LONDON - Antisoma plc has taken ownership of Cancer Therapeutics Ltd. (CTL), the 50-50 joint venture it set up with the Imperial Cancer Research Fund (ICRF) to speed development of drugs discovered by the charity. The deal gives London-based Antisoma full control of a novel treatment for ovarian cancer, Theragyn, which is currently in pivotal Phase III trials in the U.S. and Europe.

Under terms of the agreement, Antisoma has bought ICRF's half-share of CTL from the charity's commercial arm, Imperial Cancer Research Technology (ICRT), including rights to all products and technology held in the joint venture. Antisoma also has acquired rights to the monoclonal antibody PR1A3, identified by ICRF scientists as a vector of antitumor and imaging agents.

In return, ICRT has acquired 13.6 percent of Antisoma, through the issue of 5.7 million new ordinary shares. This is the largest holding by ICRT in any company, and ICRT will receive royalties on the sales of products incorporating Antisoma's technology.

Glyn Edwards, recently appointed CEO of Antisoma, told Bioworld International, “This is an evolutionary thing. In the early stage, a joint venture was a good vehicle because it preserved the ICRF's direct interest in research it had funded. Now, the Theragyn program is accelerating fast. We are well into clinical development rather than basic research, and there is a benefit to the program from Antisoma having complete control.

“It was anticipated that this would happen at the time the joint venture was established,“ Edwards added, “and the mechanism for achieving it was in the original document. But the change in control has come about faster than expected.“

The ICRT's willingness to surrender control was “a vote of confidence in what we're doing,“ Edwards said, welcoming ICRT's shareholding in Antisoma as the basis of an important relationship with the charity.

“It will not give us formal preferential access to ICRF research, but it will mean we keep in touch with developments in tumor targeting, which is our main focus,“ Edwards said.

CTL will remain as a separate legal entity, but Edwards said day-to-day operations will be performed by Antisoma.

The PR1A3 monoclonal antibody included in the deal has already been tested by ICRF, in conjunction with an imaging agent for tumors. It identifies an antigen which is expressed by a wide variety of tumor cells and which circulates in the blood. But, unlike other such antibodies, PR1A3 only binds to the antigen on tumor cells. This specificity makes it an attractive vector for anticancer agents, Edwards said.

Injection Of Theragyn Avoids Side Effects

Antisoma aims to link PR1A3 to the radionuclide yttrium-90, though this project is still at the preclinical stage. Theragyn, the company's lead product, also is based on a monoclonal antibody linked to yttrium-90, which kills cancer cells with radiation.

“While the concept of a radionuclide linked to an antibody has been around for a long time, if it is delivered by intravenous injection it takes a long time for the antibody to localize to the tumor, and other tissues are exposed to the radionuclide,“ Edwards noted. “Theragyn is not delivered systemically but by injection into the peritoneum, avoiding these side effects.“

In Phase II, Theragyn significantly improved five-year survival rates among ovarian cancer patients, compared with the best alternative therapy. Enrollment of 300 patients in the Phase III study is expected to be completed within the next year, with results due 18 months to two years after that. Edwards said the company is just beginning to think about potential marketing partners, but an announcement is not imminent.

Antisoma has one licensing deal, with the Japanese company Nihon Medi-Physics Co. Ltd., of Tokyo, for its lead imaging agent, Pepscan, a radiolabeled peptide for imaging epithelial cancers.

At present Antisoma has sufficient cash to last until the end of this year. Edwards, who joined two months ago from Therapeutic Antibodies Inc., of Nashville, where he was vice-president of business development, said there will be a fund raising before the end of the year “to raise around £10 million [US$16.3 million].“ This will probably come in the form of a private placement, with a public offering to follow “at some stage,“ Edwards said. *