Kharfan-Dabaja, M.

Abstract Chimeric antigen receptor (CAR)-T cell therapy has revolutionized the treatment of B-cell malignancies. Despite the clinical success of CD19-targeted approaches, relapsed/refractory (R/R) disease—often driven by antigen loss or immune escape—remains a major challenge. To overcome this, we developed a novel CAR-T cell therapy targeting BAFF-R, a receptor consistently expressed in chronic lymphocytic leukemia (CLL) and other B-cell malignancies. We developed a new anti-BAFF-R monoclonal antibody and engineered the MC10029 CAR construct using its scFv. Antigen-specific cytotoxicity was validated in both in vitro and in vivo models, including Nalm-6 (leukemia) and Z138 (lymphoma), and CD19-knockout tumor cells to model (R/R) disease. MC10029 CAR-T cells were generated from healthy donors and CLL patients, and their cytotoxicity was evaluated against MEC-1, a CLL cell line, as well as autologous CLL patient tumor samples. These studies demonstrated potent and specific antitumor efficacy. We transitioned to clinical-grade production, using GMP-compliant lentivirus to manufacture MC10029 CAR-T cells under regulatory guidelines. With FDA IND approval, we initiated a Phase 1 clinical trial to evaluate safety and dosing. Our first patient, treated with a low-dose, single infusion, achieved a complete metabolic response within 2 months. The therapy is well tolerated, with no severe advent events such as cytokine release syndrome or neurotoxicity, supporting both the safety and efficacy of the therapy. Conclusion: This study represents Mayo Clinic’s first homegrown CAR-T cell therapy, developed entirely in-house—from antibody discovery and CAR design to GMP manufacturing and clinical trial—marking a significant step toward personalized, next-generation immunotherapy for B-cell malignancies. Citation Format: Yan Luo, Shaohua Guo, Yaqing Qie, Martha E. Gadd, Tanya Hundal, Hemant S. Murthy, Mohamed A. Kharfan-Dabaja, Hong Qin. From gene to bedside: Mayo Clinic’s first-in-house BAFF-R CAR-T [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3719.

Abstract Several allogeneic CAR T-cell therapies are in clinical trials to evaluate safety, many of which rely on CRISPR/Cas-based genome editing. However, the Cas enzyme’s random repair mechanism elevates the risk of undesired, off-target effects, posing a challenge for safe allogeneic CAR T-cell generation. To mitigate the risk of therapy-related oncogenesis, we sought to pursue an alternative safe strategy to manufacture allogeneic CAR T-cells distinct from the preexisting ones in the clinic. We have developed a CRISPR RNA (crRNA) targeting T-cell receptor beta constant (TRBC) gene, which in conjunction with AsCas12a Ultra enzyme, causes site-specific editing by eliciting a predictable microhomology-mediated end joining (MMEJ) DNA repair pathway, which mitigates off-targeting risk. Targeted amplicon sequencing was employed to evaluate off-targeting and repair mechanisms. Graft versus host alloreactivity as well as CAR T persistence was evaluated using immunocompromised mice. In vivo tumor challenge study was conducted for over 3 months. Engraftment confirmation was done using immunohistochemistry and flow cytometry. Interestingly while evaluating the edited T-cells, we sequestered a unique T-cell population that showed TCR disruption yet remained CD3-positive and did not cause in vivo alloreactivity. These CD3-Retained, Allogeneically Functioning T-cells (CRAFT-cells) showed a similar growth rate as unedited T-cells and were then used as a platform to produce CD19-targeted CAR T-cells and BAFF-R-targeted CAR T-cells. When compared to the standard CD3-disrupted allogeneic CAR T-cells, CRAFT CAR T-cells displayed an equally robust cytotoxicity while possessing a safer genomic profile. CRAFT CAR T-cells could function as effector cells for bispecific T-cell engager (BiTE) and induce CD3-dependent cytotoxicity against tumor cells. Pertinently, CRAFT CAR T-cells as opposed to CD3-disrupted CAR T-cells, were present in mouse xenografts without alloreactivity. Having the onset of MMEJ-directed repair and minimal off-targeting, positions this CRAFT crRNA to generate safer allogeneic CAR T-cells with an overall reduced genotoxic profile in a clinical setting. This unique CRAFT CAR T-cell population displays in vivo persistence. Additionally, CRAFT CAR T can be combined with BiTE therapy, offering a promising and potentially more durable alternative to preexisting ex vivo allogeneic CAR T-cell therapies. Citation Format: Tanya Hundal, Yan Luo, Yaqing Qie, Martha E. Gadd, Shaohua Guo, Mohamed A. Kharfan-Dabaja, Hong Qin. CD3-positive allogeneic CAR T-cells: A novel platform with persistence, BiTE-capture, and no alloreactivity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4283.

