Pharmacotherapeutic group: antimycotics for systemic use, other antimycotics for systemic use, ATC code: J02AX04
Mechanism of action
Caspofungin acetate is a semi-synthetic lipopeptide (echinocandin) compound synthesised from a fermentation product of Glarea lozoyensis. Caspofungin acetate inhibits the synthesis of beta (1,3)-D-glucan, an essential component of the cell wall of many filamentous fungi and yeast. Beta (1,3)-D-glucan is not present in mammalian cells.
Fungicidal activity with caspofungin has been demonstrated against Candida yeasts. Studies in vitro and in vivo demonstrate that exposure of Aspergillus to caspofungin results in lysis and death of hyphal apical tips and branch points where cell growth and division occur.
Pharmacodynamic effects
Caspofungin has in vitro activity against Aspergillus species (Aspergillus fumigatus [N = 75], Aspergillus flavus [N = 111], Aspergillus niger [N = 31], Aspergillus nidulans [N = 8], Aspergillus terreus [N = 52], and Aspergillus candidus [N = 3]). Caspofungin also has in vitro activity against Candida species (Candida albicans [N = 1,032], Candida dubliniensis [N = 100], Candida glabrata [N = 151], Candida guilliermondii [N = 67], Candida kefyr [N = 62], Candida krusei [N = 147], Candida lipolytica [N = 20], Candida lusitaniae [N = 80], Candida parapsilosis [N = 215], Candida rugosa [N = 1], and Candida tropicalis [N = 258]), including isolates with multiple resistance transport mutations and those with acquired or intrinsic resistance to fluconazole, amphotericin B, and 5-flucytosine. Susceptibility testing was performed according to a modification of both the Clinical and Laboratory Standards Institute (CLSI, formerly known as the National Committee for Clinical Laboratory Standards [NCCLS]) method M38-A2 (for Aspergillus species) and method M27-A3 (for Candida species).
Susceptibility testing breakpoints
MIC (minimum inhibitory concentration) interpretive criteria for susceptibility testing have been established by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) for caspofungin and are listed here: https://www.ema.europa.eu/documents/other/minimum-inhibitory-concentration-mic-breakpoints_en.xlsx
Mechanism of resistance
Isolates of Candida with reduced susceptibility to caspofungin have been identified in a small number of patients during treatment (MICs for caspofungin > 2 mg/l (4- to 30-fold MIC increases) have been reported using standardized MIC testing techniques approved by the CLSI).The mechanism of resistance identified is FKS1 and/or FKS2 (for C. glabrata) gene mutations. These cases have been associated with poor clinical outcomes.
Development of in vitro resistance to caspofungin by Aspergillus species has been identified. In limited clinical experience, resistance to caspofungin in patients with invasive aspergillosis has been observed. The mechanism of resistance has not been established. The incidence of resistance to caspofungin by various clinical isolates of Aspergillus is rare.
Caspofungin resistance in Candida has been observed but the incidence may differ by species or region.
Clinical efficacy and safety
Invasive Candidiasis in Adult Patients: Two hundred thirty-nine patients were enrolled in an initial study to compare caspofungin and amphotericin B for the treatment of invasive candidiasis. Twenty-four patients had neutropenia. The most frequent diagnoses were bloodstream infections (candidaemia) (77%, n=186) and Candida peritonitis (8%, n=19); patients with Candida endocarditis, osteomyelitis, or meningitis were excluded from this study. Caspofungin 50 mg once daily was administered following a 70 mg loading dose, while amphotericin B was administered at 0.6 to 0.7 mg/kg/day to non-neutropenic patients or 0.7 to 1.0 mg/kg/day to neutropenic patients. The mean duration of intravenous therapy was 11.9 days, with a range of 1 to 28 days. A favourable response required both symptom resolution and microbiological clearance of the Candida infection. Two hundred twenty-four patients were included in the primary efficacy analysis (MITT analysis) of response at the end of IV study therapy; favourable response rates for the treatment of invasive candidiasis were comparable for caspofungin (73% [80/109]) and amphotericin B (62% [71/115]) [% difference 12.7 (95.6 % CI -0.7, 26.0)]. Among patients with candidaemia, favourable response rates at the end of IV study therapy were comparable for caspofungin (72 % [66/92]) and amphotericin B (63% [59/94]) in the primary efficacy analysis (MITT analysis) [% difference 10.0 (95.0% CI -4.5, 24.5)]. Data in patients with non-blood sites of infection were more limited. Favourable response rates in neutropenic patients were 7/14 (50%) in the caspofungin group and 4/10 (40%) in the amphotericin B group. These limited data are supported by the outcome of the empirical therapy study.
