T-91825 (PPI-0903M), an N-phosphono-type cephalosporin, is the active form of TAK-599. T-91825 is active against both gram-positive and gram-negative bacteria[1][2].
PPI-0903M is very active against S. aureus (MIC50=0.25 μg/mL), including methicillin-resistant (MRSA) strains (MIC50=1 μg/mL)[1].PPI-0903M is active against hetero-vancomycin-intermediate S. aureus (100 strains), with MIC50s ranging from 0.25 to 4 μg/mL[1].
AK-599 (20 mg/kg; s.c. three times a day for 2 days) decreases the bacterial cell counts in lungs more than 99.9% in a mouse pneumonia model caused by MRSA[2].
[1]. Sader HS, et, al. Antimicrobial activity and spectrum of PPI-0903M (T-91825), a novel cephalosporin, tested against a worldwide collection of clinical strains. Antimicrob Agents Chemother. 2005 Aug;49(8):3501-12.
[2]. Iizawa Y, et, al. In vitro antimicrobial activity of T-91825, a novel anti-MRSA cephalosporin, and in vivo anti-MRSA activity of its prodrug, TAK-599. J Infect Chemother. 2004 Jun;10(3):146-56.