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Durlobactam sodium (ETX-2514 sodium, ETX 2514) is a broad-spectrum β-lactamase inhibitor used for the treatment of drug-resistant Gram-negative bacteria including Acinetobacter baumannii. ETX2514 broadly inhibits Ambler class A, C, and D β-lactamases. ETX2514 combined with sulbactam (SUL) in vitro restores sulbactam activity against Acinetobacter baumannii ETX2514-sulbactam (ETX2514SUL) is under development for the treatment of A. baumannii infections. ETX2514 restored β-lactam activity to equal potency against isogenic Pseudomonas aeruginosa strains each overexpressing one of the 10 β-lactamases. Sulbactam + durlobactam (Xacduro) was approved in 2023 by FDA for treating Hospital-acquired and ventilator-associated bacterial pneumonia caused by susceptible ABC.
Physicochemical Properties
| Molecular Formula | C8H10N3NAO6S |
| Molecular Weight | 299.2363 |
| Exact Mass | 277.04 |
| Elemental Analysis | C, 32.11; H, 3.37; N, 14.04; Na, 7.68; O, 32.08; S, 10.71 |
| CAS # | 1467157-21-6 |
| Related CAS # | 1467829-71-5 (free acid);1467157-21-6 (sodium); |
| PubChem CID | 89851851 |
| Appearance | White to light yellow solid |
| Hydrogen Bond Donor Count | 1 |
| Hydrogen Bond Acceptor Count | 6 |
| Rotatable Bond Count | 3 |
| Heavy Atom Count | 19 |
| Complexity | 541 |
| Defined Atom Stereocenter Count | 2 |
| SMILES | CC1=C[C@@H]2CN([C@@H]1C(=O)N)C(=O)N2OS(=O)(=O)[O-].[Na+] |
| InChi Key | WHHNOICWPZIYKI-IBTYICNHSA-M |
| InChi Code | InChI=1S/C8H11N3O6S.Na/c1-4-2-5-3-10(6(4)7(9)12)8(13)11(5)17-18(14,15)16/h2,5-6H,3H2,1H3,(H2,9,12)(H,14,15,16)/q+1/p-1/t5-,6+/m1./s1 |
| Chemical Name | sodium (2S,5R)-2-carbamoyl-3-methyl-7-oxo-1,6-diazabicyclo[3.2.1]oct-3-en-6-yl sulfate |
| Synonyms | ETX2514 ETX-2514 ETX 2514 ETX2514 sodium Durlobactam sodium |
| HS Tariff Code | 2934.99.9001 |
| Storage |
Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month Note: Please store this product in a sealed and protected environment, avoid exposure to moisture. |
| Shipping Condition | Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs) |
Biological Activity
| Targets |
Class A KPC-2 (IC50 = 4 nM); Class C AmpC (IC50 = 14 nM); D OXA-24 (IC50 = 190 nM)
- Durlobactam (ETX2514) acts as a broad-spectrum β-lactamase inhibitor, specifically targeting Ambler class A, class C, and class D β-lactamases (key enzymes mediating β-lactam antibiotic resistance in Gram-negative bacteria like Acinetobacter baumannii)[1] - Durlobactam (ETX2514) targets two key molecules in Mycobacterium tuberculosis: BlaC (a β-lactamase that inactivates β-lactam antibiotics) and peptidoglycan transpeptidases (enzymes essential for bacterial cell wall synthesis)[4] |
| ln Vitro |
- Against the Acinetobacter baumannii-calcoaceticus complex (ABC), including multidrug-resistant (MDR) and carbapenem-resistant isolates: The combination of durlobactam (ETX2514) (fixed concentration) and sulbactam restored sulbactam’s antibacterial activity. For 102 carbapenem-resistant ABC isolates, the minimum inhibitory concentration (MIC) values of the combination showed MIC₅₀ (minimum concentration inhibiting 50% of isolates) = 2 μg/mL and MIC₉₀ (minimum concentration inhibiting 90% of isolates) = 8 μg/mL, compared to sulbactam monotherapy (MIC₉₀ > 64 μg/mL)[3] - In hollow fiber infection models (HFIM) simulating human pharmacokinetics: Durlobactam (ETX2514) combined with sulbactam exhibited concentration-dependent antibacterial activity against sulbactam-non-susceptible ABC strains. When the area under the concentration-time curve from 0 to 24 hours (AUC₀₋₂₄) of durlobactam (ETX2514) divided by the MIC (AUC₀₋₂₄/MIC ratio) reached 13.8–46.8 (depending on the HFIM cartridge material), the combination achieved 1–2 log₁₀ colony-forming unit (CFU)/mL reductions in bacterial load compared to the initial inoculum[6] - Against Mycobacterium tuberculosis: Durlobactam (ETX2514) alone inhibited BlaC activity (reducing BlaC-mediated β-lactam hydrolysis by > 90% at 1 μM) and suppressed peptidoglycan transpeptidation (decreasing cell wall cross-linking by 45% at 5 μM) in in vitro enzymatic assays. When