Orphan diseases/drugs

Orphan diseases / drugs

Orphan drugs are treatments for rare life threatening or chronically debilitating diseases with a patient population of 1 case per 2,000 inhabitants. There are approximately 7,000 rare diseases, affecting about 30 to 40 million patients. Several methodological issues play a role in the evaluation of orphan drugs, particularly related to small patient numbers and limited knowledge on disease and intervention. The Netherlands has been at the forefront of economic evaluations of orphan drugs.

Costing study

Several costing studies and burden of illness studies in rare diseases have been performed by iMTA. For example, a costing study for untreated adult patients with 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

iMTA worked on several economic evaluations in orphan drugs, despite methodologically challenges commonly experienced in orphan drugs. iMTA developed four de novo economic models for the evaluation of enzyme replacement therapy for Pompe disease (classic-infantile and adults) and for Mucopolysaccharidosis (type 2 and type 6). In addition, iMTA has worked on several economic model adaptations for rare diseases. For example, iMTA recently worked on the adaptation of a global model for the gene therapy Luxturna for treatment of inherited retinal diseases. In addition to the challenges associated with the limited number of patients, iMTA also dealt with the uncertainties associated with gene therapy.

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.