DHFR-IN-24 is a benzothiazole derivative and a dihydrofolate reductase (DHFR) inhibitor. It exhibits inherent antibacterial activity against both Gram-positive and Gram-negative bacteria. Additionally, DHFR-IN-24 can synergistically enhance antibacterial efficacy against multidrug-resistant pathogens by combining DHFR inhibition with photodynamic therapy (PDT).

DHFR-IN-24 (compound 12) inhibits methicillin-resistant Staphylococcus aureus (MRSA) ATCC 33591, Staphylococcus aureus (S. aureus) ATCC 25923, Staphylococcus epidermidis (S. epidermidis) CICC 10436, Acinetobacter baumannii (A. baumannii) Bio 34235, A. baumannii Bio 53272, Escherichia coli (E. coli) ATCC 25922, and Klebsiella pneumoniae (K. pneumoniae) CICC 21611, with minimum inhibitory concentrations (MIC) of 0.5 μg/mL, 0.5 μg/mL, 2 μg/mL, 16 μg/mL, 16 μg/mL, 4 μg/mL, and 8 μg/mL, respectively. It exhibits enhanced antibacterial efficacy up to 64-fold upon photodynamic activation through efficient reactive oxygen species (ROS) generation in MRSA. DHFR-IN-24 shows inherent antibacterial activity, which is significantly increased upon photodynamic activation. The compound demonstrates a marked time- and concentration-dependent antibacterial effect against both Gram-positive and Gram-negative bacteria. It exhibits potent photo-enhanced anti-biofilm activity against MRSA and A. baumannii. Furthermore, DHFR-IN-24 does not show significant cytotoxicity towards human embryonic kidney cells (HEK293T) and cervical cancer cells (HeLa).

DHFR-IN-24 (compound 12) at a concentration of 0.5 mg/mL, applied externally for 14 days, enhances full-thickness wound closure under visible light activation and eradicates MRSA bacteria infection in Balb/c mice. The healing effect of DHFR-IN-24 alone is moderate, surpassing that of the Vancomycin group, yet still inferior to the photodynamic therapy group.