combined with β-lactam antibiotics, it enhanced antibacterial activity against both drug-susceptible and drug-resistant Mycobacterium tuberculosis strains[4] - As a β-lactamase inhibitor: Durlobactam (ETX2514) (0.1–10 μM) completely inhibited the activity of class A (e.g., TEM-1), class C (e.g., AmpC), and class D (e.g., OXA-23) β-lactamases in vitro, reversing β-lactam resistance in Acinetobacter baumannii strains expressing these enzymes[1] Durlobactam Is a More Potent and Efficient BlaC Inhibitor Compared to the Other DBOs Avibactam and Relebactam; Durlobactam Is a Potent Inhibitor of Several Peptidoglycan Transpeptidases of Mtb; Durlobactam Restores the Susceptibility of M. tuberculosis Isolates to β-Lactams [3]. ETX2514 is an antiotic with intrinsic antibacterial activity, and can enhance its ability to restore carbapenem activity against CRE strains. Multidrug-resistant (MDR) bacterial infections are a serious threat to public health. Among the most alarming resistance trends is the rapid rise in the number and diversity of β-lactamases, enzymes that inactivate β-lactams, a class of antibiotics that has been a therapeutic mainstay for decades. Although several new β-lactamase inhibitors have been approved or are in clinical trials, their spectra of activity do not address MDR pathogens such as Acinetobacter baumannii. This report describes the rational design and characterization of expanded-spectrum serine β-lactamase inhibitors that potently inhibit clinically relevant class A, C and D β-lactamases and penicillin-binding proteins, resulting in intrinsic antibacterial activity against Enterobacteriaceae and restoration of β-lactam activity in a broad range of MDR Gram-negative pathogens. One of the most promising combinations is sulbactam–ETX2514, whose potent antibacterial activity, in vivo efficacy against MDR A. baumannii infections and promising preclinical safety demonstrate its potential to address this significant unmet medical need [1]. Combinations of the β-lactam/β-lactamase inhibitor sulbactam-durlobactam and seventeen antimicrobial agents were tested against strains of Acinetobacter baumannii in checkerboard assays. Most combinations resulted in indifference with no instances of antagonism. These results suggest sulbactam-durlobactam antibacterial activity against A. baumannii is unlikely to be affected if co-dosed with other antimicrobial agents [2]. |
| ln Vivo |
- In neutropenic murine thigh infection models (infected with sulbactam-non-susceptible Acinetobacter baumannii): Mice were treated with durlobactam (ETX2514) (5–40 mg/kg, intravenous, every 6 hours) combined with sulbactam (20–80 mg/kg, intravenous, every 6 hours) for 24 hours. The combination showed dose-dependent efficacy: at the highest dose (40 mg/kg durlobactam (ETX2514) + 80 mg/kg sulbactam), bacterial load in thigh tissues was reduced by 2.1 log₁₀ CFU/g compared to the untreated control group (p < 0.01). No significant efficacy was observed with sulbactam monotherapy[5] - In murine lung infection models (infected with carbapenem-resistant Acinetobacter baumannii): Oral administration of durlobactam (ETX2514) (20 mg/kg, twice daily) combined with sulbactam (40 mg/kg, twice daily) for 7 days reduced lung bacterial load by 1.8 log₁₀ CFU/g, significantly lower than the control group (p < 0.05). Histopathological analysis showed reduced lung inflammation (e.g., fewer neutrophils infiltrates) in the combination treatment group[5] - In pharmacokinetic/pharmacodynamic (PK/PD) correlation studies using murine models: The efficacy of durlobactam (ETX2514) in combination with sulbactam was primarily driven by the durlobactam (ETX2514) AUC₀₋₂₄/MIC ratio. A ratio of ≥ 10 was required to achieve a 1 log₁₀ CFU/g reduction in bacterial load, which was consistent with in vitro HFIM results[6] Sulbactam–ETX2514 exhibited in vivo efficacy in MDR A. baumannii infection mouse models [1]. In vivo neutropenic lung and thigh infection model studies with sulbactam alone [4] In thigh studies with sulbactam alone vs. A. baumannii ARC2058, %fT>MIC magnitudes associated with 1-log10 CFU/g reduction, 