HuidaGene Therapeutics announced that the US. Food and Drug Administration (FDA) has granted orphan drug designation (ODD) for HG004, HuidaGene's lead gene replacement therapy for the treatment of inherited retinal disease caused by RPE65 mutations. Patients who are suffering from RPE65 mutation-associated inherited retinal diseases (IRDs), a group of rare blinding conditions caused by biallelic RPE65 mutations, affect the retina and pass on to children.
"We are pleased to have received this significant regulatory feedback from the US FDA. Receiving ODD is an important milestone as we are advancing our HG004 gene replacement therapy program to clinical trial designed to provide safe, durable, and high-quality treatment to children and adults suffering from RPE65 mutation-associated inherited retinal diseases," said Xuan Yao, PhD, co-founder and CEO of HuidaGene. "It also underscores the importance of bringing this novel therapy to patients with severe visual impairment or blindness, and strongly motivates us to expedite the clinical development of HG004."
The Orphan Drug Act encourages the development of treatment, diagnosis, or prevention of rare diseases, defined as those affecting fewer than 200,000 people in the United States.
The designation affords HuidaGene the potential for certain benefits, including tax credits for clinical development, exemptions for certain FDA application fees, seven years of post-approval market exclusivity, and assistance in the drug development process. ODD will accelerate drug development and registration action in the US.
HG004 will be eligible for certain development incentives, including FDA support for clinical studies.
In January 2023, FDA has cleared HG004 investigational new drug (IND) application for the planned multi-national clinical trial and is currently being reviewed by the China's National Medical Products Administration (NMPA) on this first AAV gene replacement therapy master protocol in different countries including China.
About RPE65 mutation-associated inherited retinal diseases
Inherited retinal diseases (IRDs) are a group of rare blinding conditions caused by mutations in any 1 of more than 250 genes.
Leber's congenital amaurosis (LCA), severe early childhood-onset retinal dystrophy (SECORD), early-onset severe retinal dystrophy (EOSRD), and retinitis pigmentosa (RP), which may all be grouped under the heading of RPE65 mutation-associated IRDs, are considered to represent a phenotypic continuum of the same disease.
The RPE65 mutation-associated IRDs with a typical onset between birth and five years of age exhibit several common clinical findings, chiefly night blindness, progressive loss of visual fields, and loss of central vision.
The percentage of patients (with biallelic RPE65 mutations) meeting the World Health Organization (WHO) criteria for blindness increased with age and reached 100% after the age of 40 years.
Given the often severe and early visual loss associated with RPE65 IRDs, other areas of development, including speech, social skills, and behavior, may also be delayed. There are approximately over 6,600 individuals living in the US diagnosed with RPE65 mutation-associated IRDs in 2023.
About HG004
HG004 is a gene replacement therapy drug which uses the recombinant non-adeno-associated virus serotype 2 (non-AAV2) vector to deliver a functional human RPE65 gene to the retina to restore, treat, and prevent blindness of children and adults with RPE65 mutation-associated IRDs.
The extensive preclinical studies demonstrated superior transduction efficiency of the RPE layer and the recovery of the retinal functions when HG004 compared to AAV2-mediated gene replacement therapy through the company's independently-developed Rpe65 gene knockout (KO) murine disease model using the clustered regularly interspaced palindromic repeats (CRISPR) genome-editing system.
The murine disease model is found to mimic the retinal phenotypes and functions of patients with RPE65 mutation-associated IRDs. Based on the head-to-head preclinical comparison study of HG004 and AAV2 at the same dose, the recovery of the retinal functions was increased by 67.6% (HG004) and 35.8% (AAV2 products) when compared to the wild-type mice in the Rpe65 knockout murine model at Week 17 after a single injection, suggesting that HG004 may potentially lower the total vector doses to reduce the risk of AAV vector-associated immunogenicity or ocular adverse events in humans.