RARE Daily

FDA Grants Rare Pediatric Disease Designation to Avrobio’s Hunter Syndrome and OS Sciences’ Osteosarcoma Therapies

November 3, 2021

The U.S. Food and Drug Administration granted Rare Pediatric Disease designation to Avrobio’s lentiviral gene therapy candidate AVR-RD-05 for the treatment of Hunter syndrome, and to OS Therapies’ OST-HER2 for the treatment and cure of osteosarcoma.

The FDA grants Rare Pediatric Disease designation for serious or life-threatening diseases with manifestations in individuals aged from birth to 18 years, including access to the FDA’s expedited review and approval process. The designation makes the developing company eligible for a Rare Pediatric Disease Priority Review voucher upon approval of the therapy by the FDA.

The vouchers can be used to reduce the time of an FDA new drug approval review to six months from ten months. The vouchers are potentially lucrative because they are transferable. Most recently, Albireo sold a priority review voucher for $105 million.

Hunter syndrome, or mucopolysaccharidosis type II (MPSII), is a rare and seriously debilitating lysosomal disorder that primarily affects young boys, with a prevalence estimated at one in 100,000 to one in 170,000 males worldwide. It causes devastating complications throughout the body and brain, including severe cardiac and respiratory dysfunction, skeletal malformations, and hearing impairment. Children with severe cases of Hunter syndrome typically show early symptoms of the disease in their toddler years and begin to regress developmentally, losing basic motor skills and cognitive function over a few years. The current standard of care is weekly enzyme replacement therapy (ERT), which can delay some health complications but does not halt overall progression of the disease and has not been demonstrated to address the central nervous system issues. Even with ERT, people with Hunter syndrome face life-limiting symptoms and a significantly reduced lifespan.

Avrobio’s planned investigator-sponsored phase 1/2 clinical trial for Hunter syndrome is expected to commence in the second half of 2022. The program was developed by Brian Bigger, professor of cell and gene therapy at the University of Manchester, U.K. Bigger has published preclinical data demonstrating that ex vivo lentiviral gene therapy deploying an optimized, proprietary tag has the potential to correct peripheral disease and normalize brain pathology.

Osteosarcoma is a solid tumor of the bone that predominantly occurs in adolescent and young adults. Standard treatment includes surgery and chemotherapy. For patients with initially metastatic or recurrence after chemotherapy, there is a significantly poorer prognosis.

The OST-HER2 (Listeria monocytogenes) platform technology has already been administered into approximately 450 volunteers in successful and completed clinical trials. OS Therapies recently initiated a potentially pivotal, phase 2b clinical trial intended to prevent metastasis and improve overall survival osteosarcoma. OST-HER2 has already received Orphan Drug designations by the FDA and EMA, and the company plans to file for Breakthrough designation next year.

“The timing and determination by the FDA that OST-HER2 is a potentially much-needed new treatment in this underserved disease underscores the importance of our recently initiated phase 2b clinical trial in recurred, resected osteosarcoma” said Paul Romness, CEO of OS Therapies. “The RDD ensures a well-deserved expedited review by the FDA, as well as a Priority Review Voucher if our current trial is successful.”

Author: Rare Daily Staff

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