Measurable residual disease (MRD) has established prognostic significance in patients with myeloid disorders; however, there is limited data regarding its prognostic and predictive value and the optimal technique for measurement in the setting of post allogeneic hematopoietic cell transplantation (allo-HCT). A multi-gene next generation sequencing (NGS) panel can overcome the limitations of conventional techniques for measurement of MRD and can shed light onto the longitudinal evolution and genomic complexity of patients undergoing allo-HCT for acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). In this study, patients with AML or MDS who underwent their first allo-HCT and completed NGS testing at day +100 and were in a state of morphological remission were identified from the transplant registry of Mayo Clinic in Florida. The primary aim was to evaluate the prognostic impact of somatic variants detected via NGS at day +100 post allo-HCT on long-term outcomes. In total, 105 patients who underwent allo-HCT for AML and MDS and completed NGS testing on day +100 were included in the study population. Seventeen patients were found to have detectable variants, and 88 patients were without a detectable variant. At a median follow up of 1.4 years (0.1–5.5), presence of any variant at day +100 was associated with inferior 4-year overall survival (OS) (32% vs. 69%, P < 0.001), decreased progression free survival (PFS) (34% vs. 61%, P < 0.001), and a higher incidence of relapse (64% vs. 23%, P < 0.001). In univariate models, a lower Karnofsky performance score and presence of variants post allo-HCT remained significantly associated with inferior OS, higher relapse incidence, and a decreased PFS. The presence of variants at day +100 post allo-HCT remained significant in multivariate models for relapse ( P = 0.002) but not for OS ( P = 0.06) and PFS ( P = 0.08). These results indicate that the presence of detectable somatic variants at day +100 is associated with poor long-term outcomes and are predictive of a higher incidence of relapse.

T cell fitness has emerged as a critical determinant of the efficacy and persistence of Chimeric Antigen Receptor (CAR)-T cell therapy. Defined by the capacity of T cells to proliferate, resist exhaustion, persist in vivo , and exert sustained effector functions, T cell fitness reflects the integration of a dynamic network of intrinsic and extrinsic regulatory mechanisms. In this review, we present a comprehensive synthesis of the molecular and cellular foundations underlying T cell fitness, emphasizing the influence of differentiation trajectories, signaling pathways, metabolic reprogramming, and epigenetic modifications. We further discuss the impact of patient-specific conditions such as age as well as disease biology, prior therapeutic exposures, and timing and quality of T cell collection, on the phenotypic and functional efficacy of CAR-T cell products. Beyond delineating these determinants, we highlight emerging strategies aimed at enhancing T cell fitness. Importantly, we propose T cell fitness as an integrated, multi-layered systems property emerging from the interaction between differentiation state, signaling architecture, metabolic–mitochondrial competence, epigenetic stability, and host-specific inflammatory and treatment-related pressures. We introduce a mechanistic framework that links these layers across the CAR-T therapeutic timeline from leukapheresis to post-infusion tumor engagement and outline how this framework can be operationalized into measurable parameters to guide patient stratification, manufacturing decisions, and rational therapeutic interventions.