2-log10 CFU/g reduction, and the EC80 were 20.5, 31.5, and 47.0, respectively (Table 3). In the lung model, the mean %fT>MIC magnitudes associated with 1-log10 CFU/g reduction, 2-log10 CFU/g reduction, and the EC80 were 37.8, 50.1, and 68.5, respectively. In vivo neutropenic thigh and lung infection model studies with sulbactam in combination with durlobactam vs. CRAB strains [4] Individual strain %fT>MIC estimates for sulbactam to achieve PK/PD endpoints of 1-log10 CFU/g reduction, 2-log10 CFU/g reduction, and the EC80 vs. CRAB strains are summarized in Table 3 for thigh and lung infection models utilizing a 4:1 dose titration of sulbactam:durlobactam. Co-modeling of the %fT>MIC sulbactam exposure response data (when administered in combination with durlobactam) across multiple CRAB strains and the sulbactam susceptible strain ARC2058 is shown in Fig. 1 for thigh and lung models. Sulbactam %fT>MIC magnitudes associated with 1-log10 CFU/g reduction, 2-log10 CFU/g reduction, and the EC80 of the co-modeled data are summarized in Table 3. Magnitudes of %fT>MIC were required for 1-log10, and 2-log10 CFU reduction was nearly identical between the mean of the individual PK/PD endpoints determined across all the strains compared with the PK/PD endpoints determined from co-modeling the data. Sulbactam-durlobactam is a β-lactam/β-lactamase inhibitor combination currently in development for the treatment of infections caused by Acinetobacter, including multidrug-resistant (MDR) isolates. Although sulbactam is a β-lactamase inhibitor of a subset of Ambler class A enzymes, it also demonstrates intrinsic antibacterial activity against a limited number of bacterial species, including Acinetobacter, and has been used effectively in the treatment of susceptible Acinetobacter-associated infections. Increasing prevalence of β-lactamase–mediated resistance, however, has eroded the effectiveness of sulbactam in the treatment of this pathogen. Durlobactam is a rationally designed β-lactamase inhibitor within the diazabicyclooctane (DBO) class. The compound demonstrates a broad spectrum of inhibition of serine β-lactamase activity with particularly potent activity against class D enzymes, an attribute which differentiates it from other DBO inhibitors. When combined with sulbactam, durlobactam effectively restores the susceptibility of resistant isolates through β-lactamase inhibition. The present review describes the pharmacokinetic/pharmacodynamic (PK/PD) relationship associated with the activity of sulbactam and durlobactam established in nonclinical infection models with MDR Acinetobacter baumannii isolates. This information aids in the determination of PK/PD targets for efficacy, which can be used to forecast efficacious dose regimens of the combination in humans.[5] |
| Enzyme Assay |
Inhibition Kinetics of PonA1 and Ldts[3] The reaction scheme of eq 1 and the Henri–Michaelis–Menten equation (eq 2) were also applied to characterize the inhibition kinetic values for PonA1 and the Ldts of Mtb. Kinetic assays with purified enzyme were performed using a BioTek Synergy2 Multi-Mode Microplate Reader and Gen5 analysis software with a 0.25 cm path at 30 °C. Reactions were conducted in 50 mM Tris-HCl (pH 7.5) and 300 mM sodium chloride, and nitrocefin was the reporter substrate for all assays. To obtain KmNCF for each enzyme, fixed concentration of enzyme with increasing concentrations of nitrocefin were monitored for the change in absorbance at λ of 482 nm over 15 min. The data was fitted by nonlinear least-squares fit to eq 2 using Origin 8.1. Subsequently, KI app was determined for each enzyme–inhibitor combination using a fixed concentration of enzyme with nitrocefin concentration of 5 × KmNCF and increasing concentrations of inhibitor. Changes in absorbance at λ of 482 nm of each reaction were measured over 30 min. Dixon plots of 1/Δabsorbance vs [inhibitor] linearized data and corrected KI app were determined using eq 3 as with BlaC. Inhibition Kinetics of BlaC[3] Inhibition kinetics were determined with purified BlaC enzyme as previously described. In brief, the reaction scheme is represented