New Paradigm for Tuberculosis Prevention?

A 1-month regimen of rifapentine plus isoniazid was non-inferior to 9 months of isoniazid alone for prevention of tuberculosis in HIV-infected patients, researchers found.

The primary endpoint — first diagnosis of tuberculosis infection or death from tuberculosis — was reported in 2% of patients in the intervention group and 2% of patients in the 9-month control group, for incidence rates of 0.65 and 0.67 per 100 person-years, respectively, reported Richard Chaisson, MD, of Johns Hopkins University School of Medicine in Baltimore, and colleagues.

Patients assigned to the 1-month combo regimen also had a lower incidence of adverse events, and were more likely to complete treatment than did controls, the authors wrote in the New England Journal of Medicine.

The rate difference was -0.02 per 100 person-years, upper limit of 95% confidence interval 0.30 — well within the prespecified non-inferiority margin of <1.25 events per 100 person-years.

The standard of care for tuberculosis prevention in high-risk patients has been 6-9 months of isoniazid, Chaisson and colleagues explained, but it’s been less than satisfactory because of the difficulty in keeping patients adherent, particularly in resource poor settings. That has prompted a search for shorter regimens that don’t sacrifice efficacy. Mouse studies had pointed to rifapentine plus isoniazid as a good candidate, the researchers wrote.

The Brief Rifapentine–Isoniazid Efficacy for TB [Tuberculosis] Prevention/A5279 trial (BRIEF TB/A5279) was a randomized, open-label phase III trial conducted in 10 countries in Africa, Asia, South America, North America, and the Caribbean. Participants were ages ≥13 and either lived in an area with tuberculosis presence of >60 cases per 100,000 persons or tested positive for latent tuberculosis.

Patients had antiretroviral therapy (ART) with efavirenz or nevirapine for the first month, and then use of any other ART was permitted after that. They were followed up every 2 weeks until week 36 and then every 12 weeks thereafter for a median of about 3 years.

Overall, 1,488 patients were randomized to receive a 1-month regimen of rifapentine plus isoniazid, while 1,498 patients were randomized to receive 9 months of isoniazid alone. Median age was 35 and 54% were women. Median CD4 count was 470, half of patients were receiving ART at entry, and three-quarters of those patients had an undetectable viral load.

Serious adverse events occurred in 6% of patients in the intervention group and 7% of controls (P=0.07); 97% of patients in the intervention group completed their assigned treatment versus 91% of controls (P<0.001).

An accompanying editorial by Matthew J. Saunders, MRCP, of University College London in England, and Carlton A. Evans, PhD, of Universidad Peruana Cayetano Heredia in Peru, noted that there are several alternatives to traditional isoniazid therapy for tuberculosis, including “isoniazid and rifapentine administered weekly for 3 months, 3 months of daily isoniazid and rifampin, and 4 months of daily rifampin monotherapy.”

However, Saunders and Evans added that “the cost of rifapentine may be an important barrier to implementation in the lower-income settings where most tuberculosis occurs.” The editorialists also noted that globally, the great majority of tuberculosis cases occur in persons without HIV infection, emphasizing the importance of evaluating preventive therapies in all populations.

“Improving the brevity, acceptability, and safety of preventive therapy is important and will potentially have a major effect,” Saunders and Evans wrote. “However, such therapy has to be considered in the context that several billion people … are believed to have asymptomatic latent tuberculosis infection.”

Shorter Therapy Regimen Non-Inferior for Patients with MDR TB

A second study published in NEJM by Andrew J. Nunn, PhD, of the MRC Clinical Trials Unit at UCL (University College London) in England, and colleagues, indicated that treatment of rifampin-resistant tuberculosis could also be shortened from the current standard.

In particular, a 9-11 month regimen including moxifloxacin was non-inferior to 20 months of therapy as recommended in the 2011 World Health Organization guidelines, in patients susceptible to fluoroquinolones and aminoglycosides.

The Standard Treatment Regimen of Anti-Tuberculosis Drugs for Patients with MDR-TB (STREAM) trial was a randomized, phase III, non-inferiority trial conducted in Africa and Asia. Patients were ages ≥18 and had pulmonary tuberculosis with evidence of resistance to rifampin. Patients were randomized 2:1 to the short versus long regimen.

Overall, 282 patients were randomized to the shorter regimen group and 142 were randomized to the longer regimen group, with the modified intention-to-treat population comprised of 383 patients. Of this population, a little over a third were infected with HIV.

At 132 weeks, 78.8% of patients randomized to receive the short regimen achieved a “favorable status” (defined as cultures negative for Mycobacterium tuberculosis at 132 weeks and a previous occasion, with no intervening positive culture or unfavorable outcome) compared to 79.8% in the long-regimen group. After adjusting for HIV status, the difference was 1.0 percentage point (95% CI -7.5 to 9.5, P=0.02 for non-inferiority). Non-inferiority was defined as an upper 95% confidence limit of <10 percentage points difference in favorable status.

Severe adverse events including death did not differ significantly between groups (48.2% short vs 45.4% long treatment). ECG monitoring found that prolongation of the QT interval occurred in a higher portion of participants in the short versus long regimen group (11.0% vs 6.4%).

An accompanying editorial by Gavin J. Churchyard, PhD, of Aurum Institute in Parktown, South Africa, said that while these results provided evidence for the efficacy of a shorter regimen, it “by no means represents a triumph for patients or practitioners.”

While severe side effects “did not differ notably” between the two groups, Churchyard noted, “importantly, the shorter regimen still includes 4 months of painful injections with an aminoglycoside that includes the associated risk of ototoxic and nephrotoxic effects.”

He concluded that while the shorter regimen is “definitely better” when it comes to treating MDR-TB, “it is not good enough” and “we have a long way to go to turn back the tide.”