β-lactamase
Target: Serine-β-lactamases (SBLs, Classes A, C, D) and Metallo-β-lactamases (MBLs, Class B) [1, 2].
Specific IC50 values against isolated enzymes:Class A SBL (TEM-116): 0.126 µM [1]
Class A SBL (CTX-M-15): 0.03 µM [2]
Class A SBL (SHV-5): 0.0004 µM [2]
Class A SBL (KPC-2): 0.03 µM [2]
Class B1 MBL (IMP-1): 2.51 µM [1] / 39.8 µM [2]
Class B1 MBL (NDM-1): 0.0163 µM [1] / 0.19 µM [2]
Class B1 MBL (VIM-1): 0.0079 µM [1]
Class B1 MBL (VIM-2): 0.00053 µM [1] / 0.026 µM [2]
Class B2 MBL (CphA): 2.51 µM [1]
Class B3 MBL (L1): >10 µM [1]
Class C SBL (AmpC from P. aeruginosa): 0.301 µM [1]
Class C SBL (CMY-2): 0.007 µM [2]
Class C SBL (p99 AmpC): 0.03 µM [2]
Class D SBL (OXA-10): 0.234 µM [1] / 0.42 µM [2]
Class D SBL (OXA-48): 0.537 µM [1] / 0.54 µM [2]
Class D SBL (OXA-1): 0.16 µM [2]
Taniborbactam targets beta-lactamases, the enzymes produced by Gram-negative bacteria that hydrolyze and inactivate beta-lactam antibiotics. It inhibits serine-beta-lactamases (SBLs; classes A, C, D) and metallo-beta-lactamases (MBLs; class B) with IC50s of 8-530 nM. Specific IC50 values include: Class A (KPC-2): 0.03 uM; Class B1 (NDM-1): 0.0163-0.19 uM; Class B1 (VIM-2): 0.00053-0.026 uM; Class C (CMY-2): 0.007 uM; Class D (OXA-48): 0.537-0.54 uM. It is the only known beta-lactamase inhibitor in advanced clinical development that blocks class B carbapenemases.

Taniborbactam demonstrates broad-spectrum inhibition of both serine- and metallo-β-lactamases, with potent sub-micromolar IC50 values against major clinically relevant enzymes including TEM, CTX-M, KPC, NDM, and VIM. It shows significantly lower activity against IMP-1 MBL and does not inhibit subclass B3 MBL L1. [1]
In antimicrobial susceptibility tests, Taniborbactam at a fixed concentration of 10 µg/mL significantly reduces the minimum inhibitory concentrations (MICs) of meropenem and cefepime against clinical isolates of E. coli and K. pneumoniae producing NDM-1. For six NDM-1-producing isolates, the MIC range for cefepime alone was >64 µg/mL, which was reduced to a range of 0.25-16 µg/mL in combination with Taniborbactam. Similarly, the MIC range for meropenem alone was >64 µg/mL, reduced to 0.125-1 µg/mL in combination with Taniborbactam. [1]
Taniborbactam (20) potentiates the activity of piperacillin, cefepime, and meropenem against multi-drug resistant Gram-negative clinical isolates producing various β-lactamases (KPC, OXA, VIM, NDM). Compared to early analogs (1, 3, 17), it shows superior rescue of antibiotic activity, particularly against strains producing class D or class B enzymes. [2]
Taniborbactam (20) rescues cefepime activity against serine-β-lactamase-producing Enterobacteriaceae. In a panel of isolates producing ESBLs, KPCs, class C, or class D enzymes, the cefepime/Taniborbactam combination resulted in MICs below the susceptible-dose dependent breakpoint of 8 µg/mL, whereas cefepime/tazobactam showed only modest activity. [2]
Taniborbactam (20) rescues cefepime activity against metallo-β-lactamase-producing Gram-negative pathogens. In 14 clinical isolates expressing VIM or NDM MBLs, cefepime alone had MICs ranging from 32 to >512 µg/mL. The addition of Taniborbactam (4 µg/mL) reduced the MIC range to 0.125-4 µg/mL (MIC50 = 1 µg/mL, MIC90 = 4 µg/mL). In contrast, tazobactam and avibactam showed no such effect. [2]
Taniborbactam (20) has no intrinsic antibacterial activity when tested alone against a panel of Gram-positive and Gram-negative bacteria, including wild-type and β-lactamase-producing strains, with MICs >128 µg/mL. This contrasts with meropenem and oxacillin, which showed potent activity against susceptible strains. [2]

