In a remarkable case that could reshape how oncologists approach one of blood cancer’s most feared complications, physicians in Türkiye have reported that a 73-year-old woman with heavily pre-treated multiple myeloma achieved a complete and durable remission of central nervous system involvement after receiving a BCMA-targeted bispecific antibody combined with intrathecal chemotherapy. The case, published as an open-access case report in Annals of Hematology, documents eighteen months of ongoing remission in a patient whose disease had already resisted six prior lines of therapy and had spread to the membranes surrounding her brain and spinal cord, a complication that historically carries a prognosis measured in weeks to a few months.
Central nervous system involvement in multiple myeloma is rare, occurring in only a small fraction of patients, but it is among the most devastating manifestations of the disease. When malignant plasma cells seed the leptomeninges, the delicate layers of tissue enveloping the brain and spinal cord, patients typically experience rapid neurological deterioration. Standard myeloma therapies, including proteasome inhibitors, immunomodulatory agents, and monoclonal antibodies, are designed to act within the bone marrow and bloodstream, and most penetrate the blood-brain barrier poorly, if at all. For decades, this pharmacological frontier has left clinicians with few options beyond intrathecal methotrexate, which can temporarily clear malignant cells from the cerebrospinal fluid but rarely controls the systemic disease driving the relapse.
The patient at the center of the new report presented with high-risk immunoglobulin G kappa multiple myeloma harboring two ominous cytogenetic abnormalities: a deletion of the short arm of chromosome 17, which implicates the TP53 tumor suppressor gene, and a deletion of chromosome 13q. Both alterations are associated with aggressive disease biology and shortened survival. By the time of her CNS relapse, she had undergone two autologous stem cell transplants and had become refractory to all three major drug classes used against myeloma, a status known as triple-class refractory disease. Her malignant plasma cells had also escaped the bone marrow, forming extramedullary masses, a further signal of highly aggressive, treatment-resistant biology.
The clinical picture at CNS relapse was unambiguous. Cerebrospinal fluid cytology revealed abundant atypical and binucleated plasma cells, the morphological hallmark of malignant plasma cell infiltration of the meninges. Magnetic resonance imaging of the brain and spine showed diffuse leptomeningeal enhancement, indicating widespread disease along the neural axis. In most published series, patients with leptomeningeal myeloma at this stage of treatment refractoriness survive only a few months, and many die within weeks of diagnosis.
Rather than pursuing conventional salvage chemotherapy, the treating physicians, Sinan Mersin of Mersin University Faculty of Medicine and Ömür Gökmen Sevindik of İstanbul Demiroğlu Science University, Florence Nightingale Hospital, elected to combine a systemic immunotherapy with a CNS-directed strategy. The systemic component was elranatamab, a bispecific antibody that binds B-cell maturation antigen, or BCMA, a protein expressed almost universally on malignant plasma cells, on one arm and CD3, a component of the T-cell receptor complex, on the other. By physically linking a patient’s own T lymphocytes to myeloma cells, elranatamab converts the immune system into a targeted killing machine, bypassing the need for the antigen-presentation machinery that many tumors evade.
Because bispecific antibodies can trigger an uncontrolled inflammatory response as T cells activate and release cytokines, the drug was introduced using a standard step-up dosing schedule. Lower initial doses prime the immune system and reduce the risk of cytokine release syndrome, the potentially life-threatening inflammatory storm characterized by fever, hypotension, and organ dysfunction. Intrathecal therapy, consisting of methotrexate delivered directly into the cerebrospinal fluid together with dexamethasone, was administered concurrently to attack the malignant plasma cells already circulating within the CNS compartment. The logic of the combination is compelling: the intrathecal drugs provide immediate local control while the bispecific antibody, once fully dosed, generates a sustained systemic immune assault against BCMA-expressing clones wherever they reside.
The response was both rapid and complete. Within two months of starting therapy, follow-up MRI demonstrated complete resolution of the leptomeningeal enhancement, and cerebrospinal fluid examination showed no cells at all, indicating that malignant plasma cells had been eradicated from the CNS. Crucially, the systemic disease responded in parallel. Evaluation according to the criteria of the International Myeloma Working Group confirmed a complete response, with normalization of serum immunofixation, protein electrophoresis, and free light chain measurements, the laboratory pillars used to track myeloma burden. The monoclonal protein that had defined her disease could no longer be detected.
Equally notable was the tolerability of the regimen. The patient experienced no cytokine release syndrome and no neurotoxicity, the two toxicities that most commonly complicate bispecific antibody therapy and that are of particular concern when the CNS is already compromised. The step-up dosing schedule, combined with careful monitoring, appears to have allowed the immune activation to proceed without crossing the threshold into clinical toxicity. This safety profile is especially relevant for patients with CNS disease, in whom fever or neurological changes can be difficult to distinguish from disease progression and can delay potentially curative treatment.
