No free rides: management of toxicities of novel immunotherapies in ALL, including financial - PMC.
Unique and important toxicities related to blinatumomab
Cytokine release syndrome.
Cytokine release syndrome (CRS) is one of the notable toxicities of blinatumomab, and along with neurotoxicity, it is included as a boxed warning. The rates of CRS observed in each study are tabulated in Table 1. In the phase 2 and phase 3 studies, prephase dexamethasone was instituted in patients with high disease burden along with stepwise escalation of dose in cycle 1 (9 µg/d for 1 week followed by 28 µg/d).14,36 This was established in an earlier study where 2 patients with high leukemia burden developed grade 4 CRS prior to introduction of stepwise dose escalation and prephase dexamethasone.37
What is CRS with blinatumomab?
CRS refers to a systemic inflammatory response resulting from antigen-antibody interactions when using monoclonal antibodies that leads to activation of cytotoxic T cells that release inflammatory cytokines. The exact mechanism remains unclear, but elevation in interleukin-6 (IL-6), IL-10, and interferon-γ has been noted in patients receiving blinatumomab for ALL.40 It has also been hypothesized that a mechanism similar to hemophagocytic lymphohistiocytosis or macrophage activation syndrome may be responsible for blinatumomab-related CRS.41
Who is at risk?
The 2 patients who developed grade 4 CRS in the earlier study were started on full-dose blinatumomab and had high leukemia burden (88% and 90% blasts) in addition to extramedullary ALL involvement in 1 patient.37 Of note, both of these patients were showing good response to blinatumomab therapy in contrast with nonresponders, none of whom had CRS. This infers that a higher disease burden and a higher initial starting dose of infusion are associated with a higher risk of CRS.
What is neurotoxicity from blinatumomab?
Neurotoxicity attributed to blinatumomab can range from headache, malaise, confusion, somnolence, or disorientation to more ominous forms, such as ataxia, seizure, aphasia, and stupor. Due to a similar occurrence with CAR-T, one plausible mechanism proposed is disruption of the blood-brain barrier by activated T cells and cytokine release on binding to CD19-positive B cells in the central nervous system (CNS).43 Data suggest variable expression of CD19 in the CNS, which may explain the occurrence of neurotoxicity only in a subset of patients.44