Carrie Baker Brachmann

SPARC Expression Did Not Predict Efficacy of nab-Paclitaxel plus Gemcitabine or Gemcitabine Alone for Metastatic Pancreatic Cancer in an Exploratory Analysis of the Phase III MPACT Trial

Purpose: nab-Paclitaxel plus gemcitabine was superior to gemcitabine alone for patients with metastatic pancreatic cancer (MPC) in the phase III MPACT trial. This study evaluated the association of secreted protein acidic and rich in cysteine (SPARC) levels with efficacy as an exploratory endpoint. Experimental Design: Patients with previously untreated MPC (N = 861) received nab-paclitaxel plus gemcitabine or gemcitabine alone. Baseline SPARC level was measured in the tumor stroma and epithelia (archival biopsies) and plasma. Experiments were performed in pancreatic cancer mouse models in which SPARC was intact or deleted. Results: SPARC was measured in the tumor stroma of 256 patients (30%), the tumor epithelia of 301 patients (35%), and plasma of 343 patients (40%). Stroma-evaluable samples were from metastases (71%), from the pancreas (11%), or of unidentifiable origin (insufficient tissue to determine; 17%). For all patients, stromal SPARC level [high (n = 71) vs. low (n = 185)] was not associated with overall survival (OS; HR, 1.019; P = 0.903); multivariate analysis confirmed this lack of association. There was no association between stromal SPARC level and OS in either treatment arm. Neither tumor epithelial SPARC nor plasma SPARC was associated with OS. Results from a SPARC knockout mouse model treated with nab-paclitaxel plus gemcitabine revealed no correlation between SPARC expression and tumor progression or treatment efficacy. Conclusions: SPARC levels were not associated with efficacy in patients with MPC. This exploratory analysis does not support making treatment decisions regarding nab-paclitaxel plus gemcitabine or gemcitabine alone in MPC based on SPARC expression. Clin Cancer Res; 21(21); 4811–8. ©2015 AACR.

Albumin-bound nanoparticle (nab) paclitaxel exhibits enhanced paclitaxel tissue distribution and tumor penetration

Purposenab-paclitaxel demonstrates improved clinical efficacy compared with conventional Cremophor EL (CrEL)-paclitaxel in multiple tumor types. This study explored the distinctions in drug distribution between nab-paclitaxel and CrEL-paclitaxel and the underlying mechanisms.MethodsUptake and transcytosis of paclitaxel were analyzed by vascular permeability assay across human endothelial cell monolayers. The tissue penetration of paclitaxel within tumors was evaluated by local injections into tumor xenografts and quantitative image analysis. The distribution profile of paclitaxel in solid-tumor patients was assessed using pharmacokinetic modeling and simulation.ResultsLive imaging demonstrated that albumin and paclitaxel were present in punctae in endothelial cells and could be observed in very close proximity, suggesting cotransport. Uptake and transport of albumin, nab-paclitaxel and paclitaxel were inhibited by clinically relevant CrEL concentrations. Further, nab-paclitaxel causes greater mitotic arrest in wider area within xenografted tumors than CrEL- or dimethyl sulfoxide-paclitaxel following local microinjection, demonstrating enhanced paclitaxel penetration and uptake by albumin within tumors. Modeling of paclitaxel distribution in patients with solid tumors indicated that nab-paclitaxel is more dependent upon transporter-mediated pathways for drug distribution into tissues than CrEL-paclitaxel. The percent dose delivered to tissue via transporter-mediated pathways is predicted to be constant with nab-paclitaxel but decrease with increasing CrEL-paclitaxel dose.ConclusionsCompared with CrEL-paclitaxel, nab-paclitaxel demonstrated more efficient transport across endothelial cells, greater penetration and cytotoxic induction in xenograft tumors, and enhanced extravascular distribution in patients that are attributed to carrier-mediated transport. These observations are consistent with the distinct clinical efficacy and toxicity profile of nab-paclitaxel.

