The Antimicrobial Drugs Advisory Committee of the Food and Drug Administration has voted to recommend plazomicin, a new aminoglycoside, for systemic use in the treatment of complicated urinary tract infections (cUTI) but rejected it for treatment of blood stream infections (BSIs) that are caused by multidrug resistant (MDR) Enterobacteriaceae.

Advisers voted unanimously to recommend plazomicin for cUTI, but rejected the drug for BSIs in an 11-4 no vote, based on the results of two phase 3 clinical trials: EPIC and CARE.

The spread of antibiotic resistance is a pressing public health issue. Carbapenem-resistant Enterobacteriaceae (CRE) and Enterobacteriaceae with extended-spectrum beta-lactamases (ESBL) bacteria are frequently resistant to many treatments from the aminoglycoside class of antibiotics. This view was echoed by Michael Green, MD, of the University of Pittsburgh Medical Center.

“Today’s meeting brought the committee face to face with the crisis of multidrug resistant bacteria,” he said. “Results of the 009 [EPIC] study, in my mind, clearly showed plazomicin met the noninferiority endpoints.”

EPIC study

EPIC was a phase 3 clinical trial to assess the noninferiority of plazomicin to meropenem in patients with cUTI and/or acute pyelonephritis (AP). Many patients with drug resistant infections have limited treatment options, so plazomicin was reviewed under the Limited Population Antibacterial Drug pathway.

Patients in the study were stratified by geographical region and infection type – cUTI or acute pyelonephritis (AP). In total, 609 patients were randomized in the intent-to-treat (ITT) group with 306 and 303 receiving plazomicin or meropenem, respectively. Using the coprimary efficacy endpoints of microbiological eradication and clinical cure, a measure known as composite cure was developed to assess efficacy at Day 5 and the test of cure (TOC) visit in the microbiological modified intent-to-treat (mMITT) population. The mMITT group consisted of all patients who had received any dose of study drug and had at least one qualified baseline pathogen with 105 or more colony-forming units/mL that was susceptible to both meropenem and plazomicin.Plazomicin was noninferior to meropenem with a margin of 15%. At day 5, the composite cure rate was 88% in the plazomicin group, compared with 91.4% in the meropenem group. Similar results were seen at the test of cure visit, with composite cure rates of 81.7% and 70.1% in the plazomicin and meropenem groups, respectively.

In a secondary analysis of microbiologically evaluable populations, or patients who had an appropriately collected urine specimen yielding interpretable culture results, plazomicin again showed noninferiority. Composite cure rates at Day 5 were 89.4% in the plazomicin group, compared with 94.2% in the meropenem group. TOC composite scores also were similar, at 89.4% and 75.1%, respectively.An analysis of composite cure scores at the end of the intravenous therapy visit revealed that Day 5 scores were comparable between the plazomicin and meropenem groups at 93.7% and 94.9%, respectively, demonstrating that high cure rates were achieved with IV treatment, irrespective of the drug used.

In a pooled safety analysis of a phase 2 trial and the EPIC trial, 22.5% experienced a treatment-emergent adverse event (TEAE); of these, 2.9% had a severe TEAE and 2.7% experienced a TEAE that led to discontinuation of the intravenous study drug. All adverse events were related to renal function, diarrhea, headache, nausea, and vomiting.

CARE study

CARE was an open-label trial to assess the safety and efficacy of plazomicin as compared with colistin in patients with hospital-acquired bacterial pneumonia or ventilator-associated bacterial pneumonia (HABP/VABP) or bloodstream infections caused by CRE. The primary endpoint in the study was all-cause mortality at Day 28 or significant disease-related complications in the mMITT population, which included all patients with a confirmed CRE pathogen who had at least one dose of the study drug.

Overall, CARE enrolled 69 patients and split them into two cohorts. In Cohort 1, there were 39 randomized patients; 30 with blood stream infections and 9 with HABP or VABP. Cohort 2 was uncontrolled and consisted of 30 total patients; 27 patients who were in the mMITT population included 14 patients with BSI, 9 with HABP/VABP, and 4 with cUTI, all of whom received plazomicin.

Overall in Cohort 1, all-cause mortality at Day 28 or significant disease-related complications were lower with plazomicin than with colistin (23.5% vs. 50.0%). Because of the small patient HABP/VABP population in Cohort 1, the trial focused on patients with blood stream infections.

The rates of all-cause mortality and significant disease-related complications at Day 28 were much lower with plazomicin therapy than with colistin for patients with blood infections (14.3% vs. 53.3%, respectively). All-cause mortality alone at Day 28 was 7.1% in the plazomicin patients and 40.0% in colistin patients.

In the BSI subgroup, plazomicin reduced the rate of death by 86% and 63% on days 28 and 60, respectively, compared with colistin.

The uncontrolled data from Cohort 2 were supportive of the all-cause mortality rate in Cohort 1, with a rate of 14.3% at Day 28.

Because this was a severely ill patient population, there was a higher rate of adverse events. In fact, nearly all the patients in this study (16/18) experienced one treatment-emergent adverse event; 61.1% experienced severe TEAEs, with 11.1% severe enough to discontinue the study drug use.

Despite the study results, many of the panel members were not comfortable recommending it for approval.

Dr. Green, who supported plazomicin for use in cUTI but rejected it for use in BSIs, shared some of his concerns: “Because of the clear need, I was really tempted to vote yes and I actually came here today, thinking that I was going to vote yes. But this study clearly had a number of limitations that impacted the interpretation of results to support the approval for bloodstream infection,” he said. “The limitation that I could just not overcome was the small numbers [of participants].”

Plazomicin has a Prescription Drug User Fee Act date of June 25 of this year by which time the FDA will decide on its approval. While the FDA does not always follow the recommendations of these committees, they usually accept them and proceed accordingly.

ilacy@mdedge.com

FDA advisory committee votes to recommend first once-daily aminoglycoside antibiotic