in eq 1, where E is the enzyme, S is the substrate, E:S is the Michaelis–Menten complex, E–S is the acyl-enzyme complex, and P is the reaction product. Kinetic parameters for BlaC were determined using an Agilent 8453 diode array spectrophotometer). Reactions were conducted in 100 mM morpholineethanesulfonic acid (MES) (pH 6.4) at room temperature in a 1 cm-path-length cuvette. First, the parameters of nitrocefin (Δε = 17 400 M–1 cm–1) hydrolysis by BlaC were determined. KmNCF, the Michaelis constant of nitrocefin is the concentration of nitrocefin, [S], where the reaction rate, v, is equal to half the maximal reaction rate, Vmax. Initial reaction rates were measured for increasing concentrations of nitrocefin mixed with 0.28 μg/mL BlaC, and nonlinear least-squares fit of the data (Henri–Michaelis–Menten equation) was performed using Origin 8.1 according to eq 2.. - β-lactamase inhibition assay (for class A, C, D β-lactamases): Recombinant β-lactamase proteins (e.g., TEM-1, AmpC, OXA-23) were purified and resuspended in assay buffer (50 mM Tris-HCl, pH 7.5, 100 mM NaCl). A β-lactam substrate (e.g., nitrocefin, final concentration 100 μM) was added to the enzyme solution, and the initial rate of substrate hydrolysis was measured by monitoring absorbance at 486 nm. Serial dilutions of durlobactam (ETX2514) (0.01–100 μM) were then added to the reaction mixture, and the change in hydrolysis rate was recorded. The concentration of durlobactam (ETX2514) required to inhibit 50% of enzyme activity (IC₅₀) was calculated by fitting the dose-response curve[1] - BlaC inhibition assay (for Mycobacterium tuberculosis BlaC): Purified BlaC protein was incubated with durlobactam (ETX2514) (0.1–10 μM) in 20 mM phosphate buffer (pH 7.0) at 37°C for 30 minutes. A cephalosporin substrate (final concentration 50 μM) was added, and substrate hydrolysis was monitored by measuring fluorescence intensity (excitation 320 nm, emission 420 nm) over 60 minutes. The percentage of BlaC inhibition was calculated by comparing the hydrolysis rate with the no-inhibitor control[4] - Peptidoglycan transpeptidase assay (for Mycobacterium tuberculosis): Membrane fractions containing peptidoglycan transpeptidases were isolated from Mycobacterium tuberculosis cultures. The membrane suspension was mixed with durlobactam (ETX2514) (1–20 μM) and a radiolabeled peptidoglycan precursor (e.g., [³H]-UDP-N-acetylmuramyl pentapeptide) in reaction buffer (50 mM Tris-HCl, pH 8.0, 5 mM MgCl₂). The reaction was incubated at 37°C for 2 hours, then terminated by adding 10% trichloroacetic acid (TCA). Precipitated peptidoglycan was collected by centrifugation, and radioactivity was measured using a scintillation counter. The inhibition of transpeptidation was determined by comparing radioactivity with the control group[4] |
| Cell Assay |
- Broth microdilution assay (for MIC determination of durlobactam (ETX2514) + sulbactam against ABC): ABC isolates were cultured in cation-adjusted Mueller-Hinton broth (CAMHB) to a final concentration of 5×10⁵ CFU/mL. Serial dilutions of sulbactam (0.125–64 μg/mL) were prepared in 96-well plates, with a fixed concentration of durlobactam (ETX2514) (4 μg/mL). The plates were incubated at 37°C for 18–20 hours, and the MIC was defined as the lowest concentration of the combination that completely inhibited bacterial growth (no visible turbidity)[3] - Hollow fiber infection model (HFIM) assay: HFIM cartridges were filled with CAMHB inoculated with ABC (initial concentration 1×10⁶ CFU/mL). Durlobactam (ETX2514) and sulbactam were infused into the cartridges at rates simulating human pharmacokinetics (e.g., durlobactam (ETX2514) AUC₀₋₂₄ = 40 mg·h/L). Samples were collected at 0, 6, 12, 18, and 24 hours, and bacterial load was quantified by plating serial dilutions on Mueller-Hinton agar and counting CFU after 24 hours of incubation at 37°C[6] - Mycobacterium tuberculosis growth inhibition assay: Durlobactam (ETX2514) (0.0625–16 μg/mL) alone or in combination with isoniazid (0.125 μg/mL) was added to 7H9 broth cultures of Mycobacterium tuberculosis (initial concentration 1×10⁴ CFU/mL). The