Tenapanor demonstrates effective phosphorous control with reduced pill burden
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A study of patients receiving hemodialysis in Japan demonstrated the efficacy of tenapanor for treating hyperphosphatemia with fewer daily pills required in a 26-week period.
“Phosphate binders act by binding to phosphoric acid in the gastrointestinal tract and promoting phosphorus excretion into the feces. However, some phosphate binders lead to adverse drug reactions, including iron deposition in organs, hypercalcemia, and gastrointestinal symptoms (eg, diarrhea, changes in stool color),” Tadao Akizawa, MD, of Showa University School of Medicine in Tokyo, and colleagues wrote. “Additionally, adherence to treatment is another major issue with phosphate binder treatment. These drugs need to be taken before or after every meal, and tablets are usually large and require many pills per dose; thus, this treatment results in a substantial pill burden. These factors have a detrimental effect on drug adherence.”
Study design, methods
Seeking to assess the impact of tenapanor — defined as “a first-in-class, non-binder, phosphate absorption inhibitor” — on phosphorous control, Akizawa and colleagues added the drug to the daily pre-enrollment phosphate binder regimen of 43 patients who had serum phosphorous levels between 3.5 mg per dL and 7 mg per dL.
“The dose of phosphate binders was adjusted according to the investigators’ judgment, with the aim of achieving a serum phosphorus level within the baseline range [plus or minus] 0.5 mg/dL for each patient,” the researchers explained of the study methods. “If an [adverse event] AE occurred for which a causal relationship with a phosphate binder could not be ruled out, the dose could be reduced. Restricted concomitant medications and therapies were calcium preparations for supplementation, active vitamin D preparations, calcimimetics and hemodialysis.”
Patients received 30 mg of oral tenapanor twice daily (taken immediately before meals), with researchers considering the percentage of patients who achieved at least a 30% decrease in the number of phosphate binders and tenapanor tablets prescribed daily as the primary endpoint.
Impact of tenapanor on pill burden
The addition of tenapanor reduced the mean total number of phosphate binder tablets per day from 14.7 at baseline to 3 at week 26, with the primary endpoint achieved in 71.6% of patients.
Further, 28.4% of patients had their phosphate binder “completely switched” to tenapanor.
Regarding phosphorus control, researchers observed a change from mean levels of 5.19 mg per dL at baseline to 4.71 mg per dL at week 26.
The most frequent AE associated with tenapanor was diarrhea, which was reported by 74.6% of patients.
“In conclusion, by adding tenapanor to existing phosphate binder regimens, patients could reduce not only the phosphate binder pill burden, but some also successfully switched from the prescribed phosphate binder regimen completely,” Akizawa and colleagues wrote.
“ ... Even though many patients experienced diarrhea, few discontinued the study due to diarrhea over the 6-month dosing period. For more widespread use of tenapanor, an increased understanding of the optimal management of drug-related diarrhea will be necessary.”
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