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DD-02PHARMACODYNAMIC BIOMARKER ASSESSMENTS IN A PHASE I/II TRIAL OF THE HYPOXIA-ACTIVATED PRODRUG TH-302 AND BEVACIZUMAB IN BEVACIZUMAB-REFRACTORY RECURRENT GLIOBLASTOMA

ABSTRACT: BACKGROUND: Glioblastoma (GBM) remains an incurable malignancy with rapid progression and poor survival. GBM exhibits a hypoxic nature, and treatment with bevacizumab (BEV) may increase intratumoral hypoxia. TH-302 is an investigational prodrug that selectively releases the DNA cross-linker (Br-IPM) under hypoxic conditions. A phase I/II trial (NCT01403610) is evaluating the safety and efficacy of combined TH-302 and BEV treatment in patients with BEV-refractory GBM and investigating pharmacodynamics biomarkers. METHODS: Patients were randomized to TH-302 single dose (575 mg/m2) or placebo, administered one day before surgery, followed by TH-302 (240-670 mg/m2) + BEV treatment until disease progression. Before surgery, pimonidazole (Pimo) was administered to label hypoxia and the excised tumor tissue was processed for immunohistochemistry. Endogenous plasma metabolites and plasma carbonic anhydrase IX (CA-IX) were also assessed. RESULTS: Immunohistochemistry was conducted on 11 resected tumors. A strong correlation and co-localization was observed between Pimo (exogenous hypoxia marker) and CA-IX (endogenous hypoxia marker) expression (r = 0.9, p < 0.001). Plasma CA-IX levels correlated well with tissue CA-IX expression. The hypoxic fraction tended to be higher in patients with a stable disease or partial tumor responses. Patients treated with TH-302 prior to surgery tended to have higher levels of ?H2AX positive cells, indicating increased DNA damage, and lower Ki67 (a proliferation marker) compared with patients who received placebo. Patients treated with a single dose of TH-302 prior to surgery with higher levels of ?H2AX-positive cells tended to have better outcome. Metabolomic profiles in plasma and in tumor tissue differed with degree of hypoxia. CONCLUSION: The results suggest that CA-IX as a hypoxia marker might be a predictive biomarker for TH-302 and ?H2AX a response biomarker for TH-302. Correlative studies show metabolomic profile varies with tumor hypoxia degree, indicating plasma metabolites for further study as potential prognostic or treatment response markers.

SUBMITTER: Cavazos D

PROVIDER: S-EPMC4218032 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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Project description:BackgroundHypoxic niches in solid tumors harbor therapy-resistant cells. Hypoxia-activated prodrugs (HAPs) have been designed to overcome this resistance and, to date, have begun to show clinical efficacy. However, clinical HAPs activity could be improved. In this study, we sought to identify non-pharmacological methods to acutely exacerbate tumor hypoxia to increase TH-302 activity in pancreatic ductal adenocarcinoma (PDAC) tumor models.ResultsThree human PDAC cell lines with varying sensitivity to TH-302 (Hs766t > MiaPaCa-2 > SU.86.86) were used to establish PDAC xenograft models. PDAC cells were metabolically profiled in vitro and in vivo using the Seahorse XF system and hyperpolarized (13)C pyruvate MRI, respectively, in addition to quantitative immunohistochemistry. The effect of exogenous pyruvate on tumor oxygenation was determined using electroparamagnetic resonance (EPR) oxygen imaging. Hs766t and MiaPaCa-2 cells exhibited a glycolytic phenotype in comparison to TH-302 resistant line SU.86.86. Supporting this observation is a higher lactate/pyruvate ratio in Hs766t and MiaPaCa xenografts as observed during hyperpolarized pyruvate MRI studies in vivo. Coincidentally, response to exogenous pyruvate both in vitro (Seahorse oxygen consumption) and in vivo (EPR oxygen imaging) was greatest in Hs766t and MiaPaCa models, possibly due to a higher mitochondrial reserve capacity. Changes in oxygen consumption and in vivo hypoxic status to pyruvate were limited in the SU.86.86 model. Combination therapy of pyruvate plus TH-302 in vivo significantly decreased tumor growth and increased survival in the MiaPaCa model and improved survival in Hs766t tumors.ConclusionsUsing metabolic profiling, functional imaging, and computational modeling, we show improved TH-302 activity by transiently increasing tumor hypoxia metabolically with exogenous pyruvate. Additionally, this work identified a set of biomarkers that may be used clinically to predict which tumors will be most responsive to pyruvate + TH-302 combination therapy. The results of this study support the concept that acute increases in tumor hypoxia can be beneficial for improving the clinical efficacy of HAPs and can positively impact the future treatment of PDAC and other cancers.

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DD-02PHARMACODYNAMIC BIOMARKER ASSESSMENTS IN A PHASE I/II TRIAL OF THE HYPOXIA-ACTIVATED PRODRUG TH-302 AND BEVACIZUMAB IN BEVACIZUMAB-REFRACTORY RECURRENT GLIOBLASTOMA

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