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Antimicrobial Agents and Chemotherapy, September 2000, p. 2333-2340, Vol. 44, No. 9
Glaxo Wellcome S.A., Parque Tecnológico
de Madrid, 28760 Tres Cantos, Madrid, Spain,1
and Glaxo Wellcome R&D, Greenford, Middlesex, UB6 0HE,
United Kingdom2
Received 5 November 1999/Returned for modification 27 February
2000/Accepted 10 June 2000
Sordarins are a new class of antifungal agents which selectively
inhibit fungal protein synthesis (FPS) by impairing the function of
elongation factor 2. The present study investigates possible correlations between sordarin pharmacokinetic (PK) properties and
therapeutic efficacy, based on a murine model of invasive systemic
candidiasis, and provides a rationale for dose selection in the first
study of efficacy in humans. A significant correlation between PK
parameters and the in vivo activity of GM 237354, taken as a
representative FPS inhibitor, was demonstrated in a murine model of
lethal systemic candidiasis. Area under the concentration-time curve
(AUC) and maximum concentration of drug in serum
(Cmax) over 24 h were determined after a
single GM 237354 subcutaneous (s.c.) dose (50 mg/kg of body weight) in
healthy animals (no significant PK changes with infection were observed
for other sordarin derivatives). These results have been used to
simulate PK profiles obtained after several doses and/or schedules in
animal therapy. A PK-pharmacodynamic (PD) parameter such as the time
that serum drug concentrations remain above the MIC (t > MIC) was also determined. Treatment efficacies were evaluated in
terms of the area under the survival time curve (AUSTC), using
Kaplan-Meier survival analysis and in terms of kidney fungal burden
(log CFU/gram) after s.c. doses of 2.5, 5, 10, 20, and 40 mg/kg every
4, 8, or 12 h (corresponding to total daily doses of 5 to 240 mg/kg). The results show all treatments to significantly prolong
survival versus that of infected and nontreated controls
(P < 0.05). Relationships between simulated PK and
PK-PD parameters and efficacy were explored. A good correlation independent of the dosing interval was observed with AUC (but not
Cmax or t > MIC) and both
AUSTC and kidney burden. Following repeated dosing every 8 h,
AUC50 (AUC at which 50% of the maximum therapeutic
efficacy is obtained) was estimated as 21.7 and 37.1 µg · h/ml
(total concentrations) for AUSTC and kidney burden using a sigmoid
Emax and an inhibitory sigmoid
Emax PK-PD model, respectively. For an efficacy
target of 90% survival, AUC was predicted as 67 µg · h/ml. We
conclude that the PK-PD approach is useful for evaluating relationships
between PK parameters and efficacy in antifungal research. Moreover,
the results obtained with this approach could be successfully applied
to clinical studies.
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Pharmacokinetics-Pharmacodynamics of a Sordarin
Derivative (GM 237354) in a Murine Model of Lethal
Candidiasis

*
Corresponding author. Mailing address: GlaxoWellcome
S.A., Parque Tecnológico de Madrid, Severo Ochoa, 2, 28760 Tres
Cantos, Madrid, Spain. Phone: 34-91-8070301. Fax: 34-91-807.05.95. E-mail: DGV28867{at}glaxowellcome.co.uk.
Present address: GlaxoWellcome S.p.A., 37137 Verona, Italy.
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