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The half-life of taniborbactam hydrochloride (VNRX-5133 hydrochloride) is 0.5 nM for Klebsiella pneumoniae strains KPC-2, OXA-48, and VIM-4, and 0.5 nM for P. aeruginosa strain VIM-2. The minimum inhibitory concentration (MIC) ranges for cefepime hydrochloride/taniborbactam (10 μg/mL), 0.5 nM, and meropenem/taniborbactam combinations against Escherichia coli and Klebsiella pneumoniae were 16-0.25, respectively. together with 1-0.125 μg/mL[1].

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In vitro, taniborbactam demonstrates broad-spectrum inhibition of both serine- and metallo-beta-lactamases with potent sub-micromolar IC50 values against major clinically relevant enzymes including TEM, CTX-M, KPC, NDM, and VIM. It shows significantly lower activity against IMP-1 MBL and does not inhibit subclass B3 MBL L1. In antimicrobial susceptibility tests, taniborbactam at a fixed concentration of 10 ug/mL significantly reduces MICs of cefepime against carbapenem-resistant Enterobacteriaceae and P. aeruginosa.

In a neutropenic mouse lung infection model using a CTX-M-14-producing K. pneumoniae strain, a single subcutaneous dose of cefepime/Taniborbactam (32 mg/kg and 16 mg/kg, respectively) achieved a >4 log10 reduction in viable bacterial counts in lung tissue at 24 hours. Cefepime alone at 32 mg/kg was not effective. The positive control, ceftazidime/avibactam (32:8 mg/kg), achieved a >3 log10 reduction. [2]
In a mouse ascending urinary tract infection model using a CTX-M-15-producing E. coli strain, twice-daily subcutaneous doses of cefepime/Taniborbactam (16 mg/kg and 8 mg/kg, respectively) for 3 days resulted in a >2 log10 reduction in viable bacterial counts in the kidneys at day 7. [2]

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In a neutropenic mouse lung infection model, a single dosage of cefepime (32 mg/kg) and tantaborbactam hydrochloride (VNRX-5133 hydrochloride; 16 mg/kg; sc) increased survival. Bacterial population reduction more than 4 log10 and against strains of K. pneumoniae that produce CTX-M-14 [2]. Cefepime (16 mg/kg) and tanibobactam hydrochloride (16 mg/kg; subcutaneous injection; twice daily for 7 days) together produced >2 log10 decrease against CTX-M-15-producing E. coli strains and raised live bacterial counts in the kidneys of an ascending urine infection model [2]. In mice, taniborbactam hydrochloride has a T1/2 of 0.16 hours, a CL of 618 mL/h/kg, and a Vss of 143 mL/kg[2].

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In vivo, cefepime-taniborbactam has demonstrated efficacy in animal models of infection, including murine thigh infection and urinary tract infection models. It has successfully completed a global Phase 3 clinical trial (CERTAIN-1) for patients with complicated urinary tract infections (cUTI), demonstrating superiority over meropenem. It is also being studied in a Phase 3 trial for hospital-acquired and ventilator-associated bacterial pneumonia (HABP/VABP).

