Washington Editor

Sunesis Pharmaceuticals Inc. acquired exclusive worldwide rights to a cancer compound discovered by a Japanese firm that says the drug has demonstrated efficacy potential in preclinical testing.

The candidate, referred to as SPC-595, acts as a cell-cycle modulator and is a member of a class of compounds known as naphthyridines, which have not been used in cancer therapy, Sunesis said. SPC-595 (formerly called AG-7352) was discovered and licensed to Sunesis by Dainippon Pharmaceutical Co. Ltd., of Osaka, Japan.

Dan Swisher, chief operating officer and chief financial officer of Sunesis, of South San Francisco, described the financial agreement with Dainippon as a typical arrangement with an up-front payment, milestones based on success and product royalties. He told BioWorld Today the initial payment is modest and the initial milestones would not significantly increase Sunesis' burn rate. Development costs will be the primary expenses associated with the program, he said.

Sunesis, a privately held company founded in 1998, has $40 million in cash, an amount sufficient to support the company for two-plus years, it said.

Swisher referred to the acquisition of SPC-595 as a "transforming event for Sunesis," saying the company has always had a vision of being a fully integrated pharmaceutical company. "This moves us that much faster into development, and I think this creates a very positive pull in the organization to grease the skids for our own internal programs," he said.

Sunesis uses its Tethering technology to discover its own candidates and for partnering projects with the likes of Merck & Co. Inc., of Whitehouse Station, N.J.; Biogen Inc., of Cambridge, Mass.; and Johnson & Johnson Pharmaceutical Research & Development, a unit of New Brunswick, N.J.-based Johnson & Johnson. The technology is a way of identifying fragments of drugs that bind to specific sites on a target surface. (See BioWorld Today May 7, 2002; Jan. 8, 2003; and Feb. 20, 2003.)

SPC-595 would be Sunesis' first candidate to enter the clinic, said Swisher, who estimated that the company would file an investigational new drug application and enter Phase I sometime in mid-2004. The company will explore the product in multiple cancer settings.

Dainippon has tested SPC-595 in vivo in various murine syngeneic and human xenograft tumor models, comparing the efficacy of SPC-595 with the activity of marketed cytotoxic therapies, Sunesis said.

In the studies, SPC-595 showed inhibition rates up to 99 percent with some complete tumor regressions, while irinotecan and paclitaxel showed significantly less activity in three different murine syngeneic solid tumor models. Also, Sunesis' statement said, in xenograft models, SPC-595 demonstrated broad efficacy in all models and inhibited tumor growth by more than 80 percent in eight of the 10 cancer lines evaluated.

And, in three drug-resistant human cancer models, SPC-595 showed tumor inhibition rates ranging from 73 percent to 87 percent, while irinotecan and paclitaxel showed less efficacy, ranging from 19 percent to 58 percent tumor inhibition, Sunesis said.

Concerning the finding of such a promising candidate, Swisher said, "There's a lot of junk out there, so we had to kiss a lot of frogs to find a diamond in the rough."

He added that SPC-595 fit into Sunesis' areas of expertise - oncology and inflammation.

Sunesis started its product search about a year ago.

"One important thing in this process is to have a very good set of filters where you know what you are looking for because you can quickly get overwhelmed doing diligence on compounds that don't fit strategically," Swisher said.

Dainippon chose to outlicense SPC-595 because of its changing business plan.

"Consistent with our shift in marketing focus on alimentary and metabolic, respiratory and allergic, vascular, psychiatric and neurological diseases, we have made the strategic decision to license this oncology program to Sunesis," Kenjiro Miyatake, Dainippon's president, said in a prepared statement.