Waterstone Pharmaceuticals Announces Positive Top-Line Phase III Data for WS016 in the Treatment of Hyperkalemia

For patients with advanced chronic kidney disease, a routine blood test can deliver alarming news: potassium levels have climbed dangerously high. The condition, hyperkalemia, affects up to 50% of late-stage CKD patients and carries a grim consequence—doctors are often forced to pull them off the very heart and kidney drugs that keep them alive.

Now Waterstone Pharmaceuticals, a Wuhan-based biotech company, says it has a potential answer. The company announced on August 25, 2026, that its experimental drug WS016 met all primary and key secondary endpoints in a Phase III trial for hyperkalemia, setting the stage for a new drug application to China’s National Medical Products Administration (NMPA) in the near term.

The results, if they hold up under regulatory scrutiny, could reshape how one of nephrology’s most stubborn complications is managed—and give doctors a reason to keep patients on life-saving therapies they might otherwise abandon.

A Trial Built on Real-World Complexity

The WS016CT301 trial, led by Professor Liu Bicheng at Zhongda Hospital of Southeast University, enrolled more than 400 patients across 50 clinical research centers in China. The study design was rigorous: a multicenter, randomized, double-blind, placebo-controlled Phase III trial split into two parts—Part A, a prospective dose-finding study with multiple dose groups, and Part B, an open-label extension.

What made the trial particularly noteworthy was the patient population. The enrolled subjects carried severe baseline kidney impairment, including a significant subgroup in end-stage renal disease (CKD Stage 5, baseline eGFR below 15 ml/min/1.73 m²). These are precisely the patients who face the highest hyperkalemia risk and have the fewest treatment options.

Part A met its primary endpoint and all key secondary endpoints, achieving preset statistical thresholds.

Fast Potassium Reduction

WS016, a Class 1 macromolecular innovative drug formulated as a dry suspension, demonstrated rapid potassium-lowering effects. Just 24 hours after the first dose, blood potassium levels in the WS016 treatment group dropped significantly from baseline compared with placebo. More than 60% of treated subjects saw their potassium return to normal range.

The results were even more striking in the CKD Stage 5 subgroup. Within 48 hours of the first dose, over 85% of these end-stage patients achieved potassium target levels—a clinically meaningful outcome for a population that is notoriously difficult to treat.

Sustained Control Over 28 Days

Long-term potassium management proved equally compelling. After 28 days of maintenance therapy, all three WS016 treatment groups—6g, 12g, and 18g—maintained average blood potassium within the normal range of 3.5 to 5.0 mmol/L (inclusive of boundary values). By contrast, the placebo group’s average potassium crept above 5.0 mmol/L.

The differences between each treatment group and placebo were all statistically significant.

Safety Profile Holds Up

No unexpected serious safety signals emerged. Adverse event rates across all trial phases were comparable to placebo, and overall tolerability was favorable.

Among drug-related adverse events, hypokalemia (abnormally low potassium) showed a dose-dependent increase, but all cases were mild to moderate. Hypomagnesemia and peripheral edema occurred at rates similar to placebo, with no dose-related pattern as WS016 doses increased.

The Clinical Stakes

Hyperkalemia is far more than a lab abnormality. It is a common and potentially fatal complication for patients with chronic kidney disease and heart failure, particularly those in CKD stages 4 and 5.

According to China’s 2026 annual blue book on hyperkalemia management, approximately 75% of CKD patients who develop hyperkalemia are forced to reduce or discontinue RASi/MRA medications—cornerstone therapies for heart and kidney protection. After discontinuation, the rates of adverse cardio-renal events and mortality climb to 34.3% and 11.0%, respectively.

The data underscore a harsh reality: chronic or recurrent hyperkalemia is an independent risk factor for poor cardio-renal outcomes and death in CKD patients. Long-term potassium management is not optional—it is essential for improving survival.

What Comes Next

If approved, WS016 dry suspension would add a new option to China’s limited hyperkalemia treatment arsenal, offering patients a potentially safer and more accessible way to keep potassium in check over the long term. Waterstone Pharmaceuticals is now preparing to file its new drug application with the NMPA, aiming to bring the therapy to market as quickly as possible.

For the hundreds of thousands of CKD patients caught between controlling potassium and staying on life-extending medications, that can’t come soon enough.

This article does not constitute investment advice or medical treatment recommendations. All data sourced from company announcements and the original report. For official information, refer to company disclosures.