Hypersensitivity reactions are relevant adverse effects of asparaginase therapy. Therefore, children treated with native Escherichia coli asparaginase in induction therapy of acute lymphoblastic leukaemia (ALL) or non‐Hodgkin's lymphoma (NHL) were switched to the pegylated enzyme for reinduction under drug monitoring. Seventy children, including four patients with allergic reactions during induction, were given one dose of OncasparTM 1000 U/m2 intravenously. Activity was determined every third or fourth day until it dropped below the limit of quantification. In current reinduction protocols [ALL/NHL‐Berlin–Frankfurt–Münster (BFM) 95 trials], four doses of 10 000 U/m2E. coli asparaginase deplete asparagine for about 2–3 weeks, therefore activities of ≥ 100 U/l up to day 14 and ≥ 50 U/l up to day 21 were targeted. In 66 patients without an allergic reaction during induction, the mean activity was 606 ± 313 U/l, 232 ± 211 U/l and 44 ± 50 U/l after 1, 2 and 3 weeks respectively. In 44/66 patients, activity was ≥ 100 U/l after 14 d. A rapid decline in activity was seen in the remaining 22 patients, including 8/22 patients who showed no activity after 1 week. Toxicity was low and comparable to the native enzymes but, in contrast to about 30% of hypersensitivity reactions with conventional reinduction therapy, no allergic reaction was seen. Substituting 4 × 10 000 U/m2 asparaginase medac for one dose of 1000 U/m2 OncasparTM was safe and well tolerated. Comparable pharmacokinetic treatment intensity was achieved in about two‐thirds of patients.

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Native forms of asparaginase stem from different biological sources. Previously reported data from children treated with Erwinase showed significantly lower trough levels and pharmacokinetic dose intensity than after E. coli-derived preparations. Hence, schedule optimization was initiated to achieve relevant serum activities. 21 children on reinduction therapy received Erwinase on Mondays, Wednesdays and Fridays for 3 weeks (9 x 20000 IU/m2 i.v.) instead of 4x 10 000IU/m2 of E. coli asparaginase (twice weekly for 2 weeks). Asparaginase trough activities were measured as the primary parameter, targeting 100-200 IU/I after 2 d and >50 IU/l after 3 d. Concurrently, asparagine trough concentrations were monitored. The mean trough activity was 156+/-99 IU/l, with 2/108 samples showing no detectable activity. Regarding trough levels per individual (three or more measurements/patient), means ranged from 52+/-29 to 276+/-114 IU/l (20 patients, 106 samples), with nine, six, and five children inside, below, and above the target range, respectively. The mean 3 d trough activity was 50+/-39 IU/l (20 patients, 51 samples). In 11 of these samples no activity was measurable. Mean trough activities calculated per individual ranged from < 20-84+/-30 IU/l (14 patients, 42 samples) with seven children below the target limit of 50 IU/l and asparagine concentrations <0.2 - 1.5microM. We concluded that an increased dose of 9x20000 IU/m2 of Erwinia asparaginase within 3 weeks resulted in a pharmacokinetic dose intensity comparable to former observations made with 4 x 10 000IU/m2 of the E. coli product Crasnitin which is no longer marketed. High interindividual variability and the phenomenon of 'silent' inactivation necessitate monitoring wherever possible.

The combination of liposomal amphotericin B (LAMB) and caspofungin (CAS) holds promise to improve the outcome of opportunistic invasive mycoses with poor prognosis. Little is known, however, about the safety and pharmacokinetics of the combination in patients at high risk for these infections. The safety and pharmacokinetics of the combination of LAMB and CAS were investigated in a risk-stratified, randomized, multicenter phase II clinical trial in 55 adult allogeneic hematopoietic stem cell recipients (aHSCT) with granulocytopenia and refractory fever. The patients received either CAS (50 mg/day; day 1, 70 mg), LAMB (3 mg/kg of body weight/day), or the combination of both (CASLAMB) until defervescence and granulocyte recovery. Safety, development of invasive fungal infections, and survival were assessed through day 14 after the end of therapy. Pharmacokinetic sampling and analysis were performed on days 1 and 4. All three regimens were well tolerated. Premature study drug discontinuations due to grade III/IV adverse events occurred in 1/18, 2/20, and 0/17 patients randomized to CAS, LAMB, and CASLAMB, respectively. Adverse events not leading to study drug discontinuation were frequent but similar across cohorts, except for a higher frequency of hypokalemia with CASLAMB (P < 0.05). Drug exposures were similar for patients receiving combination therapy and those randomized to monotherapy. There was no apparent difference in the occurrence of proven/probable invasive fungal infections and survival through day 14 after the end of therapy. CASLAMB combination therapy in immunocompromised aHSCT patients was as safe as monotherapy with CAS or LAMB and had similar plasma pharmacokinetics, lending support to further investigations of the combination in the management of patients with invasive opportunistic mycoses.Invasive opportunistic fungal infections are an important cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation. Depending on the presence of well-characterized risk factors, rates of infection by opportunistic fungal pathogens are between 10 and 25%. The case fatality rates vary between 35 and 50% for invasive candidiasis and 65 and 90% for invasive aspergillosis and infections by other filamentous fungi (8, 15).The existence of antifungal agents with different molecular targets is providing new opportunities to improve the efficacy of antifungal chemotherapy through combination therapy. Potential target populations include profoundly immunocompromised patients with prolonged granulocytopenia or following allogeneic hematopoietic stem cell transplantation, patients with fulminant or refractory infections, or those with infections in compartments that are difficult to treat and infections by fungal pathogens with decreased microbiological susceptibility (23,31,39,48,49,50).Based on its favorable microbiologic and pharmacokinetic properties (16), well-documented efficacy against Candida and Aspergillus infections, and excellent safety (24,28,32,45), the echinocandin lipop...

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