Dr. Meymandi, who has treated more Chagas patients than has any other U.S. clinician, said that treatment has changed somewhat since the JAMA article was published. In 2007, she said, nifurtimox was the main drug available through CDC, while benznidazole, which is somewhat better tolerated and has shorter treatment duration, has since become the first-line agent.
“We’ve lowered the dose of benznidazole, maxing out at 400 mg/day to decrease the toxicity,” she said. Also, treatment is now being extended to some patients aged 60 years and older.
The decision to treat or not treat, clinicians say, depends on the patient’s age, disease progression, comorbidities and potential serious drug interactions, and willingness to tolerate side effects that, with nifurtimox especially, can include skin sloughing, rash, and psychological and neurologic symptoms including depression and peripheral neuropathy.
“If you don’t have side effects, you’re not taking the drugs,” Dr. Meymandi said. Dr. Woc-Colburn noted that polypharmacy was a major consideration when treating older adults for Chagas. “If I have a patient who has diabetes, obesity, [and] end-stage renal disease, it’s not going to be ideal to give [benznidazole].”
Recent, highly anticipated results from BENEFIT, a large randomized trial (n = 2,854) showed that benznidazole reduced parasite load but was not helpful in halting cardiac damage at 5 years’ follow-up in patients with established Chagas cardiomyopathy (N Engl J Med. 2015 Oct;373:1295-306. doi:10.1056/NEJMoa1507574).
Dr. Meymandi, whose earlier research established that Chagas cardiomyopathy carries significantly higher morbidity and mortality than does non–Chagas cardiomyopathy (Circulation. 2012;126:A18171), said that the BENEFIT results underscore the need for physicians to be bullish in their approach to treating Chagas soon after diagnosis.
“It doesn’t matter if they’re symptomatic or asymptomatic. You can’t wait till they progress to treat. If you wait for the progression of disease you’ve lost the battle. You can’t wait and follow conservatively until you see the complications, because once those complications have started the parasitic load is too high for you to have an impact,” she said.
Dr. Yun said that given the toxicity of current treatment, she hoped to see more studies show clearer evidence of clinical benefit, “either reductions in mortality or reductions in end organ disease.” Most studies “have focused on clearance of parasite, which is important, but it’s not as important decreasing the risk of death or cardiomyopathy or heart failure.”
Rick Tarleton, Ph.D.
Rick Tarleton, Ph.D., a biologist the University of Georgia, in Athens, who has worked on Chagas for more than 30 years, said that because Chagas pathology is directly tied to parasite load – and not, as people have suggested in the past, an autoimmune reaction resulting from parasite exposure – drug treatment may prove to be worthwhile even in patients with significant cardiac involvement.
“You get rid of the parasite, you get rid of the progression of the disease,” Dr. Tarleton said. Even the findings from the BENEFIT trial, he said, did not lead him to conclude that treatment in people with established cardiac disease was futile.
“If you’re treating people who are already chronically infected and showing symptoms, the question is not have you reversed the damage, it’s have you stopped accumulating damage,” he noted. “And a 5-year follow-up is probably not long enough to know whether you’ve stopped accumulating.”
“We have drugs, they’re not great, they do have side effects, they don’t always work,” Dr. Tarleton said. “But they’re better than nothing. And they ought to be more widely used.”
Dr. Meymandi said that current supplies of benznidazole at CDC are low and that a dozen patients at her clinic are awaiting treatment. Meanwhile, access may soon be complicated further by the announcement, this month, that KaloBios Pharmaceuticals had bought the rights to seek FDA approval of benznidazole and market it in the United States.
The same company’s CEO came under fire in recent months for acquiring rights to an inexpensive drug to treat toxoplasmosis in AIDS patients, then announcing a price increase from $13.50 to $750 a pill.
“Everyone’s really concerned,” Dr. Meymandi said, “because Chagas is a disease of the poor.”