Herpesviruses are effective against a broad spectrum of human tumors. G207 is a mutant HSV with deletions in both copies of y^4.5, and a mutation in UL39 (Table 1). This attenuated virus was first described in the treatment of malignant gliomas, and further research has demonstrated its efficacy in treating a wide range of tumors types, including breast, bladder, colon, gallbladder, stomach, liver, pancreas, and the oro-digestive tract (10,12-17). In these studies, G207 has been able to effectively kill cancer cells in vitro and reduce experimental animal tumor burdens in vivo. Furthermore, G207 has demonstrated preclinical safety in BALB/c mice and Aotus monkeys. In BALB/c mice, doses of 1 x 107 plaque-forming units (pfu) of G207 injected intrace-rebrally did not produce any adverse effects (18). Likewise, a dose of 1 x 109 pfu in Aotus monkeys did not result in any pathology (19). Clinical safety has been further confirmed in a phase I clinical trial of patients with malignant gliomas resistant to standard therapies subjected to direct intratumoral injections of G207. None of the patients in this study developed serious adverse effects, and eight patients had radiographic reduction in tumor volume (Table 2) (5).
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