In a second study, patients with invasive candidiasis received daily doses of caspofungin at 50 mg/day (following a 70-mg loading dose on Day 1) or caspofungin at 150 mg/day (see section 4.8). In this study, the caspofungin dose was administered over 2 hours (instead of the routine 1-hour administration). The study excluded patients with suspected Candida endocarditis, meningitis, or osteomyelitis. As this was a primary therapy study, patients who were refractory to prior antifungal agents were also excluded. The number of neutropenic patients enrolled in this study was also limited (8.0%). Efficacy was a secondary endpoint in this study. Patients who met the entry criteria and received one or more doses of caspofungin study therapy were included in the efficacy analysis. The favourable overall response rates at the end of caspofungin therapy were similar in the 2 treatment groups: 72% (73/102) and 78% (74/95) for the caspofungin 50 mg and 150 mg treatment groups, respectively (difference 6.3% [95% CI -5.9, 18.4]).
Invasive Aspergillosis in Adult Patients: Sixty-nine adult patients (age 18-80) with invasive aspergillosis were enrolled in an open-label, non-comparative study to evaluate the safety, tolerability, and efficacy of caspofungin. Patients had to be either refractory to (disease progression or failure to improve with other antifungal therapies given for at least 7 days) (84% of the enrolled patients) or intolerant of (16% of enrolled patients) other standard antifungal therapies. Most patients had underlying conditions (haematologic malignancy [N = 24], allogeneic bone marrow transplant or stem cell transplant [N = 18], organ transplant [N = 8], solid tumour [N = 3], or other conditions [N = 10]). Stringent definitions, modelled after the Mycoses Study Group Criteria, were used for diagnosis of invasive aspergillosis and for response to therapy (favourable response required clinically significant improvement in radiographs as well as in signs and symptoms). The mean duration of therapy was 33.7 days, with a range of 1 to 162 days. An independent expert panel determined that 41% (26/63) of patients receiving at least one dose of caspofungin had a favourable response. For those patients who received more than 7 days of therapy with caspofungin, 50% (26/52) had a favourable response. The favourable response rates for patients who were either refractory to or intolerant of previous therapies were 36 % (19/53) and 70% (7/10), respectively. Although the doses of prior antifungal therapies in 5 patients enrolled as refractory were lower than those often administered for invasive aspergillosis, the favourable response rate during therapy with caspofungin was similar in these patients to that seen in the remaining refractory patients (2/5 versus 17/48, respectively). The response rates among patients with pulmonary disease and extrapulmonary disease were 47% (21/45) and 28% (5/18), respectively. Among patients with extrapulmonary disease, 2 of 8 patients who also had definite, probable, or possible CNS involvement had a favourable response.
