ZS-9, A Potassium Binder That is Tested and Works
ZS-9 is a novel, selective potassium trap. Per the speaker, it is very different than sodium polystyrene sulfonate (Kayexalate) which is a cation exchange resin. ZS-9 is a crystal with an ion selective pore designed like biologic ion channels. The speaker was quite proud of the ion selectivity and pointed out that SPS binds more calcium than potassium. According to their data gram for gram it binds 9 times as much potassium as SPS. He first presented a phase-2 human trial. It was a multicenter, placebo controlled, randomized controlled trial with dose escalation. Patient with potassiums ranging from 5-6 mEq/L were randomized to placebo, 0.3, 3 or 10 grams. The primary end-point was the rate of potassium fall. The binder worked at the 3 and 10 g dose. No difference from placebo was seen at 0.3g. The rate of decline was 0.04 mEq/L/hour following a single dose of 10 grams. The rate was 0.01 mEq/L/hour for placebo.
He then discussed a phase 3 trial. This time they studied 753 patients, the largest potassium binder study ever. I wonder if it is the largest study on the treatment of hyperkalemia ever. The 10 gram dose lowered the potassium 0.78 mEq/L after 14 hours. Pretty good.
GI side effects were no greater than placebo.
Given the recent controversies surrounding SPS, it will be great to have safe, effective and well studied alternative. I wish them good luck at the FDA.
Post written by Dr. Joel Topf, eAJKD Advisory Board member.