Hexadecylphosphocholine (miltefosine) has broad-spectrum fungicidal activity and is efficacious in a mouse model of cryptococcosis.
The alkyl phosphocholine drug miltefosine is structurally similar to natural substrates of the fungal virulence determinant phospholipase B1 (PLB1), which is a potential drug target. We determined the MICs of miltefosine against key fungal pathogens, correlated antifungal activity with inhibition of the PLB1 activities (PLB, lysophospholipase [LPL], and lysophospholipase-transacylase [LPTA]), and investigated its efficacy in a mouse model of disseminated cryptococcosis. Miltefosine inhibited secreted cryptococcal LPTA activity by 35% at the subhemolytic concentration of 25 microM (10.2 microg/ml) and was inactive against mammalian pancreatic phospholipase A2 (PLA2). At 250 microM, cytosolic PLB, LPL, and LPTA activities were inhibited by 25%, 51%, and 77%, respectively. The MICs at which 90% of isolates were inhibited (MIC90s) against Candida albicans, Candida glabrata, Candida krusei, Cryptococcus neoformans, Cryptococcus gattii, Aspergillus fumigatus, Fusarium solani, Scedosporium prolificans, and Scedosporium apiospermum were 2 to 4 microg/ml. The MICs of miltefosine against Candida tropicalis (n = 8) were 2 to 4 microg/ml, those against Aspergillus terreus and Candida parapsilosis were 8 microg/ml (MIC90), and those against Aspergillus flavus (n = 8) were 2 to 16 microg/ml. Miltefosine was fungicidal for C. neoformans, with rates of killing of 2 log units within 4 h at 7.0 microM (2.8 microg/ml). Miltefosine given orally to mice on days 1 to 5 after intravenous infection with C. neoformans delayed the development of illness and mortality and significantly reduced the brain cryptococcal burden. We conclude that miltefosine has broad-spectrum antifungal activity and is active in vivo in a mouse model of disseminated cryptococcosis. The relatively small inhibitory effect on PLB1 enzyme activities at concentrations exceeding the MIC by 2 to 20 times suggests that PLB1 inhibition is not the only mechanism of the antifungal effect.
Widmer
Fred
F
Centre for Infectious Diseases and Microbiology, University of Sydney at Westmead, and Department of Infectious Diseases, ICPMR Building, Westmead Hospital, Westmead, NSW 2145, Australia.
Wright
Lesley C
LC
Obando
Daniel
D
Handke
Rosemary
R
Ganendren
Ranjini
R
Ellis
David H
DH
Sorrell
Tania C
TC
D000217:Acyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology*; D003453:Cryptococcosis / Q000188:drug therapy*; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005658:Fungi / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D008245:Lysophospholipase / Q000037:antagonists & inhibitors / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008826:Microbial Sensitivity Tests; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use
D000935:Antifungal Agents; D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D010767:Phosphorylcholine; C039128:miltefosine; D000217:Acyltransferases; D008245:Lysophospholipase; C021782:lysophospholipase-transacylase