Perhaps the most striking finding is the durability of the remission. At the time of the report, eighteen months after initiating elranatamab, the patient remains in ongoing complete remission, including sustained clearance of the CNS. For a disease state in which median survival is typically measured in single-digit months, this duration of response represents an extraordinary departure from the expected natural history. The authors suggest that BCMA-targeted bispecific antibodies, when combined with CNS-directed therapy, may be capable of inducing deep and durable remissions even in patients whose myeloma has breached the blood-brain barrier after extensive prior treatment.
The case also carries broader implications for the evolving landscape of myeloma immunotherapy. Bispecific antibodies have transformed the treatment of relapsed and refractory multiple myeloma in recent years, offering off-the-shelf alternatives to chimeric antigen receptor T-cell therapy, which requires individualized manufacturing and is logistically demanding. Elranatamab received accelerated approval for relapsed or refractory disease based on promising results in clinical trials, and other BCMA-targeted bispecifics have shown similar efficacy. Whether these agents penetrate the CNS in meaningful concentrations remains an open question, but this case demonstrates that, at minimum, systemic BCMA redirection combined with intrathecal chemotherapy can achieve CNS clearance. Some evidence from CAR-T studies suggests that BCMA-directed cellular therapies can themselves cross the blood-brain barrier and exert intracranial activity, and it is plausible that activated T cells recruited by bispecific antibodies behave similarly.
The authors emphasize that their report describes a single patient and therefore cannot establish standard of care. Case reports in rare disease states serve as hypothesis generators, and the appropriate next step, they argue, is formal investigation of bispecific antibodies in CNS-involved myeloma, ideally through prospective clinical trials that incorporate CNS response endpoints and standardized intrathecal regimens. The subcutaneous administration route used for elranatamab, which allows outpatient management after the step-up phase, could make such an approach practical compared with hospital-based CAR-T infusions.
For patients and families facing a diagnosis of CNS-involved myeloma, the message from this case is one of cautious hope. A complication long regarded as a terminal event may become a tractable therapeutic target as immunotherapies mature and as clinicians learn to pair systemic immune redirection with direct CNS drug delivery. The eighteen-month remission documented in this Turkish case is a single data point, but it is a data point that challenges decades of therapeutic nihilism and points toward a future in which even the blood-brain barrier no longer offers sanctuary to malignant plasma cells.
Subject of Research: Durable CNS remission achieved with the BCMA-targeted bispecific antibody elranatamab combined with intrathecal methotrexate and dexamethasone in a patient with triple-class refractory, relapsed/refractory multiple myeloma with leptomeningeal CNS involvement.
Subject of Research: Cancer
Article Title: Durable CNS remission with elranatamab and intrathecal therapy in relapsed/refractory multiple myeloma
Article References: Mersin, S., & Sevindik, Ö. G. (2026). Durable CNS remission with elranatamab and intrathecal therapy in relapsed/refractory multiple myeloma. Annals of Hematology, 105(9), Article 408. https://doi.org/10.1007/s00277-026-07226-3
Image Credits: AI Generated
DOI: 10.1007/s00277-026-07226-3
Keywords: Multiple myeloma, Elranatamab, Bispecific antibody, BCMA, Leptomeningeal disease, Central nervous system, Intrathecal therapy, Complete remission
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Nathaniel Bowman. (September 10, 2026). Elranatamab plus intrathecal therapy sustains CNS remission in myeloma. Scienmag. https://scienmag.com/elranatamab-plus-intrathecal-therapy-sustains-cns-remission-in-myeloma/
Nathaniel Bowman. “Elranatamab plus intrathecal therapy sustains CNS remission in myeloma.” Scienmag, 10 September 2026, https://scienmag.com/elranatamab-plus-intrathecal-therapy-sustains-cns-remission-in-myeloma/. Accessed 10 September 2026.
Nathaniel Bowman. “Elranatamab plus intrathecal therapy sustains CNS remission in myeloma.” Scienmag. September 10, 2026. https://scienmag.com/elranatamab-plus-intrathecal-therapy-sustains-cns-remission-in-myeloma/
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Tags: BCMA-targeted therapybispecific antibodies in hematologybispecific antibody therapyblood-brain barrier penetrationcase report in hematologycase report on CNS myelomacentral nervous system myelomaCNS complications in blood cancersdurable CNS remissiondurable remission in myelomainnovative myeloma therapiesintrathecal chemotherapyleptomeningeal diseaseleptomeningeal disease treatmentmultiple myeloma remissionmultiple myeloma treatmentmyeloma CNS involvementneuro-oncology advancementsnovel myeloma therapiestreatment-resistant multiple myeloma
