Lefamulin acetate (formerly BC3781; Xenleta), the acetate salt form of lefamulin, is a semi-synthetic, orally bioactive pleuromutilin antibiotic that acts as an inhibitor for the synthesis of bacterial protein. It is an approved medication for the treatment of community-acquired bacterial pneumonia. Lefamulin acts by binding to the peptidyl transferase center, or PTC, on the bacterial ribosome in such a way that it interferes with the interaction of protein production at two key sites known as the 'A' site and the 'P' site, resulting in the inhibition of bacterial proteins and the cessation of bacterial growth. Lefamulin's binding occurs with high affinity, high specificity and at molecular sites that are different than other antibiotic classes. Lefamulin exhibited MIC50 and MIC90 values of 0.12 and 0.25 μg/ml, respectively, against the entire collection (n = 822). Similar results were obtained for lefamulin against each of the most common serotypes as well as against multidrug-resistant isolates and strains that are nonsusceptible to ceftriaxone or erythromycin. Lefamulin may be useful for the treatment of community-acquired respiratory tract infections.

Physicochemical Properties

Molecular Formula	C30H49NO7S
Molecular Weight	567.77756857872
Exact Mass	567.322
Elemental Analysis	C, 63.46; H, 8.70; N, 2.47; O, 19.72; S, 5.65
CAS #	1350636-82-6
Related CAS #	Lefamulin;1061337-51-6
PubChem CID	86346053
Appearance	Solid powder
Hydrogen Bond Donor Count	4
Hydrogen Bond Acceptor Count	9
Rotatable Bond Count	6
Heavy Atom Count	39
Complexity	882
Defined Atom Stereocenter Count	11
SMILES	S([C@@H]1CC[C@H](C[C@H]1O)N)CC(=O)O[C@@H]1C[C@](C=C)(C)[C@H]([C@H](C)[C@]23CCC([C@H]2[C@@]1(C)C(C)CC3)=O)O.OC(C)=O
InChi Key	WSMXIQXWHPSVDE-ZPJPNJFZSA-N
InChi Code	InChI=1S/C28H45NO5S.C2H4O2/c1-6-26(4)14-22(34-23(32)15-35-21-8-7-18(29)13-20(21)31)27(5)16(2)9-11-28(17(3)25(26)33)12-10-19(30)24(27)281-2(3)4/h6,16-18,20-22,24-25,31,33H,1,7-15,29H2,2-5H31H3,(H,3,4)/t16-,17+,18-,20-,21-,22-,24+,25+,26-,27+,28+/m1./s1
Chemical Name	(3aR,4R,5R,7S,8S,9R,9aS,12R)-8-hydroxy-4,7,9,12-tetramethyl-3-oxo-7-vinyldecahydro-4,9a-propanocyclopenta[8]annulen-5-yl 2-(((1R,2R,4R)-4-amino-2-hydroxycyclohexyl)thio)acetate acetic acid (1:1)
Synonyms	BC3781.Ac; BC-3781; BC 3781; BC3781; Xenleta;BC-3781.Ac; BC 3781.Ac;
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

ln Vitro	Lefamulin acetate (0–1 mg/L) exhibits inhibitory activity against M. genitalium, N. gonorrhoeae, and C. trachomatis[2]. Lefamulin acetate has MIC values of ≤0.008 μg/mL, indicating strong activity against all strains of M. pneumoniae[3].
ln Vivo	Lefamulin (10-140 mg/kg, s.c.) acetate inhibits inflammation in a mouse model of lung neutrophilia caused by lipopolysaccharide [4]. Lefamulin (1.25-160 mg/kg, s.c.) acetate exhibits antimicrobial activity in lung infection-challenged mice challenged with S. pneumoniae or S. aureus[5].
Cell Assay	Cell Line: C. trachomatis, N. gonorrhoeae, and M. genitalium Concentration: 0-1 mg/L Incubation Time: Result: demonstrated inhibition of bacterial activity at MIC50s of 0.02 mg/L, 0.063 mg/L, and 0.12 mg/L, in that order.
Animal Protocol	Animal Model: LPS-induced lung neutrophilia mouse model[4] Dosage: 10-140 mg/kg Administration: Subcutaneous injection (s.c.) Result: decreased numbers of BALF neutrophil cells. Diminished levels of MMP-9, chemokines (CXCL-1, CXCL-2, and CCL-2) and pro-inflammatory cytokines (TNF-α, IL-6, IL-1β, and GM-CSF) in mouse lung tissue.
References	[1]. Lefamulin: Review of a Promising Novel Pleuromutilin Antibiotic. Pharmacotherapy. 2018 Sep;38(9):935-946. doi: 10.1002/phar.2166. Epub 2018 Aug 20. [2]. In Vitro Activity of Lefamulin against Sexually Transmitted Bacterial Pathogens. Antimicrob Agents Chemother. 2018 Apr 26;62(5):e02380-17. [3]. In Vitro Activities of Lefamulin and Other Antimicrobial Agents against Macrolide-Susceptible and Macrolide-Resistant Mycoplasma pneumoniae from the United States, Europe, and China. Antimicrob Agents Chemother. 2017 Jan 24;61(2):e02008-16. [4]. Anti-inflammatory activity of lefamulin versus azithromycin and dexamethasone in vivo and in vitro in a lipopolysaccharide-induced lung neutrophilia mouse model. PLoS One. 2021 Sep 29;16(9): e0237659. [5]. Pharmacokinetics/pharmacodynamics of lefamulin in a neutropenic murine pneumonia model with Staphylococcus aureus and Streptococcus pneumonia. J Antimicrob Chemother. 2019 Apr 1;74(Suppl 3):iii11-iii18.
Additional Infomation	See also: Lefamulin Acetate (annotation moved to). Drug Indication Xenleta is indicated for the treatment of community-acquired pneumonia (CAP) in adults when it is considered inappropriate to use antibacterial agents that are commonly recommended for the initial treatment of CAP or when these have failed. Consideration should be given to official guidance on the appropriate use of antibacterial agents.

Solubility Data

Solubility (In Vitro)

DMSO : ≥ 100 mg/mL (176.12 mM ) Ethanol : ~100 mg/mL H2O : 1~100 mg/mL (~1.76 mM)

Solubility (In Vivo)

Solubility in Formulation 1: ≥ 2.5 mg/mL (4.40 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 25.0 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. Solubility in Formulation 2: 2.5 mg/mL (4.40 mM) 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; with ultrasonication. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 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. Solubility in Formulation 3: ≥ 2.5 mg/mL (4.40 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 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.. Solubility in Formulation 4: 10% DMSO+90% (20% SBE-β-CD in Saline): 2.5 mg/mL (4.40 mM) Solubility in Formulation 5: 100 mg/mL (176.12 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	1.7612 mL	8.8062 mL	17.6125 mL
	5 mM	0.3522 mL	1.7612 mL	3.5225 mL
	10 mM	0.1761 mL	0.8806 mL	1.7612 mL

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.