Lorus Therapeutics Inc. will collaborate with Sumitomo Pharmaceuticals Co. Ltd. and Koken Co. Ltd. to develop a cancer drug using Lorus' antisense oligonucleotides.

The agreement calls for Toronto-based Lorus to provide GTI-2601, a preclinical antisense drug candidate aimed at reducing the levels of thioredoxin, with a delivery system jointly developed by Sumitomo and Koken, both of Tokyo, based on collagen complexed with macromolecules.

"What we're working toward is actually creating a new formulation strategy around antisense and then taking it into the clinic," said Bruce Rowlands, senior vice president of Lorus.

Any compounds that result from the collaboration will be shared among the three companies, and the "formula is set up so Lorus will own 50 percent of the new asset and Sumitomo and Koken will share the other 50 percent," he told BioWorld Today.

Further financial details were not disclosed.

Rowlands described GTI-2601 as "an antisense molecule that targets thioredoxin," a hydrogen-carrying protein that contributes to biochemical reactions such as ribonucleotide reduction. Thioredoxin is involved in tumor formation, as well as cancer progression and metastasis, and Lorus reported in preclinical findings that levels of thioredoxin are related to disease prognosis.

Tissue samples from a number of different cancer types, such as lung, colon, cervical, gastric and hepatocellular carcinoma, myeloma and non-Hodgkin's lymphoma, all appeared to have elevated thioredoxin levels. The company's preclinical studies also indicated that resistance to chemotherapy might be directly linked to an overexpression of thioredoxin.

Although still in preclinical development, Lorus said GTI-2601 demonstrated activity against cancer cells when evaluated through in vitro and in vivo screening processes, though the company hopes the collaboration with the Japanese companies will yield a product with greater efficacy using the collagen technology.

GTI-2601 is not the only antisense drug candidate Lorus has in development; the company recently completed a Phase II trial of GTI-2040 in renal-cell carcinoma in combination with capecitabine, and Rowlands said it expects data "in the coming weeks."

Lorus also has an ongoing agreement with the U.S. National Cancer Institute for six Phase II trials of GTI- 2040, including trials in colon, lung, breast, prostate and solid-tumor cancers and acute myeloid leukemia.

A second antisense compound in clinical development, GTI-2501, is in a Phase II study for hormone-refractory prostate cancer in combination with docetaxel.

The company's lead product is Virulizin, designed as an immunomodulatory activator of human macrophages and in Phase III trials in pancreatic cancer. The 436-patient study completed enrollment in June and results are expected around the end of the year. Virulizin has been granted orphan drug designation and fast-track status.

Additional preclinical studies are ongoing for other immunotherapeutic, antisense and small-molecule candidates in cancer treatment.

Lorus recently raised C$15 million (US$12.3 million) through a private placement of convertible secured debentures. The first tranche closed in October, and the company completed the second tranche early this year.

Shares of Lorus (AMEX:LRP) rose 6 cents Tuesday to close at 63 cents.