*2.4. NV1020*

NV1020 is a derivative of the HSV-1 strain R7020 that was initially developed as a vaccine against HSV-2 and has been attenuated by several genetic modifications including deletions of one allele of the genes for *ICP0*, *ICP4*, and γ*34.5*, as well as *UL56*, thereby reducing infectiousness, viral replication, and neuroinvasiveness; additionally, NV1020 has been altered by a deletion in the region of the

thymidine kinase (*tk*) gene and insertions of a fragment of HSV-2 DNA and the *tk* gene [18]. NV1020 has been shown to be successful in the treatment of various preclinical cancer models such as pleural, gastric, and hepatic cancer as well as head and neck squamous cell carcinoma [18,34–36]. Combined treatment of NV1020 with 5-FU, SN38 and oxaliplatin proved to act additively or synergistically in the treatment of colon cancer models [37]. It was first applied in a clinical setting in a phase I study for liver metastases of colorectal cancer to evaluate safety and tolerability [38]. Patients received a single dose of NV1020 via hepatic arterial infusion followed by implantation of a hepatic arterial infusion pump for local delivery of chemotherapy. Virus-associated adverse events that appeared directly after administration of NV1020 included pyrexia, headache, and muscle stiffness. NV1020-related individual cases of increased GGT (gamma glutamyl transferase) levels, gastroenteritis, and leukocytosis were registered. Analysis of cytokine and T-cell serum levels did not indicate a measurable immunogenic effect of NV1020 and evaluation of anti-tumor efficacy with CT scans 28 days after treatment showed tumor reduction in 17% and stable disease in 58% of the patients, while 25% were diagnosed with further progression. Radiologic assessment up to 12 months after treatment showed partial responses to chemotherapy after NV1020 in all patients; the authors also observed a 24% median decrease of the tumor marker CEA (carcinoembryonic antigen) [39]. The median survival was 25 months; after 62 months of observation, one patient was still alive. A follow-up study by Geevarghese et al. [40] examined safety and efficacy of NV1020 for the same disease type. NV1020 was administered into the hepatic artery weekly in four fixed doses, followed by adjuvant treatment at the physician's discretion. Similar to the first study by Kemeny et al., pyrexia, chills, headache, nausea, myalgia, and fatigue were registered as adverse events within 24 h after NV1020 infusion. Although no shedding of NV1020 could be detected, infrequent HSV-1 shedding was observed. Higher doses of NV1020 were associated with stable disease in 50% of the patients and additional chemotherapy resulted in a clinical control rate of 68%. Immunologically, a dose-associated increase in levels of IL-6, TNF-α, and IFN-γ was noted by the authors and therefore 1 <sup>×</sup> <sup>10</sup><sup>8</sup> pfu (plaque forming units) was defined as the optimal biological dose.
