BioWorld International Correspondent

LONDON - Avidex Ltd. agreed to a deal with Dow Chemical Corp. to create the first in a new generation of cancer therapeutics targeting antigens generated within tumor cells by linking a monoclonal T-cell receptor (mTCR) to a radioisotope.

Coinciding with the agreement, Avidex is setting out on its next funding round, to raise £20 million to £25 million (US$31.7 million to $36.7 million).

Under the agreement Dow's recently acquired radiopharmaceutical services arm, ChelaMed, will attach a radioisotope to Avidex's EsoDex mTCR, which targets the cancer antigen NY-ESO.

Neill Moray MacKenzie, chief business officer of Avidex, told BioWorld International, "We have started the work and it is looking quite promising."

After the initial feasibility study, Avidex will decide whether to commit to further development with ChelaMed, which offers an end-to-end development and commercialization program. That includes hospital-based infrastructure to attach the radionuclide to the mTCR at the time of treatment, avoiding problems with radioactive decay.

"Although we found other companies for a lot of this technology [radiolabeling], only Dow could offer radiolabeling at the hospital," MacKenzie said.

NY-ESO is a very specific tumor-associated antigen, but it is internally generated and thus cannot be targeted by monoclonal antibodies. EsoDex, and Avidex's other mTCRs, can specifically bind to fragments of internal antigens after they are presented on the surface of tumor cells by HLA Class I molecules.

NY-ESO, discovered by the Ludwig Institute in New York, is expressed by lung and bladder tumors in particular. It is one of a number of intracellular tumor antigens in the public domain yet to be exploited because they cannot be targeted by monoclonal antibodies. Since its formation in July 2000 Avidex has overcome stability, solubility and affinity issues to develop the capability to make any human T-cell receptor, and claims it can target any internal tumor antigen.

"We are offering a completely different route, and are the only company with natural TCRs," MacKenzie said. The company has a further collaboration to attach a toxic small molecule to its TCRs for cancer chemotherapy. In immune system diseases it is developing TCRs to prevent naturally occurring T cells from binding to the antigens.

MacKenzie said he expects the first product to enter the clinic next year, but it is yet to be decided which it will be.

Abingdon-based Avidex has put its business plan together for its fund-raising. The company has raised £23.2 million to date, taking £11.5 million in its last round in September 2002.

"What we are trying to do is make sure we do not have to come back to raise more money before [we have products at] the end of Phase II," said MacKenzie.

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