A Phase 2 interventional study of Part A: ATM-AVI Single Dose, Cohorts 1-4 and Part B: Multiple-dose ATM-AVI, Cohorts 1-4 in Gram-negative Bacterial Infection, sponsored by Pfizer. Recruiting at 32 sites in 9 countries. Open to participants aged Up to 39 Weeks. Per ClinicalTrials.gov, last updated 2026-10-15.
Sponsored by Pfizer · Phase 2, Interventional, and Basic science
The purpose of this study is to learn about the safety and effects of ATM-AVI for the possible treatment of infections caused by a type of bacteria called gram-negative bacteria.
The study medicine is a combination of an antibiotic, aztreonam (ATM), and another medicine, avibactam (AVI), which is used to help stop bacteria from being resistant to antibiotics. Antibiotics are medicines that fights bacteria and infections.
The study will include newborns and infants up to 9 months of age who are admitted in the hospital.
The study is conducted in 2 parts: Part A and Part B.
In Part A, all participants will receive a single intravenous (injected directly into a vein) infusion of ATM-AVI. This is to study the safety and effects of a single amount.
In Part B, all participants will receive multiple intravenous infusions of ATM-AVI as treatment for a possible or confirmed infection with gram-negative bacteria.
This is a 2-part Phase 2a, non-randomized, multicenter, open-label, single and multi-dose study to assess pharmacokinetics (PK), safety, and tolerability of ATM-AVI in hospitalized neonates and infants aged birth, including preterm birth, to \<9 months. A total of 48 participants will be enrolled in 4 age cohorts of 12 each, 6 Part A and 6 Part B. Part A will begin enrolling before Part B and no infant may participate in both parts. Cohort 1 will include full term infants age ≥13 weeks to \<39 weeks and preterm infants postmenstrual age ≥50 weeks to \<75 weeks. Cohort 2 will include full term infants age ≥28 weeks to \<13 weeks and preterm infants postmenstrual age ≥40 weeks to \<50 weeks and ≥28 days of age. Cohort 3 will include full term infants age birth to \<28 days. Cohort 4 will include preterm infants age birth to \<28 days or postmenstrual age \<40 weeks.
Participants in Part A must be hospitalized and receiving intravenous antibiotic treatment for a suspected or confirmed bacterial infection. Participants will receive a single 3 hour intravenous infusion of ATM-AVI and have 3 ATM-AVI blood level assessments during and up to 5 hour after the infusion. Participants will be observed for 48 hours following the infusion to assess safety and toleration and will have a final follow-up safety assessment which may be conducted by telephone 4-5 weeks following the infusion. The single infusion of ATM-AVI is administered to assess the safety, tolerability, and pharmacokinetics of a single dose of ATM-AVI and is not intended as treatment for the bacterial infection. The total duration of study participation in Part A is expected to be 5 weeks through the end of the final safety follow-up.
Participants in Part B must be hospitalized with suspected or confirmed aerobic gram-negative bacterial infection requiring intravenous antibacterial therapy. Part B participants will receive multiple 3 hour intravenous infusions of ATM-AVI every 6 hour (8 hours for preterm infants) for 3-14 days as treatment for their bacterial infection and to assess ATM-AVI pharmacokinetics, safety, tolerability, and efficacy. Participants with complicated intra-abdominal infection (cIAI) will also receive intravenous metronidazole and all participants will have the option to receive other intravenous antibiotic treatment for gram-positive bacteria, as appropriate. Participants who have a good clinical response after 72 hours of intravenous ATM-AVI treatment may be switched to a different orally administered antibiotic, if clinically appropriate. Part B participants will have a total of 5 ATM-AVI blood level assessments over the first 2 or more days following the start of ATM-AVI infusions and will have their clinical response assessed at the End of Treatment (intravenous and oral, if applicable), and at a Test-of-Cure (TOC) evaluation 7 to 14 days after the last antibiotic treatment (intravenous or oral). A final safety assessment which may be conducted by telephone will occur 4-5 weeks after the last dose of ATM-AVI. The total duration of study participation in Part B is expected to be up to 7 weeks through the end of the final safety follow-up.
