CRISPR-Edited HLA Donor Liver Transplant to Reduce Rejection

Organ transplant rejection is primarily driven by immune recognition of donor HLA (human leukocyte antigen) molecules as foreign. Mismatches in HLA-A and HLA-B (class I) in particular are strongly immunogenic and can provoke T-cell mediated graft rejection. HLA class II molecules (HLA-DR, DQ, DP), expressed on donor antigen-presenting cells, can also activate CD4⁺ T cells and contribute to rejection. Current therapy relies on immunosuppressive drugs, which carry significant risks. Preclinical research has shown that genetically "erasing" HLA molecules from donor cells can blunt immune responses: for example, cells with HLA-A, HLA-B, and HLA-DR knocked out via CRISPR elicited little to no T cell proliferation in vitro, indicating greatly reduced immunogenicity. Similarly, in xenotransplant models, triple knockout of genes (including class I and the class II regulator CIITA) in donor animals significantly weakened human T-cell activation and prolonged graft survival. These findings provide a strong rationale that an HLA-edited donor organ could evade the human immune system to a large extent, potentially reducing or delaying rejection.

Gene-Editing of Donor Liver Ex Vivo: In this trial, deceased-donor livers will undergo ex vivo CRISPR-Cas9 genome editing prior to transplantation. The editing targets are HLA-A and HLA-B (to eliminate the major class I alloantigens) and CIITA (class II transactivator, whose knockout abolishes HLA-DR/DQ/DP expression on donor cells). By knocking out HLA-A and -B, while leaving HLA-C expression intact, the goal is to remove the most immunogenic class I molecules yet maintain some HLA presence to mitigate natural killer cell "missing-self" responses. Disabling CIITA will prevent expression of HLA class II proteins, thus reducing CD4⁺ T cell activation against the graft. The CRISPR editing is performed during machine perfusion of the donor liver (a period in which the organ is kept alive outside the body). A CRISPR-Cas9 ribonucleoprotein (Cas9 enzyme complexed with guide RNAs for HLA-A, HLA-B, and CIITA) is delivered into the liver tissue through the perfusion circuit. Editing takes place ex vivo, avoiding direct in vivo gene therapy to the recipient. Before transplantation, the graft is assessed for successful gene knockout (for example, by biopsy immunostaining or flow cytometry to confirm absence of HLA-A/B/DR on the cell surface). Only livers with confirmed high-efficiency editing (e.g. >90% target gene disruption) are used for transplant to ensure maximal immune-evasion benefit.

Inclusion criteria

• Adults aged 16-85 (inclusive) with end-stage liver disease or acute liver failure who are eligible for liver transplantation.
• Require a liver transplant and have been allocated a donor liver graft (from a deceased donor) that will be used in the study after gene editing.
• No immediately available fully HLA-matched donor (since the study targets patients who would otherwise receive an HLA-mismatched organ; standard allocation generally does not consider HLA matching for liver, so most patients will qualify).
• Medically suitable for transplant surgery and able to tolerate standard immunosuppressive therapy (no contraindications to transplant such as uncontrolled infection or other active serious disease that would preclude surgery).
• Informed Consent: Able to understand the investigational nature of the trial and provide written informed consent. Patients (and their legal representatives if applicable) must consent to the use of a genetically modified organ and to long-term follow-up including multiple biopsies and immune monitoring.
• Willingness to comply with all study procedures and availability for the duration of follow-up (including frequent monitoring visits).

Exclusion criteria

• Active uncontrolled infection (e.g., sepsis, active tuberculosis) that would severely increase transplant risk or confound interpretation of immune-related outcomes.
• Uncontrolled HIV or chronic viral infections that are not well-managed. (Note: Patients with hepatitis B or C may be included if adequately treated or under control, as these are common in liver failure, but such patients should not have active, replicating virus at transplant if possible.)
• Multi-organ transplant requirement: Patients needing more than a liver alone (e.g., liver-kidney dual transplant) are excluded, as the trial is only evaluating single organ (liver) outcomes.
• Pregnancy or breastfeeding: Female participants of childbearing potential must have a negative pregnancy test prior to transplant and must agree to use effective contraception. The effects of a gene-edited organ transplant on a fetus/infant are unknown, and immunosuppressive drugs can also harm a pregnancy.
• Severe concurrent illness not related to liver disease that would limit survival to <1 year or make the patient an unsuitable candidate (e.g., advanced heart failure, uncontrolled diabetes with complications, etc.).
• Allergy or hypersensitivity to study-related products: If any components used in the ex vivo gene editing (such as a specific vehicle or enzyme) have known severe allergies in the recipient, they will be excluded. (For instance, although unlikely, if a patient had a documented severe immune reaction to Streptococcus pyogenes Cas9 or similar proteins, they would not be enrolled.)
• Inability to follow the protocol or comply with follow-up: this includes psychiatric, social or logistical factors that would prevent adhering to the intense monitoring schedule (for example, lack of reliable transportation or support).