Chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment of hematologic malignancies, offering durable responses for patients with otherwise refractory disease. However, its clinical success is accompanied by a spectrum of immune-related toxicities, which remain a major challenge in practice.
Among these complications, immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS) has emerged as a rare but potentially fatal condition. IEC-HS is often underrecognized due to its significant overlap with reported severe cytokine release syndrome (CRS), particularly in terms of clinical presentation and laboratory findings. This overlap frequently leads to delayed diagnosis and suboptimal management, ultimately affecting patient outcomes.
A recent review published in the Chinese Medical Journal provides a comprehensive overview of IEC-HS, focusing on its differentiation from reported severe CRS, the identification of high-risk factors, and current therapeutic strategies.
One of the key clinical challenges is distinguishing IEC-HS from reported severe CRS. Although both conditions are characterized by systemic inflammation, they differ in several important aspects. CRS typically occurs within 5–8 days after CAR-T infusion, whereas IEC-HS tends to present later, often around two weeks post-infusion. In addition, IEC-HS is associated with persistently elevated ferritin levels rather than a rapid decline, along with marked increases in lactate dehydrogenase (LDH) and aspartate aminotransferase (AST). The inflammatory response in IEC-HS is also more sustained, with prolonged elevation of interferon-γ (IFN-γ) and other cytokines. These temporal and biochemical differences provide important clues for early identification.
The development of IEC-HS is driven by multiple factors. Patient-related characteristics, such as elevated baseline inflammation and reduced natural killer (NK) cell counts, may predispose individuals to this complication. Disease-related factors also play a role, particularly high tumor burden and a history of severe CRS. In addition, CAR-T product-related variables are increasingly recognized as important contributors. These include the use of CD22-targeted CAR-T cells, CD28 costimulatory domains, higher infusion doses, and excessive in vivo expansion. Emerging evidence also suggests that genetic alterations, such as TET2 mutations, may influence susceptibility to IEC-HS.
Management of IEC-HS primarily focuses on controlling the hyperinflammatory state. Corticosteroids remain the cornerstone of treatment and are widely used as first-line therapy. Etoposide may be considered in severe cases, although its potential impact on CAR-T cell efficacy requires careful consideration. With advances in understanding the underlying mechanisms, targeted therapies have gained increasing attention. Interleukin-1 (IL-1) blockade with anakinra is now recommended as a first-line targeted option. Janus kinase (JAK) inhibitors, such as ruxolitinib, can be used in refractory or second-line settings, while interferon-γ blockade with emapalumab may be considered for more severe or resistant cases. Notably, current consensus guidelines do not recommend the use of interleukin-6 (IL-6) inhibitors alone for the treatment of IEC-HS.
From a clinical perspective, the key to improving outcomes lies not only in treatment but also in early recognition. Integrating the timing of symptom onset, dynamic laboratory changes, and individual risk factors can help clinicians distinguish IEC-HS from CRS more effectively. As diagnostic criteria continue to evolve and new biomarkers are identified, more precise and timely interventions are expected to further improve patient prognosis.
In conclusion, IEC-HS represents a critical but underrecognized complication of CAR-T therapy. Increased awareness, accurate differentiation from CRS, and the application of targeted treatment strategies are essential for optimizing patient outcomes and ensuring the safe implementation of CAR-T therapy.
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Reference
DOI: 10.1097/CM9.0000000000004066
About Yuhua Li from Southern Medical University
Yuhua Li is a Chief Physician, Professor, and Doctoral Supervisor at Zhujiang Hospital, Southern Medical University, where she serves as Director of the Department of Hematology. Her research focuses on hematologic malignancies and precision immune cell therapy. She has led more than 20 national research projects and holds multiple patents. She has published over 70 SCI-indexed papers in leading journals, including Nature Nanotechnology , Nature Biomedical Engineering , and PNAS . She currently serves in several national academic societies in hematology and oncology.
About Yanjie He from Southern Medical University
Yanjie He is a Chief Physician and Master’s Supervisor at the Department of Hematology, Zhujiang Hospital, Southern Medical University, and Deputy Director of the department. Her research interests include hematologic malignancies and immunotherapy. She has led multiple national and provincial research projects and published over 20 academic papers in international and domestic journals. She has received several professional honors, including recognition as an Outstanding Young Medical Talent of Guangdong Province.
About Mengsu (Michael) Yang from City University of Hong Kong
Mengsu (Michael) Yang is the Senior Vice President of City University of Hong Kong, Yeung Kin Man Chair Professor of Biomedical Sciences, and Director of the Tung Biomedical Sciences Centre. He received his PhD from the University of Toronto and completed postdoctoral training at The Scripps Research Institute. His research focuses on biochip technology, nanobiotechnology, and their biomedical applications. He has published over 300 peer-reviewed papers and holds multiple international patents. He has been recognized among the world’s top 2% most-cited scientists (Stanford University, 2020–2024).
Chinese Medical Journal
Literature review
Not applicable
Chimeric antigen receptor T-cell therapies related to immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome: Diagnosis, high-risk factors, and management
30-Mar-2026