The hyperkalemia (HK) symposium at the spring National Kidney Foundation conference in Boston was a popular event. On Thursday April 28th, hundreds crowded into the ZS Pharma-sponsored talk. What is the excitement for? Those treating chronic kidney disease (CKD) patients are all too familiar with the balancing act of preventing HK while maintaining blood pressure (BP) control with the antihypertensive RAAS inhibitors. HK is common in CKD patients; for those patients in whom potassium-sparing diets are not enough, removing modifiable causes of elevated serum potassium levels like RAAS inhibitors or adding low-dose sodium polystyrene sulfonate/Kayexalate can be the only options. That was then. Now we have two agents before us, one FDA approved (Relypsa’s Veltassa) and the other under review (ZS Pharma/AstraZeneca’s ZS-9), with demonstrated efficacy in chronic HK management.
Chronic HK management is new and exciting territory. Primary research by Decision Resources Group finds that 31% of nondialysis and 44% of dialysis patient have HK (TreatmentTrends®: Hypkeralemia (US) 2015 report) and that one-third of all HK patients are considered chronic. Currently marketed agents, like Kayexalate, are only approved for use in the acute setting and are met with high patient resistance because of their unpleasant GI side-effects. For patients with higher baseline potassium deemed at risk for HK, the new and emerging potassium binders may offer long-term clinical benefits- the largest being the continued use of RAAS inhibitors.
While these new and emerging agents usher in a new era, there are still many unknowns. Can Veltassa and ZS-9 control HK for longer than 52 weeks? What are the impacts of HK management on clinical outcomes? Will any rare safety risks emerge, like the colonic necrosis seen in SPS-treated patients? Will costs prevent patients from gaining access to these potassium binders?
Leading nephrologists and session moderators Linda Fried, MD MPH, from University of Pittsburg, Csaba Kovesdy, MD, from University of Tennessee Health Science Center, and Ishir Bhan, MD MPH, from Massachusetts General Hospital agreed that both Veltassa and ZS-9 demonstrated efficacy in treating HK in CKD patients who remain on RAAS inhibitors. They were excited about their use in the chronic setting, but cautioned that long-term data is needed. In addition, Dr. Kovesdy noted that we are lacking the tools to continuously monitor HK, which may be important when prescribing in the chronic management setting. Of course use in the chronic setting would be highly impacted by cost. The moderators could not speculate on the cost of the potassium binders as they themselves had no experience with Veltassa because they are not yet able to prescribe it.
Despite these questions, the kidney community is undoubtedly excited about the future benefits Veltassa and ZS-9 can provide in the management of chronic HK.