“The actual threshold is not the number of molecules. What matters is whether patients and clinicians see measurable and meaningful improvements.”Gaurav Sadnani, Epicerica CEO

ARCI is most commonly caused by mutations in TGM1, the gene encoding transglutaminase 1, an essential enzyme for cross-linking the outermost layer of the skin barrier. The most common mutation is a splice site mutation called c.877-2A>G, which accounts for about one-third of all cases.

In this study, we used eTd-CBE, a cytosine base editor, to restore mutant nucleotides to wild type. A key technical challenge was that the target was located right next to a “bystander” base that had to remain untouched. The researchers exploited the narrow editing window of eTd-CBE to achieve up to 26% on-target editing in patient-derived keratinocytes without detecting bystander editing. This is a feat the authors say is one of the first demonstrations of therapeutic splice site repair using cytosine base editors.

Human skin blocks biopolymers from reaching the living cell layer beneath the stratum corneum. The research team’s solution was clinically approved laser microablation. Short pulses from a commercially available dermatological laser create small, controlled pores that penetrate to a defined depth. Pores close again within 16 hours.

For Sadnani, this laser step is not a bottleneck but a strategic asset. “This procedure can be performed with commercially available lasers that are available at many dermatology centers,” he says. » Dermatologists are already familiar with laser skin treatments, so from a practical point of view, this fits naturally into existing clinical workflows. « Multiple short sessions may be required to cover the entire adult skin surface area of ​​1.5 to 2 square meters, he added. Epithelica has filed a patent covering its core platform.

“The central unresolved issue is durability. Specifically, are we editing stem cell populations that sustain long-term tissue regeneration?”Sarah Hedtrich, University of British Columbia

Laser steps also offer safety features. Targeting the non-vascularized epidermis limits the exposure of the gene editor to the tissue of interest. Using fluorescence imaging, qPCR, and DESI metabolic mass spectrometry imaging, the team found no evidence of systemic distribution of the nanoparticles or gene cargo to any organs, even after repeated administration.

In 3D ARCI disease models built from patient-derived cells, the team achieved on-target genetic correction of approximately 12% on average, reaching 24% in some samples. This corresponds to approximately 3% recovery of normal TG1 enzyme activity. Studies on other sexual dermatitis suggest that restoring wild-type protein levels by just 5-10% can reduce severe symptoms, and Epithelica’s numbers are well within the clinically relevant range.

Durability remains unknown

“The real threshold is not the number of molecules,” Sadnani argues. » What matters is whether patients and clinicians see measurable and meaningful improvement. In dermatology, clinical endpoints are often based on visual scoring and quality of life, as these diseases have a strong psychosocial component. ”

The most important unresolved question is whether treatment can be sustained. Single-cell RNA-seq data showed that approximately 39% of the transfected cells were basal keratinocytes, the layer that contains stem and progenitor cells in the skin. If these cells are permanently corrected, the edited genes can proliferate through natural epidermal turnover, potentially resulting in long-term healing.

Hedtrich is blunt. » I don’t think there are any biological uncertainties that fundamentally prevent First-in-Human clinical trials. A central unresolved question is durability, and in particular whether editing stem cell populations sustain long-term tissue regeneration. ”

But she reframes the stakes. Even if durability proves to be limited, “a therapy requiring repeated administration every few weeks that reliably reverses the clinical phenotype would be a significant improvement over already existing options.”

“Our main focus right now is on ARCI,” says Sadnani. »Prioritizing core assets that balance speed, regulatory pathways, and patient impact provides the best foundation for expansion into additional indications”Gaurav Sadnani, Epicerica CEO

Comprehensive off-target analysis using four independent methods showed that off-target editing was negligible. in vivo Toxicity studies in mice conducted under a protocol agreed with Germany’s Paul Ehrlich Institute found no deaths, body weight changes, skin irritation, significant immune cell infiltration, or systemic cytokine elevations even after repeated doses. The lead LNP formulation did not cause significant immune activation in dendritic cells and showed minimal immune activation compared to comparison formulations including the mRNA vaccine control used for benchmarking purposes.

