Cilta-cel Induces Universal MRD Negativity in High-Risk Smoldering Multiple Myeloma

Intercepting Progression in Precursor Plasma Cell Disorders

The management of high-risk smoldering multiple myeloma remains a significant clinical challenge, as these patients face a high probability of progression to symptomatic end-organ damage, often characterized by the CRAB criteria of calcium elevation, renal insufficiency, anemia, and bone lesions [1, 2]. While quadruplet-based induction regimens and autologous stem cell transplantation have improved outcomes in newly diagnosed cases, these intensive approaches are not curative, and nearly all patients eventually relapse [2, 3]. Recent advances in B-cell maturation antigen (BCMA) directed therapies, including bispecific antibodies and chimeric antigen receptor T-cell (CAR T) products, have transformed the treatment of relapsed or refractory disease [4, 5]. However, the efficacy of these immunotherapies in later lines is often limited by T-cell exhaustion (a state of T-cell dysfunction resulting from chronic antigen exposure) and the increasing genomic complexity of the tumor [6, 7]. Researchers are now investigating whether utilizing these potent agents during the precursor stage, when the patient's immune fitness is more preserved, can achieve deeper and more durable responses [8, 7].

Frontline CAR T-Cell Monotherapy Without Induction

The CAR-PRISM phase 2 trial evaluated the efficacy and safety of ciltacabtagene autoleucel, a chimeric antigen receptor T-cell therapy directed against B-cell maturation antigen, in a specific cohort of 20 patients with high-risk smoldering multiple myeloma. Unlike standard protocols for symptomatic disease that typically require several cycles of chemotherapy to reduce tumor burden before cell infusion, this study was conducted without the use of induction or bridging therapy. To ensure a manageable tumor burden for this frontline approach, the researchers excluded patients with greater than 40% bone marrow involvement, focusing instead on those at high risk of progression who still maintained relatively lower levels of plasma cell infiltration. This strategy tests whether early intervention can eliminate the malignant clone before it acquires the complex mutations that drive treatment resistance. As of February 11, 2026, the 20 treated patients received ciltacabtagene autoleucel at weight-based doses of either 0.3 to 0.5 x 10^6 or greater than 0.5 x 10^6 viable CAR-positive T cells per kilogram. The trial was designed with primary endpoints focused on safety, specifically monitoring for dose-limiting toxicities (a predefined set of severe side effects occurring within a specific window after infusion) and treatment-emergent adverse events. Secondary endpoints were established to measure the depth of the clinical response, including the achievement of minimal residual disease negativity (the absence of detectable cancer cells at a sensitivity of one in one million bone marrow cells).

Safety Profile and Neurologic Sequelae

The CAR-PRISM trial met its prespecified endpoints, demonstrating a safety profile for ciltacabtagene autoleucel that aligns with previous observations in symptomatic multiple myeloma populations. Notably, no dose-limiting toxicities occurred during the study, which is a critical finding for a therapy administered without prior induction or bridging treatment. The most frequent adverse events were hematologic in nature, specifically transient cytopenias (a reduction in mature blood cell counts) which occurred in 90% of patients at grade 3 or 4 severity. These events were manageable and followed the expected recovery patterns for patients undergoing lymphodepletion (the use of chemotherapy to clear space for the infused cells) and chimeric antigen receptor T-cell infusion. Systemic inflammatory responses were universal but limited in severity. Cytokine release syndrome (a systemic inflammatory response caused by the rapid activation of infused T cells) occurred in 100% of patients, yet all cases were restricted to grade 1 or 2. This suggests that the lower tumor burden in high-risk smoldering multiple myeloma may mitigate the risk of high-grade inflammatory complications. However, the researchers identified specific neurologic toxicities categorized as non-immune effector cell-associated neurotoxicity syndrome (NINTs), which occurred in seven patients. These neurologic sequelae are distinct from the more common immune effector cell-associated neurotoxicity syndrome (ICANS) and often present with delayed or focal symptoms, such as movement disorders or cranial nerve deficits. The clinical presentation of these neurologic events varied among the affected cohort. Of the seven NINT cases, four involved cranial nerve palsies that completely resolved following appropriate management. The remaining three patients experienced persistent grade 1 neurologic symptoms at the time of the last follow-up. Despite these neurologic observations, the absence of high-grade cytokine release syndrome suggests that ciltacabtagene autoleucel can be administered safely to patients with high-risk smoldering multiple myeloma, provided there is rigorous monitoring for both early inflammatory and delayed neurologic adverse events.

