Topoisomerase IV; Topoisomerase II
Marbofloxacin targets DNA-gyrase and topoisomerase IV in bacteria. [2]
For Staphylococcus aureus, the Minimum Inhibitory Concentration (MIC) was 0.25 μg/mL. [2]
The MIC90 for Staphylococcus aureus was 0.21 μg/mL. The MIC90 for Enterobacteriaceae was 0.027 μg/mL. [3]

Marbofloxacin treatment at the therapeutic dose is not effective in significantly reducing clinical signs and does not eradicate M. hyopneumoniae, as 87.5 to 100% of the pigs remain positive at the conclusion of the assays. However, treatment with marbofloxacin appears to lower the lung lesion scores.[1] Treating a Staphylococcus aureus infection in tissue cages in ponies with a once-daily dose of marbofloxacin at a dose of 6 mg/kg for seven days does not effectively eradicate S. aureus infections from isolated locations.[3]

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In a tissue cage (TC) infection model, marbofloxacin was administered intravenously at 6 mg/kg once daily for 7 days to ponies with TC inoculated with Staphylococcus aureus. A slight decrease in bacterial counts was observed initially, but the infection was not eliminated and abscesses formed. The body temperatures dropped within a few days after treatment start and were normal by day 6 post-inoculation. Signs of inflammation lessened after a few days. Abscessation occurred one day after the last treatment. [2]
The clinical efficacy of marbofloxacin was evaluated using surrogate markers (AUIC, Cmax/MIC ratio). Based on breakpoint values for fluoroquinolones in human medicine (AUIC24 ≥ 125), a dosage regimen of 2 mg/kg/24 h i.v., SC, or oral was deemed appropriate for treating infections with MIC90 around 0.03 μg/mL (e.g., Enterobacteriaceae) and possibly efficacious for bacteria with MIC90 up to 0.2 μg/mL (e.g., S. aureus). For S. aureus (MIC90 = 0.21 μg/mL), simulated daily administration of 2 mg/kg for 5 days maintained plasma concentrations above MIC90 for only 16-50% of the 120-hour period. [3]

The enzyme activity assay was based on determining the Minimum Inhibitory Concentration (MIC) of marbofloxacin against bacterial pathogens. A microdilution technique was used. The concentration of marbofloxacin that inhibited the visible growth of 50% and 90% of the strains tested (MIC50 and MIC90) was designated for each species. The MIC of the Staphylococcus aureus strain used in the tissue cage infection model was 0.25 μg/mL, determined using Mueller Hinton Broth and the microdilution method. [2][3]

For the tissue cage infection model, tissue cage fluid (TCF) samples were collected for bacterial counts and white blood cell (WBC) counts. Colony counts were determined by a plate count method using 10-fold dilutions of the TCF in saline. After incubating the plates for 48 hours, CFU were counted from plates with 30-300 colonies. The limit of detection was 1.0 x 10^2 CFU/mL. Total WBC counts in TCF were performed using a Coulter counter. [2]
For the pharmacokinetic study, blood samples were collected from horses into heparinised tubes and centrifuged to obtain plasma, which was stored at -20°C until assayed. Marbofloxacin concentrations in plasma and tissue cage fluid were measured using high-pressure liquid chromatography (HPLC) with fluorescence detection. For plasma, the limit of quantification was 0.01 μg/mL. For TCF, the limit of quantification was 0.05 μg/mL. [2][3]

SPF piglets inoculated intratracheally with M. hyopneumoniae strain 116
~2 mg/kg/day
Intramuscular injection

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Tissue cages (TC), implanted subcutaneously in the neck in eight ponies, were inoculated with Staphylococcus aureus (S. aureus) to determine the clinical efficacy of marbofloxacin in the treatment of this infection. From 21 h after inoculation, marbofloxacin (6 mg/kg) was administered intravenously (i.v.) once daily for 7 days. Samples of the tissue cage fluid (TCF) were taken to determine marbofloxacin concentrations (days 1, 3 and 7), using high-pressure liquid chromatography, and numbers of viable bacteria [colony forming units (CFU)] (days 1, 3, 7, 14 and 21). Statistical analysis was used to compare CFU before and after treatment. Clinical signs and CFU were used to evaluate the efficacy of treatment. Although, there was a slight decrease in CFU in all TC initially, the infection was not eliminated by marbofloxacin treatment in any of the ponies and abscesses formed. As the MIC (0.25 microg/mL) did not change during treatment and the concentration of marbofloxacin during treatment (mean concentration in TCF was 0.89 microg/mL on day 1, 0.80 microg/mL on day 3 and 2.77 microg/mL on day 7) was above MIC, we consider that the treatment failure might be attributable to the formation of a biofilm by S. aureus. Based on the present results, i.v. administration of marbofloxacin alone is not suitable for the elimination of S. aureus infections from secluded sites.[2]

