Epigenome editing

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.

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.