Fast Track, Breakthrough and Priority Reviews: Sanofi and ViiV


The U.S. Food and Drug Administration (FDA) has four distinct approaches to speeding the drug approval process. They are Priority Review, Breakthrough Therapy, Accelerated Approval and Fast Track designation.

Fast Track Designation (FTD) is an FDA process meant to facilitate the development and review of drugs for serious disease and to fill unmet medical need. It can lead to an Accelerated Approval and Priority Review if specific criteria are met.

Breakthrough Therapy designation is designed to expedite the development and review of drugs that may have substantial improvement over current available therapies.

Accelerated Approval is for drugs for serious diseases that filled an unmet medical need and can be approved based on a surrogate endpoint. A surrogate endpoint is a marker, such as a laboratory result, radiographic image, physical sign or other measurement that is believed to predict clinical benefit, but is not itself a measure of clinical benefit.

A Priority Review designation means the FDA will take action on a New Drug Application (NDA) or Biologics License Application (BLA) within six months, instead of the more typical 10 months.

Several of today’s announcements had one or more of these designations.

Sanofi’s Avalglucosidase Alfa for Pompe Disease

Sanofi’s Biologics License Application (BLA) for avalglucosidase alfa for long-term enzyme replacement therapy for treatment of Pompe disease (acid alpha-glucosidase deficiency) received Priority Review from the U.S. Food and Drug Administration (FDA). It has a target action date (PDUFA) of May 18, 2021.

The drug is an enzyme replacement therapy to improve the delivery of acid alpha-glucosidase (GAA) enzyme to muscle cells. Pompe disease is a rare, degenerative muscle disease that can affect the patients’ ability to move and breath. It affects about 3,500 people in the U.S.

“The hallmarks of Pompe disease are the relentless and debilitating deterioration of the muscles, which causes decreased respiratory function and mobility,” said Karin Knobe, head of Development for Rare Diseases and Rare Blood Disorders at Sanofi. “Avalglucosidase alfa is specifically designed to deliver more GAA enzyme into the lysosomes of the muscle cells. We have been greatly encouraged by positive clinical trial results in patients with late-onset and infantile-onset Pompe disease.”

Sanofi’s Rilzabrutinib for Immune Thrombocytopenia

The FDA also granted Sanofi’s Burton’s tyrosine kinase (BTK) inhibitor rilzabrutinib Fast Track Designation for immune thrombocytopenia (ITP). The company also initiated a Phase III trial of the drug for ITP after positive Phase I/II data. The drug also received Orphan Drug Designation from the FDA for ITP in October 2018. Orphan Drug designations are for drugs and diseases that are fairly rare and confers certain development incentives, including tax credits for qualified clinical testing.

ITP is marked by immune-mediated destruction of platelets and impairment of platelet production. This leads to downstream thrombocytopenia and a predisposition to bleeding.

“By awarding Fast Track Designation to rilzabrutinib, an investigational candidate for the treatment of ITP, the FDA has recognized rilzabrutinib’s potential to meaningfully improve outcomes for patients with this debilitating disease,” said Dolca Thomas, chief medical officer of Principia, a Sanofi company. “This is an excellent acknowledgement as we initiate our Phase III study. FTD is designed to facilitate the development and expedite the review of investigational treatments that demonstrate the potential to address unmet medical needs in serious or life-threatening conditions.”

ViiV Healthcare’s Cabotegravir for HIV Prevention

ViiV Healthcare, majority owned by GlaxoSmithKline, with Pfizer and Shionogi as shareholders, received Breakthrough Therapy Designation from the FDA for its long-acting, injectable cabotegravir for HIV pre-exposure prophylaxis (PrEP). The designation was based on efficacy and safety data from HPTN 083, a Phase IIb/III trial comparing cabotegravir to daily oral emtricitabine/tenofovir disoproxil fumarate 200 mg and 300 mg (FTC/TDC) (Gilead Sciences’ Truvada) for preventing HIV infection in men who have sex with men and transgender women who have sex with men.

“New medicines that decrease the risk of HIV acquisition in at-risk populations are an essential tool to help us end the global HIV epidemic,” stated Kimberly Smith, head of Research & Development at ViiV. “Our data from the HPTN 083 and 084 studies show that long-acting cabotegravir is superior to daily oral FTC/TDF tablets for HIV prevention. We are looking forward to working closely with the FDA to make this prevention option available to people at risk of acquiring HIV.”


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