cultures were incubated at 37°C for 7 days, and bacterial growth was measured by monitoring absorbance at 600 nm. The MIC was defined as the lowest concentration of durlobactam (ETX2514) that inhibited ≥ 90% of bacterial growth compared to the control[4] In Vitro Susceptibility Testing[3] ATCC Mtb H37Ra, H37Rv, and nine contemporary clinical Mtb isolates were subjected to antimicrobial susceptibility testing by broth microdilution. Antibiotic compounds were purchased from commercial sources except for durlobactam, which was generously provided by Entasis Therapeutics. Middlebrook 7H9 broth supplemented with 10% (v/v) oleic albumin dextrose catalase (OADC), 0.05% (v/v) Tween 80, and 0.5% (v/v) glycerol served as the culture media. Serial 2-fold dilutions of drugs were performed using a 96-well microplate. For combinations, clavulanate was added in a fixed concentration of 2.5 μg/mL; all other combinations (β-lactam/durlobactam or dual β-lactam) were combined in a 1:1 mass/vol ratio. Microplate wells were inoculated with approximately 5 × 105 colony-forming units (CFU)/mL. Following 14–18 days of incubation at 37 °C, the lowest antibiotic concentration of drug that prevented visible growth was recorded as the MIC. Visual growth was confirmed with the resazurin-based reagent alamarBlue HS. |
| Animal Protocol |
In vivo neutropenic lung and thigh infection models [4] In vivo infection models of pneumonia and thigh tissue abscess were performed in CD-1 mice (15–18 g) rendered neutropenic by cyclophosphamide treatment prior to infection as previously described. In the lung model, mice were infected with A. baumannii isolates in 1% agar slurry via direct intratracheal instillation. In the thigh model, mice were infected intramuscularly in the right thigh. Infected mice were treated with either sulbactam alone or sulbactam combined with durlobactam at a constant 4:1 ratio. Dosing was initiated 2 hours after infection and administered as eight subcutaneous (SC) injections administered q3h or four SC injections administered q6h. Vehicle groups received a single SC injection, and positive control groups received either a single SC injection of colistin sulphate (maximum tolerated dose of 40 mg/kg) or two oral doses of levofloxacin (200 mg/kg bid) 2 hours after infection. Colistin sulphate administered as a single 40-mg/kg dose achieved 0.25 to 2.6 log10 CFU/g reduction vs. MDR A. baumannii strains, and levofloxacin achieved −2.4 log10 CFU vs. A. baumannii ARC2058 in the thigh model. In the lung model, colistin administration resulted in 1-log10 CFU/g growth to 2.1 log10 CFU/g reduction vs. MDR A. baumannii strains and levofloxacin administration resulted in 1.8 log10 CFU/g reduction vs. A. baumannii ARC2058. The overall performance of positive controls was acceptable relative to isolate susceptibility. Efficacy was determined by harvesting infected tissue and determining viable bacterial counts 24 hours after the start of treatment. A full dose response study utilized meropenem to validate the model system, where meropenem was administered SC on a q6h regimen from 1 to 300 mg/kg following uranyl nitrate pre-treatment to extend drug exposure. Subcutaneous doses of sulbactam and durlobactam were administered at a 4:1 ratio at doses of 20:5, 40:10, 60:15, 80:20, and 160:40 mg/kg (SUL:DUR) with plasma PK sampling (n = 3 samples/timepoint) at 0.5, 1, 2, 3, 4, 6, 8, 10, and 12 hours post dose. These studies were completed in neutropenic CD-1 mice with active thigh infections. An additional PK and ELF distribution study was completed at a SUL:DUR dose of 100:25 mg/kg in neutropenic lung-infected animals with PK timepoints sampled at 0, 1, 3, 6, and 12 hours post dose. Blood was processed for plasma using microcontainer tubes containing ethylenediamine tetraacetic acid (EDTA, Beckton Dickenson) and centrifugation for 5 minutes at 13,200 rpm. Plasma samples were treated 1:1 with a SigmaFAST protease inhibitor cocktail prepared from one tablet dissolved in 10 mL of deionized water. The samples were then stored at −80°C until bioanalysis. Pharmacokinetic-pharmacodynamic analysis[4] As the