Topoisomerase II; Topoisomerase IV
- Bacterial DNA gyrase (subunit A/B) and topoisomerase IV (subunit A/B): - For Mycobacterium tuberculosis (H37Rv strain): MIC₉₀ (minimum inhibitory concentration inhibiting 90% growth) = 0.25 μg/mL (DNA gyrase inhibition-driven) [5]
- For Staphylococcus aureus (MSSA): MIC₉₀ = 0.5 μg/mL (topoisomerase IV as primary target) [2]
- For Escherichia coli: Ki = 1.2 μM (DNA gyrase ATPase activity inhibition) [3]

1. Antibacterial Activity Against Gram-Positive Bacteria: - Inhibits 90% of Staphylococcus aureus (MSSA/MRSA) strains at MIC₉₀ = 0.5–1 μg/mL; no cross-resistance with β-lactams. Time-kill curves show concentration-dependent bactericidal activity: 4× MIC reduces bacterial counts by >3 log₁₀ CFU/mL within 24 hours [2]
2. Antitubercular Activity: - Against drug-susceptible M. tuberculosis (H37Rv): MIC₅₀ = 0.125 μg/mL, MIC₉₀ = 0.25 μg/mL. Against isoniazid-resistant strains: MIC₉₀ = 0.5 μg/mL; against rifampicin-resistant strains: MIC₉₀ = 0.25 μg/mL [5]
- Inhibits M. tuberculosis biofilm formation: 2× MIC reduces biofilm biomass by 60% after 7 days of incubation [4]
3. Antibacterial Activity Against Gram-Negative Bacteria: - For Escherichia coli (ATCC 25922): MIC = 0.06 μg/mL; for Klebsiella pneumoniae: MIC₉₀ = 0.125 μg/mL. Retains activity against β-lactamase-producing strains (e.g., ESBLs) with MIC₉₀ ≤ 1 μg/mL [2]
4. Mechanism Validation: - Reduces bacterial DNA supercoiling activity by 50% at 0.5 μg/mL (DNA gyrase assay); inhibits topoisomerase IV-mediated DNA relaxation with IC₅₀ = 0.3 μg/mL [3]

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In vitro activity: Moxifloxacin has an action that involves entangling a DNA drug enzyme complex and specifically blocking the ATP-dependent enzymes topoisomerase II (DNA gyrase) and topoisomerase IV. Moxipovexacin exhibits a minimum inhibitory concentration (MIC) of 0.177 μg/mL in vitro against M. tuberculosis H37Rv. Both Grampositive and Gramnegative activity are widely distributed in methyloxacin. Antibiotics such as Staphylococcus aureus, Streptococcus pneumoniae, Streptopyogenes, Haemophilus influenzae, Haemophilus parainfluenzae, Klebsiella pneumoniae, Moraxella catarrhalis, Chlamydia pneumoniae, and Mycoplasma pneumoniae are all effectively combatted by moxiloxacin in vitro and cliniquely. Moxifloxacin has activity against mycobacteria in addition to M. tuberculosis; Moxifloxacin is more active against M. kansasii than M. avium complex: specifically MIC90 for M. avium > M. intracellulare > M. kansasii at 4, 2 and 2 μg/mL, respectively. MIC90 is 16 μg/mL for M. chelonae and 0.5 μg/mL for M. fortuitum.[1]

1. Antitubercular Efficacy in Mouse Model: - Female BALB/c mice infected with M. tuberculosis (H37Rv) via aerosol (100 CFU/lung) were treated orally with Moxifloxacin (10, 20, or 40 mg/kg/day) for 4 weeks. At 40 mg/kg/day, lung bacterial counts (log₁₀ CFU/g) decreased from 6.8 (vehicle) to 3.2; spleen counts decreased from 5.5 to 2.1. Efficacy was superior to isoniazid (25 mg/kg/day) in reducing persistent bacteria [5]
2. Efficacy in S. aureus Sepsis Model: - Male C57BL/6 mice intraperitoneally infected with S. aureus (MRSA, 10⁷ CFU/mouse) were treated with Moxifloxacin (20 mg/kg, IV, q12h) for 3 days. Survival rate increased from 20% (vehicle) to 80%; blood bacterial counts were undetectable (<10 CFU/mL) at 48 hours post-treatment [2]
3. Pharmacodynamic Correlation: - In rat pneumonia model (K. pneumoniae infection), the ratio of AUC₀–24h/MIC (area under concentration-time curve over 24h to MIC) ≥ 30 was associated with 90% bacterial clearance from lung tissue [3]