Andecaliximab/GS-5745 Alone and Combined with mFOLFOX6 in Advanced Gastric and Gastroesophageal Junction Adenocarcinoma: Results from a Phase I Study

Purpose: Matrix metalloproteinase-9 (MMP9) is implicated in protumorigenic processes. Andecaliximab (GS-5745, a monoclonal antibody targeting MMP9) was evaluated as monotherapy and in combination with mFOLFOX6. Patients and Methods: Three dosages of andecaliximab monotherapy [200, 600, and 1800 mg i.v. every 2 weeks (q2w)] were investigated in patients with advanced solid tumors (n = 13 in a 3+3 design). After determining a recommended dose, patients with advanced HER2-negative gastric/gastroesophageal junction (GEJ) adenocarcinoma (n = 40) received 800 mg andecaliximab + mFOLFOX6 q2w. Pharmacokinetics, pharmacodynamics, safety, and efficacy were assessed. Results: Andecaliximab monotherapy demonstrated no dose-limiting toxicity (DLT) in any cohort, displaying target-mediated drug disposition at the lowest dose (200 mg) and linear pharmacokinetics at higher doses. Based on target engagement, recommended doses for further study are 800 mg q2w or 1,200 mg q3w. Maximal andecaliximab target binding, defined as undetectable andecaliximab-free MMP9 in plasma, was observed in the gastric/GEJ adenocarcinoma cohort. We observed no unusual toxicity, although there were four deaths on study not attributed to andecaliximab treatment. In first-line patients (n = 36), median progression-free survival (PFS) was 9.9 months [95% confidence interval (CI), 5–13.9 months], and the overall response rate (ORR) was 50%. Among all patients (n = 40), median PFS was 7.8 (90% CI, 5.5–13.9) months, and ORR was 48%, with a median duration of response of 8.4 months. Conclusions: Andecaliximab monotherapy achieved target engagement without DLT. Andecaliximab + mFOLFOX6 showed encouraging clinical activity without additional toxicity in patients with HER2-negative gastric/GEJ adenocarcinoma. A phase III study evaluating mFOLFOX6 ± andecaliximab in this setting is ongoing. Clin Cancer Res; 24(16); 3829–37. ©2018 AACR.

Abstract 4663: Exploratory serum biomarker analysis in gastric cancer patients treated with GS-5745, an MMP9 Inhibitor, in combination with mFOLFOX6

In the tumor microenvironment, matrix metalloproteinase 9 (MMP9) cleaves and activates substrates such as VEGF, IL8 and TGFβ that promote tumor growth through angiogenesis and immune suppression. Data from preclinical models supports the hypothesis that inhibition of MMP9 reduces local immune suppression, resulting in increased anti-tumor immunity. GS-5745 is a monoclonal antibody in clinical development that is a selective inhibitor of MMP9. The effect of GS-5745 + mFOLFOX6 (GS+chemo) on systemic biomarkers related to MMP9 activity, and immune suppression and activation, was explored in samples from patients in the gastric cancer cohort of the phase 1b study, NCT01803282. Immunoassay analysis of a set of serum proteins based on MMP9 biology and preclinical data (including 10 MMP9 substrates, 5 MMP/TIMPs and 25 inflammatory markers) are reported; exploratory analyses of a larger set will be presented. Total and GS-5745-free MMP9 was measured using a proprietary validated assay. Serum was collected at baseline and the start of every 28-day cycle from 40 gastric cancer patients treated with GS+chemo every 2 weeks. Biomarker area under the curve (AUC) of fold change over time was tested using the Wilcoxon signed rank test. Multiple testing adjustment was based on false discovery rate. GS+chemo treatment resulted in a significant decrease of 3 MMP9 substrates in serum (TGFβ, VEGF and CXCL5), with non-significant trends observed for 3 others (Kit-L, IL8 and CXCL1). MMP3, associated with MMP9 activation, was significantly increased by the combination treatment. MMP2 (an MMP9 homolog) and its binding partner, TIMP2, also showed an increased trend over time. All MMP9 was bound by GS-5745 after one cycle of GS+chemo treatment, but total MMP9 was unchanged. Analysis of biomarkers in the inflammatory set primarily identified trends; factors (10) related to immunosuppressive monocyte chemoattraction or activation decreased, whereas a few markers (3) of immune activation increased. TIMP-2 and TPO were identified by random forests as key markers of a potential baseline biomarker signature to distinguish responders from non-responders (best overall response: n=20 and 9, respectively) with 82.8% accuracy (AUC of ROC=0.83). This exploratory analysis of serum proteins in gastric cancer patients treated with GS+chemo identified pharmacodynamic changes in biomarkers related to MMP9 biology, immune suppression and innate inflammation, consistent with the hypothesis of MMP9-inhibition based upon preclinical models. Modulation of these systemic biomarkers may reflect inhibition of MMP9 activity in the tumor consequent with reduced suppression of anti-tumor immunity; however, conclusions from this study are limited by the fact that all patients were treated with GS+chemo. Confirmation of these findings will require a controlled prospective study. First two authors contributed equally. Citation Format: Marianna Zavodovskaya, Yafeng Zhang, Yuanyuan Xiao, Julie Maltzman, Victoria Smith, Carrie Baker Brachmann, Scott D. Patterson. Exploratory serum biomarker analysis in gastric cancer patients treated with GS-5745, an MMP9 Inhibitor, in combination with mFOLFOX6 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4663. doi:10.1158/1538-7445.AM2017-4663

