slide scanned IHC images. The pix H-score is an unsupervised algorithm that only requires the specification of intensity thresholds for the biomarker and the nuclear-counterstain channels. We present the detailed implementation of the pix H-score in two different whole-slide image analysis software packages Visiopharm and HALO. We consider three biomarkers P-cadherin, PD-L1, and 5T4, and show how the pix H-score exhibits tight concordance to multiple orthogonal measurements of biomarker abundance such as the biomarker mRNA transcript and the pathologist H-score. We also compare the pix H-score to existing automated image analysis algorithms and demonstrate that the pix H-score provides either comparable or significantly better performance over these methodologies. We also present results of an empirical resampling approach to assess the performance of the pix H-score in estimating biomarker abundance from select regions within the tumor tissue relative to the whole tumor resection. We anticipate that the new metric will be broadly applicable to quantify biomarker expression from a wide variety of IHC images. Moreover, these results underscore the benefit of digital image analysis-based approaches which offer an objective, reproducible, and highly scalable strategy to quantitatively analyze IHC images.

Abstract Purpose: We investigated safety, tolerability, pharmacokinetics, and antitumor activity of the protein tyrosine kinase 7 (PTK7)-targeted, auristatin-based antibody–drug conjugate (ADC) PF-06647020/cofetuzumab pelidotin (NCT02222922). Patients and Methods: Patients received PF-06647020 intravenously every 3 weeks at 0.2–3.7 mg/kg or every 2 weeks at 2.1–3.2 mg/kg, in sequential dose escalation, following a modified toxicity probability interval method. In dose expansion, pretreated patients with advanced, platinum-resistant ovarian cancer, non–small cell lung cancer (NSCLC), or triple-negative breast cancer (TNBC) received PF-06647020 2.8 mg/kg every 3 weeks. Results: The most common, treatment-related adverse events for PF-06647020 administered every 3 weeks were nausea, alopecia, fatigue, headache, neutropenia, and vomiting (45%–25%); 25% of patients had grade ≥ 3 neutropenia. Two patients experienced dose-limiting toxicities (grade 3 headache and fatigue) at the highest every 3 weeks dose evaluated. The recommended phase II dose was 2.8 mg/kg every 3 weeks. The overall safety profile observed with PF-06647020 administered every 2 weeks was similar to that of the every 3 weeks regimen. Systemic exposure for the ADC and total antibody generally increased in a dose-proportional manner. Antitumor activity was observed in treated patients with overall objective response rates of 27% in ovarian cancer (n = 63), 19% in NSCLC (n = 31), and 21% in TNBC (n = 29). Responders tended to have moderate or high PTK7 tumor expression by IHC. Conclusions: This PTK7-targeted ADC demonstrated therapeutic activity in previously treated patients with ovarian cancer, NSCLC, and TNBC at a dose range of 2.1–3.2 mg/kg, supporting further clinical evaluation to refine dose, schedule, and predictive tissue biomarker testing in patients with advanced malignancies.

To elucidate the effects of neoadjuvant chemotherapy (NAC), we conduct whole transcriptome profiling coupled with histopathology analyses of a longitudinal breast cancer cohort of 146 patients including 110 pairs of serial tumor biopsies collected before treatment, after the first cycle of treatment and at the time of surgery. Here, we show that cytotoxic chemotherapies induce dynamic changes in the tumor immune microenvironment that vary by subtype and pathologic response. Just one cycle of treatment induces an immune stimulatory microenvironment harboring more tumor infiltrating lymphocytes (TILs) and up-regulation of inflammatory signatures predictive of response to anti-PD1 therapies while residual tumors are immune suppressed at end-of-treatment compared to the baseline. Increases in TILs and CD8+ T cell proportions in response to NAC are independently associated with pathologic complete response. Further, on-treatment immune response is more predictive of treatment outcome than immune features in paired baseline samples although these are strongly correlated.

