The Role of Clonally Expanded CD8+ Non-CAR-T Cells in Neurocognitive and Hypokinetic Movement Disorder after BCMA-Targeting CAR-T Cell Therapy
Authors: Kadel Sofie-Katrin , Scheller Lukas , Leipold Alexander M. , Krammer Tobias , Raskó Tamás , Alb Miriam , Weis Philipp , Leberzammer Maria , Schmitt Friederike , Reichel Clara , Tamamushi Yoko , Duell Johannes , Topp Max S. , Mersi Julia , Köberle Philipp , Reich Martin , Musacchio Thomas , Doppler Kathrin , Volkmann Jens , Kallius Matthias , Buck Andreas , Waldschmidt Johannes , Einsele Hermann , Hudecek Michael , Saliba Antoine-Emmanuel , Rasche Leo , Kortüm K. Martin 
Published: December 2024

Introduction: The use of ciltacabtagen autoleucel (cilta-cel) in RRMM patients within the CARTITUDE-1 study has exposed previously unknown late onset neurotoxicities, referred to as movement, neurocognitive treatment emergent events (MNT) (Cohen, A et al., 2022). In addition to their late occurrence, MNTs are characterized by their failure to respond to standard therapy such as corticosteroids. Hence, this patient population (5.0 % in CARTITIUDE-1) is at high risk of severe and persistent neurological complications evoking the necessity for further research into the yet poorly understood pathophysiology of MNTs. So far, CAR-T “on-target-off-tumor”-toxicity due to BCMA expression in the basal ganglia has been proposed as one of the driving pathomechanisms of MNTs (Van Oekelen, O et al., 2021). We report the case of a 63-year-old male patient with IgA-kappa myeloma, who received 7 prior lines of treatment. Besides prolonged CRS °I, which was successfully managed by a single dose of tocilizumab, no other adverse events or signs of neurotoxicity occurred immediately post CAR-T infusion.

Patient case and methods: 14 days post CAR-T infusion the patient presented with shakiness, subjective slowing of motor skills and concentration disorders. However, it was not until a second hospitalization period 30 days post CAR-T, when neurological examination confirmed a clinical syndrome of parkinsonism including bradykinesia, rigor, tremor and postural instability. Consistent with the clinical presentation, 123I-FP-CIT-SPECT-imaging revealed reduced presynaptic dopamine transporter density in the striatum. On day 54 after CAR-T, the patient developed a massive deterioration of parkinsonism reflected by an increased MDS-UPDRS part III score of 65. Ultimately, the patient was treated with intrathecal chemotherapy, dasatinib orally, cyclophosphamide and corticosteroids. From 149 days post CAR-T a slight improvement of parkinsonism was observed (MDS-UPDRS part III score of 32) following levodopa/benserazide delivery via PEG, and after achieving CAR-T eradication with prior therapies. Multimodal analysis, including flow cytometry, and simultaneous scRNA- and scTCR-seq, was performed on peripheral blood (PB) and cerebrospinal fluid (CSF) longitudinally to the course of illness.

Results: CAR-T expansion in PB peaked in the first month post CAR-T (day 17: 7966.7 CAR-T/µl, day 30: 8299.6 CAR-T/µl), while peak infiltration of the CSF occurred at day 57 (367 cells/µl) coinciding with parkinsonism deterioration. Throughout the patient's course, CAR-T were the most abundant cell population in the CSF, with CD4+ CAR-T dominating at the beginning (day 17-30). We performed scRNA-seq and scTCR-seq on 7 longitudinally collected samples (d20-d143 post CAR-T) of the patient's CSF and 6 matched PB samples, collectively representing 74603 cells. CAR-T as well as non-CAR-T cells were present in the CSF with CAR-T proportions decreasing over time. CD8+ as well as CD4+ CAR-T showed marked expression of cytotoxicity associated genes (PRF1, granzymes, GNLY). While CAR-T did not clonally expand, scTCR-seq revealed clonally expanded CD8+ non-CAR-T in the CSF concurring with the deterioration of parkinsonism. Major CD8+ non-CAR-T clones were detectable from day 30 post CAR-T, albeit at low numbers, and were also detectable in the PB. Phenotypically, these clones were marked by the expression of cytotoxicity genes, and tissue residency markers (ZNF683). Cell-cell interaction inference indicated activating signaling of CD4+ CAR-T towards clonally expanded CD8+ non-CAR-T in CSF. Furthermore, we observed an increased interferon response in the CSF that preceded the deterioration of the patient, which was absent in PB. Notably, the interferon response was abrogated after treatment with dasatinib, consistent with reduced activation of CAR-T and non-CAR-T as determined by flow cytometry.

Conclusion: Our longitudinal case study shows for the first time that CD4+ CAR-T are most likely the initiators of MNTs and that clonally expanded CD8+ non-CAR-T cells could drive the deterioration of parkinsonism. These findings are consistent with recent reports that CD8+ T cells promote neurodegeneration in other diseases. The coincidence of an interferon response with clinical worsening and the potential abrogation of this response by dasatinib requires further investigation.