But, a news briefing (Thursday 21 November) at the EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics[1], in Frankfurt, Germany, was told that although there was a structural similarity between the natural product and rViscumin, that was where the similarity ended.
"The content of mistletoe lectin in the natural product is variable and the concentrations in commercially available plant extracts are very low," said lead investigator Dr Patrick Schöffski from Hannover Medical School in Germany. "According to cell culture and animal experiments rViscumin is a highly potent drug, which has been developed in a very conventional manner like other innovative cytotoxic agents, but using gene technology to ensure the end product has a stable and consistent quality."
He said the study under way in Hanover and Nantes in France was the very first phase I trial using rViscumin administered intravenously and was being run in parallel with another phase I study where the drug is administered subcutaneously. The trials are being backed by the EORTC and further Phase I studies are being considered.
Dr Schöffski said: "It is very early days yet. We are still at the stage where we are escalating the dosage. But, a very preliminary laboratory analysis of samples from a first patient cohort from the trial shows that rViscumin stimulated releases of cytokines, including interleukins (IL-1b and IL-6) and interferon gamma, and is also associated with inducing anti rViscumin antibodies. So we are seeing a definite immune system response to the drug, although at this stage it is far too early to draw any conclusions about possible clinical significance or benefits to patients. This observation will have to be confirmed during the further conduct of the trial and in future studies."
Involved in the clinical trial are the Hannover Medical School, Germany, Centre Rene Gauducheau, Nantes-St.Herblain, France, the EORTC New Drug Development Group, Brussels, Belgium, VISCUM AG, Zwingenberg, Germany and Leopold-Franzens-Universität, Innsbruck, Austria.
Note:
[1] EORTC [European Organisation for Research and Treatment of Cancer; NCI [National Cancer Institute]; AACR [American Association for Cancer Research].
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