ION582 is an investigational antisense oligonucleotide (ASO) developed by Ionis Pharmaceuticals and delivered by intrathecal injection. It is designed to inhibit the UBE3A antisense transcript (UBE3A-ATS), allowing the normally silenced paternal copy of the UBE3A gene to be expressed in neurons. In the Phase 1/2 HALOS study, 97% of participants in the medium and high dose groups showed improvement on the Angelman Syndrome Clinical Global Improvement Change scale, with consistent benefits across communication, cognition, and motor function. The FDA granted Breakthrough Therapy designation in 2025, and the pivotal Phase 3 REVEAL trial is now enrolling.

GTX-102 (apazunersen) is an investigational antisense oligonucleotide (ASO) developed by Ultragenyx and delivered via intrathecal administration. It targets the UBE3A antisense transcript (UBE3A-AS) to prevent silencing of the paternally inherited UBE3A allele and reactivate expression of the deficient protein. The pivotal global Phase 3 Aspire study completed enrollment in July 2025 with approximately 129 children ages 4 to 17 with a genetically confirmed full maternal UBE3A deletion; results are expected in the second half of 2026. A companion Aurora study is evaluating GTX-102 in additional genotypes and age groups. GTX-102 has received Breakthrough Therapy, Orphan Drug, Rare Pediatric Disease, and Fast Track designations from the FDA.

Rugonersen is an investigational antisense oligonucleotide (ASO) originally developed by Roche and licensed to Oak Hill Bio in April 2025. It is designed to boost expression of the paternal copy of the UBE3A gene by reducing levels of the UBE3A antisense transcript. In Roche’s open-label Phase 1 TANGELO study, rugonersen demonstrated encouraging effects on multiple clinical measures and on EEG delta power (a pharmacodynamic biomarker of brain function) compared to natural history. Oak Hill Bio plans to initiate a pivotal Phase 3 trial.

NNZ-2591 is an oral synthetic analog of cyclic glycine proline (a peptide naturally found in the brain) being developed by Neuren Pharmaceuticals. It is designed to restore normal communication between brain cells in conditions where neuronal signaling is impaired. In Phase 2 trial results announced in August 2024, NNZ-2591 was well tolerated as a twice-daily oral solution and produced statistically significant improvements in communication, behavior, cognition, and motor abilities in children with Angelman syndrome. The therapy has received Orphan Drug designation from both the U.S. FDA and the European Medicines Agency.

MVX-220 is an investigational gene therapy developed by MavriX Bio that delivers a functional copy of the UBE3A gene to neurons using an adeno-associated virus (AAV) vector administered via a single intra-cisterna magna injection. It is designed to restore UBE3A expression at the source of the disorder and may be applicable to multiple Angelman genotypes, including deletion, uniparental disomy, and imprinting center defects. Originally developed at the University of Pennsylvania with funding from FAST, MVX-220 has received FDA Fast Track and Orphan Drug designations. The Phase 1/2 ASCEND-AS trial dosed its first patient in November 2025 — the first clinical evaluation of a gene therapy for Angelman syndrome.

Blarcamesine (ANAVEX 2-73) is an investigational oral small molecule developed by Anavex Life Sciences that activates the sigma-1 receptor (SIGMAR1). Sigma-1 receptor activation is intended to restore neuronal cellular homeostasis and enhance autophagy, processes that support healthy brain function. Anavex has reported solid preclinical data supporting blarcamesine as a potential treatment for Angelman syndrome and has received a U.S. patent covering its use in Angelman and related neurodevelopmental disorders. The therapy is being studied in multiple indications including Alzheimer’s disease, Rett syndrome, and Parkinson’s disease dementia.

OPC A-186 is a preclinical oligodendrocyte precursor cell (OPC)-based therapy under investigation at Brown University. Like the broader OPC program, it aims to address the abnormal myelination patterns observed in Angelman syndrome by restoring the function of cells responsible for producing myelin in the brain. Improved myelination may help support neuronal signaling and brain development.

HLX-0553 is an investigational oral small molecule being developed by Healx for Angelman syndrome. Healx uses an AI-driven drug discovery platform to identify and reposition small molecules for rare diseases. HLX-0553 is in preclinical development as a potential treatment for Angelman syndrome.

Researchers at UC Davis are developing artificial transcription factors (ATFs) based on engineered zinc finger proteins to treat Angelman syndrome. These designer proteins can be programmed to bind specific DNA sequences and activate gene expression. In Angelman syndrome, ATF-ZF technology may be used to reactivate the silenced paternal UBE3A gene in neurons, restoring UBE3A protein levels. This program is in preclinical development.

CourageAS is developing a CRISPR-based gene-editing approach for Angelman syndrome. CRISPR technologies allow precise modification of DNA sequences, and in the context of Angelman syndrome may be used to activate the silenced paternal UBE3A gene or correct mutations in the maternal copy. This preclinical program is exploring CRISPR as a potential one-time, disease-modifying therapy.

