New Rett Syndrome Treatment Heralded But With Some Concerns | Asembia Specialty Pharmacy Summit

The new treatment is not a cure, but it does provide incremental improvement in communication, interaction and a variety of other features of Rett syndrome.

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A new FDA-approved treatment for Rett syndrome is offering new hope to people affected the disease, who are mainly girls and women, and families shouldering decades of the caregiving and financial burdens associated with the disease. But the treatment is also coming with concerns about the price and relatively short phase 3 trial on which the approval was based.

Abigail Jastrab, Pharm.D., senior manager of clinical systems at PANTHERx Rare Pharmacy in Pittsburgh, and Alan K. Percy, M.D., a professor emeritus, Department of Pediatrics, and former head of Child Neurology, University of Alabama at Birmingham, spoke at a session on the evolving treatment for Rett syndrome today at Asembia’s 2023 Specialty Pharmacy Summit in Las Vegas.

Rett syndrome is a brain disorder caused mutations in the MECP1 gene that produces proteins crucial to brain development. As outlined by Jastrab and Percy, it is characterized by a host of problems with communication, learning, breathing, sleep, movement, behavior and growth, including small head size (microcephaly). One of its cardinal features is loss of purposeful control of the hands and repetitive wringing or clapping motions called hand stereotypies.

Estimates of the incidence vary, but the Rett Syndrome Research Trust says that 1 in 10,000 girls are born with Rett syndrome, which the trust says would work out to about 15,000 affected girls and women in the U.S. Percy noted that women are living longer with the conditions these days and surviving into their 50s.

The FDA approved Daybue (trofinetide) as a treatment for Rett syndrome on March 10; the FDA’s news release calls it the first treatment for Rett syndrome. Acadia Pharmaceuticals, the San Diego biotech company that developed the drug, announced on April 17 that it was available.

“This is not a cure, but it does provide incremental improvement in communication, interaction and a variety of other features of Rett syndrome,” said Percy, who was one of the investigators of the phase 3 trial, called LAVENDER, that led to its approval.

The trial, which include 93 participants in the treatment arm and 94 in the placebo, was conducted for 12 weeks. Given that Rett syndrome is a lifelong condition, that was brief, Percy said.

“One of the investigators’ complaints of the trial was that it was only 12 weeks. We thought that the placebo-controlled portion should have been — I felt it should have been six months,” Percy said in a short interview with Managed Healthcare Executive.

Percy noted, though, results from an open-label follow-up study showed that the girls and women in the placebo arm who switched over and started taking Daybue had improvements comparable to the girls and women in the treatment group in the original study. Investigators used the Rett Syndrome Behaviour Questionnaire, a 45-item questionnaire filled out by caregivers, and the Clinical Global Impression-Improvement (CGI-I), a structured clinical assessment made by clinicians, to measure the drug’s efficacy.

About 80% of the girls and women in the treatment experienced diarrhea as a side effect. Because constipation is a frequent symptom of Rett syndrome and patients often take laxatives to address it, Jastrab and Percy said families will need to be informed about the diarrhea side effect and adjust the routine use of laxatives accordingly.

When Daybue was approved, Acadia said it would be priced so the annual cost, at its list price, would be between $575,000 and $595,000.

Percy noted that it will likely fall to private and public insurers to pay for the medication, not families. Because people with Rett syndrome are living longer, the lifetime cost per patient will be high, he added.