A Chiesi Farmaceutici drug for a rare enzyme deficiency is now approved by the FDA, making it the first U.S. treatment for a disorder that leads to a range of cognitive and muscle problems.

The regulatory decision announced late Thursday covers the treatment of children and adults who have alpha-mannosidosis (AM), a disease caused by a genetic mutation that leads to defective or inactive forms of an enzyme called alpha-D-mannosidase. Chiesi’s drug, velmanase alfa, is an engineered version of that enzyme. The privately held Italian company will market its new FDA-approved drug as Lamzede, the same name for the product in Europe, where the drug was approved in 2018.

AM is rare, affecting about one in every 500,000 people, according to the FDA. The enzyme these patients lack is needed to break down certain complex sugars. In AM, those sugars build up in organs and tissues, leading to a wide range of problems in the body. Symptoms can include recurrent chest and ear infections, hearing loss, muscle weakness, and cognitive problems. FDA approval of Lamzede does not cover treatment of central nervous system manifestations of the disease. That’s consistent with the marketing authorization in Europe, where the European Medicines Agency noted that the engineered enzyme does not cross the blood-brain barrier and is not expected to have an effect on the neurological aspects of AM.

The FDA based its decision on the results of a placebo-controlled Phase 3 study that evaluated the Chiesi drug over a 52-week period. The study enrolled 25 patients, 13 of them adults. Efficacy of the drug, administered in the study as a once-weekly infusion, was determined by a three-minute stair climbing test, six-minute walk test, and an assessment of lung capacity. The FDA said all measures favored the Lamzede group. In addition, blood tests showed a reduction in the concentration of complex sugars characteristic of AM.

The most common problems reported in the study were hypersensitivity reactions, including anaphylaxis. This risk is flagged on the drug’s label with a boxed warning advising that cardiopulmonary equipment and other medical support measures be readily available to address such complications.

Chiesi will commercialize its new product in the U.S. through Chiesi Global Rare Diseases, a Boston-based subsidiary that the company formed in 2020. In addition to lysosomal storage disorders such as AM, the Chiesi subsidiary is developing therapies in hematology and ophthalmology.

Last month, Chiesi expanded to rare skin diseases, reaching a $1.25 billion deal to acquire Amryt Pharma. Ireland-based Amryt developed Filsuvez, a treatment for epidermolysis bullosa, a rare inherited disorder that that causes skin to become very fragile and prone to blistering. European regulators approved Filsuvez last year but the drug was rejected by the FDA, which asked the company to provide more information about its efficacy.

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