Denali Therapeutics is developing an investigational antisense oligonucleotide (ASO) for Angelman syndrome using its proprietary Oligonucleotide Transport Vehicle (OTV) platform. The OTV platform is designed to improve delivery of ASOs into the brain by leveraging transferrin receptor-mediated transport across the blood-brain barrier. This approach may allow for less invasive administration compared to intrathecal injection. The program is in preclinical development.

Transformatx Biotherapeutics is developing a hematopoietic stem cell (HSC) gene therapy approach for Angelman syndrome. HSC gene therapy involves modifying a patient’s own blood-forming stem cells to express a functional copy of a missing or deficient gene, which is then reintroduced into the patient. This preclinical program is exploring whether modified HSCs can deliver functional UBE3A protein to the central nervous system.

Researchers at the University of North Carolina are investigating a CRISPR-Cas9 gene-editing approach to treat Angelman syndrome. Rather than delivering a replacement gene, CRISPR-based therapies aim to directly modify or activate the existing paternal UBE3A gene that is naturally silenced in neurons. This preclinical program seeks to provide a potentially permanent correction of the underlying genetic defect.

Researchers at the University of North Carolina are developing a dual-isoform UBE3A gene therapy using an adeno-associated virus (AAV) vector. UBE3A is naturally produced in two main isoforms in neurons, and delivering both forms may better recapitulate normal protein function than restoring only one. This preclinical program aims to provide a one-time gene therapy that addresses the underlying genetic cause of Angelman syndrome.

Brown University researchers are exploring a novel oligodendrocyte precursor cell (OPC)-based approach for Angelman syndrome. Oligodendrocytes are the cells that produce myelin, the protective sheath around nerve fibers that allows efficient electrical signaling in the brain. Disrupted myelination has been observed in Angelman syndrome, and therapies targeting OPCs may help restore healthy myelin formation and improve neuronal communication. This program is in preclinical development.

Researchers at Brown University are investigating Brain-Derived Neurotrophic Factor (BDNF) as a therapeutic approach for Angelman syndrome. BDNF is a protein that supports the growth, survival, and function of neurons. Reduced BDNF signaling has been implicated in the cognitive and motor deficits seen in Angelman syndrome, and restoring BDNF activity may help improve synaptic function and learning. This program is in preclinical development.

ETX201 is an investigational gene therapy developed by Encoded Therapeutics that uses an AAV9 vector to deliver a vectorized microRNA (miRNA) designed to reduce expression of the UBE3A antisense transcript (UBE3A-ATS) and unsilence the paternal UBE3A allele in neurons. In non-human primate studies, ETX201 was well tolerated following a single intracerebroventricular administration and produced dose-dependent upregulation of paternal UBE3A across multiple disease-relevant brain regions. Following FDA guidance, Encoded has initiated IND-enabling studies to support a potential IND filing.

This preclinical program represents a collaborative effort across multiple institutions — the University of Pennsylvania, UNC-AskBio, Bamboo-Pfizer, and StrideBio-Sarepta — to develop adeno-associated virus (AAV) gene therapies for Angelman syndrome. AAV-based gene therapies aim to deliver a functional copy of the UBE3A gene directly to neurons in a single treatment, potentially providing long-lasting restoration of the protein that is missing or deficient in Angelman syndrome. These programs are at varying stages of preclinical development.

BIO017 is an investigational cannabidiol (CBD)-based therapy developed by Biom Therapeutics for Angelman syndrome and other rare epilepsies. Preclinical studies in an Angelman mouse model showed that BIO017 reduced the frequency and severity of induced seizures and normalized abnormal EEG patterns. The therapy received Orphan Drug Designation from the FDA in 2021 — the first cannabinoid-based candidate for Angelman syndrome to receive this status. Biom is working to advance BIO017 toward clinical trials.

UNC-Pinnacle Hill is conducting discovery-stage research into small molecule therapies for Angelman syndrome. Small molecule drugs offer advantages including oral administration, broad distribution throughout the brain, and well-established manufacturing processes. This early-stage program is exploring novel chemical compounds that may help address the underlying biology of Angelman syndrome.

Researchers at the Keck Graduate Institute are developing a cell-penetrating peptide approach to deliver CRISPR-based gene editing machinery for Angelman syndrome. Cell-penetrating peptides may offer a non-viral delivery method for CRISPR components, potentially reducing immunogenicity concerns associated with viral vectors. This early-stage program is exploring the feasibility of peptide-based CRISPR delivery to neurons.

Researchers at the Keck Graduate Institute are exploring enzyme replacement therapy for Angelman syndrome. Because UBE3A is an enzyme (a ubiquitin ligase), directly supplying functional UBE3A protein to neurons could potentially compensate for the deficient enzyme activity that causes Angelman syndrome. This discovery-stage program is investigating approaches to deliver functional UBE3A protein to the central nervous system.

Researchers at the University of California San Francisco are developing a CRISPR activation (CRISPRa) approach for Angelman syndrome. Unlike traditional CRISPR which cuts DNA, CRISPRa uses a modified Cas9 enzyme to activate gene expression without altering the underlying DNA sequence. In Angelman syndrome, CRISPRa may be used to reactivate the naturally silenced paternal UBE3A gene in neurons. This program is in discovery-stage research.