Haematologica study finds Pairidex test detects leukemia relapse earlier

A peer-reviewed Haematologica study found Pairidex’s FusionMRD blood test detected relapse in KMT2A-rearranged acute leukemia weeks to months before standard testing in every relapsing patient with stored samples. The findings could close a major gap in measurable residual disease monitoring for fusion-driven blood cancers.

Why it matters: - Acute leukemia relapse can be missed until the disease is already clinically apparent, limiting treatment options. - The study suggests FusionMRD could give clinicians earlier warning for patients with fusion-driven leukemias that do not have a standard molecular MRD assay. - Blood-based monitoring may reduce reliance on repeated bone marrow biopsies while tracking disease more closely over time.

What happened: - Pairidex announced a peer-reviewed study in Haematologica on personalized digital PCR testing for patients with KMT2A-rearranged acute leukemia. - In every case where patients relapsed and treatment-period samples had been banked, the test detected disease weeks to months before standard-of-care testing. - The study was led by Andrew L. Young, MD, PhD, Pairidex co-founder and chief scientific officer, and a Washington University School of Medicine in St. Louis faculty member. - The technology used in the study is exclusively licensed from Washington University to Pairidex and is now offered as FusionMRD.

The details: - The observational study designed and verified personalized gene fusion assays for 20 patients. - Researchers tested 133 bone marrow or peripheral blood samples collected during or after treatment. - Seven patients with serial samples during initial therapy experienced treatment failure, and FusionMRD detected fusion transcripts before standard testing or clinical progression in all seven. - The median lead time was 92 days, with a range of 36 to 145 days. - In one patient, the blood test was positive 106 days before a bone marrow biopsy detected recurrence by FISH. - A biopsy two weeks earlier had been negative by flow cytometry MRD testing. - In one long-term surveillance case, the test detected recurrence in blood more than two years after diagnosis and months before clinical relapse. - Fusion transcript levels in paired blood and marrow samples were highly concordant, with an R² of 0.99. - Patients whose fusion transcripts became undetectable and stayed negative did not relapse during follow-up. - The study was observational, and results were not returned to patients or physicians. - The authors said larger studies are needed to determine whether earlier detection improves outcomes. - The publication also notes a broader MRD gap: 10% to 20% of acute myeloid leukemia patients who test negative by flow cytometry-based MRD still relapse within a few months. - PCR-based molecular assays are highly sensitive but exist only for a small number of genetic alterations. - KMT2A rearrangements can fuse with dozens of partners, leaving no single standard assay that covers them all. - Hundreds of other oncogenic fusions present the same challenge.

Between the lines: - The results point to a practical path for personalizing MRD monitoring around the exact fusion driving each patient’s leukemia, rather than relying on one-size-fits-all assays. - The work also highlights a commercialization step: Pairidex is moving from validation data toward clinical deployment of a laboratory-developed test. - Because the study was observational and non-interventional, the data support detection performance more strongly than patient-outcome benefit.

What's next: - Pairidex plans to put FusionMRD into the hands of clinicians and continue building evidence for its use in fusion-driven leukemia monitoring. - The company says FusionMRD is a laboratory-developed test run in its CLIA-certified laboratory and has not been cleared or approved by the FDA. - The publication is: Noor A, Cao X, Cox MJ, et al., “Non-invasive personalized fusion measurable residual disease detection in acute myeloid leukemia using digital PCR,” Haematologica, published online July 30, 2026. - More information is available at Pairidex.com.