Epigenome editing

01Overview and value chain

Markers: [EC: ATMP Regulation & GMO Directive 2001/18/EC | OECD: bio-pharma | Regulator: FDA (US), EMA (EU), NMPA (CN)]

Epigenome editing regulates gene expression — activating or silencing a target gene — by rewriting DNA methylation and histone marks rather than the underlying DNA sequence, most commonly by fusing catalytically dead Cas9 (dCas9) to an epigenetic enzyme domain (a DNA methyltransferase, demethylase or histone acetylase) or by using zinc-finger proteins as an alternative DNA-binding scaffold. Tune Therapeutics’ TEMPO platform produced the clearest 2026 clinical proof point: TUNE-401, an intravenously delivered LNP-RNA epigenetic silencer, reported positive Phase 1b/2a data at EASL 2026 as a first-in-class epigenetic therapy for hepatitis B. Chroma Medicine has published its RENDER platform for transient delivery of programmable CRISPR epigenome editor ribonucleoproteins and holds patent filings covering epigenetic-editing compositions that modify epigenetic state without altering the DNA sequence. Sangamo Therapeutics, working with zinc-finger transcription factors rather than dCas9, has partnered with Genentech to develop an epigenetic Alzheimer’s therapy and holds patent filings on zinc-finger repressors targeting alpha-synuclein for neurological disease. Because a durable epigenetic mark can be inherited by daughter cells through subsequent divisions, a single administration can in principle produce a long-lasting therapeutic effect without permanently altering the genome.

The key directions of epigenome editing are:

1. Gene silencing (CRISPRi-style): fusing dCas9 to a KRAB repressor domain, alone or combined with a DNA methyltransferase (DNMT3A), to durably switch off a disease-driving gene such as a hepatitis B viral promoter or PCSK9.
2. Gene activation (CRISPRa-style): fusing dCas9 to activator domains (VP64, p65, RTA) to turn on a therapeutic or tumor-suppressor gene without inserting new DNA.
3. Zinc-finger epigenetic repression: using engineered zinc-finger proteins, rather than dCas9, as the DNA-binding scaffold for a repressor domain — Sangamo’s approach to targets like alpha-synuclein.
4. Multiplex and reversible control: simultaneously regulating dozens of genes with a guide-RNA pool, or using light-sensitive mediator proteins (optoepigenetics, e.g., CRY2/CIB1) for spatiotemporal control of methylation.

Sectoral value chain

[Chromatin Mapping & Target Selection] ──> [dCas9-Effector Fusion Design] ──> [Epi-Editor mRNA/gRNA Production]
                                                                                        │
                                                                              (Delivery to target nuclei)
                                                                                        │
                                                                                        ▼
[Expression & Methylation Stability Control] <─── [DNA Methylation at Target Locus]

Value chain levels

Cross-cutting technologies of the sector:

• Multiplex epigenetic editing: simultaneously regulating expression of dozens of genes with a guide-RNA pool to reprogram cellular phenotypes without the chromosomal-aberration risk of DNA-cutting approaches.
• Optoepigenetics: light-sensitive mediator protein pairs (e.g., CRY2/CIB1) that give spatiotemporal control over DNA methylation using laser illumination.
• Deactivated Cas9 (dCas9, D10A/H840A): a catalytically “dead” Cas9 variant that binds DNA tightly without introducing single- or double-strand breaks, serving as the universal DNA-targeting scaffold for epigenetic effector domains.

02US

The US leads the commercial epigenetic-therapy sector, with venture-funded startups advancing the first clinical epigenetic silencers and established gene-editing companies extending into epigenetic mechanisms.

clinical epigenetic silencers, zinc-finger epigenetic platforms, FDA durability requirements

• Tune Therapeutics: its TEMPO platform produced TUNE-401, an IV-delivered LNP-RNA epigenetic silencer that reported positive Phase 1b/2a proof-of-concept data at EASL 2026 as a first-in-class epigenetic therapy for hepatitis B.
• Chroma Medicine: has published its RENDER platform for transient delivery of programmable CRISPR epigenome editor ribonucleoproteins and holds patent filings on epigenetic-editing compositions and methods.
• Sangamo Therapeutics: uses zinc-finger transcription factors rather than dCas9 as its DNA-binding scaffold, partnering with Genentech to develop an epigenetic Alzheimer’s therapy and holding patent filings on zinc-finger repressors targeting alpha-synuclein.
• FDA durability requirements: the FDA requires evidence that an epigenetic gene “knockdown” does not spontaneously revert for months after treatment ends, a core evaluation criterion specific to this modality.

