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the mineral is almost ubiquitous in foods, including leafy greens, potatoes, carrots, tomatoes, oranges, bananas and a number of other fruits. Some diuretics can be used to flush out potassium. In addition, there’s an approved drug class that dates back to the 1950s called sodium polystyrene sulfonate, which includes the brand-name drug Kayexalate from Sanofi-Aventis. That drug’s downsides include side effects such gastric irritation, nausea, vomiting, constipation, and less commonly, diarrhea and perforation of the intestine.
Both Relypsa and a rival drug developer, Coppell, TX-based ZS Pharma, see an unmet need for a better therapy for millions of patients with hyperkalemia, who often suffer from related disorders—diabetes, heart failure, and kidney disease. Orwin estimates the potential market for patiromer at 2.4 million people in the United States alone.
Patiromer, a polymer suspended in fluid and taken by mouth, is designed to pass through the body without being digested. But when it reaches the colon, it binds to positively charged potassium ions and carries them out of the body as the polymer is eliminated from the digestive tract.
In data released in November from late-stage trials, Relypsa said patiromer reduced blood potassium levels to the normal range for 76 percent of trial participants after about a month of treatment. Relypsa points to other trial results to support the use of patiromer as a maintenance drug that could be taken over extended periods of time to keep potassium levels in check. In one study, trial participants remained on patiromer for as long as a year.
To see whether continued treatment was needed after potassium levels had been lowered with patiromer, Relypsa studied two classes of participants in its late-stage trial. Those who stopped taking patiromer were more likely to see their blood potassium rise again, while potassium levels were more likely to remain steady for those still on the drug.
“If you withdraw the product, the problem is going to come back,” Berman says.
ZS Pharma has also completed late-stage trials of its drug candidate for hyperkalemia. The compound, ZS-9, is a crystalline form of the inorganic molecule zirconium silicate that was also designed to bind potassium ions. In trial results released over the past few months, ZS Pharma has reported success with ZS-9 in lowering blood potassium levels in as little as 48 hours. The experimental drug, taken orally, was well tolerated and maintained control of potassium levels in trial participants receiving ZS-9 for 12 days, the company announced.
ZS Pharma plans to test ZS-9 in further trials for periods up to a year. The company intends to seek FDA approval by early 2015. Its rival, Relypsa, plans to file for FDA approval of patiromer by the third quarter of 2014.
In late 2013, Relypsa had hopes that its pending IPO would raise $120 million to fund the company through the process of securing FDA approval of patiromer. At the time, the number of health care IPOs had been surging. Also, Relypsa’s drug candidate had already been through late-stage clinical trials, while other companies seeking to go public were further behind.
“We saw the interest when we went on the road,” Orwin says.
But demand flagged during the week in November when Relypsa priced its offering, Orwin says. He thinks investors were fatigued after reviewing a rash of IPOs through the year; several companies even suspended their attempts to go public. Relypsa dropped its price to $11 a share, raising a net $77 million.
Since then, however, Relypsa’s shares have climbed steadily, and are now trading at more than $30.
“People started to more appropriately value the company,” Orwin says.
But while the additional share value is good for investors, it doesn’t add to Relypsa’s trove of operating cash. Orwin says the company will need to raise more money—probably through a combination of equity, debt, and a partnership deal for patiromer in markets outside the U.S. Relypsa holds worldwide royalty-free commercialization rights to patiromer. Relypsa acquired the drug when the company was founded in 2007 as a spinout of Santa Clara, CA-based Ilypsa, which was acquired that year by biotechnology giant Amgen of Thousand Oaks, CA.
The 69-employee company plans to build its own sales force to market the drug to kidney and heart specialists in the United States if the FDA approves it for sale, says Orwin, former CEO of Affymax and a former marketing executive at Genentech.