Efficacy of laronidase therapy in patients with mucopolysaccharidosis type I who initiated enzyme replacement therapy in adult age. A systematic review and meta-analysis.

BACKGROUND: The efficacy of starting enzyme replacement therapy (ERT) in adults with Muchopolysaccharidosis Type I (MPS-I) is controversial. Evaluating the benefits reported by patients initiating ERT with laronidase at adult age might help physicians decide whether the use of ERT in these patients is worthwhile from a clinical point of view.

OBJECTIVE: To assess every effectiveness variable modified in MPS-I patients who initiated laronidase at adult age.

METHODS: A systematic search of the literature, from inception to July 2016, was conducted using MEDLINE, EMBASE, CENTRAL and LILACS to identify randomized trials or observational studies including ≥1 MPS-I patients with ERT initiated in adult age (≥18years) and evaluating ERT efficacy. A meta-analysis of studies evaluating the same effectiveness outcome was performed and the evidence was rated according to GRADE criteria. Heterogeneity was assessed by the Chi-squared test and the I-squared statistic. Case reports were excluded from meta-analysis but their main outcomes were separately evaluated. The decrease in urine glycosaminoglycans (uGAGs) levels as patient percentage with reduction in uGAGs and with normalization was the primary outcome.

RESULTS: Nineteen clinical studies and 12 case reports were selected. ERT decreased uGAG levels (high evidence) and liver volume (high), improved 6-min walking test (6MWT) (moderate) and increased blood anti-ERT antibody levels (high). There was no conclusive results (low or very low evidence) regarding improvement/stabilization of respiratory function, change in shoulder flexion, cardiac improvement/stabilization, improvement in symptoms of nocturnal hypoventilation and sleep apnea, improvement in quality of life, visual acuity, otolaryngologic function, bone mineral density or effectiveness of intrathecal therapy.

LIMITATIONS: Excluding case reports, there was no study conducted specifically in the target population (ERT ≥18years). Data were from subgroup analyses of selected studies. There was a great heterogeneity between designs and clinical outcomes evaluated.

CONCLUSIONS: ERT improves uGAGs and liver volume in MPS-I patients initiating therapy as adults, although the putative clinical benefit associated to these improvements is unclear. Moderate evidence was shown for improvement in 6MWT. Systematic review registration number (PROSPERO): 42,016,041,306.