Gene editing technologies are moving forward in preclinical development with innovative strategies designed to treat diseases at their root and even reverse them. However, many approaches still struggle to reach target cells or tissues – either they fail to arrive, or their efficacy is low. In vivo therapies face numerous challenges, but despite these hurdles, 2025 has marked a year of remarkable progress.

Viatris Inc. has announced FDA clearance of its IND application for MR-146, an Enriched Tear Film (ETF) AAV gene therapy candidate for the treatment of neurotrophic keratopathy. The company plans to initiate a phase I/II trial in patients with neurotrophic keratopathy in the first half of next year.

Superoxide dismutase 1 (SOD1) mutations were among the first genetic causes identified in familial amyotrophic lateral sclerosis (ALS) and confer a toxic gain-of-function that drives motor neuron degeneration via protein misfolding, oxidative stress, mitochondrial dysfunction and neuroinflammation.

Gene editing can repair mutations that prematurely halt protein synthesis, resulting in incomplete peptides that cause various diseases. However, other approaches achieve the same effect without altering the genome. Startup Alltrna Inc. has developed a strategy based on transfer RNA (tRNA) to bypass the premature stop codons that end early protein translation. The company already has a first clinical candidate that could treat metabolic diseases such as methylmalonemia (MMA) or phenylketonuria (PKU).

Epilepsygtx Ltd. has raised a $33 million series A to fund a phase I/IIa trial of EPY-201, a gene therapy for treating drug-resistant focal epilepsy. EPY-201 uses an adeno-associated viral vector to deliver KCNA1, the gene encoding Kv1.1, a potassium ion channel that modulates neuronal excitability.

Latus Bio Inc. has reported IND clearance by the FDA for LTS-101, a gene therapy candidate to treat the CNS manifestations of late-infantile neuronal ceroid lipofuscinosis type 2 (CLN2) disease. The FDA has also granted orphan drug, rare pediatric disease and fast track designations to LTS-101.

The number of deaths caused by prion diseases reaches about 30,000 annually. Only 5 months pass from the diagnosis of seemingly healthy patients to the fatal outcome of this neurodegenerative condition, and just 1 month until quality of life is completely lost. Removing the brain protein that causes this genetic or infectious disorder could be achieved thanks to new gene-silencing techniques. At a special meeting of the American Society of Gene & Cell Therapy, in “AAV-mediated epigenetic editing for prion disease,” Sonia Vallabh presented not just the data of her research, but the impact of this disease on her family and on herself.

A 24‑week pregnant woman fears for her unborn baby, who is developing with a sacrococcygeal teratoma so large and vascularized that it nearly surpasses the size of the fetus itself. Faced with this threat, surgeons operate inside the uterus in an open procedure that partially exposes the baby to remove the tumor and give the baby a chance to survive until birth. According to scientists presenting at the American Society of Gene & Cell Therapy's special meeting on Breakthroughs in Targeted In Vivo Gene Editing, this could be avoided.

The field of gene therapy is experiencing major advances driven by precise editing technologies, such as base and prime editing, and by the design of increasingly sophisticated vectors to deliver payloads that could reverse the effects of diseases. However, in the transition to in vivo applications many approaches still fail in their attempt to effectively reach target tissues or cells.