Dr. Steve Kleiboeker, DVM, PhD is the Vice President of Research and Development and Lab Director at Eurofins Transplant Genomics. Recently, he and his team have worked on launching OmniGraf Liver, a noninvasive tool to help clinical teams monitor transplant health in liver transplant recipients using gene expression and donor-derived cell-free DNA (dd-cfDNA).

Dr. Kleiboeker recently led a webinar to introduce OmniGraf Liver. The information from his presentation is summarized in the article below.

The Unbalanced Paradigm of Immunosuppression

Immunosuppression is a critical factor in post-transplant survival, but current immunosuppression protocols can create unbalanced risks for liver transplant patients. Dr. Kleiboeker points out that if immunosuppression is not adequate, acute rejection can occur. However, the scales can tilt too far in the other direction, leading to complications such as malignancy, infection, CV disease, metabolic syndrome, and rapidly declining GFR.

The burden of these complications can be high. For example, in cases of nephrotoxicity, patients may end up needing dialysis or kidney transplants. That can result in a patient who has already undergone a liver transplant returning to the organ donor wait list and embarking on the expensive and difficult journey of getting a kidney transplant.

Infections impact around 80% of liver transplant patients in the first year, leading to increased hospitalizations and the potential for long-term impacts, and metabolic disorders impact more than half of liver transplant recipients. A third of those impacted by metabolic disorders may deal with cardiovascular incidents, and this can lead to hospitalizations related to stroke or heart attack.

The juggling act related to under- or over-immunosuppression may be partly at fault for the lack of improvement in long-term survival outcomes post-liver transplant. While 1-year survival rates have seen great progress in past decades — increasing from around 66% in 1987 to more than 92% in 2015 — long-term outcomes have not changed significantly in the past 37 years.

OmniGraf Liver: Enhancing Monitoring Through Gene Expression and dd-cfDNA

Clinical teams have traditionally relied on tools such as liver function tests, biopsies, close follow-up, cancer screening, and viral monitoring to help them understand whether immunosuppression is well-balanced. However, many of these tools don’t raise red flags until there are already problems, and biopsies are invasive and expensive.

In more recent years, blood-based biomarkers and gene expression assays were discovered that correlated heavily with acute rejection. A study published in 2022 explored a 59-gene biomarker subset that could distinguish, with promising accuracy, liver transplant recipients with acute rejection as opposed to patients with stable transplants or those experiencing other reasons for graft injury.

Dr. Kleiboeker also discussed donor-derived cell-free DNA, which is produced by the transplanted organ and can be differentiated from the recipient DNA. The levels of dd-cfDNA can help differentiate patients who are headed toward acute rejection from those who are not.

Combining gene expression and dd-cfDNA data can drive even more accurate results that help clinicians proactively understand the nature of graft health. This is what OmniGraf Liver seeks to do.

OmniGraf Performance and Validation

Internal validation of OmniGraf Liver indicates an AUC of 0.8435 based on the Receiver Operating Characteristic Curve Analysis.

When compared to the overall performance characteristics of the assay, the internal validation team found:

• Specificity to be 82%

• Accuracy to be 82%

• Sensitivity to be 80%

• Negative predictive value to be 93%

• Positive predictive value to be 60%

This internal validation data indicates a high level of accuracy in helping to identify potential graft duress and acute rejection — but an even higher accuracy in ruling out AR. The 93% negative predictive value means that if OmniGraf Liver results are negative, it is highly likely there is no acute rejection.

Clinical Application of OmniGraf in Immunosuppression Titration

The level of insight that OmniGraf Liver provides through noninvasive monitoring can help clinical teams better manage immunosuppression balance. It allows teams to move faster through immunosuppression reduction with a lower risk to graft health, supporting more comprehensive positive health outcomes.

A potential immunosuppression titration process with OmniGraf Liver might be:

• A baseline check. Test the OmniGraf score to understand the risk of acute rejection before considering a patient for immunosuppression reduction.

• Make a change. Assuming the risk is low, the clinical team can choose to reduce immunosuppression. The OmniGraf risk score threshold is 50, so clinicians would want to ensure that the score is under 50 before moving forward with this change.

• Follow up. Around a month after the reduction in immunosuppression, use OmniGraf Liver to check for risks. Ensure that the risk score remains below 50 and make further changes from there.

Benefits of Minimizing Immunosuppression With OmniGraf Liver

A randomized study to assess the safety of immunosuppression withdrawal in liver patients indicated that 67% of patients achieved minimization up to 50% of the original dose, and 10 patients achieved minimization to zero. However, 67 of the 95 patients in the study did experience a negative event of some type due to the immunosuppression changes. Of those, 45 had a biopsy, and 71% of those patients did have some level of rejection.

OmniGraf Liver provides ongoing insight into the risks of acute rejection in a manner that allows clinical teams to individualize their approach to post-transplant treatment. It also removes some of the guesswork out of immunosuppression balance, allowing teams to reduce immunosuppression to ward off infections and other complications while keeping an eye on graft function to reduce outcomes such as those demonstrated by the study mentioned above.

Future Directions for Liver Transplant Monitoring With OmniGraf Liver

OmniGraf Liver makes it easy for teams to assess potential rejection risks. The biomarker test requires 15mL of blood in three vials, which can be mailed to the Eurofins Transplant Genomics lab. There, RNA is extracted and measured, and dd-cfDNA is quantified. Results from these tests are put through an algorithm that generates the risk score from 0 to 100, with 50 being the threshold for acute rejection.

The first test for a patient has a turn-around time of 4-5 days; subsequent tests are faster and have a turn-around time of 3-4 days.

This quick access to insights regarding liver transplant function will allow post-transplant treatment teams to continuously improve and personalize immunosuppression, hopefully leading to increasing rates of positive long-term outcomes for liver transplant recipients.

A New Era in Transplant Monitoring

OmniGraf Liver offers a significant advancement in liver transplant care, providing clinical teams with the data they need to make quicker, more accurate decisions about immunosuppression needs for each individual patient. A more data-backed immunosuppression protocol allows teams to enhance survival rates while reducing the risks of complications that create financial and health burdens for patients and hospitals alike.