Oxxon Therapeutics Inc. signed an exclusive licensing agreement to use Xenova Group plc's DISC-HSV vector platform to develop immunotherapeutic drugs for cancer and chronic infectious diseases

The deal is worth up to $83 million, including up-front and milestone payments to Slough, UK-based Xenova.

"I'm very pleased with this new deal," said Deirdre Gillespie, president and CEO of Oxxon. The DISC-HSV platform "is a good asset for Oxxon."

Though financial details were not disclosed, Gillespie said Oxxon's up-front fee will be paid over a two-year period. The company would make milestone payments on the first four products to be commercialized, but not until they reach Phase III trials, she added. Royalties would be paid on sales of products derived from the DISC-HSV platform.

Oxxon also has the option to develop products for other indications using the platform, subject to additional fees.

"Our focus is in immunotherapeutics to treat infectious diseases and cancers," Gillespie said. "We do this through the development of proteins that target a specific immune response, and then we take those proteins from tumors or infectious agents and incorporate them into the vector."

Xenova's DISC-HSV (Disabled Infectious Single Cycle - Herpes Simplex Virus) vector was designed to deliver heterologous genes to the immune system, stimulating responses such as helper and cytotoxic T-cell responses.

"HSV is a well-characterized vector used in several hundred patients effectively and can hold a large number of proteins," Gillespie told BioWorld Today. "We've been evaluating it over the last 12 months in preclinical models."

She said Xenova's vector platform delivers a response using priming or boosting techniques, adding it will work well with Oxxon's PrimeBoost technology, which was designed with both techniques. "Overall, it meets Oxxon's needs extremely well," Gillespie said. "This particular vector is very good for us."

The agreement also includes Xenova's DISC-GM-CSF, an oncology product based on the DISC-HSV vector platform.

DISC-GM-CSF, which uses the vector to deliver the granulocyte macrophage-colony stimulating factor (GM-CSF) gene to tumor cells, has completed a Phase I study in patients with metastatic melanoma. Xenova said results indicated that the product was well tolerated and, following injection, the drug did not spread beyond the therapeutic area.

Though used primarily as a delivery platform for other protein-based treatments, DISC-HSV initially was studied as a stand-alone product for genital herpes. In 2001, Xenova, which had partnered with London-based GlaxoSmithKline plc, reported that a Phase II trial failed to meet clinical endpoints.

Apart from its recent agreement with Xenova, Oxford, UK-based Oxxon has three products of its own in development, including two in Phase II trials. Gillespie said the company is enrolling about 41 patients in a Phase II study for the PrimeBoost melanoma therapy. The trial will assess immune responses and measure clinical effect based on tumor size. Results are expected next quarter.

Phase II studies involving 70 patients with chronic hepatitis B are ongoing to evaluate Oxxon's PrimeBoost therapeutic for immune response and viral loads. Results of those studies also are expected next quarter.

The company's HIV immunotherapy drug is in the final stages of preclinical development. Oxxon expects to file an investigational new drug application and begin Phase I trials during the second half of the year.

Xenova, which develops cancer and addiction products, has several drugs in development. TransMID, designed to treat high-grade glioma, is in Phase III trials. It also has DNA-targeting agents and a product called XR303 in Phase I studies for cancer. Xenova also is working on therapeutic vaccines for cocaine addiction, in Phase II trials, and nicotine addiction, in Phase I trials.

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