Universal Minimal Residual Disease Negativity

The efficacy data from the CAR-PRISM trial demonstrate a profound depth of response following a single infusion of ciltacabtagene autoleucel. At a median follow-up of 15.3 months, 100% of patients achieved minimal residual disease (MRD) negativity at a threshold of 10^-6, meaning that no more than one malignant plasma cell was detected per one million bone marrow cells. This deep molecular response was achieved with remarkable speed; all patients reached MRD negativity by 2 months post-treatment and have remained MRD negative throughout the duration of the study. For clinicians, this suggests that the therapy can rapidly clear the bone marrow of detectable clones in the precursor stage of the disease, potentially preventing the clonal evolution that typically leads to symptomatic multiple myeloma. The clinical outcomes further underscore the potency of this approach in the high-risk smoldering multiple myeloma population. Among the cohort, sixteen patients with follow-up greater than 6 months achieved a complete response, defined as the total disappearance of monoclonal protein from the blood and urine along with less than 5% plasma cells in the bone marrow. Most notably, the researchers reported that no disease progression or deaths were observed during the study period. These findings indicate that ciltacabtagene autoleucel may fundamentally alter the natural history of high-risk smoldering multiple myeloma by inducing sustained, deep remissions that have not yet been observed with standard-of-care observation or less intensive therapeutic interventions, raising the prospect that future diagnostic tools could match patients to definitive, curative-intent therapy before end-organ damage occurs.

References

1. Nadeem O, Santos DMCD, Nikiforow S, et al. Ciltacabtagene autoleucel in high-risk smoldering multiple myeloma: the CAR-PRISM phase 2 trial.. Nature medicine. 2026. doi:10.1038/s41591-026-04365-y

2. Rehman RU. Lynozyfic (Linvoseltamab): A First‐in‐Class Off‐the‐Shelf T‐Cell Redirector for Refractory Multiple Myeloma. eJHaem. 2025. doi:10.1002/jha2.70182

3. Kumar S, Baizer L, Callander NS, et al. Gaps and opportunities in the treatment of relapsed-refractory multiple myeloma: Consensus recommendations of the NCI Multiple Myeloma Steering Committee. Blood Cancer Journal. 2022. doi:10.1038/s41408-022-00695-5

4. Lesokhin AM, Tomasson MH, Arnulf B, et al. Elranatamab in relapsed or refractory multiple myeloma: phase 2 MagnetisMM-3 trial results. Nature Medicine. 2023. doi:10.1038/s41591-023-02528-9

5. Morè S, Offidani M, Corvatta L, Petrucci MT, Fazio F. Belantamab Mafodotin: From Clinical Trials Data to Real-Life Experiences. Cancers. 2023. doi:10.3390/cancers15112948

6. Goel U, Zanwar S, Cowan AJ, Banerjee R, Khouri J, Dima D. Ciltacabtagene Autoleucel for the Treatment of Relapsed/Refractory Multiple Myeloma: Efficacy, Safety, and Place in Therapy. Cancer Management and Research. 2025. doi:10.2147/cmar.s510408

7. Corrado F, Bidikian N, Bosch-Vilaseca A, et al. Single-cell immune profiling reveals enhanced immune fitness of endogenous and engineered T cells in patients with high-risk smoldering myeloma compared to Relapsed/Refractory myeloma following bispecific antibodies or CAR-T cell therapies.. Blood. 2025. doi:10.1182/blood-2025-921

8. Nadeem O, Nikiforow S, DeBraganca K, et al. Early Safety and Efficacy of CAR-T Cell Therapy in Precursor Myeloma: Results of the CAR-PRISM Study Using Ciltacabtagene Autoleucel in High-Risk Smoldering Myeloma. Blood. 2024. doi:10.1182/blood-2024-202676