Biomarkers in the U.S.: Initial Results From the TRULO Study

Initial data is now available from the?TRULO study, a 2-year trial using TruGraf and TRAC biomarkers to monitor renal transplant recipients for allograft rejection. The findings suggest that TruGraf's gene expression profile testing may be useful as an alternative to invasive and risky?surveillance biopsies.

Dr. John Friedewald a transplant nephrologist in Chicago, IL, presented interim results as authored by Leca N, Kew C, Westphal S, Karim M, Bunnapradist S, Leeser D, Alhamad T, Von Visger J, Fleming J, Holman J, Weems J, Agboli I, Irish W, and Shihab F at the 2023 European Society for Organ Transplantation (ESOT) Congress. Check out our article to learn more: at the 2023 European Society for Organ Transplantation (ESOT) Congress. Researchers around the globe gather annually at this premier platform for science and education, sharing original research and developments in the field of organ transplantation to advance knowledge and best practices.

A leader in the field of nephrology research, Dr. Friedewald serves as Professor of Medicine and Surgery at Northwestern University in Chicago and Medical Director of Kidney and Pancreas Transplantation at Northwestern Memorial Hospital. He has a particular interest in developing proteogenomic biomarkers for use in transplantation.

What Is the TRULO Study?

The TRULO study was an observational trial evaluating clinical outcomes in renal transplant patients over a 2-year period using biomarkers. A biomarker — or biological marker — is a measurable characteristic in the body that can be used to assess normal biological processes, the presence or progress of disease, or response to treatment.

The?TRULO study focused on two molecular biomarkers:

????????? TruGraf is a blood test that rules out subclinical acute rejection and an alternative to risky and invasive surveillance biopsies. By measuring differentially expressed genes, the test identifies patients who are likely adequately?immunosuppressed.?

????????? Viracor TRAC is a blood test that rules out injury to the transplanted organ (kidney) that could be due to rejection. Next generation sequencing is used to identify the percentage of donor derived cell-free DNA of the donor allograft present in the recipient’s blood sample.

TRULO Study Participants

The TRULO study monitored long-term clinical outcomes of kidney transplant recipients using the two biomarkers, TruGraf and TRAC. By determining the value of these non-invasive surveillance methods, researchers hope to improve care for kidney transplant patients.

There were 2,000 participants enrolled at 50 transplant centers across the United States. Eligible participants were:

????????? Adult kidney transplant patients

????????? At least 3 months post-transplant

-?????? Initially the enrollment was for those who were 2 years post-transplant, but as the study neared completion, it accepted patients 3 months post-transplant.

????????? Had stable serum creatinine

????????? Participants had a mean serum creatinine of 1.34 and mean eGFR of 53.9 ml/min at enrollment.

????????? Treated with any?immunosuppression regimen

The initial results are drawn from a subset of 589 subjects with follow-up over a 1-year period. This cohort was 45.64% female and 54.36% male and had a mean age of 59.37 years. Dr.?Friedewald noted that their ethnicities reflect the transplant population in the United States:

????????????? White: 63.74%

????????????? Black or African American: 25.82%

????????????? Asian: 6.67%

????????????? Other: 7.52%

The standard mean post-transplant enrollment was 4.6 years, with a median of 2.18 years. The 25th percentile was 1.13 years and the 75th percentile was 5.27 years.

The causes of end-stage renal disease in this cohort were?as follows:

????????????? Diabetic Nephropathy: 22%

????????????? HTN Nephrosclerosis: 20%

????????????? Polycystic Kidney Disease: 14%

????????????? Focal Segmental Glomerulosclerosis: 8%

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TRULO Study Methodology

As an observational trial, the TRULO study didn't?set out specific treatments or management plans for participants. Patient care is delivered according to local standards. The study takes place over a 2-year period, with patients receiving Omnigraf testing — both TruGraf and TRAC — every 3 months. Study sites were encouraged to monitor patients per the algorithm, and clinicians performed additional testing if there were concerns of organ rejection.

The goal of the study was to provide long term data regarding the benefits of using Trugraf and TRAC surveillance of stable kidney transplant recipients to rule out subclinical rejection. The primary endpoints used to evaluate outcomes were:

????????? Composite of the first occurrence of biopsy-proven acute rejection (from a for-cause biopsy) during the primary study period, or

????????? Decrease in eGFR > 10 ml/min at the end of the 2-year primary study period

TRULO Study Results

Dr. Friedewald began by presenting two sets of statistics, the first summarizing TruGraf test results and the second looking at TRAC test results among the 589 patients.

