Potentially Practice-Changing Bacterial Therapy Trials Analyzed

Neil Osterweil

October 30, 2020

A new formulation of an existing antibacterial agent and a potential therapeutic approach to a challenging clinical problem were the focus of a session on potentially practice-changing clinical trials in antimicrobial therapy presented during IDWeek 2020, an annual scientific meeting on infectious diseases.

"I know it has been a big year for viral disease of course, with COVID, but there has been some really good work that has gone on in the bacterial space, and of course as those of you who are on service know, you may have your fair share of COVID patients, but these are infections that we still deal with on a daily basis," said Michael Satlin, MD, an infectious disease specialist at Weill Cornell Medicine in New York.

He combed through studies published during the previous 12 months in leading medical journals, including the New England Journal of Medicine, JAMA network publications, Lancet Infectious Diseases, Lancet Respiratory Medicine, Clinical Infectious Diseases, and Clinical Microbiology and Infection, looking for randomized trials of interventions to treat bacterial infections, and selecting those most likely to change practice of U.S. infectious diseases practitioners.

He excluded meta-analyses, post hoc analyses, evaluations of diagnostic tests, stewardship, or any studies presented previously at IDWeek.

Two of the trials he highlighted are described here.

Fosfomycin for Injection

In the United States, fosfomycin, the only antibiotic in its class, is currently available only in an oral sachet formulation (Monurol), "and typically we've only given this for patients with cystitis because we know that we don't achieve significant levels [of drug] in the kidney or in the bloodstream for other types of infections," Satlin said.

In Europe, however fosfomycin for injection (ZTI-01) has been available for several years.

"There's been a lot of interest in fosfomycin because it has a different mechanism of action from other agents. It's an epoxide antibiotic that inhibits early peptidoglycan synthesis by binding to MurA," he explained.

The phase 2/3 randomized ZEUS trial compared ZTI-01 with piperacillin/tazobactam (pip/taz) for treatment of complicated urinary tract infection (UTI) including acute pyelonephritis.

A total of 465 hospitalized adults with suspected or microbiologically confirmed complicated UTI or acute pyelonephritis were randomized to 6 g of ZTI-01 every 8 hours or 4.5 g of intravenous pip/taz every 8 hours for a fixed 7-day course with no oral switch; patients with concomitant bacteremia (about 9% of the study population) could receive the assigned therapy for up to 14 days.

The primary endpoint of noninferiority of ZTI-01 was met and clinical cure rates were high and similar between the treatments, at approximately 91% each. Treatment-emergent adverse events, including hypokalemia and elevated serum aminotransferases, were mostly mild and transient.

The hypokalemia seen in the trial may be attributable to the high salt load of fosfomycin relative to pip/taz, Satlin said.

"How might this change your practice? Well, if IV fosfomycin is ever FDA [Food and Drug Administration] approved – and my understanding is that the delays have been more related to manufacturing than scientific quality of data – it could potentially be an alternative to beta-lactams and fluoroquinolones" and has activity against most extend spectrum beta-lactamase (ESBL)–producing Enterobacteriaceae, he said.

Fosfomycin susceptibility testing is challenging, however, with no Clinical & Laboratory Standards Institute (CLSI) or FDA breakpoints for Enterobacterales other than Escherichia coli, and there are questions about the step-down therapy.

"Do you just give a 3-gram sachet chaser when they walk out the door? Do you switch to another agent? I think that needs to be worked out," he said.

Inhaled Amikacin

"We know that some IV antibiotics, particularly for resistant organisms, may not achieve sufficient concentrations in the lung to treat pneumonia. We know that inhaled antibiotics can give a lot of concentration of that drug right at the at the site of infection, but we don't really have [randomized controlled trial] data to see whether it really helps," Satlin said.

The INHALE trial was a double-blind, placebo-controlled superiority trial to see whether adding inhaled amikacin to IV standard-of-care antibiotics could improve outcomes for mechanically ventilated patients with gram-negative pneumonia.

The investigators enrolled 725 adults who were receiving mechanical ventilation for pneumonia, 45% of who had ventilator-associated pneumonia (VAP). Of the total cohort, 508 patients analyzed for efficacy had gram-negative pathogens, including 32% with Pseudomonas aeurginosa, 29% with Acinetobacter baumannii, 30% with E. coli, and the remainder with Klebsiella pneumoniae.

Patients were randomized to standard-of-care intravenous antibiotics plus either inhaled amikacin 400 mg twice daily for 10 days or inhaled saline placebo.

"Of note, the median standard-of-care antibiotics in this study was 18 days, which is certainly longer than what our guidelines recommend."

There was no significant difference between study arms in the primary endpoint of survival at days 28-32 for all patients who had received at least one dose of study drug, were infected with a gram-negative pathogen, and an Acute Physiology and Chronic Health Evaluation (APACHE) II score of at 10 or higher at diagnosis. The respective survival rates for the inhaled amikacin and placebo groups were 75% and 77%. The incidence of treatment-emergent adverse events or serious treatment-emergent adverse events were similar between the two treatment arms.

"No matter how you sliced and diced it — days of mechanical ventilation, duration of ICU stay — essentially they looked the same. Even for [extensively drug resistant] pathogens where you might expect that you'd see the benefit of inhaled amikacin, they didn't really see a mortality benefit in this study," Satlin said.

The study is practice changing, he said "because I think inhaled aminoglycosides should not be routinely added to the standard of care IV antibiotics for pneumonia in ventilated patients," he said.

It's still unclear whether inhaled aminoglycosides might play a role in the treatment of select patients infected with organisms resistant to all beta-lactams and fluoroquinolones, he added.

Tempting Strategy

"Adding inhaled antibiotics is a tempting strategy for treatment of ventilated pneumonia, which often has poor outcomes," commented Thomas Holland, MD, a hospitalist and infectious disease specialist at Duke University Hospital in Durham, N.C. "This is valuable and practical information as clinicians choose antibiotics regimens for this difficult-to-treat syndrome," he said in an interview.

Holland comoderated the session in which Satlin presented the study findings and opinions.

No funding source for the presentation was reported. Satlin reported consulting for Shionogi and Achaogen and research grants from Allergan, Merck, and BioFire Diagnostics. Holland disclosed consulting fees and other material support from Basilea Pharmaceutica, Genetech, Karius and Theravance.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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