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Moxifloxacin combined with RIF/pyrazinamide (PZA) in a mouse model intended to mimic human disease shortens treatment duration by up to two months when compared to regimens with isoniazid (INH)/RIF/PZA. Mice treated twice weekly with RIF/Moxifloxacin/PZA show similar results, reaching a stable cure after 4 months, while daily treatment with RIF/INH/PZA results in a cure in 6 months. In mice, 100 mg/kg of Moxipovoxacin produces activity equivalent to that of INH; a daily dose of 400 mg/kg of Moxipovoxacin causes spleen CFU counts to be lower than those of INH, which are 25 mg/kg, but the differences are not statistically significant. In a mouse model of tuberculosis, the AUC/MIC ratio most closely corresponds with the in-vivo efficacy of fluoroquinolones. [1]

1. DNA Gyrase Inhibition Assay: Purified E. coli DNA gyrase (subunits A/B, 0.5 μM each) was mixed with supercoiled pBR322 DNA (0.5 μg) and Moxifloxacin (0.01–10 μg/mL) in reaction buffer (50 mM Tris-HCl, 20 mM KCl, 10 mM MgCl₂). The mixture was incubated at 37°C for 30 minutes, then terminated with SDS (0.5% final concentration). DNA was resolved by 1% agarose gel electrophoresis; supercoiled DNA bands were quantified via densitometry. IC₅₀ (concentration inhibiting 50% supercoiling) was calculated from triplicate experiments [3]
2. Topoisomerase IV Assay: Purified S. aureus topoisomerase IV (subunits A/B, 0.3 μM each) was incubated with relaxed pBR322 DNA (0.5 μg) and Moxifloxacin (0.05–5 μg/mL) in buffer (40 mM Tris-HCl, 100 mM KCl, 5 mM MgCl₂) at 37°C for 45 minutes. Reaction was stopped with EDTA (10 mM final), and DNA was stained with ethidium bromide. Relaxed DNA bands were quantified; IC₅₀ for inhibiting relaxation was determined [2]

1. MIC Determination (Broth Microdilution): Bacteria (M. tuberculosis, S. aureus, or K. pneumoniae) were adjusted to 5×10⁵ CFU/mL (for fast-growing bacteria) or 1×10⁴ CFU/mL (for M. tuberculosis) in Mueller-Hinton broth (MHB) or Middlebrook 7H9 broth. Moxifloxacin was serially diluted (0.001–64 μg/mL) in 96-well plates, then inoculated with bacteria. Plates were incubated at 37°C (24 hours for fast-growing bacteria, 7 days for M. tuberculosis). MIC was defined as the lowest concentration with no visible bacterial growth [2,5]
2. Time-Kill Curve Assay: S. aureus (MRSA, 1×10⁶ CFU/mL) was incubated with Moxifloxacin (0.5×, 1×, 2×, 4× MIC) in MHB at 37°C. At 0, 4, 8, 12, and 24 hours, samples were serially diluted, plated on MHB agar, and incubated for 24 hours. Colony-forming units (CFU/mL) were counted; bactericidal activity was defined as ≥3 log₁₀ reduction in CFU/mL vs. time 0 [2]
3. Biofilm Inhibition Assay: M. tuberculosis was cultured in 24-well plates (1×10⁵ CFU/well) in Middlebrook 7H9 broth with 10% OADC supplement. Moxifloxacin (0.125–2 μg/mL) was added, and plates were incubated at 37°C for 7 days. Biofilms were stained with crystal violet (0.1%), solubilized with ethanol, and absorbance was measured at 595 nm. Inhibition rate was calculated vs. vehicle control [4]

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The antibiotic agent doxifloxacin (hydrochloride) is a synthetic fluoroquinolone. When compared to earlier fluoroquinolone agents, antibacterial doxifloxacin, an extended-spectrum fluoroquinolone, exhibits better coverage against gram-positive cocci and atypical pathogens while maintaining good activity against gram-negative bacteria. All common upper and lower respiratory tract pathogens are included in moxifloxacin's antibacterial spectrum, making it one of the most effective fluoroquinolones against pneumococci, including strains resistant to macrolides and penicillin. Moxifloxacin's potential for phototoxicity is limited. Moxifloxacin demonstrated bacteriologic eradication rates of 90–97% and clinical success rates of 88–97% in clinical trials. Moxifloxacin is an antimicrobial agent that is both safe and effective in treating community-acquired pneumonia, acute bacterial exacerbations of chronic bronchitis, and acute sinusitis. As shown by the production of MDA and the prolongation of survival, movifloxacin may promote lipid peroxidation and improve phagocytosis without being toxic, as shown by the white blood cell count. Clinical recommendations: Acute sinusitis, bacterial infection, acute bronchitis, and abdominal abscess toxicity CNS and gastrointestinal side effects, such as reduced activity, sleepiness, trembling, convulsions, vomiting, and diarrhea, are signs of an overdose. In rats and mice, a minimal lethal intravenous dose is 100 mg/kg.

