Orphan diseases/drugs

Orphan diseases / drugs

Orphan drugs are treatments for life threatening or chronically debilitating diseases with a patient population of 1 case per 2,000 inhabitants. The Netherlands is at the forefront of economic evaluations in orphan drugs. That is due to the fact that reimbursement policy required economic evaluations after a period conditional reimbursement of costly inpatient medicines.

Costing study

The costing study for untreated adults Pompe disease was included in a burden of illness study. Health care consumption, informal care use and productivity losses accounted for about 22,500 Euro of health care costs, mostly caused by health care consumption.

Economic evaluations

Economic evaluations for orphan drugs are challenging. Nevertheless, iMTA recently completed three economic evaluations for enzyme replacement therapy for Pompe disease and for Mucopolysaccharidosis (type 2 and type 6). There are about 120 patients of Pompe disease in The Netherlands, both adult and infantile. Hence, the challenge is in the numbers. For infantile patients, iMTA estimated and incremental cost effectiveness ratio of 1 million Euro per QALY. For adults, this ratio is less favorable, since increased survival is limited. In Mucopolysaccharidosis, there were about 10 patients per subtype. Evidence was very limited with no published information on survival and natural course. Using proxy endpoints, iMTA estimated an incremental cost-effectiveness ratio of about 2.1 million Euro per QALY Enzyme replacement therapies for above mentioned conditions are currently reimbursed in The Netherlands.

Multi-criteria decision analysis

Orphan drugs are high on the HTA agenda in many countries, as budget impact can be significant. Also, orphan drugs are often seen as a ‘test-case’ for applying HTA principles such as a cost-per-QALY threshold in a decision making context. iMTA performed multi criteria decision analysis (MCDA) concerning orphan drugs. The study design was hypothetical in nature: what if you have a limited budget from which all orphan drugs are to be funded? Which would be reimbursed and which would not be reimbursed? Using a stakeholder panel and analytical hierarchy processing to analyse results, several principles were compared (i.e. rarity, heredity, cost per QALY, availability of alternative treatment, burden of disease, age of the patient) to see which principles are considered crucial for decision making. Most weight to the criteria ‘effectiveness of the drug’ and ‘lifethreatening nature of the disease’.

Preference measurement / DCE & TTO

Preference measurement / DCE & TTO
A crucial element in economic evaluation is an adequate measurement of health utilities (referred to as health related quality of life). To make sure that the economic evaluation for Pompe disease was based on the instrument that best captures health effects in this population, a head on comparison of EQ5D and SF6D was performed in about 80 adult Pompe patients. Results showed that SF6D was most sensitive to change, had the largest mean change and largest effect size and is the preferred measure of outcome.