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 The findings are from two separate studies financed by the
manufacturers and released Friday by the New England Journal of
Medicine.
The oral drugs are sodium zirconium cyclosilicate (also known as
ZS-9 and being developed by ZS Pharma) and patriomer (developed by
Relypsa). Both drugs treat high potassium by binding to it as they
travel through the gut.
If the drugs are approved -- and longer-term tests are needed before
that happens -- they could change the way doctors treat kidney
disease and heart failure.
That's because a high potassium level in the blood, or hyperkalemia,
is a potentially deadly side effect of a specific class of drugs
used for kidney and heart problems, called RAAS inhibitors.
"Doctors are paranoid about hyperkalemic death when they use these
kidney- and heart- protective drugs. So they won't use them, or they
use them in much lower doses than they should," said Dr. Matthew
Weir of the University of Maryland School of Medicine and chief
author of the patiromer study.
The two new drugs should alleviate some of that concern, Weir told
Reuters Health in a telephone interview.
Dr. David Packham of the University of Melbourne, chief author of
the ZS-9 study, foresees a significant benefit for the drug he
tested.
"Because the effect can be maintained, in this case for 14 days, it
has the potential for being an enabling therapy that enables you to
keep patients on treatments that benefit them that often have to be
reduced in dose because of hyperkalemia," he said by phone.
"What this does is reliably and very rapidly - within 48 hours -
dramatically reduce potassium levels," said Packham. "You could see
where the patients who were (taken off ZS-9) went back up to their
previous potassium levels over the 14-day period, whereas the levels
were maintained in the patients who were kept on ZS-9. And when they
were taken off, the levels went back up again. It was very, very
clear."
"The drug was equally effective across various subgroups, including
patients with a combination of heart failure, chronic kidney
disease, and diabetes," the researchers concluded.
"I think it will become the standard for treatment for acute
hyperkalemia," Packham said.
Weir expressed a similar sentiment for patiromer.
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That test, involving patients with high potassium levels who were
getting RAAS inhibitors for their long-term kidney disease, "is
quite a definitive study," he said. "It's a study done exclusively
in people with chronic kidney disease receiving the lone therapy we
know of that slows the progression of kidney disease."
After four weeks of patiromer therapy, potassium levels had fallen
into the normal range for 76 percent of the patients.
Among 52 volunteers who were then taken off the drug and given a
placebo instead, potassium returned to unacceptably high levels in
60 percent. Yet among the 55 patients who were kept on the drug,
only 15 percent redeveloped hyperkalemia at the eight-week mark.
Nearly half the patients on the drug had at least one side effect, a
rate that was similar among placebo recipients. The most common side
effect was mild-to-moderate constipation, which surfaced in 11
percent. Potassium levels dropped too far in 3 percent.
With ZS-9, at least one side effect was reported at some point in a
quarter of the patients in each group. The most common side effect
was diarrhea, seen in 1.8 percent of patients taking the drug and
2.5 percent with placebo. In two patients, potassium levels dropped
too far, but the effect was temporary.
Weir said the two drugs rely on different mechanisms, may have
different side effects and have yet to be pitted against each other
in a study. "But I think both are going to be heads and tails above
existing therapies."
SOURCES: http://bit.ly/1xc4ZLl and http://bit.ly/1F8Zr8V The New
England Journal of Medicine, online November 21, 2014.
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