Additional safety monitoring will be provided by an independent external Data Monitoring Committee (DMC). Enrollment for the study will begin with Part A, single dose, cohorts 1-3. Part A Cohort 4 (preterm neonates) will commence enrollment after sponsor and DMC review of plasma drug levels and safety for a least 2 participants in Part A Cohort 3 and review of ATM-AVI safety and tolerability for all participants enrolled at that time. Enrollment in the multidose Part B cohorts will be delayed until preliminary information is obtained regarding ATM-AVI multidose safety, tolerability, and drug levels for the participants 9 months to 2 years of age in the separate ongoing ATM-AVI pediatric study C3601008 [NCT05639647].
58 studies on the registry are indexed under Gram-Negative Bacterial Infections; 10 are open to participants now.
This study's planned enrollment of 48 is below the median of 70 across 43 interventional studies indexed under Gram-Negative Bacterial Infections.
Browse Gram-Negative Bacterial Infections studies →Pfizer is the lead sponsor of 3,334 studies on the registry; 149 are open to participants now.
Of its 601 completed or terminated interventional studies of FDA-regulated products, 391 (65%) have results posted.
Counted across the registry records on this site, refreshed daily.
Inclusion Criteria
Participants must meet the following key inclusion criteria to be eligible for enrollment into the study:
Participants with any of the following characteristics/conditions will be excluded:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Single dose pharmacokinetics.
Drug: Part A: ATM-AVI Single Dose, Cohorts 1-4
Multi-dose pharmacokinetics and treatment
Drug: Part B: Multiple-dose ATM-AVI, Cohorts 1-4
Single intravenous infusion of aztreonam-avibactam over 3 hours to assess pharmacokinetics, safety, and toleration.
Multiple intravenous infusions of aztreonam-avibactam over 3 hours, repeated every 6-8 hours up to 14 days to assess pharmacokinetics, safety, toleration, and efficacy.
Maximum Predicted Plasma Concentration (Cmax) of ATM and AVI
Cmax is the maximum plasma concentration of ATM and AVI as population pharmacokinetic (popPK) analysis predicts.
Time frame: Up to Day 15
Area under the Concentration-Time Curve (AUC) of ATM-AVI
AUC is a measure of the plasma concentration of ATM and AVI overtime as popPK analysis predicts.
Time frame: Up to Day 15
Plasma Elimination Half-Life (t1/2)
Half-life is the time measured for the plasma concentration of ATM and AVI to decrease by one half as popPK analysis predicts.
Time frame: Up to Day 15
Apparent Clearance (CL)
ATM and AVI clearance is a quantitative measure of the rate at which ATM and AVI are removed from the blood (rate at which ATM and AVI are metabolized or eliminated by normal biological processes). Clearance obtained after intravenous infusion dose (apparent clearance) is influenced by the fraction of the dose absorbed.
Time frame: Up to Day 15
Plasma concentrations of ATM and AVI by nominal sampling time
Plasma concentrations of ATM and AVI on Day 1 and at steady state (Day 2 or later) will be summarized by the nominal sampling time using descriptive statistics (eg number, mean, standard deviation).
Time frame: Up to Day 15
Proportion of Participants reporting Adverse Events (AE)
Proportion of participant AE reports of vital signs, physical examinations, and clinical laboratory tests overall and by age cohort. For each AE the last assessment made prior to the first dose of study drug will be defined as the baseline.
Time frame: Baseline up to Day 50
Proportion of Participants reporting Serious Adverse Events (SAE)
Proportion of participant SAE reports of vital signs, physical examinations, and clinical laboratory tests overall and by age cohort. For each SAE the last assessment made prior to the first dose of study drug will be defined as the baseline.
