Potentiation effects of amikacin and fosfomycin against selected amikacin-nonsusceptible Gram-negative respiratory tract pathogens.

The amikacin-fosfomycin inhalation system (AFIS) is a combination of 2 antibiotics and an in-line nebulizer delivery system that is being developed for adjunctive treatment of pneumonia caused by Gram-negative organisms in patients on mechanical ventilation. AFIS consists of a combination of amikacin and fosfomycin solutions at a 5:2 ratio (amikacin, 3 ml at 100 mg/ml; fosfomycin, 3 ml at 40 mg/ml) and the PARI Investigational eFlow Inline System. In this antibiotic potentiation study, the antimicrobial activities of amikacin and fosfomycin, alone and in a 5:2 combination, were assessed against 62 Gram-negative pathogens from a worldwide antimicrobial surveillance collection (SENTRY). The amikacin MICs for 62 isolates of Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae were ≥32 µg/ml (intermediate or resistant according to the Clinical and Laboratory Standards Institute [CLSI]; resistant according to the European Committee on Antimicrobial Susceptibility Testing [EUCAST]). Each isolate was tested against amikacin (0.25 to 1,024 µg/ml), fosfomycin (0.1 to 409.6 µg/ml), and amikacin-fosfomycin (at a 5:2 ratio) using CLSI reference agar dilution methods. The median MIC values for amikacin and fosfomycin against the 62 isolates each decreased 2-fold with the amikacin-fosfomycin (5:2) combination from that with either antibiotic alone. Interactions between amikacin and fosfomycin differed by isolate and ranged from no detectable interaction to high potentiation. The amikacin-fosfomycin (5:2) combination reduced the amikacin concentration required to inhibit all 62 isolates from >1,024 to ≤ 256 µg/ml and reduced the required fosfomycin concentration from 204.8 to 102.4 µg/ml. These results support continued development of the amikacin-fosfomycin combination for aerosolized administration, where high drug levels can be achieved.

Amikacin-fosfomycin at a five-to-two ratio: characterization of mutation rates in microbial strains causing ventilator-associated pneumonia and interactions with commonly used antibiotics.

The amikacin-fosfomycin inhalation system (AFIS), a combination of antibiotics administered with an in-line nebulizer delivery system, is being developed for adjunctive treatment of ventilator-associated pneumonia (VAP). The in vitro characterization of amikacin-fosfomycin (at a 5:2 ratio) described here included determining resistance selection rates for pathogens that are representative of those commonly associated with VAP (including multidrug-resistant strains) and evaluating interactions with antibiotics commonly used intravenously to treat VAP. Spontaneous resistance to amikacin-fosfomycin (5:2) was not observed for most strains tested (n, 10/14). Four strains had spontaneously resistant colonies (frequencies, 4.25 × 10(-8) to 3.47 × 10(-10)), for which amikacin-fosfomycin (5:2) MICs were 2- to 8-fold higher than those for the original strains. After 7 days of serial passage, resistance (>4-fold increase over the baseline MIC) occurred in fewer strains (n, 4/14) passaged in the presence of amikacin-fosfomycin (5:2) than with either amikacin (n, 7/14) or fosfomycin (n, 12/14) alone. Interactions between amikacin-fosfomycin (5:2) and 10 comparator antibiotics in checkerboard testing against 30 different Gram-positive or Gram-negative bacterial strains were synergistic (fractional inhibitory concentration [FIC] index, ≤ 0.5) for 6.7% (n, 10/150) of combinations tested. No antagonism was observed. Synergy was confirmed by time-kill methodology for amikacin-fosfomycin (5:2) plus cefepime (against Escherichia coli), aztreonam (against Pseudomonas aeruginosa), daptomycin (against Enterococcus faecalis), and azithromycin (against Staphylococcus aureus). Amikacin-fosfomycin (5:2) was bactericidal at 4-fold the MIC for 7 strains tested. The reduced incidence of development of resistance to amikacin-fosfomycin (5:2) compared with that for amikacin or fosfomycin alone, and the lack of negative interactions with commonly used intravenous antibiotics, further supports the development of AFIS for the treatment of VAP.

A randomized double-blind placebo-controlled dose-escalation phase 1 study of aerosolized amikacin and fosfomycin delivered via the PARI investigational eFlow® inline nebulizer system in mechanically ventilated patients.

