ALGLUCERASE - A PHARMACOECONOMIC APPRAISAL OF ITS USE IN THE TREATMENT OF GAUCHER DISEASE

Alglucerase is a modified form of human placental glucocerebrosidase used as enzyme replacement therapy for patients with Gaucher's disease, in whom functional glucocerebrosidase is deficient. Alglucerase has provided a breakthrough in treatment for patients with this relatively rare disease. With alglucerase infusions typical disease manifestations are ameliorated or normalised: hepatosplenomegaly is reduced, haemotological parameters improve, and patients experience an increased quality of life usually within 4 to 6 months of treatment. Parameters of bone disease also respond, but generally over a longer period of treatment. Alglucerase is well tolerated by children and adults, with few adverse effects reported. Seroconversion occurs in approximately 15% of patients on high-dose therapy, but does not appear to affect the efficacy of treatment. Several dosage regimens have been used to deliver alglucerase, and the comparative benefits of these remain controversial. High-dose regimens of 60 IU/kg bodyweight administered every 2 weeks are clearly effective; however, smaller dosages given more frequently are also effective and incur a greatly reduced acquisition cost. Patient responses are variable, and the dosage regimen should be tailored to individual needs. Dosage regimens may be considerably reduced for the maintenance phase of treatment, but clinical experience is as yet insufficient to establish the minimum dosages required in the long term. Acquisition cost of alglucerase is $US3.70 per unit (1994 US dollars); thus, a dosage regimen of 60 IU/kg bodyweight administered every 2 weeks for a patient weighing 70kg costs $US404 040 per year. The minimal costs per quality-adjusted life year saved (QALY) have been estimated for 3 dosage regimens over a 10-year period. Cost per QALY was $US147 000 for 60 IU/kg bodyweight administered every 2 weeks, $US75 000 for 30 IU/kg every 2 weeks, and $US49 000 for 2.3 IU/kg administered 3 times per week. These costs were calculated assuming immediate death with no treatment, which suggests that the actual costs per QALY for most patients with type 1 or 3 disease are likely to be much higher. Drug administration costs may become a significant part of the cost during maintenance therapy; in addition, possible cost savings due to increased patient productivity and reduced palliative treatments remain unresolved. Although some patients may obtain increased benefit from high-dosage regimens, the very high cost may preclude general use of these regimens. Healthcare resources consumed by alglucerase therapy represent a large opportunity cost for other therapeutic areas. Savings in treatment costs may be achieved by frequent administration of smaller doses in a home environment (to decrease administration costs). Further research to develop less expensive means of manufacturing the enzyme is urgently required, as current acquisition costs may limit treatment to only the most severely affected patients. In conclusion, enzyme replacement therapy is the most effective and well tolerated treatment available for Gaucher's disease. However, the cost effectiveness of this expensive treatment has not yet been established.