Inhibitory activity of Taniborbactam against a panel of representative serine-β-lactamases (SBLs) and metallo-β-lactamases (MBLs) was determined using a fluorogenic assay. The assay monitored the enzymatic breakdown of the cephalosporin probe FC5, except for the subclass B2 MBL CphA, for which meropenem hydrolysis was used. The assays were conducted at room temperature in microplates. SBLs (TEM-116, AmpC, OXA-10, OXA-48) were tested in a phosphate buffer (pH 7.4) with 0.01% Triton X-100. OXA-10 and OXA-48 assays were also supplemented with 100 mM NaHCO3. MBLs (IMP-1, VIM-1, VIM-2, NDM-1, L1, CphA) were screened in HEPES buffer (50 mM, pH 7.2) containing 1 µM ZnSO4, 1 µg/mL BSA, and 0.01% Triton X-100. The enzymes were tested at specific concentrations (e.g., AmpC at 500 pM, NDM-1 at 20 pM). The probe FC5 was used at 5 or 10 µM, and meropenem at 12.5 µM for CphA. The initial rates of reaction were assessed after a 10-minute pre-incubation of Taniborbactam with the enzyme, by monitoring fluorescence intensity (λex=380 nm, λem=460 nm) or UV absorbance (λ=300 nm for CphA). Data were fitted using a four-parameter function in GraphPad Prism 6 to obtain IC50 values. Varying pre-incubation times of Taniborbactam with NDM-1 did not result in different IC50 values, supporting reversible inhibition. [1]
Inhibition assays for compound 20 were performed against a panel of β-lactamases from classes A to D. The exact methodology is not detailed in this section, but results are presented as IC50 values (µM) for enzymes including SHV-5, CTX-M-15, KPC-2, CMY-2, p99 AmpC, OXA-1, OXA-48, NDM-1, VIM-2, and IMP-1. [2]

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For in vitro enzyme inhibition assays: Purified beta-lactamase enzymes (various classes) are incubated with varying concentrations of taniborbactam (0.01-100 uM) in assay buffer (50 mM phosphate buffer, pH 7.0). Add a chromogenic beta-lactam substrate (e.g., nitrocefin at 100 uM). Measure the change in absorbance at 486 nm over time. Calculate IC50 values using nonlinear regression. For a panel of beta-lactamases, specific IC50 values are determined as reported.

Antimicrobial susceptibility was tested using the agar dilution method. Minimum inhibitory concentration (MIC) values were determined for meropenem and cefepime alone (0.06-64 µg/mL) and in combination with a fixed concentration (10 µg/mL) of Taniborbactam against a panel of six NDM-1-producing clinical isolates of E. coli and K. pneumoniae. MICs were interpreted using EUCAST/CLSI guidelines. All reported MIC values were within ±1 log2 dilution of the reference MIC values. [1]
The ability of Taniborbactam to potentiate β-lactam antibiotics (piperacillin, cefepime, meropenem) was evaluated against MDR Gram-negative clinical isolates. MICs for the β-lactam alone and in combination with a fixed concentration of BLI were determined. For compound 20, the MIC of the BLI required to restore meropenem activity (fixed at 4 µg/mL) was determined against K. pneumoniae (KPC-2, OXA-48, VIM-4 producers) and P. aeruginosa (VIM-2 producer). The rescue of cefepime activity by Taniborbactam (4 µg/mL) was tested against Enterobacteriaceae expressing ESBLs, KPCs, class C, or class D enzymes, and against 14 MBL-producing Gram-negative pathogens (including E. coli, E. cloacae, K. pneumoniae, P. aeruginosa, A. baumannii) expressing VIM or NDM. MIC testing was conducted using CLSI broth microdilution assays. [2]
The intrinsic antibacterial activity of Taniborbactam was tested against a panel of Gram-positive (S. aureus) and Gram-negative (E. coli, K. pneumoniae, E. cloacae, E. aerogenes, P. aeruginosa) strains, including wild-type and β-lactamase-producing variants. MICs were determined following CLSI guidelines. [2]

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For antimicrobial susceptibility testing: Use broth microdilution according to CLSI guidelines. Prepare serial twofold dilutions of cefepime alone and in combination with a fixed concentration of taniborbactam (4-8 ug/mL). Inoculate with 5×10⁵ CFU/mL of clinical isolates of Enterobacteriaceae, P. aeruginosa, or A. baumannii. Read minimum inhibitory concentrations (MICs) after 16-20 hours incubation at 35degC. Determine the reduction in MICs in the presence of taniborbactam.

