Orphan diseases/drugs

Several costing studies and burden of illness studies in rare diseases have been performed by iMTA. For example, a burden of illness study for patients with hereditary angioedema was conducted. Nearly 80% of patients in the Netherlands participated in this study. The study described quality of life, treatment burden and societal costs in this disease population. These results can be used to inform future economic evaluations.

iMTA worked on several economic evaluations in orphan drugs, despite methodologically challenges commonly experienced in orphan drugs. iMTA developed several de novo economic models for the evaluation orphan drugs in a variety of orphan indications.

iMTA has worked on several economic model adaptations for rare diseases. For example, iMTA 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.

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
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.