Drug Resistance

Mutants of Candida with reduced susceptibility to caspofungin have been identified in some patients during treatment. Similar observations were made in a study in mice infected with C. albicans and treated with orally administered doses of caspofungin. MIC values for caspofungin should not be used to predict clinical outcome, since a correlation between MIC values and clinical outcome has not been established. The incidence of drug resistance by various clinical isolates of Candida and Aspergillus species is unknown.

Studies in vitro and in vivo of caspofungin, in combination with amphotericin B, suggest no antagonism of antifungal activity against either A. fumigatus or C. albicans. The clinical significance of these results is unknown.

A double-blind study enrolled 1111 febrile, neutropenic (<500 cells/mm³) patients who were randomized to treatment with daily doses of CANCIDAS (50 mg/day following a 70-mg loading dose on Day 1) or AmBisome1 (amphotericin B liposome for injection, 3.0 mg/kg/day). Patients were stratified based on risk category (high-risk patients had undergone allogeneic stem cell transplantation or had relapsed acute leukemia) and on receipt of prior antifungal prophylaxis. Twenty-four percent of patients were high risk and 56% had received prior antifungal prophylaxis. Patients who remained febrile or clinically deteriorated following 5 days of therapy could receive 70 mg/day of CANCIDAS or 5.0 mg/kg/day of AmBisome. Treatment was continued to resolution of neutropenia (but not beyond 28 days unless a fungal infection was documented).

An overall favorable response required meeting each of the following criteria: no documented breakthrough fungal infections up to 7 days after completion of treatment, survival for 7 days after completion of study therapy, no discontinuation of the study drug because of drug-related toxicity or lack of efficacy, resolution of fever during the period of neutropenia, and successful treatment of any documented baseline fungal infection.

Based on the composite response rates, CANCIDAS was as effective as AmBisome in empirical therapy of persistent febrile neutropenia (see Table 1).

TABLE 1

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