Shrew saliva may detect and treat cancer

Paralytic venom in the saliva of the tiny North American short-tailed shrew, which hunts its prey on the forest floor, may hold the key to a diagnostic and therapeutic treatment for ovarian, breast and prostate cancers.

“We found out that the paralytic agent in the venom was a peptide material that we eventually named soricidin,” Jack Stewart, chairman and CSO of closely held Soricimed Biopharma of New Brunswick, says in an exclusive interview with biotuesdays.com.

His research at Mount Allison University in 2000 eventually found that soricidin was a bi-functional molecule. “One end of the molecule was paralytic, which we saw as having potential as a pain therapeutic, while the other end turned out to inhibit another calcium ion channel that initiates cell death in ovarian cancer cells models,” he recalls.

By 2005, Professor Stewart’s research was spun out of the university into a company called BioProspecting NB, which became Soricimed last April. The company learned how to separate the paralytic end of the peptide from the anti-cancer end, launching two development programs.

“It became very apparent early on that we had two opportunities in pain and cancer, so we decided to let the science decide which one we prioritized,” says CEO Paul Gunn. “Within a couple of years, the cancer program really took off, and it became much more rounded than the pain program.” In 2007, the company made a decision to focus on the development of a cancer therapeutic and potentially license-out the pain program in the future.

Soricimed now has an abundance of riches. Mr.Gunn contends that the company has one technology platform, with four potential revenue streams: therapeutics for oncology and pain; an early diagnostic for ovarian cancer; and a drug delivery system.

Early research on two derivatives of soricidin, SOR-C13 and SOR-C27, has shown efficacy in all three cancer models by reducing tumour growth. Moreover, the drugs accumulate in the lymph nodes, “which, to our knowledge, no other cancer drug does,” he says. “So that gives us the opportunity to look at cancers that have metastasized, as well as the originating tumours, and develop a potential drug delivery vehicle as well.”

Dr. Stewart’s research also found that the drugs target a specific calcium channel TRPV6 (or transient receptor potential vanilloid family number 6) that is over-expressed in cancer cells but not in healthy cells, “so we also thought it could be a biomarker for a diagnostic.”

As it turned out, the biomarker for the diagnostic is the same as a target for the drug: TRPV6. Mr. Gunn’s thinking is that if patients are positive in a diagnostic test, they “should be a good responder to our drug.” “So we have a targeted therapeutic approach,” Mr. Gunn points out.

Soricimed is now developing a suite of diagnostic tools. It has a proof of concept for a blood test to detect TRPV6 overproduction in Stage 1 ovarian cancer, a peptide-based scanning technology and biopsy test that detects and monitors the earliest stages of ovarian, breast and prostate cancers. In collaboration with the Atlantic Cancer Research Institute, a prototype diagnostic for ovarian cancer is expected to be ready this fall, which could put it several years away from a regulatory filing.

“One of our goals is to have our test seen as being at the same level as a PSA test in men,” Mr. Gunn contends. “It may sound simplistic, but if our diagnostic finds it, then our drug should kill it. It’s so specific, with the biomarker being the same as the drug target, that they work very well hand-in-hand and open up the possibility of personalized medicine.”

The company is about six months away from completing preclinical work on its cancer therapeutic and expects to begin a Phase 1 trial in 2011, with data available the following year. It recently secured $2 million in financing, which should cover operations until the end of the Phase 1 study.

Mr. Gunn says the pain drug candidate requires additional preclinical work and should be ready to license-out next year.  The clinical status of the drug delivery vehicle is still very early, he adds.

For the time being, Soricimed’s business plan involves taking the cancer drug only to the end of Phase 1 and then negotiating a co-development deal with a Big Pharma company.

“We started this company based on the cancer therapeutic, and the diagnostic has thrown a really nice wrinkle into our plans—where we might go and how we get there,” Mr. Gunn says. “The diagnostic could be licensed-out early after we finish the proof of concept and have a test kit. Or we could take a little further, or we could take it right through to the end of regulatory approval and then do a deal to get into the market. It’s something we’re still working on.”

On the other hand, he isn’t ruling out a takeover of Soricimed as an alternative to partnering on the development of the cancer drug. “A takeover would be much a cleaner exit for our investors, but we can’t take dictate how that will play out. We’re keeping our options open and making sure we’re still in shape to do either.”

Taking Soricimed public is another option. “If we ended up with a number of co-development deals and a pipeline going forward, that may be the trigger to take us public,” Mr. Gunn says. “We’re staying flexible enough that we can either take a buyout, a co-development deal or eventually go public.”