Pharmacokinetic (PK) studies of Taniborbactam (20), cefepime, and avibactam were performed in mice following intravenous administration. The specific formulation, dosing frequency, and route (IV) are mentioned, but detailed protocols like vehicle composition are not described. [2]
Neutropenic Mouse Lung Infection Model: Female CD-1 mice were rendered neutropenic. They were infected intranasally with a CTX-M-14-producing K. pneumoniae strain. Two hours post-infection, a single subcutaneous dose of cefepime (32 mg/kg) alone, cefepime/Taniborbactam (32:16 mg/kg), or ceftazidime/avibactam (32:8 mg/kg) was administered. At 24 hours post-infection, mice were euthanized, and lungs were harvested for bacterial colony-forming unit (CFU) enumeration. [2]
Mouse Ascending Urinary Tract Infection Model: Female BALB/c mice were infected transurethrally with a CTX-M-15-producing E. coli strain. Treatment began 24 hours post-infection and was administered subcutaneously twice daily for 3 days. Groups received cefepime (16 mg/kg) alone, cefepime/Taniborbactam (16:8 mg/kg), or ceftazidime/avibactam (16:4 mg/kg). On day 7 post-infection, mice were euthanized, and kidneys were harvested for CFU enumeration. [2]

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For in vivo efficacy studies in mouse models: Use a neutropenic murine thigh infection model. Mice are rendered neutropenic by cyclophosphamide treatment. Infect thighs with ~10⁶ CFU of beta-lactamase-producing bacteria. Administer cefepime alone or in combination with taniborbactam subcutaneously at various doses 2 hours post-infection. After 24 hours, euthanize mice and homogenize thighs for bacterial CFU counting. Calculate log reduction in CFU compared to untreated controls.

In mice following intravenous administration, Taniborbactam (20) exhibited a PK profile typical of highly polar, ionizable compounds, similar to β-lactams. The parameters were: t1/2 = 0.16 h, AUCint = 16,189 h·ng/mL, Vss = 436 mL/kg, and CL = 1,818 mL/h/kg. Compared to avibactam, Taniborbactam showed higher exposure (AUC) and lower clearance (CL). [2]

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In human clinical trials, taniborbactam is administered intravenously in combination with cefepime. Pharmacokinetic studies in healthy subjects have shown dose-proportional exposure with a half-life of approximately 2-3 hours, allowing for every 8-hour dosing. The combination is primarily excreted renally. No drug-drug interactions have been identified in Phase 1 studies.

Taniborbactam (20) displayed no cytotoxicity (<20% inhibition of growth) when tested up to 256 µg/mL against HeLa, MRC-5, and 3T3 mammalian cell lines. No toxicity was observed in human primary renal proximal tubule cells when tested up to 1000 µg/mL. [2]
Taniborbactam (20) had no significant activity when tested at 100 µM against a panel of 50 human enzymes and receptors. This panel included serine proteases (cathepsin G, chymotrypsin, Factor Xa, trypsin, neutrophil elastase 2), metalloproteinases (MMP-1, -2, -3, -9), cytochrome P450s (1A2, 2C9, 2C19, 2D6, 3A4), and the hERG potassium channel. [2]

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In clinical trials, cefepime-taniborbactam has been generally well tolerated. The most common adverse events were mild to moderate gastrointestinal symptoms, headache, and infusion site reactions. No significant hepatotoxicity or nephrotoxicity signals have been observed. The safety profile is consistent with other beta-lactam/beta-lactamase inhibitor combinations.

[1]. Bicyclic Boronate VNRX-5133 Inhibits Metallo- and Serine-β-Lactamases. J Med Chem. 2019 Sep 26;62(18):8544-8556.

[2]. Discovery of Taniborbactam (VNRX-5133): A Broad-Spectrum Serine- and Metallo-β-lactamase Inhibitor for Carbapenem-Resistant Bacterial Infections. J Med Chem. 2020 Mar 26;63(6):2789-2801.