Abstract 5666: Albumin and paclitaxel co-localize in endocytic vesicles in HUVEC cells, and uptake is blocked by Cremophor EL.

Nab ® -paclitaxel is an albumin-bound nanoparticle formulation of paclitaxel (ptx) that does not contain Cremophor EL (CrEL), and results in higher drug levels in xenografts and increased clinical activity in breast and lung cancers compared to ptx formulated with CrEL (Taxol ® ). Above the critical micellar concentration of 0.009%, CrEL forms long-lived micelles in circulation that can sequester ptx (peak plasma concentration in clinical use is 0.3%). Previous studies have shown CrEL reduces ptx binding to albumin, and Taxol ® has reduced association with, and transport across endothelial cells compared to nab ® -ptx (Desai, CCR 2006). Endothelial cells take up albumin, which is trafficked into recycling or transcytosis pathways or into lysosomes for degradation. Here, we explore mechanisms of uptake and trafficking of albumin and ptx in endothelial cells and the effect of CrEL on these events. Using fluorescence microscopy, we visualized the uptake of rhodamine-albumin and fluorescent ptx (Flutax). Albumin was present in EEA1-positive early endosomes and LAMP1-positive lysosomes. Notably, ptx was also present in vesicular structures and was often co-localized with albumin. The uptake of albumin was blocked by increasing concentrations (0.003%-0.3%) of CrEL, and also by inhibitors of caveolin-mediated endocytosis including indomethacin (blocks internalization of caveolae) and methyl-β-cyclodextrin (prevents formation of lipid rafts). The effect of CrEL on paclitaxel and albumin cellular uptake was confirmed by flow cytometry studies. 0.3% CrEL reduced the uptake of Flutax in DMSO, Flutax-modified nab ® -ptx, and FITC-labeled albumin to close to background levels in both HUVEC and PC3 cells. Thus, in addition to its drug sequestration activity, CrEL directly affects endocytosis. We further evaluated CrEL effects on Flutax and ptx transport across endothelial monolayers in transwell chambers using a fluorescence detection assay. Two-fold more ptx crossed monolayers exposed to Flutax-containing nab ® -ptx as compared to Taxol ® . The effects of 0.001% to 0.3% CrEL on ptx transport at varying timepoints were investigated by mass spectrometry. Dose-dependent inhibition was observed, with a 3-fold reduction in transported ptx at 24 hrs. In summary, we have demonstrated that ptx co-localizes with albumin in endothelial cells, suggesting that the nab-ptx complex can remain intact within cells. Furthermore, CrEL interferes with albumin uptake at clinically relevant concentrations, thereby affecting paclitaxel cellular uptake and transport. These mechanistic studies further elucidate the basis of increased delivery of drug into the target cells by the nab ® -ptx formulation as compared to Taxol ® . Citation Format: Xiping Liu, Carrie Brachmann, Sean Hong, Shijuan Wu, Zeen Tong, Tapas De, Willard Foss, Gondi Kumar, Sekhar Surapaneni, Rajesh Chopra, Daniel Pierce, Carla Heise. Albumin and paclitaxel co-localize in endocytic vesicles in HUVEC cells, and uptake is blocked by Cremophor EL. [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 5666. doi:10.1158/1538-7445.AM2013-5666