BACKGROUND: This clinical trial evaluated the pharmacokinetics and safety/tolerability of amikacin/fosfomycin solution using a vibrating plate nebulizer, in mechanically ventilated patients with ventilator-associated tracheobronchitis (VAT) or ventilator-associated pneumonia (VAP). METHODS: Nine adult patients were consented to receive three escalating doses of a combination of 50 mg/mL amikacin and 20 mg/mL fosfomycin; doses were separated by 24±2 hr. On day 3, patients received two blinded, randomized treatments (amikacin/fosfomycin and volume-matched placebo), separated by 2 hr. All treatments were administered with a single-patient, multitreatment nebulizer (Investigational eFlow(®) Inline Nebulizer System; PARI Pharma GmbH, positioned in the inspiratory limb tubing between the ventilator and the patient. The nebulizer remained in-line until all treatments had been delivered. Concentrations of amikacin and fosfomycin were measured in tracheal aspirate and plasma samples obtained during the 24 hr after each dose. RESULTS: Fifteen minutes after dosing with the 300/120 mg amikacin/fosfomycin combination, tracheal aspirate amikacin concentrations±SD were 12,390±3,986 µg/g, and fosfomycin concentrations were 6,174±2,548 µg/g (n=6). Airway clearance was rapid. Plasma concentrations were subtherapeutic; the highest observed amikacin plasma concentration was 1.4 µg/mL, and the highest observed fosfomycin plasma concentration was 0.8 µg/mL. Administration time was approximately 2 min/mL. No adverse effects on respiratory rate, peak airway pressures, or oxygenation were observed during or following drug or placebo administration. CONCLUSIONS: High tracheal aspirate concentrations of amikacin and fosfomycin were achieved in mechanically ventilated patients with VAT or VAP after aerosolized administration with an inline nebulizer system. Airway clearance was rapid. No adverse respiratory effects were noted during or following drug administration.

Regulatory aspects of Phase 3 endpoints for new inhaled antibiotics for cystic fibrosis patients with chronic Pseudomonas aeruginosa infections.

Available regulatory guidelines for developing inhaled anti-infective therapies offer general advice, but specific guidance often provides conflicting and outdated advice in regard to clinical trial design. For instance, the availability of two approved drugs makes the conduct of placebo-controlled trials longer than 28 days problematic. Comparator drugs require use per the product label, making comparator trials difficult to blind as taste, foaming, regimen, device, and delivery time differences are present. Currently, there is no consensus on the most appropriate endpoints for evaluation of aerosolized antimicrobials. FEV(1) is a surrogate endpoint that it is a predictor of mortality--it is standardized, reproducible, noninvasive, simple, and inexpensive to perform but small statistically significant changes may not be clinically important. FEV(1) improvement also has a ceiling effect in patients with mild lung function impairment and spirometry cannot be reliably done in patients under the age of 6 years. A patient-reported outcome is a promising clinical endpoint. However, there is not currently an accepted tool that can be used as a primary endpoint for the FDA or the EMA, although the latter recognizes the CFQ-R as a validated secondary endpoint and the FDA grandfathered acceptance of the CFQ-R respiratory domain in the pivotal aztreonam for inhalation study. Exacerbations are an important clinical endpoint that reflects morbidity and are a major driver of cost of care, but they occur infrequently and a standardized definition has not been reached. Furthermore, an exacerbation endpoint may fail even with an otherwise effective antibiotic therapy. Regulatory authorities will have a difficult time approving any new inhaled antibiotic based on one clinical endpoint alone.

Inhaled lidocaine for the treatment of asthma: lack of efficacy in two double-blind, randomized, placebo-controlled clinical studies.

BACKGROUND: Asthma with severe or persistent exacerbations is treated with chronic oral corticosteroids (OCS), such as prednisone. Although efficacious, OCS treatment is often associated with side effects; thus, corticosteroid-sparing treatments are needed. METHODS: We conducted two double-blind, placebo-controlled, clinical studies assessing lidocaine solution for inhalation (LSI; 40 mg twice daily; eFlow(®) nebulizer) to treat asthma. Study 1-Mild/Moderate included 154 patients with mild-moderate asthma [forced expiratory volume in one second (FEV(1)) ≥60% predicted, and ≥12% improvement in FEV(1) (L) after short-acting, inhaled ß-agonist; no OCS or inhaled corticosteroids (ICS) in previous month] and evaluated whether FEV(1) improved after 12 weeks of treatment. Study 2-OCS included 114 patients with more severe asthma (FEV(1) 35-85% of predicted values, treatment with OCS for ≥6 months, average daily dose between 5 and 70 mg prednisone or equivalent, stable ≥30 days) and evaluated whether 20 weeks of treatment had a corticosteroid-sparing effect, measured as reduced need for OCS. RESULTS: LSI did not improve pulmonary function in Study 1-Mild/Moderate, and did not have a corticosteroid-sparing effect in Study 2-OCS, when compared with placebo. Thus, the primary efficacy endpoints were not met. Significant improvements were not observed for asthma symptom scores, morning and evening peak expiratory flow values, FEV(1) % predicted, proportion of patients with asthma instability, and asthma quality-of-life scores at week 12 (Study 1-Mild/Moderate) or week 20 (Study 2-OCS). LSI was well tolerated. CONCLUSIONS: These results indicate that lidocaine solution for inhalation is not a useful treatment for asthma; it did not improve pulmonary function and did not have a corticosteroid-sparing effect.