Background: PF-06647020, an ADC comprising a humanized monoclonal antibody against PTK7, a cleavable valine-citrulline linker, and an auristatin payload, is being investigated in an ongoing Phase I clinical trial in pts with advanced solid tumors. We hypothesized that response to a PTK7-directed ADC would correlate with PTK7 expression in the pts tumor. We report preliminary baseline PTK7 expression in pts tumors and clinical response using a novel CLIA validated laboratory developed test (LDT). Methods: We developed and validated an LDT comprising an anti-PTK7 immunohistochemistry assay with digital tissue analysis using Flagship Biosciences Inc’s cTA® platform to detect membrane-associated PTK7 in formalin-fixed paraffin embedded (FFPE) epithelial malignancies of ovary, breast and lung. Tumor samples were immunolabeled with the LDT and image analysis was applied to derive a digital H-score. Specifically the digital image annotation included desired regions of analysis (ROA) and excluded regions not of interest. The cTA® platform identified each cell in a given ROA and quantified an overall H-score for malignant epithelial cell membranes immunolabeled for PTK7. Non-small cell lung cancer (NSCLC) pts with H-scores ≥ 56.8 were eligible for enrollment whereas ovarian cancer (OVCA) pts were enrolled unselected. Triple negative breast cancer (TNBC) pts were initially enrolled unselected, but after review a requirement for H-scores ≥ 92.8 was implemented for enrollment. Results: PTK7 IHC was performed on baseline FFPE samples from 69 pts and digital H-scores were generated (Table 1). An additional 7 pt samples were not amenable to analysis with the cTA® platform. Conclusions: A novel CLIA validated LDT was developed and implemented to assess PTK7 baseline levels in FFPE tumors from pts treated with PF-06647020. Clinical responses tended to correlate with H-scores that were higher than the mean for each tumor type. Table 1.PTK7 digital H-scores in Phase I dose expansionNumber of SamplesMinimum H-scoreMaximum H-scoreMean H-scoreMean H-score of Non-respondersMean H-score of RespondersOVCA31120089.280.2111.2NSCLC1993287167.8159.2200.3TNBC1953258159.2147.0224.3 Citation Format: Amy Jackson-Fisher, Navi Mehra, Roberto Gianani, Pamela Whalen, Pamela Vizcarra, Shibing Deng, Stephen McComish, Xiaohua Xin, Eric L. Powell. Protein tyrosine kinase 7 (PTK7) biomarker analysis in patients (pts) treated with PF-06647020, a PTK7 antibody-drug conjugate (ADC), in a phase I dose expansion study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4035.

The molecular bases underlying neoadjuvant chemotherapy (NAC) response are poorly understood. To elucidate the effects of NAC on breast tumor biology and its association with clinical outcome, we have conducted WES and RNA-Seq profiling of a longitudinal breast cancer (BC) cohort consisting of 146 cases (281 tumors, 109 pairs), including 55 (38%) that achieved pathologic complete responses (pCR) and 91 (62%) that harbored residual diseases at time of surgery. Tumor biopsies were collected for each patient at three time points - pre-treatment, three weeks after the first cycle of anthracycline and cyclophosphamide (AC) and at the time of surgery, after 3 more cycles of AC followed by 4 cycles of taxane. In addition to somatic mutations and copy number alterations, we also derived a comprehensive set of genomic and molecular features for each tumor including chromosomal instability, loss-of-heterozygosity, mutation burden, mutation signatures and expression signatures for oncogenic signaling pathways and immune cell subsets. Virtual microdissection analysis inferred 14 factors that represent distinct tissue compartment including a tumor infiltrating lymphocyte (TIL) factor and revealed that initial NAC treatment increased stromal and adjacent normal tissue fractions while reducing tumor cellularity. NAC also induced dynamic changes in immune gene expressions over time, a pattern that was validated through detecting and quantifying the density of TILs from H&E images. To investigate NAC induced changes in tumor intrinsic biology we classified tumors into five oncogenic cellular states on a reference Onco-GPS map defined by transcriptional signatures from breast cancer cell lines. We observed that, as a result of NAC treatment, tumors often change from one oncogenic state to another, transiently upregulating an EMT program that appears to mediate drug resistance and increase the likelihood of residual disease. Multiple regression and multivariate analyses were performed to identify predictive biomarkers of pCR status while adjusting for BC subtypes and tumor purity. We found that ER+ subtype and estrogen response signature but not Ki-67 were independently associated with NAC response. Within TNBC, the immunomodulatory subtype was enriched in responders while the basal-like subtype had the poorest response. Pretreatment TIL and changes in TIL level over time were independently associated with NAC response, implicating anti-tumor immunity in mediating the efficacy of chemotherapies. Through multi-omics characterization of longitudinally paired tumor biopsies, we have revealed dynamic changes in the tumor molecular states in BC patients undergoing NAC treatment, identified molecular markers of treatment outcome and derived insights into the mechanism of action as well as resistance to an important class of therapy.Citation Format: Samir Lal, Ying Ding, Jeong Eon Lee, Soo-Hyeon Lee, Se Kyung Lee, Jae-Yong Nam, Jong Han Yu, Yoon-la Choi, Seok Won Kim, Seok Jin Nam, Ji-Yeon Kim, Sripad Ram, Eric Powell, Keith A. Ching, Pablo Tamayo, William Kim, Huwate Yeerna, Soo Youn Cho, Vinicius Bonato, Shibing Deng, Jinho Kim, Hyuntae Shin, Woong-Yang Park, Paul A. Rejto, Jadwiga Bienkowska, Yeon-Hee Park, Zhengyan Kan. Multi-omics profiling of breast cancers during neoadjuvant chemotherapy identified distinct molecular changes and biomarkers associated with clinical response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1684.

