Abstract
Toxicology studies were performed in rats and rhesus macaques to establish a safe starting dose for intratumoral injection of an oncolytic vesicular stomatitis virus expressing human interferon-β (VSV-hIFNβ) in patients with hepatocellular carcinoma (HCC). No adverse events were observed after administration of 7.59 × 10
9
TCID
50
(50% tissue culture infective dose) of VSV-hIFNβ into the left lateral hepatic lobe of Harlan Sprague Dawley rats. Plasma alanine aminotransferase and alkaline phosphatase levels increased and platelet counts decreased in the virus-treated animals on days 1 and 2 but returned to pretreatment levels by day 4. VSV-hIFNβ was also injected into normal livers or an intrahepatic McA-RH7777 HCC xenograft established in Buffalo rats. Buffalo rats were more sensitive to neurotoxic effects of VSV; the no observable adverse event level (NOAEL) of VSV-hIFNβ in Buffalo rats was 10
7
TCID
50
. Higher doses were associated with fatal neurotoxicity and infectious virus was recovered from tumor and brain. Compared with VSV-hIFNβ, toxicity of VSV-rIFNβ (recombinant VSV expressing rat IFN-β) was greatly diminished in Buffalo rats (NOAEL, >10
10
TCID
50
). Two groups of two adult male rhesus macaques received 10
9
or 10
10
TCID
50
of VSV-hIFNβ injected directly into the left hepatic lobe under computed tomographic guidance. No neurological signs were observed at any time point. No abnormalities (hematology, clinical chemistry, body weights, behavior) were seen and all macaques developed neutralizing anti-VSV antibodies. Plasma interleukin-6, tumor necrosis factor-α, and hIFN-β remained below detection levels by ELISA. On the basis of these studies, we will be proposing a cautious approach to dose escalation in a phase I clinical trial among patients with HCC.
