US FDA approves Denali’s genetic disorder therapy for children

March 25 (Reuters) – The U.S. Food and Drug Administration has approved Denali Therapeutics’ therapy to treat children with a rare genetic disorder, marking the first regulatory green light for the drugmaker in the country. 

However, continued approval for the treatment may be contingent upon verification of clinical benefit in a confirmatory trial, the company said on Wednesday, adding that the therapy will be available in the U.S. shortly.  

Denali shares were up 6.9% at $22.41.

Marketed as Avlayah, the enzyme replacement therapy is aimed at treating Hunter syndrome, a rare genetic disorder that affects about 500 people in the U.S., almost exclusively males, and leads to the buildup of certain sugar molecules in the brain and body.

Caused by a deficiency of the enzyme iduronate-2-sulfatase, the disorder prevents the body from breaking down large sugar molecules called glycosaminoglycans. 

Symptoms include developmental delays, cognitive decline and behavioral abnormalities. 

Given as a once-weekly infusion, Avlayah has been approved to treat the neurologic symptoms in presymptomatic or symptomatic pediatric patients.

The FDA’s approval was based on a surrogate endpoint, or a substitute measure, that tracked the reduction of heparan sulfate, a sugar molecule linked to organ damage that accumulates due to the disorder.

The endpoint was reasonably likely to predict Avlayah’s clinical benefit, the regulator’s review team said. 

Denali is now conducting a trial to evaluate the clinical benefit of the treatment, said Tracy Beth Hoeg, acting director of FDA’s drug evaluation center.

Avlayah’s approval includes a boxed warning, the agency’s most serious kind, for severe allergic reactions associated with the drug.

Takeda Pharmaceuticals’ Elaprase has been the only FDA-approved enzyme replacement therapy for the condition in the U.S. since 2006, but it addressed only physical symptoms such as walking ability and spleen size.

(Reporting by Kunal Das and Sneha S K; Editing by Jonathan Ananda)