ExPeCT™ anti-CD19 (obe-cel) CAR T Assay
Obe-cel, also marketed as Aucatzyl,® is a second-generation anti-CD19 chimeric antigen receptor (CAR) T-cell therapy used to treat adults with relapsed or refractory B-cell acute lymphoblastic leukemia (B-ALL). It was developed with a unique "fast-off" mechanism designed to reduce toxicity, such as cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS), compared to other CAR T-cell therapies. Obe-cel has received approval from regulatory bodies including the U.S. Food and Drug Administration (FDA) and the European Commission. Eurofins Viracor has developed and validated a multiplexed quantitative real-time PCR (qPCR) assay targeting the chain variable fragment (4-1BB) for the longitudinal monitoring of CD19-directed CAR T-cell therapy.
Clinicians need more than indirect markers - they need certainty. Our PCR assay delivers precise, real-time insights into CAR T-cell (obe-cel) engraftment and persistence, empowering them to predict outcomes, intervene early, and optimize patient care. Unlike B-cell aplasia monitoring, this assay provides direct, quantitative evidence of therapeutic activity, potentially ensuring patients stay on the path to durable remission.
About test
The successes with chimeric antigen receptor (CAR) T-cell therapy involving patients with pre-B cell acute lymphoblastic leukemia (ALL) or B cell lymphomas have revolutionized anticancer therapy, providing a potentially curative option for patients who are refractory to standard treatments. CD19-targeted CAR T-cells, which have been engineered to recognize the CD19 (specifically the 4-1BB region) cell surface molecule of malignant B cells, show remarkable efficacy in patients with B cell acute lymphoblastic leukemia. Some patients relapse due to the CAR T therapy not persisting in the body, leading to antigen loss, tumor escape (frameshift mutation), or exhaustion.
In the clinical setting, long-term remission in patients with hematological malignancies is associated with sustained persistence of CAR T-cells. In the clinical oncology setting, CAR T-cell expansion and persistence correlates with response and attaining remission in patients. Because of this observation, establishing a reliable and direct method of tracking CAR T-cell numbers is particularly important, not only in the estimation of effectiveness of CAR T-cell therapy, but in terms of evaluation in post-infusion monitoring. Serious side effects of clinical CAR T-cell therapy have been noted, one of the most severe being cytokine release syndrome (CRS) and is associated with CAR T-cell expansion in vivo. In addition, a major concern for recipients of allogenic CAR T-cells is GvHD.
The persistence/expansion of CAR T-cells is key for determining anti-tumor efficacy, which depends on several factors such as structure of CAR T therapeutic, the manufacturing process, the lymphodepletion regimen, the infused cell phenotype, tumor burden, and disease. Persistence of CAR T-cell population is considered a critical factor of anti-tumor efficacy (therapy effectiveness).
Understanding the limitations of anti-CD19 CAR T-cell therapy is critical to realizing the full potential of this treatment approach. Growing experience with these agents has revealed that remissions may be brief in a substantial number of patients owing to poor CAR T-cell persistence and/or cancer cell resistance resulting from antigen loss or escape. The Viracor ExPeCT™ anti-CD19 (obe-cel) CAR T expansion and persistence assay is an adjunct monitoring tool to evaluate and validate the efficacy of anti-CD19 (obe-cel) CAR T therapy. CAR T-cells are regulated as a gene therapy product under the FDA’s framework for biological products.
ProcedureExtraction of genomic acid from whole blood specimen followed by PCR amplification of CAR and Rnase P targets using real-time PCR methods. An internal control is added to ensure that extraction was performed correctly and that the PCR reaction was not inhibited.
SpecificityViracor’s ExPeCT anti-CD19 (obe-cel) CAR T Expansion and Persistence Monitoring qPCR assay is not expected to cross react with human genomic DNA or commensal organisms present in whole blood specimens, as determined by in silica specificity analysis.
Specificity against human genomic DNA was demonstrated experimentally during validation, with no CAR vector signal detected in negative whole blood specimens.
24 hours from receipt of specimen, performed Monday - Saturday
| Specimen Type | Test Code | CPT Code | NY Approved | Volume | Assay Range | Special Instructions |
|---|---|---|---|---|---|---|
| whole blood | 33566 | 80299 | No | 2 mL (min 0.5 mL) |
N/A |
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Ship Monday through Friday. Friday shipments must be labeled for Saturday delivery. All specimens must be labeled with patient's name and collection date. A Eurofins Viracor test requisition form must accompany each specimen. Multiple tests can be run on one specimen. Ship specimens FedEx Priority Overnight® to: Eurofins Viracor, 18000 W 99th St. Ste, #10, Lenexa, KS 66219.
Causes for RejectionSpecimens beyond their acceptable length of time from collection as listed in the specimen handling.
Specimens are approved for testing in New York only when indicated in the Specimen Information field above. The CPT codes provided are based on Eurofins Viracor’s interpretation of the American Medical Association's Current Procedural Terminology (CPT) codes and are provided for informational purposes only. CPT coding is the sole responsibility of the billing party. Questions regarding coding should be addressed to your local Medicare carrier. Eurofins Viracor assumes no responsibility for billing errors due to reliance on the CPT codes illustrated in this material.
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- The Leukemia & Lymphoma Society. Immunotherapy Facts. https://www.lls.org/booklet/immunotherapy. Revised December 2019. Accessed October 19, 2021
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Pathology. 2021 Apr;53(3):408-415. doi: 10.1016/j.pathol.2021.02.002. Epub 2021 Mar 5. - Evaluation of commercially available CAR detection reagents…(ASH Abstract 2367) Hussain, R., Farag, Y., Patel, A., Srinagesh, H., Muffly, L., Sahaf, B., Miklos, D., Ferrari, M., Day, W., & Lao Sirieix, P. (2025). Evaluation of commercially available chimeric antigen receptor (CAR) detection reagents for monitoring of CAR T cell expansion and persistence in patients treated with obecabtagene autoleucel (obe cel) [Conference abstract]. ASH Annual Meeting, Abstract 2367
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Roddie C, Sandhu KS, Tholouli E, et al. Obecabtagene autoleucel in adults with B cell acute lymphoblastic leukemia. N Engl J Med. 2024;391(23):2219 2230. doi:10.1056/NEJMoa2406526 - Roddie C, Sandhu KS, Tholouli E, et al. Safety and efficacy of obecabtagene autoleucel (obe cel, AUTO1), a fast off rate CD19 CAR, in relapsed/refractory adult B-cell acute lymphoblastic leukemia (r/r B ALL): Top line results of the pivotal FELIX study. Presented at: ASCO Annual Meeting; 2023.-a-fast-off-rate-cd19-car-in-relapsed.pdf)