HSV G207 Alone or With a Single Radiation Dose in Children With Progressive or Recurrent Supratentorial Brain Tumors

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Outcomes for children with recurrent or progressive supratentorial malignant brain tumors are very poor, and there are a lack of effective salvage therapies once a patient fails standard treatments. G207 is an oncolytic herpes simplex virus-1 (HSV) that has been successfully engineered to introduce ...

Outcomes for children with recurrent or progressive supratentorial malignant brain tumors are very poor, and there are a lack of effective salvage therapies once a patient fails standard treatments. G207 is an oncolytic herpes simplex virus-1 (HSV) that has been successfully engineered to introduce mutations in the virus that enable it to selectively replicate in and kill cancer cells, but not normal cells. Replication of G207 in the tumor not only kills the infected tumor cells, but causes the tumor cell to act as a factory to produce new virus. These virus particles are released as the tumor cell dies, and can then proceed to infect other tumor cells in the vicinity, and continue the process of tumor kill. In addition to this direct oncolytic activity, the virus engenders an anti-tumor immune response; the virus is immunogenic and produces a debris field which exposes cancer cell antigens to immune cells which can target other cancer cells. Thus, the oncolytic effect of the virus and the immune response that the virus stimulates provide a one-two punch at attacking cancer cells. In preclinical studies, a single 5 Gy dose of radiation within 24 hours of virus inoculation to the tumor increased virus replication and tumor cell killing. The University of Alabama at Birmingham has conducted three phase I trials of G207 injected into the recurrent tumor alone or combined with a single dose of radiation in adults with recurrent high-grade gliomas. In these trials, high doses (up to 3 x 10^9 plaque-forming units) of virus were safely injected directly into the tumor or surrounding brain tissue without serious toxicities. Radiographic and neuropathologic evidence of an antitumor response was seen in some patients. Preclinical laboratory studies have demonstrated that a variety of aggressive pediatric brain tumor types are sensitive to G207. This study is a phase I, open-label, single institution clinical trial of G207 alone or combined with a single low dose of radiation in children with recurrent or progressive supratentorial brain tumors. The primary goal is to determine safety. The secondary aims are to obtain preliminary information on the effectiveness of and immune response to G207. A traditional 3 + 3 design will be used with four patient cohorts. The first two cohorts will receive G207 at one of two doses, and the second two cohorts will receive G207 at one of two doses followed by a 5 Gy dose of radiation.

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