because the drug was approved under the FDA’s DESI program, which classified all pre-1962 drugs that were already on the market as either effective, ineffective, or needing further study. So, he added, Kayexalate, did not go through clinical trials and produce data that could be compared with drugs such as ZS-9.
Alexander says the difference between the two is that the existing product is an organic polymer that binds calcium, potassium, and sodium, while ZS-9 is an inorganic crystal that has the ability to select only potassium for removal. A big issue with Kayexalate is that most patients experience diarrhea. In the Phase III trial of the ZS Pharma drug, about 3.5 percent of patients experienced gastrointestinal distress, compared with 5.1 percent who reported that effect while on the placebo, Alexander says.
“The highest dose was the best tolerated in all our dosing groups,” he added.
ZS plans to do another study that follows patients for 28 days, with a similar design to the recently completed 12-day study. Alexander declined to specify the number of patients or the dosage amounts in the next study. Upon successful completion, he added that the company plans to file a new drug application with the Food and Drug Administration in the fourth quarter of next year.
ZS is not the only life sciences startup looking for a better way to treat hyperkalemia. Redwood City, CA-based Relypsa (NASDAQ: [[ticker:RLYP]]) went public earlier this month, and has said it plans to file a new drug application to the FDA before the end of 2014.
ZS was founded in 2008 by Alvaro Guillem, who is now the startup’s CEO, Jeffrey Keyser, the current chief operating officer, and Stephen Ash, a nephrologist at Indiana University Health. Alexander first met up with them in 2010 when he was at Alta Partners but didn’t decide to invest in their work until 2012.
“It was, frankly, shocking how quickly they went from animal data to the human proof of concept stage,” he says. “Their Phase II data looked fantastic.”
That mid-stage study examined the safety and efficacy of three doses of the drug, at 0.3 grams, 3 grams, and 10 grams.
So far, ZS Pharma has raised about $56 million, $10 million of which came from the Texas Emerging Technologies Fund and Series B round led by Devon Park BioVentures. Its most sizable funding came in last October, a Series C round led by Devon, Alta Partners, RiverVest, Salem Partners, and 3×5 Special Opportunity Partners.
Alexander left Alta to join ZS in March. He says the startup will likely go out to raise an additional round of money next year but declined to provide specifics. He says the plan is to develop and market the drug in the United States alone, without the help of a partner. “Assuming we are a standalone company, sometime in the future, we would look to partner to launch the product ex-North America,” he added.
