FDA Reviewers Skeptical About Expanded Use of TolvaptanAug 5, 2013
A U.S. Food and Drug Administration (FDA) review panel may not be prepared to approve the use tolvaptan (Samsca) to treat autosomal dominant polycystic kidney disease (ADPKD). The panel, which is to meet today, expressed concern about missing clinical trial data.
A single phase III trial showed the drug slowed the loss of renal function in patients with relatively healthy kidneys but deemed at high risk of failure, FDA reviewers noted in briefing documents prepared for the agency's Cardiovascular and Renal Drugs Advisory Committee, MedPage Today reports.
The committee will consider trial results and vote on recommending approval of tolvaptan for slowing kidney disease in adults at risk of rapidly progressing ADPKD. "However, because of missing data in a sizeable portion of the study population and particularly so in the tolvaptan arm, the size of the treatment effect is unclear," FDA staff noted. "Treatment effects on other endpoints—kidney volume and renal pain events requiring medical intervention—were supportive of the drug's activity."
Tolvaptan was approved in 2009 to treat low serum sodium levels, but drug maker Otsuka is seeking expanded approval to treat patients with ADPKD. There are no approved products for slowing the progression of kidney disease in patients with ADPKD, according to MedPage Today.
In a randomized, controlled trial of 1,445 patients, gains in total kidney volume were higher for patients treated with placebo compared with those on tolvaptan (5.5% per year versus 2.8% per year) (P<0.001). But reviewers noted that a sizeable portion of trial enrollees dropped out of the trial (23% of tolvaptan and 14% of placebo patients). Some of these randomized subjects, therefore, never entered into efficacy endpoints analyses while others contributed information for only a limited period of time, MedPage Today reports.
Reviewers were also concerned with the lack of data on patients with more advanced stages of kidney disease, making it "difficult to project tolvaptan's likely benefit in delaying the onset of end-stage renal disease." In April the FDA warned about the risk of liver injury, advising that tolvaptan should be taken for no more than 30 days and should not be used by patients with underlying liver disease, MedPage Today reports.