An immunohistochemistry (IHC) assay was developed to detect protein tyrosine kinase 7 (PTK7) membrane staining in formalin-fixed paraffin embedded (FFPE) human tumors with the intention of selecting non-small cell lung carcinoma (NSCLC) patients, breast cancer (BrCa) patients, or ovarian cancer (OVCA) patients for enrollment in an early stage clinical trial for a PTK7-ADC (antibody drug conjugate) experimental therapeutic. The IHC assay was developed using an anti-PTK7 specific antibody and a panel of five cancer cell lines with a range of constitutive PTK7 expression as characterized by gene transcript and protein based assays. PTK7 messenger RNA (mRNA) and protein levels were highly correlative in the control cell lines in vitro and the corresponding cell line xenografts. A pre-analytic variables study (PAV) using these characterized control cell line xenografts demonstrated that the PTK7 IHC assay was robust to the pre-analytic variables of under-fixation and ischemia. This IHC assay was used to profile PTK7 levels in human lung cancers, breast cancers, and ovarian cancers, and a dynamic range of PTK7 H-scores was detected (see Table 1). The resulting PTK7 H-scores correlated with orthogonal methods for measuring PTK7 protein and gene transcript levels in the human tumors. Table 1.PTK7 H-scoresNumber of SamplesMinimum H-scoreMaximum H-scoreMean H-scoreMedian H-scoreNSCLC3034230117.4117OvCa2424240151151 Citation Format: Pamela M. Whalen, Amy Jackson-Fisher, Pamela Vizcarra, Cory Painter, Steven Pirie-Shepherd, Diane R. Fernandez, Joseph Lee, Eric L. Powell. Development of a novel PTK7 immunohistochemistry (IHC) assay and analytical validation in epithelial malignancies of lung, breast and ovary [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4925.