Taniborbactam (formerly VNRX-5133) is a bicyclic boronate β-lactamase inhibitor in clinical development (Phase 3 trials as of the publication). It is designed as a broad-spectrum inhibitor to combat antibiotic resistance in Gram-negative bacteria. [1, 2]
The mechanism of action involves mimicking the tetrahedral intermediate in β-lactam hydrolysis. It inhibits serine-β-lactamases (SBLs) by forming a covalent adduct with the active-site serine and inhibits metallo-β-lactamases (MBLs) by interacting with the active-site zinc ions, acting as a "high-energy-intermediate" analogue. [1, 2]
Crystallographic studies reveal that Taniborbactam binds to SBLs (e.g., OXA-10, CTX-M-15) via a covalent bond to the catalytic serine. In MBLs (e.g., NDM-1, VIM-2), the tetrahedral boron interacts with the zinc ions. An unexpected tricyclic binding form was observed in the NDM-1 active site, suggesting the boron atom can undergo further reactions. The conserved binding of the bicyclic core across enzyme classes and differing side-chain orientations imply further optimization is possible. [1, 2]
Taniborbactam is being developed in combination with the fourth-generation cephalosporin, cefepime, to treat serious Gram-negative bacterial infections, including those caused by carbapenem-resistant Enterobacteriaceae and Pseudomonas aeruginosa. This combination avoids the use of carbapenems, potentially reducing resistance-selective pressure. A Phase 3 efficacy trial for cefepime/Taniborbactam (NCT03840148) was in progress at the time of the second publication. [2]

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Taniborbactam dihydrochloride is an investigational drug that has completed Phase 3 clinical trials for complicated urinary tract infections (cUTI), demonstrating superiority over meropenem. It is in late-stage clinical development for hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP). It is the only beta-lactamase inhibitor in advanced clinical development that blocks both serine- and metallo-beta-lactamases. The compound is not yet FDA or EMA approved but has received regulatory designations including Qualified Infectious Disease Product (QIDP) and Fast Track status. For research purposes, it is supplied as a dihydrochloride salt, soluble in DMSO, and should be stored at -20degC.

C19H30BCL2N3O5

462.17560338974

461.165

C, 49.38; H, 6.54; B, 2.34; Cl, 15.34; N, 9.09; O, 17.31

2244235-49-0

Taniborbactam;1613267-49-4

137331954

Off-white to light yellow solid powder

7

7

7

30

544

1

Cl.Cl.O=C(CC1CCC(CC1)NCCN)N[C@@H]1B(O)OC2C(C(=O)O)=CC=CC=2C1

CKWIMFZHNCBHIX-DKZBTPFISA-N

InChI=1S/C19H28BN3O5.2ClH/c21-8-9-22-14-6-4-12(5-7-14)10-17(24)23-16-11-13-2-1-3-15(19(25)26)18(13)28-20(16)27/h1-3,12,14,16,22,27H,4-11,21H2,(H,23,24)(H,25,26)2*1H/t12-,14-,16-/m0../s1

(3R)-3-(2-{trans-4-[(2-aminoethyl)amino]cyclohexyl}acetamido)-2-hydroxy-3,4-dihydro-2H-1,2-benzoxaborinine-8-carboxylic acid dihydrochloride

Taniborbactam dihydrochloride; VNRX-5133; VNRX5133; VNRX 5133

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: (1). This product requires protection from light (avoid light exposure) during transportation and storage.  (2). Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture.

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

DMSO : ~200 mg/mL (~432.73 mM)
H2O : ~33.33 mg/mL (~72.11 mM)

Solubility in Formulation 1: ≥ 5 mg/mL (10.82 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 50.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 5 mg/mL (10.82 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 50.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
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.

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Solubility in Formulation 3: ≥ 5 mg/mL (10.82 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 50.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: ≥ 2.5 mg/mL (5.41 mM) (saturation unknown) in 5% DMSO + 40% PEG300 + 5% Tween80 + 50% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 5: ≥ 2.5 mg/mL (5.41 mM) (saturation unknown) in 5% DMSO + 95% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
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.

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Solubility in Formulation 6: ≥ 0.5 mg/mL (1.08 mM) (saturation unknown) in 1% DMSO 99% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 7: 50 mg/mL (108.18 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication.

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