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NCT Number: NCT02357966

Safety & Efficacy of True Human Antibody, 514G3, in Staphylococcus Aureus Bacteremia Hospitalized Subjects.

This study is a Phase I/II, double-blind, placebo-controlled trial investigating the True Human monoclonal antibody 514G3 in subjects hospitalized with Staphylococcus aureus bacteremia. Phase I involves dose escalation to evaluate potential toxicity and establish the recommended phase 2 dosage of 514G3. In Phase II (dose expansion), eligible subjects will be randomized at a ratio of 2:1 to receive either a single dose of 514G3 with standard IV antibiotic therapy or a single dose of placebo with standard IV antibiotic therapy, aiming to assess safety and tolerability. The trial aims to determine the safety, efficacy, and optimal dosage regimen of 514G3 in these hospitalized subjects.

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Key information

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 1 / Phase 2

Primary location

XBiotech Investigative Site, Columbus, Georgia, United States

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About this study

The Phase I/II trial aims to assess the safety and efficacy of True Human monoclonal antibody 514G3 in hospitalized subjects with Staphylococcus aureus bacteremia.

Phase I entails dose escalation, with subjects randomized (3:1) at three dose levels of the study drug (2 mg/kg, 10 mg/kg, and 40 mg/kg) and placebo, utilizing central randomization. Dose-limiting toxicities (DLTs), defined as Grade 3 or greater adverse events related to 514G3 during follow-up, guide escalation. The Maximum Tolerated Dose (MTD) is determined based on DLT occurrence.

Phase II, focusing on preliminary efficacy, randomizes eligible subjects (2:1) to receive 514G3 or placebo with standard IV antibiotic therapy. Safety and efficacy assessments are conducted for both phases, encompassing pooled data from both the study drug and placebo groups.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • One or more blood cultures positive for staphylococcus aureus within 2 days of initiating treatment with 514G3.
  • Temperature ≥ 38.0°C
  • Age ≥18, male or female subjects.
  • Adequate renal function, defined by serum creatinine ≤ 2 times the upper limit of normal (ULN).
  • Adequate hepatic function
  • Adequate bone marrow function
  • For women of childbearing potential (WOCBP), a negative serum pregnancy test result at Screening.
  • Signed and dated institutional review board (IRB)/ Ethics Committee (EC)-approved informed consent before any protocol-specific screening procedures are performed.
  • Expected survival of at least 2 months.

Exclusion criteria

  • Polymicrobial bacteremia.
  • Known or suspected osteomyelitis or meningitis.
  • Patients that are being mechanically ventilated as a result of a pulmonary infection at the time of screening. Mechanical ventilation for other reasons, such as trauma, is acceptable.
  • Presence of any removable infection source (e.g., intravascular line, abscess, or prosthesis) that will not be removed or debrided within 3 days after randomization.
  • Definite or possible left-sided endocarditis, by Modified Duke Criteria, based on screening echocardiogram. Subjects with suspected right-sided endocarditis are permitted.
  • Need for emergent valve surgery at the time of screening, and/or the presence of decompensated heart failure or cardiogenic shock.
  • Dementia or altered mental status that would prohibit the understanding or rendering of informed consent.
  • Infection with human immunodeficiency virus (HIV) and a CD4 count <200 cells/mm3.
  • Subjects with history of hypersensitivity to compounds of similar chemical or biologic composition to 514G3 or any component of its formulations.
  • Women who are pregnant or breastfeeding.

Treatment and study plan

514G3 (2 mg/kg) plus standard IV antibiotic treatment

Biological

Other names: True Human Monoclonal Antibody

514G3 (10 mg/kg) plus standard IV antibiotic treatment

Biological

Other names: True Human Monoclonal Antibody

514G3 (40 mg/kg) plus standard IV antibiotic treatment

Biological

Other names: True Human Monoclonal Antibody

Placebo plus standard IV antibiotic treatment

Other

Sterile isotonic formulation buffered at pH 6.2 - 6.5 plus standard IV antibiotic treatment

Other names: True Human Monoclonal Antibody

514G3 (40 mg/kg) plus standard IV antibiotic treatment: Phase II

Biological

A single dose of 514G3 plus standard IV antibiotic therapy

Other names: True Human Monoclonal Antibody

Placebo plus standard IV antibiotic treatment: Phase II

Other

A single dose of placebo plus standard IV antibiotic therapy

Other names: True Human Monoclonal Antibody

Primary outcomes

  1. Number of Participants Who Experienced Dose-limiting Toxicities

    Time frame: Pre-dose at Day 0 through Day 14. After day 14, samples are collected every other day including discharge, up to 30 days maximum

    Dose limiting Toxicity are defined as any Grade 3 or greater AE which is probably or definitely related to 514G3 occurring during the FU period after dosing. This measure determines and assesses the maximum tolerated dose (MTD) through participants who experienced DLT at different dose levels.

  2. Number of Participants Who Experienced the Adverse Events

    Time frame: Adverse events occurring between day 0 and day 30 or hospital discharge whichever is shorter

    A summary of SAEs and other non-serious AEs, regardless of causality

Secondary outcomes

  1. Time to Clearance of Bacteremia (Time to Sterile Culture From Date of Randomization)

    Time frame: Pre-dose at Day 0 through Day 14. After day 14, samples are collected every other day including discharge, up to 30 days maximum

    The time to sterile culture is the interval in days from the first dose of study drug until 2 consecutive days of negative blood cultures has occurred. The difference in this interval will be compared between patients randomized to placebo and those who received the highest dose of 514G3.

  2. Steady State Maximum Concentration of 514G3

    Time frame: Pre-dose at Day 0 through Day 14. After day 14, samples are collected every other day including discharge, up to 30 days maximum

    Blood samples were collected from participants who received study drug 514G3 for the determination of plasma concentration (Cmax).

  3. Length of Hospitalization (Duration of Hospitalization Stay After Randomization)

    Time frame: Pre-dose at Day 0 through Day 14. After day 14, samples are collected every other day including discharge, up to 30 days maximum

    This outcome measure assesses the impact of the treatment on the time that participants spend in the hospital. The duration of hospitalization is expressed as the average number of days hospitalized for all participants in their respective cohorts.

  4. Difference in Opsonophagocytosis Activity Between Arms (Pharmacodynamics)

    Time frame: 14 days

    Serum samples from patients will be assessed with an in-vitro Opsonophagocytosis assay which measures the ability of the serum to mediate uptake of staphylococcus aureus by white blood cells. Differences in the levels of activity will be compared between treatment and placebo. This outcome measure assesses the dose-dependent functional antibody response to 514G3, providing insights into its potential efficacy across different dosage levels compared to placebo. Higher titers in the drug-treated groups indicate better opsonophagocytic activity and thus better efficacy of the drug.

    Opsonophagocytosis activity (OPA) score quantifies the functional antibody response to the investigational drug 514G3.

    For Phase II, this score is determined using an Opsonophagocytosis assay and is calculated as follows:

    Relative Opsonophagocytosis activity = %Phagocytosis 30 minutes after treatment adjusted by baseline / %Phagocytosis of 500 ug/mL spike standard.

Sponsors and collaborators

Lead sponsor

XBiotech, Inc.

Industry

Registry information

Official study title

A Phase I-II Study of the Safety and Efficacy of a True Human Antibody, 514G3, in Subjects Hospitalized With Bacteremia Due to Staphylococcus Aureus

Important dates

Study start
2015
Primary completion
2016
Study completion
2016
First posted
Feb 6, 2015
Registry last updated
Feb 9, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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