5565 Background: PF-7020 is an ADC comprising of a humanized monoclonal antibody against PTK7, a cleavable valine-citrulline linker and auristatin payload that is being investigated in an ongoing Phase I clinical trial in pts with advanced solid tumors resistant to standard of care (SoC). Here we report safety results and clinical activity of PF-7020. Methods: Eligible patients received PF-7020 intravenously once every three weeks (Q3W) in doses ranging from 0.2 - 3.7 mg/kg (mpk) in sequential dose escalation cohorts. Dose limiting toxicity (DLT) evaluation period was 21 days (cycle 1). Dose expansion cohorts of pts with advanced ovarian cancer (OVCA), non-small cell lung cancer (NSCLC), and triple negative breast cancer (TNBC) were treated with PF-7020 at recommended phase 2 dose (RP2D). PTK7 expression was assessed by immunohistochemistry. Adverse events (AEs) were assessed by CTCAE v4.03 and best objective response per RECIST v1.1. Results: As of 24 OCT 2017, 112 pts were treated with PF-7020 in dose escalation and expansion cohorts. The pharmacokinetic exposure of PF-7020 increased in a dose related manner, with a terminal half-life of 3 days at 2.8 mpk. 2 DLTs (Grade (Gr) 3 headache, Gr3 fatigue) were observed in the 3.7 mpk cohort, and a RP2D of 2.8 mpk was established. Toxicities were manageable, most AEs limited to Gr1 or 2 (no Gr5). Common treatment-related AEs were nausea, alopecia, fatigue, headache, neutropenia, and vomiting. Antitumor activity irrespective of PTK7 expression is summarized below and further enriched in PTK7 medium/high pts (not shown). Conclusions: Promising antitumor activity and manageable safety profile of PF-7020 were observed in pts with advanced OVCA, NSCLC and TNBC resistant to SoC. Further investigation of PF-7020 is ongoing. Clinical trial information: NCT02222922.Tumor Median Prior Lines Therapy Total Pts Pts by Dose (mpk) ORR (%) (CR/PR) DCR (%) mDOR (mo) (min - max) mPFS (mo) 95% CI 1.25 2.1 2.8 3.7 OVCA 5 44 0 1 42 1 27 (2/10) 73 4.6 (1.7 – 16.2) 2.9 (2.3; 5.6) NSCLC 3 25 2 1 22 0 16 (0/4) 56 5.8 (2.8 – 10.1) 2.9 (1.4; 6.1) TNBC 4 29 0 2 27 0 21 (0/6) 48 3.6 (1.1– 10.4) 1.7 (1.4; 4.3) DCR = disease control rate; mDOR = median duration of response

The fetal oncogene 5T4 is a cell surface protein, with overexpression observed in a variety of cancers as compared to normal adult tissue. The ability to select patients with tumors that express high levels of 5T4 may enrich a clinical trial cohort with patients most likely to respond to 5T4 targeted therapy. To that end, we developed assays to measure 5T4 in both tumors and in circulating tumor cells (CTCs). We identified the presence of 5T4 in both adenocarcinoma and squamous cell carcinoma of lung, in all clinical stages and grades of disease. CTCs were identified in peripheral blood from the majority of patients with NSCLC, and 5T4 was detectable in most samples. Although 5T4 was present in both CTCs and tumors in most patients, there was no concordance between relative amount in either sample type. Clinical response rates of patients treated with the therapies directed against 5T4 in early stage clinical trials, as determined by these assays, may provide important insights into the biology of 5T4 in tumors and the mechanisms of action of 5T4-targeting therapy.