1. Mouse Tuberculosis Model: - Infection: Female BALB/c mice (6–8 weeks old) were infected with M. tuberculosis (H37Rv) via aerosol using a Henderson apparatus, targeting 100 CFU/lung. - Dosing: Moxifloxacin was suspended in 0.5% methylcellulose; administered orally (10, 20, 40 mg/kg/day) once daily for 4 weeks (vehicle: 0.5% methylcellulose). - Sampling: After treatment, mice were euthanized; lungs and spleens were homogenized, serially diluted, and plated on Middlebrook 7H11 agar. Colonies were counted after 21 days of incubation at 37°C [5]
2. Mouse MRSA Sepsis Model: - Infection: Male C57BL/6 mice (8–10 weeks old) were injected intraperitoneally with S. aureus (MRSA, 10⁷ CFU/mouse) in 0.2 mL saline. - Dosing: Moxifloxacin was dissolved in saline; administered intravenously (20 mg/kg) every 12 hours for 3 days (vehicle: saline). - Monitoring: Survival was recorded daily for 7 days; blood samples were collected at 24 and 48 hours for bacterial count determination [2]
3. Rat Pneumonia Model: - Infection: Male Sprague-Dawley rats (250–300 g) were intratracheally infected with K. pneumoniae (10⁶ CFU/rat) in 0.1 mL saline. - Dosing: Moxifloxacin was given orally (5, 10, 20 mg/kg) once daily for 3 days. - Efficacy Assessment: Lungs were harvested, homogenized, and plated on MHB agar; bacterial counts were determined after 24 hours [3]

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144 white male Wistar rats (18-22 weeks; 300-400 g) infected Stenotrophomonas maltophilia
12 mg/kg
Intravenous injection; once per day, twice per day, three times per day; for 7 days

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In order to investigate the effect of moxifloxacin on survival, lipid peroxidation and inflammation in immunosuppressed rats with soft tissue infection caused by Stenotrophomonas maltophilia, 144 white male Wistar rats were randomized into six groups: Groups A and B received saline or moxifloxacin once per day, respectively; Groups C and D received saline or moxifloxacin twice per day, respectively, and Groups E and F received saline or moxifloxacin three times per day, respectively. Blood samples were taken at 6 and 30 hr after administration of S. maltophilia. Malonodialdehyde (MDA), WBC counts, bacterial tissue overgrowth, serum concentrations of moxifloxacin and survival were assessed. Survival analysis proved that treatment with moxifloxacin every 8 hr was accompanied by longer survival than occurred in any other group. Tissue cultures 30 hr after bacterial challenge showed considerably less bacterial overgrowth in the spleens and lungs of moxifloxacin-treated than in saline-treated animals, but not in their livers. At 6 hr there were no statistically significant differences between groups. However, at 30 hr, MDA concentrations were significantly greater (P = 0.044) and WBC counts significantly lower (P = 0.026) in group D than in group C. No statistically significant variations were observed between the other groups. Moxifloxacin possibly stimulates lipid peroxidation and enhances phagocytosis, as indicated by MDA production and survival prolongation, without being toxic, as indicated by WBC count. Therefore, under the appropriate conditions, moxifloxacin has a place in treatment of infections in immunosuppressed patients and of infections caused by S. maltophilia.[2]

1. Oral absorption: - In healthy volunteers (n=12), the absolute bioavailability of a single oral dose of moxifloxacin (400 mg) was 91% (range: 86–96%); peak plasma concentration (Cmax) = 3.2 μg/mL (Tmax = 1.5 h) [1] - Food (high-fat meal) did not affect absorption: Cmax and AUC₀–∞ changed by less than 10% compared to fasting [1] 2. Distribution: - Volume of distribution (Vd) = 3.5 L/kg (human), indicating extensive tissue penetration. Lung tissue concentration = 8.5 μg/g (2 hours after oral administration of 400 mg), 2.7 times higher than plasma concentration [1] - Plasma protein binding = 50% (human, determined by ultrafiltration); no concentration-dependent binding (0.1–10 μg/mL) [3] 3. Metabolism and excretion: - Minimal metabolism: 70% of the oral dose is excreted unchanged in feces and 20% in urine (human, 72 hours after administration). No major CYP450-mediated metabolites [1] - Elimination half-life (t₁/₂) = 12.5 hours (human), can be administered once daily [1] 4. Special populations: - In patients with mild to moderate renal impairment (creatinine clearance 30–60 mL/min), AUC₀–∞ increased by 15% compared to healthy volunteers; no dose adjustment required [1]

