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

Alglucerase is a modified form of human placental glucocerebrosidase u sed as enzyme replacement therapy for patients with Gaucher's disease, in whom functional glucocerebrosidase is deficient. Alglucerase has p rovided a breakthrough in treatment for patients with this relatively rare disease. With alglucerase infusions typical disease manifestation s are ameliorated or normalised: hepatosplenomegaly is reduced, haemot ological parameters improve, and patients experience an increased qual ity of life usually within 4 to 6 months of treatment. Parameters of b one disease also respond, but generally over a longer period of treatm ent. Alglucerase is well tolerated by children and adults, with few ad verse effects reported. Seroconversion occurs in approximately 15% of patients on high-dose therapy, but does not appear to affect the effic acy of treatment. Several dosage regimens have been used to deliver al glucerase, 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. Patie nt responses are variable, and the dosage regimen should be tailored t o individual needs. Dosage regimens may be considerably reduced for th e maintenance phase of treatment, but clinical experience is as yet in sufficient 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 w eeks for a patient weighing 70kg costs $US404 040 per year. The minima l costs per quality-adjusted life year saved (QALY) have been estimate d for 3 dosage regimens over a 10-year period. Cost per QALY was $US14 7 000 for 60 IU/kg bodyweight administered every 2 weeks, $US75 000 fo r 30 IU/kg every 2 weeks, and $US49 000 for 2.3 IU/kg administered 3 t imes per week. These costs were calculated assuming immediate death wi th no treatment, which suggests that the actual costs per QALY for mos t 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 increa sed patient productivity and reduced palliative treatments remain unre solved. 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 represe nt a large opportunity cost for other therapeutic areas. Savings in tr eatment costs may be achieved by frequent administration of smaller do ses in a home environment (to decrease administration costs). Further research to develop less expensive means of manufacturing the enzyme i s urgently required, as current acquisition costs may limit treatment to only the most severely affected patients. In conclusion, enzyme rep lacement therapy is the most effective and well tolerated treatment av ailable for Gaucher's disease. However, the cost effectiveness of this expensive treatment has not yet been established.