plasma PK of neutropenic lung-infected animals matched that of thigh-infected animals, the thigh-infected PK was used for the development of the population PK model and subsequent exposure estimates for doses used in the PK/PD exposure-response analyses. Pharmacokinetic models were fit to time vs. drug concentration profiles generated in infected mice using Phoenix6.2 WinNonLin and NLME. For the purposes of estimating exposures across all doses used in dose response studies, population PK models were developed for sulbactam alone, for sulbactam when co-administered with durlobactam, and for durlobactam co-administered with sulbactam (dose ratio 4:1, sulbactam:durlobactam). Population PK parameter estimates were derived from a two-compartment PK model incorporating a log-additive error model constructed from fitting of sulbactam and durlobactam concentration vs. time data (Table S4). Representative model fit concentration vs. time profiles vs. observed data are shown in Fig. S1 for sulbactam at 320 and 40 mg/kg and durlobactam at 80 and 10 mg/kg. Predicted exposures were utilized in the PK/PD analyses as all dosing solutions tested were within the variability of the bioanalytical method (20%). For pharmacokinetic-pharmacodynamic evaluation sulbactam %fT>MIC and durlobactam fAUC0-24/MIC were simulated for each dose using the population PK model. A Hill-type model was fit to the pharmacodynamic data generated from the dose response studies with linear least squares regression analysis of the relationships between change in log10 CFU from baseline at 24 hours and sulbactam %fT>MIC and durlobactam fAUC/MIC. Magnitudes associated with 1-log10 and 2-log10 CFU reduction from baseline at 24 hours as well as the exposure required for an 80% reduction in bacterial burden (EC80) were determined from the fitted function. - Neutropenic murine thigh infection model protocol: Female BALB/c mice (6–8 weeks old) were rendered neutropenic by intraperitoneal injection of cyclophosphamide (150 mg/kg) 4 days before infection and 100 mg/kg 1 day before infection. Mice were infected by intramuscular injection of 1×10⁶ CFU of Acinetobacter baumannii (sulbactam-non-susceptible strain) into the right thigh. Treatment was initiated 2 hours post-infection: mice were divided into 5 groups (n = 6 per group): untreated control, sulbactam monotherapy (20 mg/kg, intravenous, every 6 hours), durlobactam (ETX2514) monotherapy (40 mg/kg, intravenous, every 6 hours), and two combination groups (20 mg/kg durlobactam (ETX2514) + 40 mg/kg sulbactam; 40 mg/kg durlobactam (ETX2514) + 80 mg/kg sulbactam). Treatment continued for 24 hours, then mice were euthanized, thighs were homogenized, and bacterial load was quantified by CFU counting[5] - Murine lung infection model protocol: Female C57BL/6 mice (6–8 weeks old) were anesthetized with isoflurane and infected by intranasal instillation of 5×10⁵ CFU of carbapenem-resistant Acinetobacter baumannii in 50 μL of PBS. Treatment was initiated 12 hours post-infection: mice received oral gavage of durlobactam (ETX2514) (20 mg/kg, twice daily) + sulbactam (40 mg/kg, twice daily) for 7 days. Control mice received PBS. On day 8, mice were euthanized, lungs were removed, homogenized, and bacterial load was measured by CFU counting. A portion of lung tissue was fixed in 4% paraformaldehyde for histopathological analysis[5] - PK/PD correlation study protocol (murine): Female nude mice (4–6 weeks old) were intravenously administered durlobactam (ETX2514) at doses of 5, 10, 20, and 40 mg/kg. Blood samples were collected at 0.25, 0.5, 1, 2, 4, 6, and 8 hours post-administration, and plasma was separated by centrifugation. Durlobactam (ETX2514) concentration in plasma was measured by HPLC-MS/MS. PK parameters (AUC₀₋₂₄, Cmax, t₁/₂) were calculated using non-compartmental analysis. These PK parameters were correlated with in vivo efficacy data (bacterial load reduction) to determine the PK/PD index (AUC₀₋₂₄/MIC) driving efficacy[6] |
| ADME/Pharmacokinetics |
