A randomized pilot study to evaluate the stability, taste, and palatability of a novel liquid formulation of tenapanor.

Objective: This pilot study aimed to develop a liquid formulation of tenapanor and evaluate taste and palatability with different sweetener and flavor combinations.

Significance: Tenapanor is a first-in-class, minimally absorbed, small molecule inhibitor of intestinal sodium/hydrogen exchanger 3, indicated (as tablets) to treat adults with constipation-predominant irritable bowel syndrome. It is also approved as add-on therapy to reduce serum phosphorus in adults with chronic kidney disease on dialysis who are intolerant of, or unacceptably responsive to, any dose of phosphate binder therapy. Since many patients have difficulty swallowing pills and pediatric studies are underway, a liquid formulation was developed, and taste profiles were evaluated for overall acceptability.

Methods: Formulation of liquid tenapanor targeted a concentration of 5 mg/mL, for a dosing range of 1-50 mg twice daily. Improvements in solubility and stability of tenapanor in water were investigated with the use of buffers, cosolvents, and preservatives. Seven liquid formulations with different sweetener/flavor combinations were assessed for taste and palatability by healthy adult participants using the sip-and-spit method in a randomized design.

Results: An aqueous solution of tenapanor (5 mg/mL), pH 3.4, with 0.05 % (w/v) benzoic acid, was stable at 2-8 °C for 12 months. The formulation with sucralose and raspberry flavor had the greatest improvement in overall acceptability and taste when compared to the reference solution without sweeteners or flavors.

Conclusions: A suitable liquid formulation was identified for progression to patient studies.