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For the tissue cage (TC) infection model in ponies: Eight healthy Shetland pony geldings (5-15 years old, 138-216 kg) with one subcutaneous TC implanted in the neck were used. The TC was inoculated with Staphylococcus aureus (6.4 x 10^4 CFU per TC) on day 0. Starting 21 hours post-infection, marbofloxacin (6 mg/kg) was administered intravenously once daily for 7 days via a catheter in the jugular vein. TCF samples were collected on days 0, 1, 3, 7, 14, 21, 28 for bacterial and WBC counts. Rectal temperature was monitored twice daily for 10 days post-inoculation, and ponies were checked daily for swelling, behavior, and appetite. Abscessed TCs were removed under sedation and local analgesia. [2]
For the pharmacokinetic study in horses: Six saddle-bred horses (497-639 kg) were used in a 3-period crossover study. A nominal dose of 2 mg/kg marbofloxacin was administered intravenously (i.v. in jugular vein), subcutaneously (SC in the neck), and orally (mixed with bran before morning meal). A 15-day washout period was observed between administrations. Blood samples were collected at various time points up to 72 hours post-administration (i.v.: pre-dose and 1, 2, 4, 8, 15, 30 min, 1, 2, 4, 8, 24, 36, 48, 72 h; SC/oral: pre-dose and 10, 20, 30 min, 1, 2, 3, 4, 6, 8, 24, 36, 48, 72 h). Plasma was harvested and analyzed for marbofloxacin concentration. [3]

Marbofloxacin is a fluoroquinolone antibiotic expected to be effective in treating Gram-negative and some Gram-positive bacterial infections in horses. To develop a rational administration regimen for horses, this study conducted pharmacokinetic studies on six horses after intravenous, subcutaneous, and oral administration of a single dose of 2 mg/kg body weight of marbofloxacin, and determined its minimum inhibitory concentration (MIC) against bacteria isolated from equine pathogens. The mean clearance of marbofloxacin was 0.25 ± 0.05 L/kg/h, and the terminal half-life was 756 ± 1.99 h. The absolute bioavailability of marbofloxacin after subcutaneous and oral administration was 98 ± 11% and 62 ± 8%, respectively. The minimum inhibitory concentration (MIC90) required to inhibit 90% of the isolates was 0.027 μg/ml against Enterobacteriaceae and 0.21 μg/ml against Staphylococcus aureus. The surrogate endpoints for antimicrobial efficacy (AUIC, Cmax/MIC ratio, time above MIC90) were calculated, and the concentration curves of marbofloxacin after repeated dosing were simulated. These data were used to determine the appropriate dosing regimen for the target bacteria. Considering the breakpoint values of efficacy endpoints for fluoroquinolones, a marbofloxacin dosing regimen of 2 mg/kg body weight/24 h (intravenous, subcutaneous, or oral) was more appropriate for Enterobacteriaceae than for Staphylococcus aureus. [3]

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After intravenous administration of marbofloxacin (2 mg/kg) in horses, the clearance (Cl) was 0.249 ± 0.045 L/kg/h, the steady-state volume of distribution (Vss) was 1.48 ± 0.30 L/kg, the volume of distribution of the terminal phase (Varea) was 2.83 ± 0.75 L/kg, the mean residence time (MRT) was 5.96 ± 0.95 h, the terminal half-life (t1/2 λz) was 7.56 ± 1.99 h, and the AUC(0-inf) was 8.26 ± 1.67 μg·h/mL. [3]
After subcutaneous administration (2 mg/kg) in horses, the absolute bioavailability (F%) was 97.6 ± 11.4%, the terminal half-life was 10.41 ± 4.27 h, the MRT was 8.66 ± 1.41 h, the observed Cmax was 1.07 ± 0.30 μg/mL, and the observed Tmax was 0.72 ± 0.31 h. [3]
After oral administration (2 mg/kg) in horses, the absolute bioavailability (F%) was 62.4 ± 8.1%, the terminal half-life was 8.78 ± 2.70 h, the MRT was 8.97 ± 2.23 h, the observed Cmax was 0.89 ± 0.14 μg/mL, the observed Tmax was 0.58 ± 0.20 h, and the lag time (tlag) was 0.14 ± 0.03 h. [3]
In tissue cage fluid of ponies treated intravenously with 6 mg/kg marbofloxacin, the mean concentrations were 0.89 μg/mL on day 1 (30-90 min post-dose), 0.80 μg/mL on day 3 (trough), and 2.77 μg/mL on day 7 (4 h post-dose, approx. peak). [2]

US Patent No. 4801584: Oral LD50 in mice >2 g/kg

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Subcutaneous administration of marbofloxacin (2 mg/kg) in horses triggered an oedema of approximately 5 cm diameter at the injection site, which disappeared within 2 or 3 weeks. [3]
No signs of fluoroquinolone-induced arthropathy were observed in mature horses, although there are concerns about the potential risk in young horses. [2]
In the tissue cage infection model, abscessation of the TC occurred after treatment failure, requiring surgical removal of the TC from the standing animal under sedation and local analgesia. [2]

[1]. Marbofloxacin. Acta Crystallogr Sect E Struct Rep Online. 2012 Apr 1;68(Pt 4):o998-9.