Breast cancers (BC) in younger, premenopausal patients (YBC) tend to be more aggressive with worse prognosis, higher chance of relapse and poorer response to endocrine therapies compared to breast cancers in older patients (OBC). The proportion of YBC (age ? 40) among BC in East Asia is estimated to be 16-32%, significantly higher than the 7% reported in Western countries. Genomic and molecular characterizations have deepened our understanding of breast cancer biology in areas ranging from intrinsic subtypes to treatment responses, however, the molecular bases of Asian YBC remains poorly characterized. We have performed whole-exome sequencing (WES), whole-transcriptome sequencing (WTS) and high coverage targeted sequencing on tumor and matched normal samples from 133 Korean BC patients consisting of 74 YBC cases (age ? 40). We further performed immunohistochemistry (IHC) analyses to characterize tumor-infiltrating lymphocytes (TILs) in 46 tumors using four markers (CD45, CD4, CD8 and CD163). We found that BRCA1/2 germline deleterious mutations are enriched in YBC and the ER+/HER2- subtype, indicating that Asian ER+ YBC has a significant germline contribution. MutSig analysis4 identified ARID1A as a significantly mutated gene, implicating chromatin modeling as a cancer driver in Asian BC. Differential expression analyses suggested that Asian YBC differ in energy metabolism and are more active in protein synthesis than OBC tumors, whereas OBC is more proliferative than YBC. Using gene expression signatures representing distinct immune cell types and immunohistochemistry, we classified our cohort into four subtypes of varying TIL activities: high, medium, low and quiet. The majority of immunogenic cases with high TIL levels lie in ER+ or HER2+ subtypes although higher proportion is seen in TNBC. Moreover, YBC tumors appear to harbor lower levels of TIL activities than OBC, suggesting that younger patients may be less likely to benefit from immunomodulatory therapies than older patients. To our knowledge, this is the first large-scale multi-omics study of Asian breast cancer and would significantly contribute to the compendium of molecular data available for young, premenopausal breast cancer. While the major landmarks in the molecular and immune landscape of Asian BC look similar to that of the predominantly Caucasian BC cohorts, we have identified a number of distinguishing characteristics pointing to distinctive oncogenic mechanisms underlying Asian BC. Citation Format: Yeon Hee Park, Ying Ding, Soonweng Cho, Soo-Hyeon Lee, Hae Hyun Jung, Woosung Chung, Jinho Kim, Woong-Yang Park, Eric Powell, Pamela Vizcarra, Shibing Deng, Se Kyung Lee, Seok Won Kim, Jeong Eon Lee, Ji-Yeon Kim, Jin Seok Ahn, Young-Hyuck Im, Seok Jin Nam, Zhengyan Kan. Multi-omics and immuno-oncology profiling of an Asian breast cancer cohort enriched in young and premenopausal patients. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-325.

Disease relapse after treatment is common in triple-negative breast cancer (TNBC), ovarian cancer and non-small cell lung cancer (NSCLC). Therapies that target tumor-initiating cells (TICs) should improve patient survival by eliminating the cells that can drive tumor regrowth and metastasis. Here we identify Protein Tyrosine Kinase 7 (PTK7), a highly conserved but catalytically inactive receptor tyrosine kinase, as an antigen that is enriched on TICs in low-passage patient-derived xenografts (PDX) of TNBC, NSCLC and other tumor types. An anti-PTK7 antibody-drug conjugate (ADC) was generated from a humanized anti-PTK7 monoclonal antibody, a cleavable valine-citrulline-based linker and the Aur0101 auristatin microtubule inhibitor. The anti-PTK7 ADC induced sustained regressions of TNBC, NSCLC and ovarian cancer PDX, with improved activity over standard-of-care chemotherapy, and reduced the frequency of TICs as determined by serial transplantation experiments. Moreover, the ADC may have additional mechanisms of action, including an anti-angiogenic effect, that promote anti-tumor immune responses. Together these preclinical results indicate the potential of the anti-PTK7 ADC to improve the long-term survival of cancer patients. The ADC is currently being tested in a Phase 1 clinical trial, from which interim results will be presented. Citation Format: Marc Isaac Damelin, Alex Bankovich, Jeff Bernstein, Justin Lucas, Liang Chen, Sam Williams, Albert Park, Jorge Aguilar, Elana Ernstoff, Manoj Charati, Russell Dushin, Amy Jackson-Fisher, Monette Aujay, Christina Lee, Hanna Ramoth, Milly Milton, Johannes Hampl, Sasha Lazetic, Virginia Pulito, Douglas Armellino, Edward Rosfjord, Magali Guffroy, Hadi Falahatpisheh, Lindsay King, Frank Barletta, Robert Stull, Marybeth Pysz, Paul Escarpe, David Liu, Orit Foord, Brenda Gibson, Eric Powell, Christopher O’Donnell, Xiaohua Xin, Hans Peter Gerber, Puja Sapra, Scott Dylla. A novel PTK7-targeted antibody-drug conjugate eliminates tumor-initiating cells and induces sustained tumor regressions. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1220.

