Class A KPC-2 (IC50 = 4 nM), Class C AmpC (IC50 = 14 nM), D OXA-24 (IC50 = 190 nM)

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].

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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].

Sulbactam–ETX2514 exhibited in vivo efficacy in MDR A. baumannii infection mouse models [1].

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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.

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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]

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.

Absorption, Distribution and Excretion
Durlobactam demonstrated dose-proportional pharmacokinetics across the dose range studied (0.25 times the recommended single dose to 2 times the recommended single dose infused over 3 hours every 6 hours), with the Cmax, AUC0-24, and AUC0-6/ELF plasma ratio calculated to be 29.2 ± 13.2 µg/mL, 471 ± 240 h.µg/mL, and 0.37 respectively.
The major route of elimination of durlobactam is through the kidney, with 78% of durlobactam excreted unchanged in the urine.
The volume of distribution of durlobactam as stead state (_ss) was estimated to be 30.3 ± 12.9 L.
The clearance of durlobactam was calculated to be 9.96 ± 3.11 L/h.

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Metabolism / Metabolites
Durlobactam is minimally metabolized.

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Biological Half-Life
The elimination half-life of durlobactam was calculated to be 2.52 ± 0.77 h.

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.

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Protein Binding
The binding of durlobactam to human serum proteins was 10%.

[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.
[2]. 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.
[3]. Durlobactam, a Diazabicyclooctane β-Lactamase Inhibitor, Inhibits BlaC and Peptidoglycan Transpeptidases of Mycobacterium tubercul. ACS Infect Dis . 2024 May 10;10(5):1767-1779.
[4]. 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.
[5]. he 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.

Durlobactam is a member of the class of azabicycloalkanes that is (1R,2S,5R)-3-methyl-7-oxo-1,6-diazabicyclo[3.2.1]oct-3-ene-2-carboxamide in which the amino hydrogen at position 6 is replaced by a sulfooxy group. It has a role as an EC 3.5.2.6 (beta-lactamase) inhibitor and an antibacterial drug. It is a primary carboxamide, an azabicycloalkane, a hydroxylamine O-sulfonic acid and a monocarboxylic acid amide. It is a conjugate acid of a durlobactam(1-).
Durlobactam is a diazabicyclooctane non-beta-lactam, beta-lactamase inhibitor. It is typically given in combination with [sulbactam] to protect it from degradation by certain serine-beta-lactamases. The combination product of durlobactam and sulbactam was first approved by the FDA in May 2023. It is used to treat hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia (HABP/VABP), caused by susceptible isolates of Acinetobacter baumannii-calcoaceticus complex.
Durlobactam is a beta Lactamase Inhibitor. The mechanism of action of durlobactam is as a beta Lactamase Inhibitor.
See also: Durlobactam Sodium (active moiety of).

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Drug Indication
In combination with [sulbactam], durlobactam is indicated in adults for the treatment of hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia (HABP/VABP), caused by susceptible isolates of _Acinetobacter baumannii-calcoaceticus_ complex.

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Mechanism of Action
Durlobactam is a diazabicyclooctane non-beta-lactam, beta-lactamase inhibitor. When given in combination with [sulbactam], it protects sulbactam from degradation by certain serine-beta-lactamases. Durlobactam is carbamoylated by β-lactamase by the serine nucleophile in the enzyme active site: The covalent bond between durlobactam and β-lactamase is reversible due to recyclization by the sulfated amine group on durlobactam, demonstrating that durlobactam can be exchanged from one enzyme molecule to another, also known as acylation exchange.

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Pharmacodynamics
Durlobactam has an extended spectrum of activity compared to other β-lactamase inhibitors with a displayed potent inhibition against class A, C, and D serine β-lactamases. Durlobactam is not active against class B metallo-β-lactamases, which is an enzyme class rarely observed in _Acinetobacter_ clinical isolates. Durlobactam alone does not have antibacterial activity against _Acinetobacter baumannii-calcoaceticus_ complex isolates.

C8H11N3O6S

277.25

277.036

C, 34.66; H, 4.00; N, 15.16; O, 34.62; S, 11.56

1467829-71-5

1467829-71-5 (free acid);1467157-21-6 (sodium);

89851852

Solid powder

1.8±0.1 g/cm3

1.691

-2.53

2

6

3

18

536

2

C1(=C[C@@H]2C[N@@](C(N2OS(=O)(=O)O)=O)[C@@H]1C(N)=O)C

BISPBXFUKNXOQY-RITPCOANSA-N

InChI=1S/C8H11N3O6S/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)/t5-,6+/m1/s1

(1R,2S,5R)-2-carbamoyl-3-methyl-7-oxo-1,6-diazabicyclo[3.2.1]oct-3-en-6-yl hydrogen sulfate

ETX 2514ETX-2514 ETX2514 Durlobactam Durlobactam.

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO: > 10 mM

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.

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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).

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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)

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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).

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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

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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.

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 (Please use freshly prepared in vivo formulations for optimal results.)