Background:

Previous studies have shown that elosulfase alfa has a favorable efficacy/safety profile in Morquio A patients aged≥ 5 y. This study evaluated safety and impact on urine keratan sulfate (uKS) levels and growth velocity in younger patients.

Methods:

Fifteen Morquio A patients aged< 5 y received elosulfase alfa 2.0 mg/kg/week for 52 wk during the primary treatment phase of a phase II, open-label, multinational study. Primary endpoint was safety and tolerability; secondary endpoints were change in uKS and growth velocity over 52 wk.

Results:

All 15 patients completed the primary treatment phase. Six of 743 infusions (0.8%) administered led to adverse events (AEs) requiring infusion interruption and medical intervention. Eleven patients (73.3%) had≥ 1 study drug-related AE, mostly infusion-associated reactions. Mean z-score growth rate per year numerically improved from− 0.6 at baseline to− 0.4 at week 52. Comparison to untreated subjects of similar age in the Morquio A Clinical Assessment Program study showed a smaller decrease in height z-scores for treated than for untreated patients. Mean percent change from baseline in uKS was− 30.2% at 2 wk and− 43.5% at 52 wk.

Conclusion:

Early intervention with elosulfase alfa is well-tolerated and produces a decrease in uKS and a trend toward improvement in growth.