On September 25, 2026 IASO Biotechnology ("IASO Bio"), a commercial-stage biopharmaceutical company focused on the discovery, development, manufacturing, and commercialization of novel cell therapies and biologics for hematologic malignancies and autoimmune diseases reported that results from a retrospective analysis of FUMANBA-1 — the pivotal registration study of its world’s first fully human BCMA-targeting CAR-T cell therapy product, FUCASO (equecabtagene autoleucel injection, Eque-cel) — were presented as a poster at the 2026 International Myeloma Society (IMS) Annual Meeting[1] (Abstract No.: PA-469). The results showed that durable persistence of FUCASO CAR-T cells in patients (assessed by vector copy number [VCN] in peripheral blood) was associated with sustained minimal residual disease (MRD) negativity and prolonged time to progression (TTP); moreover, patients with del(17p), high tumor burden, and rapidly progressive disease features were more prone to early CAR-T cell clearance and MRD conversion.

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Study Design: A Retrospective Analysis Focused on "MRD Conversion"

Clinical follow-up data have shown that FUCASO can induce deep MRD negativity in patients with relapsed/refractory multiple myeloma (R/R MM), but some patients experience MRD conversion after achieving MRD negativity. To explore the potential mechanisms underlying MRD conversion and to provide hypothesis-generating evidence for optimizing full-course management following CAR-T cell infusion, this retrospective analysis enrolled 102 patients from the FUMANBA-1 study who had achieved MRD negativity. Based on whether MRD conversion occurred during follow-up, patients were divided into a sustained MRD-negative group (n=61) and an MRD-conversion group (n=41), and baseline characteristics as well as peripheral blood vector copy number (VCN) persistence (with the event defined as peripheral blood VCN below the lower limit of detection) were analyzed for both groups. VCN persistence was assessed using the Kaplan-Meier method and unadjusted Cox regression; the hierarchical correlations among time to progression (TTP), duration of MRD negativity, and VCN persistence were assessed using Kendall’s tau-b coefficient. All analyses were hypothesis-generating in nature.

Patients with MRD Conversion Had Higher-Risk Baseline Features and Shorter VCN Persistence

The analysis showed that patients who experienced MRD conversion presented with higher-risk, more rapidly progressive baseline disease characteristics: a higher proportion with del(17p) (26.8% vs 13.1%), a higher proportion of patients with bone marrow plasma cells ≥50% (26.8% vs 11.5%), a shorter median interval from diagnosis to enrollment (31.1 months vs 54.0 months), and a higher proportion receiving bridging therapy (61.0% vs 41.0%). Regarding VCN persistence, median VCN persistence was 272 days in the MRD-conversion group versus 463 days in the sustained MRD-negative group, a difference of approximately 191 days (HR 0.73, 95% CI 0.42–1.26, P=0.2568). Although the sustained MRD-negative group showed a numerical VCN persistence advantage of approximately 191 days, this difference is not sufficient to draw a statistically significant conclusion given the statistical power of the current data.

Correlation analyses revealed a consistent benefit chain of "VCN persistence — sustained MRD negativity — delayed progression": time to progression (TTP) was strongly correlated with duration of MRD negativity (tau-b=0.736, P<0.0001); time to progression (TTP) was moderately correlated with VCN persistence (tau-b=0.306, P<0.0001); and VCN persistence was correlated with duration of MRD negativity (tau-b=0.185, P=0.006).

Conclusion

This analysis suggests that more durable in vivo persistence of FUCASO CAR-T cells is associated with sustained MRD negativity and prolonged time to progression (TTP), supporting peripheral blood VCN persistence as a candidate pharmacodynamic (PD) marker of durable disease control; patients with del(17p), high tumor burden, and rapidly progressive disease are more prone to early CAR-T cell clearance and MRD conversion. These findings are hypothesis-generating in nature and may inform strategies to prolong CAR-T cell persistence as well as the use of CAR-T therapy in earlier lines of treatment.

Professor Lugui Qiu

Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences

"We are very pleased to report this follow-up analysis of FUMANBA-1 focusing on MRD conversion at this year’s IMS Annual Meeting, and the results are encouraging. MRD negativity is an important hallmark of deep response, yet some advanced patients still experience MRD conversion after achieving MRD negativity — an issue of long-standing clinical focus. This analysis suggests that durable in vivo persistence of CAR-T cells may be one of the key factors in maintaining long-term MRD negativity and delaying disease progression; patients with high-risk cytogenetic features and high tumor burden are more prone to early CAR-T cell clearance and MRD conversion. These hypothesis-generating findings point the way for research into strategies to prolong cell persistence, and also support clinical exploration of the value of CAR-T therapy at earlier stages of disease."

(Press release, IASO Biotherapeutics, SEP 25, 2026, View Source;updated-fumanba-1-analysis-of-iaso-bios-fucaso-reveals-that-in-vivo-durable-persistence-of-car-t-cells-is-associated-with-sustained-mrd-negativity-and-delayed-disease-progression-302890352.html [SID1234671095])