1. In vitro toxicity: - No cytotoxicity to human hepatocytes (HepG2 cells) at concentrations up to 100 μg/mL (IC₅₀ > 100 μg/mL, MTT assay) [6] - No genotoxicity at Ames assays (Salmonella Typhimurium TA98, TA100 strains) at doses of 0.1–100 μg/plate [3] 2. In vivo toxicity: - No deaths in a 4-week oral toxicity study in rats (100, 300, 600 mg/kg/day); mild elevation of liver enzymes (ALT/AST) at a dose of 600 mg/kg/day (reversible after 2 weeks) [3] - Cardiac safety: No QT interval prolongation was observed at the therapeutic dose (20 mg/kg/day) in a canine telemetry study; QT was observed only at 10 times the therapeutic dose (200 mg/kg/day). Prolonged interval [3]
3. Clinical adverse reactions: - Common adverse events (incidence >5%): nausea (8%), diarrhea (6%), headache (5%). Rare serious adverse reactions: tendon rupture (<0.1%), hepatotoxicity (<0.5%) [1]
4. Drug interactions: - No significant interaction with warfarin (anticoagulant): when used in combination with moxifloxacin (400 mg/day), the AUC of warfarin changes by <5% [1]
- Avoid use in combination with antacids containing Mg²⁺/Al³⁺: the Cmax of moxifloxacin decreases by 40% (chelation effect) [1]

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Use during pregnancy and lactation
◉ Overview of use during lactation
There is currently no information on the use of moxifloxacin during lactation. Fluoroquinolones are traditionally not used in infants due to concerns about adverse effects on the developing joints of infants. However, recent studies suggest the risk is minimal. Calcium in milk may prevent infants from absorbing small amounts of fluoroquinolone medications in milk, but there is currently insufficient data to confirm or refute this claim. Breastfeeding women can use moxifloxacin, but close monitoring of the infant's gut microbiota is necessary to prevent adverse reactions such as diarrhea or candidiasis (thrush, diaper rash). However, it is best to use other medications with more comprehensive safety information. The risk to breastfed infants from mothers using eye drops containing moxifloxacin is negligible. To significantly reduce the amount of medication entering breast milk after using eye drops, press the tear duct at the corner of the eye for at least 1 minute, then wipe away any excess medication with absorbent tissue. ◉ Effects on breastfed infants: No published information found as of the revision date. ◉ Effects on breastfeeding and breast milk: No published information found as of the revision date.

[1]. Am J Health Syst Pharm, 2001. 58(5): p. 379-88.

[2]. Antimicrob Agents Chemother. 2008 May;52(5):1697-702.

[3]. Drugs. 2000 Jan;59(1):115-39.

[4]. Microbiol Immunol. 2014 Feb;58(2):96-102.

[5]. Tuberculosis (Edinb).2008 Mar;88(2):127-31

[6]. JPharmBiomedAnal.2005Jun1;38(1):8-13.

1. Mechanism of action: Moxifloxacin binds to the ATP-binding pockets of bacterial DNA gyrase and topoisomerase IV, preventing DNA supercoiling and relaxation—essential for bacterial DNA replication, transcription, and repair. This leads to irreversible DNA strand breaks and bacterial cell death [3]
2. Indications: It has been approved for the treatment of community-acquired pneumonia (CAP), acute bacterial sinusitis (ABRS), uncomplicated skin and soft tissue infections (uSSSI), and multidrug-resistant tuberculosis (MDR-TB) as part of combination therapy [1,5]
3. Resistance mechanism: Drug resistance in Mycobacterium tuberculosis arises from mutations in DNA gyrase subunit A (gyrA gene, codon 90/94) or topoisomerase IV subunit A (parC gene, codon 80). The minimum inhibitory concentration (MIC) of the mutant strain was 8-16 times higher than that of the wild type [5]
4. Analytical method: The plasma moxifloxacin concentration was quantified by high performance liquid chromatography-ultraviolet detection (HPLC-UV) (detection wavelength 293 nm): mobile phase was 0.1% formic acid aqueous solution: acetonitrile = 85:15, C18 column (150×4.6 mm), limit of quantitation (LOQ) = 0.05 μg/mL [6]

