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ATRT-03. EFFICACY OF THE ONCOLYTIC ADENOVIRUS DELTA-24-RGD AS A THERAPEUTIC AGENT FOR THE TREATMENT OF PEDIATRIC EMBRYONAL BRAIN TUMORS

ABSTRACT: Abstract Atypical teratoid/rhabdoid tumors (ATRTs) and primitive neuroectodermal tumors (PNETs) are two rare primary embryonal brain tumors, which are among the most frequent solid brain tumors in infants under one year old. The outcome for these children remains dismal, especially in ATRTs which have a 2-year overall survival below 20%. Therefore, we need to find out new efficient and safe therapeutic options for these children. Delta-24-RGD (DNX-2401 in the clinic) is an oncolytic adenovirus that has already been tested in Phase I/II clinical trials in patients affected by recurrent glioblastoma (NCT00805376; NCT01956734), demonstrating anti-tumor effect without any evidence of severe side effect associated with viral administration. Of interest for pediatric brain tumors, an ongoing Phase I trial using Delta-24-RGD for the treatment of diffuse intrinsic pontine gliomas (NCT03178032) has also demonstrated a safe profile in these children. For these reasons, we propose to evaluate the anti-tumor effect of Delta-24-RGD in preclinical models of ATRT and PNET. The virus was able to infect and replicate in tumor cell cultures (three models of ATRT and four of PNET), inducing a potent cytotoxic effect. In addition, this cytotoxicity resulted in the released the immunogenic cell death markers Hsp70, Hsp90, HMGB1 and ATP, as well as an increased calreticulin exposure in the outer cell surface. Although not conclusive, the presence of these markers suggest the triggering of an anti-tumor immune response. Intratumoral administration of the virus extended significantly the overall survival of mice bearing ATRT or PNET xenografts, leading to up to 40% of long-term survivors. We are currently setting up an intraventricular model of disseminated disease, since most of patients with ATRT actually die due to the presence of metastases. In conclusion, these results demonstrate that Delta-24-RGD could be a feasible therapeutic option for children with PNETs and AT/RTs.

SUBMITTER: Garcia-Moure M

PROVIDER: S-EPMC6477196 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Project description:Abstract BACKGROUND Atypical teratoid/rhabdoid tumors (AT/RTs) are rare pediatric brain tumors affecting mainly infants and young children. However, AT/RTs encompass almost 10% of death caused by pediatric brain tumors, and the 2-year overall survival for these children remains below 20%. For this reason, AT/RT ranks among the deadliest pediatric brain tumors. Therefore, it is clear we need to find out new therapeutic options for these children. Delta-24-RGD is an oncolytic adenovirus that has already demonstrated its efficacy as in Phase I/II clinical trials in adult patients affected by high grade gliomas with no evidence of severe side effects. Of interest for pediatric brain tumors, the safety of Delta-24-RGD is has also been demonstrated in an ongoing Phase I clinical trial for the treatment of DIPGs (NCT03178032). For these reasons, we propose to evaluate the anti-tumor effect of Delta-24-RGD in preclinical models of ATRT. MATERIAL AND METHODS Our studies have been carried out in three stablished AT/RT cell lines (BT-12, CHLA-06 and CHLA-266). In vitro, AT/RT cultures were infected with Delta-24-RGD-GFP to confirm the infectivity of the virus by flow cytometry. Replication of Delta-24-RGD was ensured by titrating the PFUs generated in AT/RT infected cultures. In regard to cytolytic effect, viability assays (MTS) were conducted in AT/RT cultures infected at increasing MOIs of Delta-24-RGD. In vivo, AT/RT cell lines were engrafted in Rag-2 mice in supratentorial and infratentorial locations, and the animals were treated with Delta-24-RGD at 107 or 108 PFU/animal (intra-tumor administration), or PBS. The therapeutic benefit of Delta-24-RGD was evaluated comparing the overall survival obtained for treated and untreated animals using the Log-rank test. We have also generated models of disseminated disease through intraventricular injection of the tumor cells, thus mimicking the lesions found in patients. AT/RT cell lines were transduced with a luc-expressing lentivirus to facilitate the follow up of these tumors. Mice bearing disseminated AT/RT were treated with Delta-24-RGD at 107 or 108 PFU/animal, or PBS (control). The therapeutic effect was monitored by bioluminescence and by comparison of the survival curves (Log-rank). RESULTS The virus was able to infect and replicate in tumor three different cell culture models of AT/RT, inducing a potent cytotoxic effect that resulting in IC50 values below 1 PFU/cell. Administration of the virus in mice bearing localized AT/RT (supratentorial and infratentorial) extended significantly the survival the animals, leading to up to 20% of long-term survivors. In disseminated AT/RT models, light emission reveals reduction of tumor growth in virus treated animals, resulting in an increased overall survival. CONCLUSION In conclusion, these results demonstrate that Delta-24-RGD could be a feasible therapeutic choice for patients affected by AT/RT.

Project description:Abstract Based on promising results of recent clinical trials using oncolytic viruses, virotherapy is evolving as an alternative to treat patients with malignant glioma. Our group developed the oncolytic adenovirus Delta-24-RGD (DNX-2401) that is being tested, alone or in combination with anti-PD1, in clinical trials for recurrent glioblastoma (NCT00805376; NCT01956734; NCT02798406). The results suggest that, besides the expected oncolytic effect, the injection of the pathogen initiated, in a subset of patients, an anti-tumoral immunity that led to 20% of long-term survivors (3.5–5 years). To further enhance this effect, we have armed Delta-24-RGD to express the co-stimulatory ligand GITRL, and generated Delta-24-GREAT. The intracranial injection of Delta-24-GREAT prolonged the survival of GL261 glioma-bearing immunocompetent mice when compared to Delta-24-RGD treatment (P=0.002, log-rank test). Delta-24-GREAT treatment resulted in enhanced frequency of tumor-infiltrating lymphocytes: T lymphocytes (CD45+/CD3+) and cytotoxic T lymphocytes (CD45+CD3+CD8+). Functional studies performed by culturing splenocytes from Delta-24-GREAT-treated mice with glioma cells and analyzing secretion of Th1 cytokines, such as IL2 and IFN-?, showed that lymphocytes recognized not only viral antigens but also tumoral antigens, suggesting the triggering of anti-tumoral immunity. Of interest, Delta-24-GREAT treatment resulted in an antigen-restricted anti-tumor memory effect and in the generation of central immune memory. Thus, rechallenging the survivor mice from the first experiment with a second implantation of glioma cells did not lead to tumor growth, and we detected an increased frequency of central memory CD8+ T cells (CD45+CD62L+). However, survivor mice developed lethal tumors when implanted intracranially with B16/F10 melanoma cells, strongly indicating that the developed immune response was specific for GL261 glioma antigens. This is a novel approach using an oncolytic adenovirus expressing GITRL to target cancer and to stimulate the immunity within the tumor. Our data strongly indicate that this type of strategy may be further developed to treat patients with malignant glioblastoma.

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ATRT-03. EFFICACY OF THE ONCOLYTIC ADENOVIRUS DELTA-24-RGD AS A THERAPEUTIC AGENT FOR THE TREATMENT OF PEDIATRIC EMBRYONAL BRAIN TUMORS

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