In the first set of data, there's an association between multiple positive?TruGraf tests “(Not-TX)” and decline in renal function over a 12-month period. This?suggests that TruGraf biomarkers can be used to identify kidney transplant patients at risk of losing kidney function.?Negative TruGraf results, or TX results, correlate highly with a negative biopsy.?

Delving further into the data, Dr. Friedewald noted that subjects were broken into three groups based on testing during the 12-month period:

????????? Patients with normal test results??

????????? Patients with one abnormal (not-TX) test

????????? Patients with two or more abnormal (not-TX) tests

Within these groups, subjects were further divided according to their baseline eGFRs. Researchers found that after 1-year, renal function was impacted by both baseline?GFR and the number of positive TruGraf tests. The more positive TruGraf tests patients had, the bigger the loss in GFR, especially among those who started with a higher?GFR.

????????? In the patient group with no history of positive TruGraf tests, there was a 3.67% increase in GFR in those with a baseline GFR of 40. Those with a baseline GFR of 80 experienced a 1.7% decrease.

????????? In the patient group with one positive TruGraf test, there were decreases of 3.8% to 4.2% in GFR after 1 year.

????????? In the patient group with two or more positive TruGraf tests, there was a decrease of 8.7% in those with a baseline of 40 GFR and 13% in those with a baseline of 80 GFR.

"The biggest drops in?GFR were in patients that had the best renal function to begin with and two or more not-TX results," explained Dr. Friedewald.?

A similar analysis was performed with TRAC tests, which quantify the amount of donor-derived cell-free DNA in a patient's plasma to determine organ rejection. A result greater than or equal to 0.7% is considered a positive test. Patients were again divided into groups depending on the number of positive TRAC tests and baseline eGFR. There was no association between positive TRAC tests and renal function in this cohort over the 12-month period.

In summary, among a population of kidney transplant recipients beyond 2 years post-transplant, there is an association between multiple positive TruGraf tests and a greater decline in kidney function from baseline.

"The results support the theory that TruGraf gene expression testing has utility in chronic surveillance as a prognostic test for clinical outcomes, particularly loss of GFR,"?Dr. Friedewald noted.?

Implications for Transplant Recipients

Kidney transplant recipients must be monitored for allograft rejection, but there are limitations with current surveillance protocols (Rumpler et al., 2023). Standard approaches involve serial biopsies, which can be expensive and highly invasive, and watching for signs of organ rejection that might not appear until there's already been organ damage.?

Molecular biomarkers offer a less invasive monitoring practice than surveillance biopsy-based methods. TruGraf and TRAC tests may help improve care as surveillance tools to assess the presence of subclinical rejection. These test may also offer guidance of when to perform for-cause biopsies.

As noted by Rumpler et al, molecular advances can help identify subclinical injuries earlier and?improve patient quality of life with less invasive approaches. Clinicians then have more options for early intervention, before there are additional complications. As knowledge in the field expands, new protocols can be developed to ideally improve outcomes, "reducing costs,?extending graft survival, and improving patient quality of life." Multiple tests can provide a better picture of overall health, especially when data is processed by machine learning algorithms.

What's Next?

Once completed, the TRULO study will offer a more accurate picture of kidney transplant health, as Trugraf more strongly detects cellular rejection whereas TRAC more strongly detects antibody mediated rejection.

Following up with the TRULO study, researchers are expanding current knowledge with the SurVeil clinical trial, also launching in the United States. In this study, 600 transplant patients will be randomized to one of two patient management approaches — one with biomarker monitoring and one without biomarker monitoring. Interventions will be based on the biomarker test results.

In addition to using both TruGraf and TRAC rejection testing, this trial incorporates infectious disease testing through TRAC-ID, detecting DNA viruses such as Epstein-Barr, cytomegalovirus, and BK virus. This can help optimize immunosuppression. Clinicians may?increase immunosuppression when rejection biomarkers are positive and decrease it when there's evidence of viral replication, avoiding over-immunosuppression.

Transplant?Genomics aims to improve transplant outcomes for recipients through non-invasive treatment options. Learn more about Transplant Genomics today, or read the full TRULO Abstract here.

Citations

1. Rumpler MJ, McCloskey C, Lawrence C. A New Era in Post-Transplant Monitoring. Association for Diagnostics and Laboratory Medicine. April 1, 2023. Accessed October 7, 2023. https://www.aacc.org/cln/articles/2023/april/a-new-era-in-post-transplant-monitoring