Empirical Therapy in Febrile, Neutropenic Adult Patients: A total of 1,111 patients with persistent fever and neutropenia were enrolled in a clinical study and treated with either caspofungin 50 mg once daily following a 70 mg loading dose or liposomal amphotericin B 3.0mg/kg/day. Eligible patients had received chemotherapy for malignancy or had undergone hematopoietic stem-cell transplantation, and presented with neutropenia (< 500 cells/mm3 for 96 hours) and fever (> 38.0°C) not responding to ≥ 96 hours of parenteral antibacterial therapy. Patients were to be treated until up to 72 hours after resolution of neutropenia, with a maximum duration of 28 days. However, patients found to have a documented fungal infection could be treated longer. If the drug was well tolerated but the patient's fever persisted and clinical condition deteriorated after 5 days of therapy, the dosage of study drug could be increased to 70 mg/day of caspofungin (13.3% of patients treated) or to 5.0 mg/kg/day of liposomal amphotericin B (14.3% of patients treated). There were 1,095 patients included in the primary Modified Intention-To-Treat (MITT) efficacy analysis of overall favourable response; caspofungin (33.9%) was as effective as liposomal amphotericin B (33.7%) [% difference 0.2 (95.2% CI –5.6, 6.0)]. An overall favourable response required meeting each of 5 criteria: (1) successful treatment of any baseline fungal infection (caspofungin 51.9% [14/27], liposomal amphotericin B 25.9% [7/27]), (2) no breakthrough fungal infections during administration of study drug or within 7 days after completion of treatment (caspofungin 94.8% [527/556], liposomal amphotericin B 95.5% [515/539]), (3) survival for 7 days after completion of study therapy (caspofungin 92.6% [515/556], liposomal amphotericin B 89.2% [481/539]), (4) no discontinuation from the study drug because of drug-related toxicity or lack of efficacy (caspofungin 89.7% [499/556], liposomal amphotericin B 85.5% [461/539]), and (5) resolution of fever during the period of neutropenia (caspofungin 41.2% [229/556], liposomal amphotericin B 41.4% [223/539]). Response rates to caspofungin and liposomal amphotericin B for baseline infections caused by Aspergillus species were, respectively, 41.7% (5/12) and 8.3% (1/12), and by Candida species were 66.7% (8/12) and 41.7% (5/12). Patients in the caspofungin group experienced breakthrough infections due to the following uncommon yeasts and moulds: Trichosporon species (1), Fusarium species (1), Mucor species (1), and Rhizopus species (1).
Paediatric population
The safety and efficacy of caspofungin was evaluated in paediatric patients 3 months to 17 years of age in two prospective, multicentre clinical trials. The study design, diagnostic criteria, and criteria for efficacy assessment were similar to the corresponding studies in adult patients (see section 5.1).
The first study, which enrolled 82 patients between 2 to 17 years of age, was a randomized, double-blind study comparing caspofungin (50 mg/m2 IV once daily following a 70 mg/m2 loading dose on Day 1 [not to exceed 70 mg daily]) to liposomal amphotericin B (3 mg/kg IV daily) in a 2:1 treatment fashion (56 on caspofungin, 26 on liposomal amphotericin B) as empirical therapy in paediatric patients with persistent fever and neutropenia. The overall success rates in the MITT analysis results, adjusted by risk strata, were as follows: 46.6% (26/56) for caspofungin and 32.2% (8/25) for liposomal amphotericin B.
The second study was a prospective, open-label, non-comparative study estimating the safety and efficacy of caspofungin in paediatric patients (ages 6 months to 17 years) with invasive candidiasis, oesophageal candidiasis, and invasive aspergillosis (as salvage therapy). Forty-nine patients were enrolled and received caspofungin at 50 mg/m2 IV once daily following a 70 mg/m2 loading dose on Day 1 (not to exceed 70 mg daily), of whom 48 were included in the MITT analysis. Of these, 37 had invasive candidiasis, 10 had invasive aspergillosis, and 1 patient had oesophageal candidiasis. The favourable response rate, by indication, at the end of caspofungin therapy was as follows in the MITT analysis: 81% (30/37) in invasive candidiasis, 50% (5/10) in invasive aspergillosis, and 100% (1/1) in oesophageal candidiasis.
In a double-blind, randomized (2:1) comparator-controlled study safety, tolerability and efficacy of caspofungin (2 mg/kg/d intravenously, infused over 2 hours) vs amphotericin B deoxycholate (1 mg/kg/d) was evaluated in neonates and infants less than 3 months of age with (culture-confirmed) invasive candidiasis. Due to poor enrolment, the study was terminated early and only 51 patients were randomized. The proportion of patients with fungal-free survival at 2 weeks post-therapy in the caspofungin treatment group (71.0%) was similar to that seen in the amphotericin B deoxycholate treatment group (68.8%). Based on this study, no posology recommendations for neonates and infants can be made.