RARE Daily

FDA Grants RPDD for SiSaf’s siRNA Therapy to Treat Autosomal Dominant Osteopetrosis

May 15, 2023

Rare Daily Staff

The U.S. Food and Drug Administration granted SiSaf’s experimental therapy SIS-101-ADO for patients with autosomal dominant osteopetrosis type 2, Rare Pediatric Disease and Orphan Drug designations.

The FDA awarded SIS-101-ADO Rare Pediatric Disease Designation based on the serious or life-threatening manifestations of autosomal dominant osteopetrosis type1 (ADO2) that primarily affect children including blindness from optic nerve compression, anomalies in dental and craniofacial development, and scoliosis.

There are currently no approved treatments for osteopetrosis ADO2 and no other treatments currently in clinical trials. If approved, SiSaf’s SIS-101-ADO would thus be the first treatment for osteopetrosis ADO2 and could provide life-altering benefits for those who suffer from this debilitating disease. SiSaf is currently preparing for first-in-human clinical trials.

SIS-101-ADO combines a siRNA that suppresses the expression of CLCN7 with SiSaf’s Bio-Courier delivery technology. By downregulating the expression of CLCN7, a mutant gene expressed by osteoclasts and other cell types responsible for causing ADO2, the RNA therapy restores bone mass and quality to nearly normal levels.

Genetic skeletal disorders such as ADO2 account for five percent of all birth defects globally, yet many unmet needs and challenges remain for providing safe and effective treatments. SiSaf’s proprietary Bio-Courier technology has the potential to accelerate the development of new RNA-based treatments. The technology addresses the limitations of other RNA delivery technologies by stabilizing lipid nanoparticles with bioabsorbable silicon.

“Being granted Orphan Drug designation and Rare Pediatric Disease designation is a major milestone in our drive to move our revolutionary siRNA treatment forward to alleviate the pain and suffering that osteopetrosis ADO2 inflicts,” SiSaf’s Founder and CEO Suzanne Saffie-Siebert said. “SIS-101-ADO ushers in the potential for a new era of personalized care and treatment options for ADO2 and other rare bone and skeletal diseases.”

The FDA awards priority review vouchers to sponsors of rare pediatric disease product applications that meet certain criteria. Under this program, a sponsor who receives an approval for a drug or biologic for a rare pediatric disease may qualify for a priority review voucher that can be redeemed to receive a priority review of a subsequent marketing application, including applications for a different product.

The vouchers are potentially lucrative because they can be sold. In January, Bluebird Bio sold a Rare Pediatric Disease Priority Review Voucher for $95 million to Bristol Myers Squibb.

Photo: SiSaf’s Founder and CEO Suzanne Saffie-Siebert

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