Time frame: Baseline up to Day 50
Proportion of Participants reporting AEs leading to discontinuation of study drug
Proportion of Participants reporting AEs leading to discontinuation of study drug from baseline. For each discontinuation the last assessment made prior to the first dose of study drug will be defined as the baseline.
Time frame: Baseline up to Day 50
Proportion of Participants reporting AEs resulting in death
Proportion of Participants reporting AE resulting in death from baseline. For each death the last assessment made prior to the first dose of study drug will be defined as the baseline.
Time frame: Baseline up to Day 50
Proportion of Participants reporting liver injury and acute kidney injury
Proportion of Participants reporting liver injury and acute kidney injury from baseline. For each report of liver and acute kidney injury the last assessment made prior to the first dose of study drug will be defined as the baseline.
Time frame: Baseline up to Day 50
Part B: Proportion of participants with each clinical outcome and with a favorable clinical outcome at end of IV study treatment (EOIV)
Clinical Cure is defined baseline signs and symptoms improved such that no further antimicrobial treatment is required for an aerobic gram-negative baseline infection. Participants who receive treatment for gram-positive organisms or adjunctive therapy for Pseudomonas aeruginosa, as allowed per protocol, can still have a response of cure. Clinical improvement is defined as baseline signs and symptoms sufficiently improved to allow switching to an oral antibiotic treatment. A favorable outcome is clinical cure or clinical improvement. Failure is defined as a requirement for further antibiotic treatment, including following premature discontinuation due to an adverse event, or death after receiving at least 48 hours of treatment. Indeterminant is defined as data not available for evaluation of efficacy for any reason.
Time frame: Up to 15 days after start of IV study treatment
Part B: Proportion of participants with each clinical outcome and with a favorable clinical outcome at end of treatment (EOT)
EOT is only applicable for participants switched to an oral antibiotic treatment. Possible outcomes are cure, failure, or indeterminant.
Time frame: Within 48 hours after last dose of oral switch treatment
Part B: Proportion of participants with each clinical outcome and with a favorable clinical outcome at test of cure (TOC)
Possible outcomes are cure, failure, or indeterminant.
Time frame: 7-14 days after the last study treatment
Part B: Proportion of participants with a favorable microbiological response at TOC
A favorable response is eradication or presumed eradication. Eradication is absence of the causative pathogen from an appropriately obtained specimen at the site of infection. Presumed eradication is when a repeat culture was not performed and the clinical response is cure.
Time frame: 7-14 days after the last study treatment
Part B: Counts and proportions of pathogens with each per-pathogen microbiological response at EOIV/EOT
Possible outcomes are eradication, presumed eradication, persistence, presumed persistence or indeterminate. Presumed eradication/persistence based on repeat culture not performed and clinical outcome of cure/failure. Persistence is the causative pathogen is still present from an appropriately obtained specimen at the site of the infection. Indeterminant includes participant lost to follow-up or death after receiving less than 48 hours of study treatment.
Time frame: Up to 15 days after start of IV study treatment
Part B: Counts and proportions of pathogens with each per-pathogen microbiological response at TOC
Possible outcomes are eradication, presumed eradication, persistence, presumed persistence or indeterminate.
Time frame: 7-14 days after the last study treatment
Part B: Counts and proportions of participants with emergent infections (new infections or superinfections) during the study
Superinfection is defined as emergence of a new pathogen associated with worsening signs and symptoms of infection and a requirement for additional antibiotics during the period up to and including EOIV/EOT. New infection is defined as emergence of a new pathogen associated with worsening signs and symptoms of infection and a requirement for additional antibiotics during the period after EOIV/EOT.
Time frame: Through study completion, up to Day 50
Plan to share: Yes — Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.
Data sharing details ↗ · www.pfizer.com
Started Sep 2024 (actual). Primary completion is estimated for Apr 2027, 31 months after the start.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Gram-Negative Bacterial Infections →