Vaborbactam (INN)^[1] is a non-β-lactam β-lactamase inhibitor discovered by Rempex Pharmaceuticals, a subsidiary of The Medicines Company. While not effective as an antibiotic by itself, it restores potency to existing antibiotics by inhibiting the β-lactamase enzymes that would otherwise degrade them. When combined with an appropriate antibiotic it can be used for the treatment of gram-negative bacterial infections.^[2]

Quick Facts Clinical data, Routes ofadministration ...

Vaborbactam

Clinical data
Routes of administration	IV
ATC code	None
Identifiers
IUPAC name {(3R,6S)-2-Hydroxy-3-[2-(thiophen-2-yl)acetamido]- 1,2-oxaborinan-6-yl}acetic acid
CAS Number	1360457-46-0
PubChem CID	56649692
DrugBank	DB12107
ChemSpider	35035409
UNII	1C75676F8V
KEGG	D10998
ECHA InfoCard	100.235.136
Chemical and physical data
Formula	C12H16BNO5S
Molar mass	297.13 g·mol−1
3D model (JSmol)	Interactive image
SMILES B1([C@H](CC[C@H](O1)CC(=O)O)NC(=O)CC2=CC=CS2)O
InChI InChI=1S/C12H16BNO5S/c15-11(7-9-2-1-5-20-9)14-10-4-3-8(6-12(16)17)19-13(10)18/h1-2,5,8,10,18H,3-4,6-7H2,(H,14,15)(H,16,17)/t8-,10-/m0/s1 Key:IOOWNWLVCOUUEX-WPRPVWTQSA-N

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In the United States, the combination drug meropenem/vaborbactam (Vabomere) is approved by the Food and Drug Administration for complicated urinary tract infections and pyelonephritis.^[3]

Vaborbactam is a boronic acid β-lactamase inhibitor with a high affinity for serine β-lactamases, including Klebsiella pneumoniae carbapenemase (KPC).^[4] Vaborbactam inhibits a variety of β-lactamases, exhibiting a 69 nM K_i against the KPC-2 carbapenemase and even lower inhibition constants against CTX-M-15 and SHV-12. Boronic acids are unusual in their ability to reversibly form covalent bonds with alcohols such as the active site serine in a serine carbapenemase. This property enables them to function as transition state analogs of serine carbapenemase-catalyzed lactam hydrolysis and thereby inhibit these enzymes.^[2]

Carbapenemases can be broadly divided into two different categories based on the mechanism they use to hydrolyze the lactam ring in their substrates: Metallo-β-lactamases contain bound zinc ions in their active sites and are therefore inhibited by chelating agents like EDTA, while serine carbapenemases feature an active site serine that participates in the hydrolysis of the substrate.^[5] Serine carbapenemase-catalyzed hydrolysis employs a three-step mechanism featuring acylation and deacylation steps analogous to the mechanism of protease-catalyzed peptide hydrolysis, proceeding through a tetrahedral transition state.^[5][6]

Given their mechanism of action, the possibility of off-target effects brought about through inhibition of endogenous serine hydrolases is an obvious possible concern in the development of boronic acid β-lactamase inhibitors, and in fact boronic acids like bortezomib have previously been investigated or developed as inhibitors of various human proteases.^[2] Vaborbactam, however, is a highly specific β-lactamase inhibitor, with an IC₅₀ >> 1 mM against all human serine hydrolases against which it has been tested.^[2] Consistent with its high in vitro specificity, vaborbactam exhibited a good safety profile in human phase I clinical trials, with similar adverse events observed in both placebo and treatment groups.^[7] Hecker et al. argue this specificity results from the higher affinity of human proteases to linear molecules; thus it is expected that a boron heterocycle will have zero effect on them.