Abstract The fetal oncogene 5T4 is a cell surface protein, with over-expression observed in a variety of cancers as compared to normal adult tissue. Recent studies have shown that expression of 5T4 appears to be associated with the undifferentiated state and the epithelial-mesenchymal transition (EMT), and thus has been associated with a more invasive phenotype. We have developed assays to measure the expression of the fetal oncogene, 5T4, in both the primary tumor compartment and in the circulating tumor cell compartment. These assays were then used to investigate 5T4 expression in a small cohort of patients with NSCLC. We obtained matched primary tumor and blood samples, with the blood being obtained prior to resection of the primary tumor. The expression of 5T4 was found to be robust and measurable in both the primary and circulating tumor compartments. We observed expression of 5T4 in both adenocarcinoma and squamous cell carcinoma, in all stages and grades of tumor, with no specific correlation between expression and stage, grade or pathology. We further observed robust enumeration of CTCs in NSCLC samples. The expression of 5T4 was heterogeneous in the CTC compartment with no correlation to grade, stage or pathology. Finally, we observed no concordance between 5T4 expression in the primary tumor and the circulating tumor cell compartment. We discuss the current utility of target expression in predicting response to targeted therapy in the context of antibody based therapy, and the role that CTCs may have in the clinic. Citation Format: Steven R. Pirie-Shepherd, Shibing Deng, Jonathon Golas, Pamela Vizcarra, Eric Tucker, Dena Marrinuci, Hans-Peter Gerber, Eric L. Powell. The expression of fetal oncogene 5T4 in CTCs obtained from NSCLC patients is discordant with the expression measured in the primary tumor. [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 564. doi:10.1158/1538-7445.AM2015-564

Clinical development of cancer therapies is associated with attrition rates as high as 80-95%. This high attrition suggests that standard preclinical pharmacology models do not accurately reflect clinical responses. The development of more predictive preclinical models requires several considerations; the relevance of the in vivo model, the administration of test agent, and the interpretation of efficacy data. PDX are cancer models developed from the direct transfer of patient tumor tissue into immunocompromised mice. A collection of PDX models, by retaining the genetic and histologic characteristics of the patients from which they were derived, represents the complexity and heterogeneity of human cancer. To minimize the clinical attrition rates of oncology compounds, we are developing hundreds of PDX models in seven major cancer indications. The collection is being molecularly profiled by RNAseq, WES, and proteomics. Profiling has identified models with robust expression of target proteins or mutant oncogenes that are likely to respond in preclinical efficacy tests. Conversely, the PDX models may provide an understanding of resistance, for example evaluating models with good target expression that fail to respond to therapy. Patient and tumor information, if known, has been collected for each PDX model including age, sex, cancer stage and grade, diagnosis, primary or metastatic site, and prior treatments. In addition to the improvements provided by the PDX models, a preclinical paradigm shift away from treatment with maximally tolerated dose towards clinically relevant dose (CRD), taking into consideration such aspects as exposure, formulation, route and schedule, is critical when attempting to predict clinical outcome from preclinical data. Also essential is the incorporation of clinically meaningful endpoints (regression) when assessing preclinical activity. We have initiated studies on cohorts of non small cell lung and breast PDX models to predict the likely clinical efficacy of candidate compounds for clinical development and to determine the CRD for standard of care (SOC) regimens required to define the most promising Phase II/III combination therapies. Anti-tumor activities were characterized using RECIST criteria of progressive disease (PD), stable disease (SD), partial response (PR), and complete response (CR). Target expression was evaluated by RNA, proteomics and immunohistochemistry. Preliminary results demonstrate a spectrum of responses against experimental therapeutics, including Phase I ADCs and are defining the CRD required for combination treatments with SOC. Identification of the most critical parameters of PDX models predicting clinical outcome will help in validating the utility of ‘n of 1′ studies with the PDX collection, inform patient enrollment strategies, guide combination therapies, and provide insight for identifying new tumor indications. Citation Format: Edward Rosfjord, Xin Han, Danielle Leahy, Erik Upeslacis, Justin Lucas, Jonathon Golas, Andrea Hooper, Fred Immermann, Bingwen Lu, Jeremy Myers, Zhengyan Kan, James Hardwick, Eric Powell, Puja Sapra, Paul Rejto, Hans-Peter Gerber, Judy Lucas. Patient derived xenograft (PDX) models: improving predictability of experimental cancer therapies. [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 1469. doi:10.1158/1538-7445.AM2015-1469