LAUSR

Patient registries for rare diseases enable systematic data collection and can also be used to facilitate post-authorization safety studies (PASS) for orphan drugs. This study evaluates the PASS for betaine anhydrous (Cystadane®), conducted as public private partnership (PPP) between the European network and registry for homocystinurias and methylation defects (E-HOD) and the marketing authorization holder (MAH). Prospective data collection, 2013-2016, in a non-interventional, international, multicenter, registry study. Putative adverse and severe adverse events were reported to the MAH's pharmacovigilance. 130 individuals with vitamin B6 non-responsive (N = 54) and partially responsive (N = 7) cystathionine beta-synthase (CBS) deficiency, as well as 5,10-methylenetetrahydrofolate reductase (MTHFR; N = 21) deficiency and cobalamin C (N = 48) disease were included. Median (range) duration of treatment with betaine anhydrous was 6.8 (0-9.8) years. The prescribed betaine dose exceeded the recommended maximum (6 g/day) in 49% of individuals older than 10 years because of continued dose adaptation to weight; however, with disease-specific differences (minimum: 31% in B6 non-responsive CBS deficiency, maximum: 67% in MTHFR deficiency). Despite dose escalation no new or potential risk was identified. Combined disease-specific treatment decreased mean ± SD total plasma homocysteine concentrations from 203 ± 116 μmoL/L to 81 ± 51 μmoL/L (P < 0.0001), except in MTHFR deficiency. Recommendations for betaine anhydrous dosage were revised for individuals older than 10 years. PPPs between MAH and international scientific consortia can be considered a reliable model for implementing a PASS, reutilizing well-established structures and avoiding data duplication and fragmentation.