Patients with a rare enzyme disorder known as Morquio A syndrome will no doubt be welcoming news that US regulators have issued a green light for the first drug therapy for the disease.

The US Food and Drug Administration has approved BioMarin's Vimizim (elosulfase alfa), an enzyme replacement therapy to treat condition (also called Mucopolysaccharidosis type IVA), after clinical trials showed it induced an improvement across multiple efficacy measurements.

The move means that Vimizim is now the "first and only therapy designed to address the condition at the cellular level, fulfilling a large unmet medical need for patients and their families," noted Jean-Jacques Bienaime, BioMarin's Chief Executive.

Morquio A syndrome affects around 3,000 patients in the developed world, and can lead to significant morbidities and diminished functional capacity, impaired quality of life, and early mortality. 

Approval was based on data from the MOR-004 study, which showed that patients taking a weekly dose of Vimizim showed a significant improvement of 22.5 metres in the six-minute walk test compared to those in the control arm.

On the secondary endpoint of three-minute stair climb, patients on BioMarin's therapy showed a trend toward improvement at 24 weeks of 1.1 additional stairs per minute over placebo.

"In clinical trials, Vimizim was shown to significantly improve endurance, which possibly could change the course of the disease," and its approval "is an important advance" for patients and their families, moving treatment "beyond supportive care to treating the underlying cause of the disease," said Paul Harmatz, Associate in Gastroenterology and Nutrition at the Children's Hospital and Research Center in Oakland, California, and clinical investigator of the Phase III trial.

Shipments of Vimizim to US distribution channels and will commence immediately, BioMarin said.

Marketing applications are also under review in the European Union, Brazil, Australia, Canada, and Mexico.