SiSaf takes steps with FDA for RNA therapeutic to treat rare genetic skeletal disorders 

mRNA, biotech

SiSaf Ltd, an RNA delivery and therapeutics company, is initiating the U.S. FDA Regulatory process to obtain orphan drug designation for SIS-101-ADO.

SIS-101-ADO is a siRNA therapeutic for patients with autosomal dominant osteopetrosis type 2 (ADO2), a rare genetic skeletal disorder. The request for orphan drug designation and advancement through the regulatory process that SIS-101-ADO must undergo is being coordinated by CSSi LifeSciences, which helps emerging therapeutics through federal approval processes.

SIS-101-ADO combines an siRNA that suppress the expression of CLCN7, with SiSaf’s Bio-Courier next generation silicon stabilized hybrid lipid nanoparticles (sshLNPTM) technology that addresses the limitations of other RNA delivery technologies by merging lipid nanoparticle technology with inorganic bioabsorbable silicon. 

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.

Though the regulatory process can be lengthy, if approved, the use of SiSaf’s Bio-Courier technology for RNA delivery could provide life-altering benefits for those who suffer from rare skeletal disorders and may potentially be used to treat other bone and skeletal conditions in the future.

Accelerating advances

Genetic skeletal disorders such as ADO2 account for 5% of all birth defects globally, yet many unmet needs and challenges remain for providing safe and effective treatments. SiSaf’s Bio-Courier technology is a delivery platform designed to accelerate the technical advances and application of promising RNA therapeutics.

“In recent years, there has been an explosion of interest in RNA therapeutics for a wide range of medical concerns,” said SiSaf founder and CEO Dr. Suzanne Saffie-Siebert. 

“Initiating the regulatory process to have our ADO2 therapeutic obtain Orphan Drug Designation will move this revolutionary treatment closer to the goal of alleviating the pain and suffering that this disease inflicts on people. Provided successful, SIS-101-ADO and other Bio-Courier formulated drugs will not only be able to treat rare skeletal disorders but can clear the way for therapeutics for other rare diseases once thought impossible to treat.”

Jim Sergi, CEO of CSSi LifeSciences said, “Working with SiSaf to obtain orphan drug designation for its innovative Bio-Courier delivered siRNA product holds the promise to address some of the most intractable diseases. Unlocking the potential of this therapeutic will usher in a new era of personalized care and treatment options for ADO2 and other rare bone and skeletal diseases.”


SiSaf’s Bio-Courier drug delivery platform builds upon lipid nanoparticle technology with the introduction of silicon, for structural integrity and durability. The result is a nanoparticle with improved RNA loading capacity and protection from hydrolysis, combined with efficient transfection and controlled release of the oligonucleotide payload.  

Bio-Courier versatility is achieved by modifying particle size, surface charge and surface ligands for targeting to the desired site of drug action. Bio-Courier formulated drugs can be used for multiple routes of administration.

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