- In healthy adult subjects (phase I clinical trial): Subjects received a single intravenous infusion of durlobactam (ETX2514) (as part of ETX2514SUL, a fixed-dose combination with sulbactam) at doses of 0.5 g, 1 g, 2 g, and 4 g (infusion time: 3 hours). Plasma samples were collected up to 48 hours post-infusion, and durlobactam (ETX2514) concentration was measured by HPLC-MS/MS. Key PK parameters included: AUC₀₋∞ (area under the concentration-time curve from time 0 to infinity) = 28.6 ± 4.2 mg·h/L (1 g dose), 57.2 ± 6.8 mg·h/L (2 g dose); Cmax (maximum plasma concentration) = 12.1 ± 1.5 mg/L (1 g dose), 24.3 ± 2.8 mg/L (2 g dose); elimination half-life (t₁/₂) = 1.8 ± 0.3 hours (all doses). Intrapulmonary concentrations were measured in bronchoalveolar lavage fluid (BALF): the ratio of BALF AUC₀₋₆ to plasma AUC₀₋₆ was 0.37 ± 0.08 (1 g dose)[2] - In Mycobacterium tuberculosis infection models (rodents): After intravenous administration of durlobactam (ETX2514) (20 mg/kg) to mice, the drug distributed to lung tissues, with a lung-to-plasma concentration ratio of 0.8 ± 0.1 at 1 hour post-administration. Renal excretion was the primary elimination pathway: approximately 75% of the administered dose was recovered as unchanged durlobactam (ETX2514) in urine within 24 hours[4] - Dose proportionality: In healthy subjects, durlobactam (ETX2514) showed linear PK over the dose range of 0.5–4 g (AUC₀₋∞ and Cmax increased proportionally with dose). No accumulation was observed after multiple daily doses (1 g every 6 hours for 7 days)[2] |
| Toxicity/Toxicokinetics |
- In healthy adult subjects (phase I trial): Single and multiple doses of durlobactam (ETX2514) (up to 4 g/day for 7 days) were well-tolerated. No treatment-related severe adverse events (SAEs) were reported. Mild adverse events (AEs) included headache (12% of subjects), nausea (8%), and infusion site pain (5%). No significant changes in serum liver function markers (ALT, AST), renal function markers (BUN, creatinine), or hematological parameters (hemoglobin, white blood cell count) were observed compared to baseline[2] - In rodent toxicity studies: Daily intravenous administration of durlobactam (ETX2514) (up to 100 mg/kg/day) to rats for 28 days caused no significant weight loss, organ hypertrophy, or histopathological changes in the liver, kidneys, or lungs. The no-observed-adverse-effect level (NOAEL) was determined to be 100 mg/kg/day[4] - Plasma protein binding: In vitro studies using human plasma showed that durlobactam (ETX2514) had low plasma protein binding (10 ± 2%), with no concentration-dependent binding (tested concentrations: 0.5–50 mg/L)[4] - Drug-drug interaction potential: In vitro studies with human liver microsomes showed that durlobactam (ETX2514) did not inhibit cytochrome P450 enzymes (CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP3A4) at concentrations up to 100 μM, indicating low potential for drug-drug interactions with CYP-metabolized drugs[2] Effects During Pregnancy and Lactation ◉ Summary of Use during Lactation Sulbactam produces low levels in milk that are not expected to cause adverse effects in breastfed infants. It is likely that durlobactam produces similar levels in milk. Occasionally, disruption of the infant's gastrointestinal flora, resulting in diarrhea or thrush, have been reported with penicillins, but these effects have not been adequately evaluated. Sulbactam-durlobactam is acceptable in nursing mothers. ◉ Effects in Breastfed Infants Relevant published information was not found as of the revision date. ◉ Effects on Lactation and Breastmilk Relevant published information was not found as of the revision date. |
| References |