Epithelica places this therapy within the existing regulatory framework

This treatment is at an unusual crossroads. Topically applied gene editing products are classified as advanced medicines under European law, but they are also products that remain on the skin.

Sadnani sees this as an opportunity. “I don’t think we’re asking regulators to invent a whole new category,” he said, referring to recent times. in vivo Base editing milestones in the liver and retina. He highlights the FDA’s proposed “plausible mechanistic pathway” to consider approval of tailored treatments when there is a clear biological mechanism and early clinical efficacy. »Under this framework, mechanistic plausibility and small cohort efficacy evidence can be combined to form the basis for marketing authorization. ”

The company has received orphan drug designation from both the FDA and EMA for ARCI, which allows for fast-track designation, small trial size, and priority review.

This paper frames the approach as a platform that can be applied to approximately 500 known cases of sexual dermatitis. Different mutations may require different guide RNAs and different base editors, but the delivery system and workflow remain the same.

No other companies have reported yet on site Perform base editing directly in human skin using a localized LNP approach. The closest clinical comparator remains ex vivo Gene therapy and viral gene enhancement strategies in epidermolysis bullosa, such as Krystal Biotech’s HSV-based platform. These approaches require repeated applications or surgical implantation, but none yet combine local delivery with permanent nucleotide modification. Epithelica’s ability to maintain its first-mover advantage will depend not only on data but also on speed.

For now, Epithelica is intentionally focused. “Our main focus right now is ARCI,” Sadnani says. »Prioritizing core assets that balance speed, regulatory pathways, and patient impact provides the best foundation for expansion into additional indications. ”

“Deeper biological questions may remain, but unanswered curiosity is not the same as unanswered risk.”Sarah Hedtrich, University of British Columbia

The deeper strategic question is whether Epithelica should ultimately be valued as a rare disease asset with platform options, or as a delivery platform company whose first indication is ARCI. If the LNP laser workflow proves to be reproducible and safe, the real long-term asset may be the delivery architecture itself, rather than a single mutation that is corrected. This difference will shape both partnership dynamics and future funding.

Funding paves the way for patients

The most pressing bottleneck is capital. Epithelica raises seed round to fund GMP manufacturing and first-in-human formulation. “The big value change is being able to successfully rescue a human patient,” Sadnani said. “But before that, the key capital inflection point is the transition from preclinical research to clinical practice.”

Hedtrich points out that disability is no longer a science. »The main bottlenecks are non-biological. Securing funding for first-in-human clinical trials and navigating the evolving IP environment around CRISPR, which poses real challenges for early clinical applications, particularly in Europe. ”

The patent landscape for CRISPR remains fragmented, with multiple institutions holding fundamental rights, especially regarding basic editing technologies. Freedom of operation, sublicense structures, and geographic patent differences can impact both the cost and speed of clinical entry. For small and medium-sized enterprises, IP strategy is as critical to business as biology. Epithelica plans to remain independent at the seed stage, but is open to partnerships to accelerate delivery to patients.

This study acknowledges its own limitations. Data were generated using immortalized patient keratinocytes rather than primary cells. 3D skin models cannot fully reproduce the complexity of the skin. in vivo human skin. Treating large body surface areas raises questions regarding the cumulative immune response. And the long-term dynamics of edited and diseased cells remain unclear.

Hedtrich makes a distinction. » Deeper biological questions may remain, but unanswered curiosity is not the same as unanswered risk. «

For the roughly 1 to 7 in 100,000 people who suffer from moderate to severe ARCI, the key is whether someone can apply that science to laser-treated skin patches and deliver them to patients. If Epithelica’s preclinical data holds true in humans, it could come sooner than the field expected.

This article is based on the following published research Separate interviews with both Gaurav Sadnani and Sara Hedtrich.