Virulizin

Virulizin has demonstrated strong antitumor efficacy in a variety of human tumor xenograft models including melanoma, pancreatic cancer, breast cancer, ovarian cancer and prostate cancer. Our previous studies have demonstrated that macrophages, NK cells, and cytokines are important in the antitumor mechanism of Virulizin. Virulizin treatment of tumor bearing mice results in the expansion as well as increased activity of monocytes/macrophages and production of cytokines IL-12 and TNFalpha and activation of NK cells. In this study we show that the inflammatory cytokine IL-17E (IL-25) is induced by Virulizin treatment and is part of its antitumor mechanism. IL-17E is a proinflammatory cytokine, which induces a T(H)2 type immune response, associated with eosinophil expansion and infiltration into mucosal tissues. IL-17E was increased in sera of Virulizin-treated mice bearing human melanoma xenografts, compared to saline-treated controls, as shown by 2D gel electrophoresis and ELISA. Treatment of splenocytes in vitro with Virulizin resulted in increased IL-17E mRNA expression, which peaked between 24 and 32 h post-stimulation. Both in vitro and in vivo experiments demonstrated that B cells produced IL-17E in response to Virulizin treatment. Furthermore, Virulizin treatment in vivo resulted in increased blood eosinophilia and eosinophil infiltration into tumors. Finally, injection of recombinant IL-17E showed antitumor activity towards xenografted tumors, which correlated with increased eosinophilia in blood and tumors. Taken together, these results support another antitumor mechanism mediated by Virulizin, through induction of IL-17E by B cells, leading to recruitment of eosinophils into tumors, which may function in parallel with macrophages and NK cells in mediating tumor destruction.

Virulizin, a biological response modifier, is a mixture of proteins and peptides that have been extracted from bovine reticuloendothelial tissue that activates macrophages. It is being developed by Lorus Therapeutics (formerly Imutec Pharma) for the treatment of various cancers and had completed phase II clinical trials in Canada for the treatment of pancreatic cancer and advanced malignant melanoma. The commencement of phase III clinical trials in Canada, for the treatment of pancreatic cancer, was delayed due to quality control problems with batches of virulizin and all clinical trials of virulizin were suspended as Lorus underwent a major restructuring programme. However, phase I/II clinical trials are now underway again in Canada in HIV-positive patients with Kaposi's sarcoma and for the treatment of pancreatic cancer. A phase I/II clinical trial is also underway in patients with pancreatic cancer in the USA. Lorus announced in June 2000 that it had completed a meta analysis of three phase I/II studies of virulizin that showed the drug increased survival and improved quality of life for pancreatic cancer patients. Based on these positive results, Lorus initiated a phase III trial to be conducted at 40 sites in North America in November 2001. The study aims to enrol 350 patients with advanced pancreatic cancer and will test the effectiveness of virulizin as first- and second-line treatment of pancreatic cancer. The study will compare virulizin + gemcitabine with gemcitabine alone as first-line therapy, while second-line treatment will involve patients who have failed to respond to gemcitabine. Some of these patients will receive virulizin + fluorouracil while another group will receive only fluorouracil. The study is scheduled to complete in 2004 or early 2005. Virulizin received orphan drug status for this indication from the US FDA in February 2001. Lorus received fast track designation from the FDA in June 2002 for virulizin for the treatment of pancreatic cancer. Virulizin is registered for the treatment of malignant melanoma in Mexico and is due to be launched there in 2002. Lorus has entered into an exclusive 7-year distribution agreement with Faulding Canada Inc., giving Faulding (now part of Mayne Group) the right to market and sell virulizin in Mexico for the treatment of melanoma. Lorus will receive royalties from sales of the product and will be responsible for its manufacture. In April 2002, Mayne exercised its option to acquire the distribution rights for virulizin in Brazil. Lorus Therapeutics has signed a collaborative agreement with NaPro BioTherapeutics, USA, to study the efficacy of virulizin in combination with paclitaxel for the treatment of lung adenocarcinoma. Lorus is conducting preclinical studies of virulizin in human breast cancer, lung, ovarian and prostate cancer, and has reported successful activity of the agent in these indications. Lorus was awarded a patent by the US Patent and Trademark Office to protect the only known process used to create virulizin. This patent, in conjunction with the patents issued in Australia, South Africa, New Zealand, Korea and Singapore, broadens and strengthens the protection of Lorus' intellectual property rights regarding the process, composition and use of virulizin.