The study consists of a screening visit, a wash out period of up to 3 weeks, when existing phosphate lowering medication is withheld, an 8-week treatment period, in which all groups receive tenapanor, and a 4-week placebo-controlled, randomized withdrawal period, during which patients are re-randomized 1:1 to either remain on their current tenapanor treatment or placebo.
Depending on the increase in serum phosphate levels, subjects can be randomized 1,2, or 3 weeks after being taken off their phosphate lowering medication.
