The European Commission has granted orphan drug designation to Chiesi and Arbor Biotechnologies’ investigational gene editing therapy ABO-101 for primary hyperoxaluria.

Chiesi Group and Arbor Biotechnologies have secured orphan drug designation from the European Commission for ABO-101, an investigational gene editing therapy for primary hyperoxaluria type 1 (PH1), marking another regulatory milestone for the rare disease programme.

The designation is intended to support the development of medicines for rare conditions affecting fewer than five in 10,000 people in the European Union. It provides incentives including regulatory support and market exclusivity if a therapy is ultimately approved.

ABO-101 is being developed as a one-time liver-directed gene editing treatment designed to reduce oxalate production by permanently disrupting the HAO1 gene in the liver. PH1 is an ultra-rare inherited disorder caused by mutations in the AGXT gene, leading to excessive oxalate production that can result in recurrent kidney stones, progressive kidney damage, kidney failure and systemic complications.

The designation builds on regulatory recognition already received in the USA, where ABO-101 was granted orphan drug designation and rare pediatric disease designation by FDA in 2025.

Mitch Goldman, senior vice president research & development at Chiesi Global Rare Diseases, said: “Receiving Orphan Drug Designation from the EC is an important recognition of the unmet need that exists for people living with PH1 and the promise of what gene editing approaches may offer.”

He added: “Beyond that recognition, the designation provides meaningful support throughout the development lifecycle, which allows us to continue advancing this research with the resources and commitment the community deserves.”

ABO-101 is currently being evaluated in the global redePHine Phase 1/2 clinical study, an open-label, dose-escalation trial assessing the safety, tolerability, pharmacokinetics, pharmacodynamics and preliminary efficacy of a single dose of the investigational therapy in adults and children with PH1.

The study is designed in two parts, with adult participants enrolled first to identify a recommended dose before expansion into paediatric patients. Participants will then enter a long-term follow-up period in line with regulatory requirements.

The companies said further details from the redePHine programme will be presented at the 15th International Hyperoxaluria Workshop in Prague, where principal investigator John Lieske will provide an overview of the clinical trial on June 26.

ABO-101 uses a lipid nanoparticle delivery system to transport messenger RNA encoding a Type V CRISPR Cas12i2 nuclease and guide RNA targeting the HAO1 gene. The therapy remains investigational and has not been approved by FDA, EMA, MHRA or any other regulatory authority.

Chiesi and Arbor entered into a global collaboration in 2025 to develop and commercialise gene editing therapies for rare diseases, with ABO-101 representing the lead programme under the agreement.