Accelerated Approval Denied & Pivotal Study Underway for Pompe Disease Treatment, AT-GAA

The US Food and Drug Administration (FDA) has denied Amicus Therapeutics’ accelerated approval for AT-GAA, a pipeline treatment for Pompe disease. However, per the FDA’s recommendation, plans for a pivotal study that is set to conclude this year are still underway, so approval could be forthcoming.

The decision followed a Type C meeting between the FDA and Amicus that discussed the regulatory path for AT-GAA. The upcoming, single pivotal study will compare AT-GAA to the current standard of care (alglucosidase alfa, an enzyme replacement therapy) and will serve as the study to support full approval.

Approximately 100 participants with Pompe disease are anticipated to enroll in the trial, which will include a population of both ERT-switch patients and ERT treatment-naïve patients. A 6-minute walk with a primary treatment period of up to 12 months will serve as the primary endpoint.

Participation in the observational study (POM-003) will not be mandatory for patient eligibility to enroll directly into the pivotal study. Eligibility for the pivotal study will also be extended to patients currently enrolled in study POM-003. Inclusion of additional populations, such as pediatric Pompe patients, are also intended by Amicus; additional studies in 2019 will aim to include these populations.

“We look forward to initiating the Pompe pivotal trial this year following collaborative discussions with regulators in the US and the EU,” John F. Crowley, JD, MBA, chairman and chief executive officer of Amicus Therapeutics Inc, said in a recent statement. “We continue to take steps forward in this vitally important program and will significantly enhance the body of clinical data for AT-GAA through the upcoming pivotal study as well as through ongoing clinical studies over the coming months.”

While the FDA indicated that the current clinical package for AT-GAA is not sufficient to support accelerated approval, Amicus plans to produce data that will fuel further discussions regarding a potential pathway for accelerated approval in 2019.

According to the recent press release, such materials will include data from up to 10 additional ERT-switch patients in a new Cohort 4 as part of the ongoing phase 1/2 study (data expected in 2019); a presentation of longer-term clinical data out to 18-months for the 19 original phase 1/2 patients (data expected in 2H 2018); and completion of a retrospective natural history study in approximately 100 ERT-treated Pompe patients (data expected in 2H 2018).

“We look forward in the near term to sharing the latest clinical results from the ongoing phase 1/2 study at the World Muscle Society in early October,” Crowley added. “Our commitment remains the same as it has always been since we initiated the development of our Pompe cell line—to deliver this potential new therapy to as many people living with Pompe disease as soon as possible.”

AT-GAA is a unique recombinant human acid alpha-glucosidase (rhGAA) enzyme with optimized carbohydrate structures, particularly mannose-6 phosphate (M6P). In order to enhance uptake, AT-GAA is co-administered with pharmacological chaperone, AT2221.

Improvements in muscle strength, increased tissue enzyme levels, and reduced glycogen levels in muscle were associated with AT-GAA in preclinical trials.