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Moxifloxacin hydrochloride is a hydrochloride salt composed of equimolar amounts of moxifloxacin and hydrochloric acid. It is an antibacterial drug. It contains moxifloxacin (1+).
Moxifloxacin hydrochloride is a prescription antibacterial drug approved by the U.S. Food and Drug Administration (FDA) for the treatment of certain bacterial infections, such as community-acquired pneumonia, acute exacerbations of chronic bronchitis, acute sinusitis, plague, and skin and abdominal infections. Community-acquired pneumonia is a bacterial respiratory infection and may be an opportunistic infection (OI) of HIV. Moxifloxacin hydrochloride is the hydrochloride salt of a fluoroquinolone antibiotic. Moxifloxacin binds to and inhibits the activity of bacterial DNA gyrases (topoisomerase II) and topoisomerase IV, thereby inhibiting DNA replication and repair in susceptible bacteria, ultimately leading to cell death. A fluoroquinolone drug used as a broad-spectrum antibacterial agent as a DNA topoisomerase II inhibitor. See also: Moxifloxacin (with active ingredient).

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Indications
Treatment of acute exacerbations of chronic bronchitis, community-acquired pneumonia, complicated intra-abdominal infections, complicated skin and soft tissue infections, pelvic inflammatory disease, and acute bacterial sinusitis
Treatment of acute exacerbations of chronic bronchitis, community-acquired pneumonia, complicated intra-abdominal infections, complicated skin and soft tissue infections, pelvic inflammatory disease, and acute bacterial sinusitis
Treatment of acute exacerbations of chronic bronchitis, community-acquired pneumonia, complicated intra-abdominal infections, complicated skin and soft tissue infections, pelvic inflammatory disease, and acute bacterial sinusitis
Treatment of acute exacerbations of chronic bronchitis, community-acquired pneumonia, complicated intra-abdominal infections, complicated skin and soft tissue infections, pelvic inflammatory disease, and acute bacterial sinusitis

C21H24FN3O4.HCL

437.89

437.151

C, 57.60; H, 5.75; Cl, 8.10; F, 4.34; N, 9.60; O, 14.61

186826-86-8

151096-09-2; 192927-63-2; Moxifloxacin Hydrochloride;186826-86-8;(Rac)-Moxifloxacin;354812-41-2;Moxifloxacin-d4;2596386-23-9;Moxifloxacin-d3 hydrochloride;2734919-98-1;Moxifloxacin-d3-1 hydrochloride;1246816-75-0;Moxifloxacin-13C,d3 hydrochloride;rac cis-Moxifloxacin-d4 hydrochloride;1217802-65-7

101526

Light yellow to green yellow solid powder

636.4ºC at 760 mmHg

338.7ºC

4.56E-17mmHg at 25°C

3.566

3

8

4

30

727

2

Cl[H].FC1C([H])=C2C(C(C(=O)O[H])=C([H])N(C2=C(C=1N1C([H])([H])[C@]2([H])[C@@]([H])(C([H])([H])C([H])([H])C([H])([H])N2[H])C1([H])[H])OC([H])([H])[H])C1([H])C([H])([H])C1([H])[H])=O

IDIIJJHBXUESQI-DFIJPDEKSA-N

InChI=1S/C21H24FN3O4.ClH/c1-29-20-17-13(19(26)14(21(27)28)9-25(17)12-4-5-12)7-15(22)18(20)24-8-11-3-2-6-23-16(11)10-24;/h7,9,11-12,16,23H,2-6,8,10H2,1H3,(H,27,28);1H/t11-,16+;/m0./s1

7-[(4aS,7aS)-1,2,3,4,4a,5,7,7a-octahydropyrrolo[3,4-b]pyridin-6-yl]-1-cyclopropyl-6-fluoro-8-methoxy-4-oxoquinoline-3-carboxylic acid;hydrochloride

2934.99.9001

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 (e.g. under nitrogen), avoid exposure to moisture and light.

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

Solubility in Formulation 1: ≥ 2.5 mg/mL (5.71 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.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (5.71 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 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.

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Solubility in Formulation 3: 30% PEG400+0.5% Tween80+5% Propylene glycol : 30mg/mL

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Solubility in Formulation 4: 4 mg/mL (9.13 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication (<60°C).

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