Nafithromycin

Nafithromycin (0.03-1 mg/liter; 72 h) exhibits in vitro activity against 10 clinical Chlamydia pneumoniae isolates, with an MIC₅₀ of 0.03 mg/liter and an MIC₉₀ of 0.25 mg/liter^[1].
Nafithromycin (WCK 4873) potently inhibits growth of erythromycin-sensitive, mef-expressing, ermB-expressing, and high-level ermB-expressing Streptococcus pneumoniae, as well as high-level ermB-expressing Streptococcus pyogenes, with MIC_s ranging from 0.015-0.03 μg/mL to 0.5 μg/mL^[2].
Nafithromycin shows non-cytotoxic effects up to 62.5 μg/mL in CHO cells, 31.25 μg/mL in MDBK, V79, HepG2, L929, and HeLa cells, and 15.6- ≤ 31.25 μg/mL in J774 cells^[2].
Nafithromycin exhibits potent in vitro activity against Streptococcus pneumoniae (MIC₅₀/MIC₉₀ 0.015/0.06 μg/mL, 100% inhibited at ≤0.25 μg/mL), Streptococcus pyogenes (MIC₅₀/MIC₉₀ 0.015/0.015 μg/mL, 100% inhibited at ≤0.5 μg/mL), and Moraxella catarrhalis (MIC₅₀/MIC₉₀ 0.12/0.25 μg/mL), bimodal activity against Staphylococcus aureus (MIC₅₀/MIC₉₀ 0.06/>2 μg/mL), and moderate activity against Haemophilus influenzae (MIC₅₀/MIC₉₀ 4/4 μg/mL) when tested against 2014 global clinical respiratory isolates via CLSI broth microdilution methods^[3].
Nafithromycin potently inhibits clinical Streptococcus pneumoniae isolates (including macrolide-resistant strains) with an MIC₅₀ of 0.03 mg/L and MIC₉₀ of 0.06 mg/L, and achieves 100% susceptibility at a PK/PD breakpoint of 0.25 mg/L^[4].
Nafithromycin potently inhibits Indian clinical Streptococcus pneumoniae isolates (including those with erm and mef-mediated macrolide resistance) with an MIC₅₀ of 0.015 mg/L and MIC₉₀ of 0.06 mg/L^[4].

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