A newly approved drug, Avlayah, has been approved by the FDA for treatment of Hunter syndrome, a rare disease that affects about 500 people in the U.S. The drug, manufactured by Denali Therapeutics, is the first FDA-approved treatment in the US. It is also the first one to penetrate the blood-brain barrier and halt the neurologic complications of the disease. While the current standard of care slows physical aspects of the illness, Denali's drug also targets cognitive decline. The approval of the drug was a welcome surprise to families of children with Hunter syndrome and the rare disease community. The FDA has faced criticism recently for rejecting several promising treatments for rare diseases.