Citations

AbstractHomologous recombination (HR) DNA repair‐deficient (HRD) breast cancers have been shown to be sensitive to DNA repair targeted therapies. Burgeoning evidence suggests that sporadic breast cancers, lacking germline BRCA1/BRCA2 mutations, may also be HRD. We developed a functional ex vivo RAD51‐based test to identify HRD primary breast cancers. An integrated approach examining methylation, gene expression, and whole‐exome sequencing was employed to ascertain the aetiology of HRD. Functional HRD breast cancers displayed genomic features of lack of competent HR, including large‐scale state transitions and specific mutational signatures. Somatic and/or germline genetic alterations resulting in bi‐allelic loss‐of‐function of HR genes underpinned functional HRD in 89% of cases, and were observed in only one of the 15 HR‐proficient samples tested. These findings indicate the importance of a comprehensive genetic assessment of bi‐allelic alterations in the HR pathway to deliver a precision medicine‐based approach to select patients for therapies targeting tumour‐specific DNA repair defects. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

248 Background: Improved understanding of TME in CCA may allow for development of novel therapeutics targeting stromal components. Hyaluronic acid (HA) is a polysaccharide that has been found in the TME of a number of solid tumors characterized by desmoplastic stroma, such as pancreatic cancer. Elevated HA levels were prognostic in these malignancies. HA prevalence and association with clinic-pathological features in CCA is unknown. Methods: A retrospective study was conducted using clinically annotated formalin-fixed paraffin embedded tissue from resected intrahepatic CCA samples. Specimens were analyzed for HA, scored using a positive pixel count algorithm (Aperio Imagescope) and positivity was calculated as % of total pixel count. Clinical variables were examined by chi-square or ANOVA F-test. Overall survival (OS) and progression-free survival (PFS) were estimated using Kaplan-Meier method and compared via log-rank test. Multivariate analysis was conducted using Cox proportional hazards regression models. Results: 142 patient samples were stained for HA. HA was identified in all samples (100%), with a range of HA positivity of 32.8 – 91.8%. Median HA value was 67.1% and 95% of patients had HA positivity ≥ 45%. Factors associated with higher than median HA ( > 67%) included perineural invasion (PNI) (40% vs. 21%, p = 0.011), necrosis (67% vs. 41%, p = 0.003), lymph node positivity (32% vs. 14%, p = 0.027), and small tumor size ( < 6.8 cm vs. > 8.4cm, p = 0.014). Stratification of HA staining by median positivity value was not an independent predictor of survival based on multivariate analysis. OS for patients with HA > 67% was 40.1 months (mo) vs 48.5 mo with HA ≤ 67%, p = 0.537. PFS for patients with HA > 67% was 14.4 mo vs. 25.7 mo with HA ≤ 67%, p = 0.177. Conclusions: Prevalence of HA staining in resected CCA is higher than seen in many solid tumors and is ubiquitous in our study. Absence of statistically significant association with OS and PFS might be attributable to ubiquitous prevalence, narrow signal range, and association with known negative prognostic factors. Further pre-clinical and clinical evaluation would be warranted.

249 Background: HA, a glycosaminoglycan in the tumor matrix, accumulates in 20-30% of solid tumors and ≥28%, ≥42% and ≥87% of colon, gastric and pancreatic ductal adenocarcinoma (PDA) tumors, respectively. Tumors that accumulate HA can develop high interstitial fluid pressure (IFP) and are resistant to chemotherapy. HA in human PDA is associated with disease progression and poor prognosis. In animal models, PEGPH20 reduced tumor-associated HA, tumor IFP and tumor growth, and increased efficacy of chemotherapy. Pharmacodynamic (PD) activity of PEGPH20 is being evaluated in Phase 1 (Ph1) trials. Methods: Two Ph1 studies in pts with advanced solid tumors refractory to prior therapy examined the safety, tolerability, PK, PD and MTD of single-agent IV PEGPH20. Dosing in Study 1 was 2x/wk and then reduced to q21d and in Study 2 is 1-2x/wk x 4wks and 1x/wk thereafter with dexamethasone pre-medication regimen. Biomarkers evaluated: Histochemistry to detect depletion of tumor HA, serum HA catabolites, Dynamic Contrast Enhanced (DCE)-MRI and FDG-PET. Results: In Study 1, the first 3 pts demonstrated musculoskeletal events (MSE; 2 pts dosed with 50 µg/kg 2x/wk, severe; 1 pt dosed with 0.5µg/kg 2x/wk, moderate) not predicted from GLP safety studies. The frequency of drug administration was reduced to q21d and the next 10 pts tolerated ≤1.5 µg/kg. In Study 2, dexamethasone pre-medication regimen was evaluated while dosing at 1-2x/wk. Nine pts were dosed ≤5.0 µg/kg. Doses ≤3.0 µg/kg administered 2x/wk were tolerated with intermittent Grade 1-2 MSE. Activity of PEGPH20 was reflected by increased HA serum catabolites. Pre- and post-dose biopsies from 2 colon pts demonstrated a 23-60% reduction in tumor HA after 4 wks of PEGPH20 dosing. DCE-MRI of PDA and FDG-PET of lung metastases increased tumor perfusion (Ktrans) and decreased metabolic activity 8 and 24hrs post-PEGPH20 dose and was still apparent after 4 wks of treatment with PEGPH20. Conclusions: Ongoing Ph1 studies have shown in vivo activity of PEGPH20 through HA plasma catabolites, tumor HA depletion, DCE-MRI and FDG-PET.