03CN

China is pursuing epigenome editing in parallel across agriculture and biomedicine, with academic institutions driving both crop trait modification and inherited-disease research.

agricultural trait editing without DNA change, epigenetic inheritance research, hepatitis B silencing pilots

• Tsinghua University: conducts epigenetic-editing and inheritance research relevant to congenital conditions such as muscular dystrophy, alongside China’s broader academic epigenetics research base.
• Agricultural applications: Chinese agricultural universities have produced crops with epigenetically altered flowering time and drought tolerance without changing the underlying DNA sequence, easing the ethical/regulatory approval path relative to conventional GMOs.
• Clinical pilots: Chinese clinical centers are conducting pilot studies of epigenetic suppression of hepatitis B virus (HBV) replication in patients’ liver cells, paralleling the hepatitis B focus seen in US clinical programs.

04EU

The EU’s contribution centers on academic gene-therapy institutes extending epigenetic tools into cell therapy and neurobiology, under an EMA framework focused on off-target methylation risk.

CAR-T epigenetic engineering, gene-therapy manufacturing scale-up, EMA off-target methylation scrutiny

• San Raffaele Telethon Institute for Gene Therapy (SR-Tiget, Italy): a leading European gene-therapy research institute exploring epigenetic editing to improve CAR-T cell function (reducing T-cell exhaustion), and in 2026 announced a manufacturing-scale-up collaboration with Cytiva to address gene-therapy production bottlenecks.
• Horizon Europe-funded neurobiology consortia: European groups, particularly in Italy and Germany, are developing epigenetic tools for neurological indications such as epilepsy and chronic pain.
• EMA regulatory focus: EMA places particular scrutiny on global off-target DNA methylation risk, requiring whole-genome bisulfite sequencing (WGBS) to map the entire cell methylome after epigenetic therapy.

05Leading companies and research institutes

06Tech stack and innovations

Modern epigenome-editing production rests on the following technology stack:

1. KRAB-DNMT3A-DNMT3L hybrid domains:
   • A triple catalytic complex that provides synergistic, durable DNA methylation with high stability, the core mechanism behind long-lasting gene-silencing effects like TUNE-401’s hepatitis B approach.
2. Deactivated Cas9 (dCas9) scaffolds:
   • A catalytically “dead” Cas9 variant (carrying D10A/H840A mutations) that binds DNA tightly without cutting it, serving as the universal targeting module onto which activator or repressor domains are fused.
3. Bisulfite sequencing (BS-seq) for methylation verification:
   • Converting unmethylated cytosines to uracil before sequencing lets researchers quantify the fraction of methylated CpG sites at the target locus, the standard method for confirming an epigenetic edit took hold.

07Value chains and production pipelines

Pipeline for validating stability of target-gene epigenetic silencing

┌───────────────────────────┐      ┌───────────────────────────┐
│ 1. sgRNA design against   │ ───> │ 2. Transfection with       │
│    target gene promoter    │      │    dCas9-KRAB-DNMT3A       │
└───────────────────────────┘      └───────────────────────────┘
                                                 │
                                                 ▼
┌───────────────────────────┐      ┌───────────────────────────┐
│ 4. Bisulfite sequencing   │ <─── │ 3. Cell harvest at 72h &  │
│    for methylation         │      │    genomic DNA extraction │
└───────────────────────────┘      └───────────────────────────┘
              │
              ▼
┌───────────────────────────┐      ┌───────────────────────────┐
│ 5. Passaging cells for    │ ───> │ 6. Final silencing check  │
│    30 generations          │      │    by RT-qPCR              │
└───────────────────────────┘      └───────────────────────────┘

Stage 1: Target design

sgRNAs are designed against CpG islands in the promoter region of the target gene (e.g., PCSK9 for cholesterol reduction).

Stage 2: Editor delivery

Target cells (e.g., hepatocytes) are transfected with mRNA encoding the dCas9-KRAB-DNMT3A fusion protein together with the sgRNA.

Stage 3: DNA extraction

Cells are harvested three days later (after the editor mRNA has degraded) and genomic DNA is extracted using commercial kits.

Stage 4: Methylation analysis

Bisulfite conversion (converting unmethylated cytosine to uracil) followed by sequencing of the target locus quantifies the fraction of methylated CpG sites.

Stage 5: Heritability test

Edited cells are passaged for 30 days (roughly 30 division cycles) in the absence of the epi-editor to test whether the silencing persists without continued treatment.

Stage 6: Expression control

RNA is extracted and RT-qPCR confirms stable transcriptional silencing of the target gene, with expression expected to remain below 10% of baseline.