[2]. Clinical efficacy of intravenous administration of marbofloxacin in a Staphylococcus aureus infection in tissue cages in ponies. J Vet Pharmacol Ther. 2006 Dec;29(6):555-60.

[3]. Pharmacokinetics of marbofloxacin in horses. Equine Vet J. 2002 Jul;34(4):366-72.

LSM-5799 belongs to the quinoline class of compounds.
Marbofloxacin is a carboxylic acid and belongs to the third-generation antibiotic class of fluoroquinolones. It is used in veterinary medicine. Marbofloxacin is marketed as a combination of clotrimazole and dexamethasone under the brand name Aurizon.

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In the title compound [systematic name: 9-fluoro-2,3-dihydro-3-methyl-10-(4-methylpiperazin-1-yl)-7-oxo-7H-pyrido[1,2,3-ij][1,2,4]benzoxadiazine-6-carboxylic acid], C(17)H(19)FN(4)O(4), the carbonyl and carboxyl groups are coplanar with the quinoline ring, with a dihedral angle of 2.39 (2)°. The piperazine ring is in a chair conformation, and the oxadiazine ring is in an envelope conformation, with the CH(2) group at the ring opening deviating 0.650 (2) Å from the plane passing through the other five atoms. Due to the presence of intramolecular OH⋯O hydrogen bonds, the molecular structure exhibits an S(6) ring structure. In the crystal, weak CH⋯F hydrogen bonds connect the molecules into a layered structure parallel to the ab plane. [1]

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Marbofloxacin is a fluoroquinolone antimicrobial agent developed for veterinary use. Unlike other fluoroquinolones, it has an oxadiazine ring which may confer pharmacokinetic advantages. Classically, fluoroquinolones have not been recommended for horses due to concerns about arthropathy in young horses, although no published data supports this in mature horses. [2]
The mechanism of action for fluoroquinolones like marbofloxacin is the inhibition of DNA-gyrase and topoisomerase IV, leading to bacterial cell death. It is bactericidal at concentrations eight times the MIC. For Gram-positive bacteria, marbofloxacin typically has time-dependent activity, while for Gram-negative bacteria it has concentration-dependent activity. Anaerobic bacteria are not susceptible. [2]
Marbofloxacin is indicated for dermatological, respiratory, and urinary tract infections due to both Gram-positive and Gram-negative bacteria and Mycoplasma. [1]
The crystal structure of marbofloxacin (systematic name: 9-fluoro-2,3-dihydro-3-methyl-10-(4-methylpiperazin-1-yl)-7-oxo-7H-pyrido[1,2,3-ij][1,2,4]benzoxadiazine-6-carboxylic acid, C17H19FN4O4) shows that the carbonyl and carboxyl groups are coplanar with the quinoline ring. The piperazine ring adopts a chair conformation and the oxadiazinane ring displays an envelope conformation. The molecular structure exhibits an S(6) ring motif due to an intramolecular O—H···O hydrogen bond. In the crystal, weak C—H···F hydrogen bonds link molecules into layers. [1]

C17H19FN4O4

362.36

362.139

C, 56.35; H, 5.29; F, 5.24; N, 15.46; O, 17.66

115550-35-1

115551-26-3

60651

Light yellow to yellow solid powder

1.6±0.1 g/cm3

570.5±60.0 °C at 760 mmHg

268-269ºC

298.8±32.9 °C

0.0±1.7 mmHg at 25°C

1.701

-0.55

1

9

2

26

636

0

FC1C([H])=C2C(C(C(=O)O[H])=C([H])N3C2=C(C=1N1C([H])([H])C([H])([H])N(C([H])([H])[H])C([H])([H])C1([H])[H])OC([H])([H])N3C([H])([H])[H])=O

BPFYOAJNDMUVBL-UHFFFAOYSA-N

InChI=1S/C17H19FN4O4/c1-19-3-5-21(6-4-19)14-12(18)7-10-13-16(14)26-9-20(2)22(13)8-11(15(10)23)17(24)25/h7-8H,3-6,9H2,1-2H3,(H,24,25)

7-fluoro-2-methyl-6-(4-methylpiperazin-1-yl)-10-oxo-4-oxa-1,2-diazatricyclo[7.3.1.05,13]trideca-5(13),6,8,11-tetraene-11-carboxylic acid

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)