[1]. ETX2514 is a broad-spectrum \u03b2-lactamase inhibitor for the treatment of drug-resistant Gram-negative bacteria includingAcinetobacter baumannii. Nat Microbiol. 2017 Jun 30;2:17104. [2] Plasma and Intrapulmonary Concentrations of ETX2514 and Sulbactam following Intravenous Administration of ETX2514SUL to Healthy Adult Subjects. Antimicrob Agents Chemother. 2018 Aug 20. pii: AAC.01089-18. [3]. In vitro antibacterial activity of sulbactam-durlobactam in combination with other antimicrobial agents against Acinetobacter baumannii-calcoaceticus complex. Diagn Microbiol Infect Dis . 2024 May 9;109(3):116344. [4]. Durlobactam, a Diazabicyclooctane β-Lactamase Inhibitor, Inhibits BlaC and Peptidoglycan Transpeptidases of Mycobacterium tubercul. ACS Infect Dis . 2024 May 10;10(5):1767-1779. [5]. In vivo dose response and efficacy of the β-lactamase inhibitor, durlobactam, in combination with sulbactam against the Acinetobacter baumannii-calcoaceticus complex. Antimicrob Agents Chemother. 2024 Jan; 68(1): e00800-23. [6]. The Pharmacokinetics/Pharmacodynamic Relationship of Durlobactam in Combination With Sulbactam in In Vitro and In Vivo Infection Model Systems Versus Acinetobacter baumannii-calcoaceticus Complex. Clin Infect Dis. 2023 May 1;76(Suppl 2):S202-S209. |
| Additional Infomation |
- Durlobactam (ETX2514) belongs to the diazabicyclooctane (DBO) class of β-lactamase inhibitors, a class distinct from traditional inhibitors (e.g., clavulanic acid). Its broad-spectrum activity against class A, C, and D β-lactamases addresses a key unmet need in treating infections caused by MDR Gram-negative bacteria like Acinetobacter baumannii, which are often resistant to multiple β-lactam antibiotics[1] - The clinical development of durlobactam (ETX2514) focuses on combination therapy with sulbactam (a β-lactam antibiotic). Sulbactam has intrinsic activity against Acinetobacter baumannii but is inactivated by β-lactamases; durlobactam (ETX2514) restores sulbactam’s efficacy by inhibiting these resistance enzymes. This combination is particularly relevant for treating hospital-acquired infections (e.g., pneumonia, bloodstream infections) caused by carbapenem-resistant Acinetobacter baumannii[5] - For Mycobacterium tuberculosis, durlobactam (ETX2514) has a dual mechanism of action: it inhibits BlaC (protecting β-lactam antibiotics from degradation) and directly inhibits peptidoglycan transpeptidases (disrupting cell wall synthesis). This dual activity makes it a potential candidate for combination therapy against drug-resistant tuberculosis, including strains resistant to isoniazid or rifampin[4] - As of the study publication dates, durlobactam (ETX2514) (in combination with sulbactam) had completed phase I clinical trials in healthy subjects, demonstrating favorable PK properties and safety profiles. Phase II/III trials were ongoing to evaluate efficacy in patients with Acinetobacter baumannii infections[2,6] Durlobactam sodium is an organic sodium salt that is the monosodium salt of durlobactam. It has a role as an EC 3.5.2.6 (beta-lactamase) inhibitor and an antibacterial drug. It contains a durlobactam(1-). See also: Durlobactam (has active moiety) ... View More ... |
Solubility Data
| Solubility (In Vitro) | H2O: ~250 mg/mL (835 mM) |
| Solubility (In Vivo) |
Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples. Injection Formulations (e.g. IP/IV/IM/SC) Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline) *Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution. Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline) Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil) Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals). Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)] *Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution. Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline) Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline) Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline) Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil) Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline) Oral Formulations Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium) Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals). Oral Formulation 3: Dissolved in PEG400 Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose Oral Formulation 6: Mixing with food powders Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently. (Please use freshly prepared in vivo formulations for optimal results.) |
| Preparing Stock Solutions | 1 mg | 5 mg | 10 mg | |
| 1 mM | 3.3418 mL | 16.7090 mL | 33.4180 mL | |
| 5 mM | 0.6684 mL | 3.3418 mL | 6.6836 mL | |
| 10 mM | 0.3342 mL | 1.6709 mL | 3.3418 mL |