Arnatar Therapeutics Emerges from Stealth with $52 million and an RPDD for Alagille Syndrome Therapy

Rare Daily Staff

Arnatar Therapeutics, a company developing RNA-based therapies, said the U.S. Food and Drug Administration granted orphan drug and rare pediatric disease designations to ART4, its experimental upregulating antisense oligonucleotide therapeutic for the treatment of Alagille syndrome, as the company emerged from stealth.

The company also announced it completed a $52 million Series A financing in 2024. Arnatar said the funding enables it to advance its DARGER platform and pipeline of RNA therapeutics, which combines best-in-class siRNA with first-in-class upregulating antisense oligonucleotides (ASOs) to deliver transformative medicines for cardiometabolic, liver, CNS, and kidney diseases.

Eight Roads and 3E Bioventures led the round. F-Prime Capital, Zhuhai Huajin Capital, Legend Star, Transfar Capital, New Alliance Capital, Yijing Capital, Gaorong Ventures, Jifeng Ventures, and Hongsheng Capital also participated. Arnatar was founded in 2022 and received seed financing from Apricot Capital.

Alagille syndrome (ALGS) is a rare, life-threatening, multisystem genetic disorder that primarily affects the liver, heart, and vasculature. About 95 percent of cases are caused by mutations in the JAG1 gene that result in insufficient protein levels and impaired liver bile duct development. As a result, patients experience toxic bile acid buildup, progressive liver damage, and systemic complications that often begin in early childhood.

ART4 is designed to target the root cause of ALGS by leveraging Arnatar’s proprietary ACT-UP1 platform to upregulate endogenous JAG1 protein expression. It is administered subcutaneously and intended for once-monthly dosing. In preclinical studies, ART4 significantly increased JAG1 protein levels, restored bile duct development, and reduced biomarkers of liver injury — including bile acids and ALT — in a validated ALGS mouse model. The drug was well-tolerated in both adult and newborn animals.

“Our approach is designed to target the underlying genetic deficiency to restore bile duct function and prevent the severe complications, including liver damage, that children with ALGS often face,” said Xuehai Liang, CEO of Arnatar Therapeutics. “We remain committed to advancing ART4 into the clinic as rapidly as possible to bring this potentially transformative therapy to patients and families who currently have no curative treatment options.”

The FDA’s rare pediatric disease designation may allow Arnatar to receive a priority review voucher (PRV) upon approval of ART4, which could be used to expedite the review of another drug candidate or be sold. Recent sales of PRVs have been priced around $150 million, but Congress has not yet passed legislation to extend the program, which expired at the end of 2024 following a brief extension.

Orphan drug designation provides benefits including seven years of market exclusivity upon approval, eligibility for tax credits on qualified clinical trials, a waiver of FDA user fees, and access to federal grants to support clinical development.