GFAP and NfL increase during neurotoxicity from high baseline levels in pediatric CD19-CAR T-cell patients

Abstract

There is a need for biomarkers to predict and measure the severity of immune effector cell-associated neurotoxicity syndrome (ICANS). Glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) are well-validated biomarkers of astroglial and neuronal injury, respectively. We hypothesized that pretreatment GFAP and NfL levels can predict the risk of subsequent ICANS and that increases in GFAP and NfL levels during treatment reflect ICANS severity. We measured cerebrospinal fluid GFAP (cGFAP) and NfL (cNfL) along with serum NfL (sNfL) levels at pretreatment and day 7 to 10 after chimeric antigen receptor (CAR) T-cell infusion in 3 pediatric cohorts treated with CD19- or CD19/CD22-directed CAR T cells. cGFAP and cNfL levels increased during grade ≥1 ICANS in patients treated with CD19-directed CAR T cells but not in those who received CD19/CD22-directed CAR T cells. The sNfL levels did not increase during ICANS. Prelymphodepletion cGFAP, cNfL, and sNfL levels were not predictive of subsequent ICANS. Elevated baseline cGFAP levels were associated with a history of transplantation. Patients with prior central nervous system (CNS) radiation had higher cNfL levels, and elevated baseline sNfL levels were associated with a history of peripheral neuropathy. Thus, cGFAP and cNfL may be useful biomarkers for measuring the severity of CNS injury during ICANS in children. Elevated baseline levels of cGFAP, cNfL, and sNfL likely reflect the cumulative injury to the central and peripheral nervous systems from prior treatment. However, levels of any of the 3 biomarkers before CAR T-cell infusion did not predict the risk of ICANS.

Graphical abstract

Figure 1.

GFAP and NfL levels are elevated at baseline and increase in the CSF during ICANS. (A) Baseline biomarker measurements. Each point represents the data from 1 patient, all 3 cohorts are combined. Bars show the median. CSF samples were obtained prelymphodepletion and serum samples are from day 1 before CAR T-cell infusion. The dotted lines show the upper bound of published reference levels (1386 pg/mL for cGFAP, 380 pg/mL for cNfL, 25 pg/mL for sNfL). Groups were compared by Mann-Whitney test. (B) Pairwise comparisons of biomarker levels show rises of cGFAP and cNfL, but not sNfL during ICANS. Note that cGFAP decreased in patients without ICANS. Each linked set of data points is from 1 patient. The “pre” time point for cGFAP and cNfL represents the prelymphodepletion sample, the “acute” time points represent the sample obtained on days 5 to 15 post CAR T-cell infusion. For sNfL, “pre” represents samples obtained on day 1 and “post” represents samples obtained from days 7 to 10. Data were analyzed by Wilcoxon matching-pairs signed-rank test.

Figure 2.

Correlation between cGFAP, cNfL, and sNfL levels in individual patients. The color of each box indicates the strength of association between the measurements in individual patients (Spearman’s r). The number in each box shows the P value for the Spearman rank-sum correlation. The “pre” time point for cGFAP and cNfL represents the prelymphodepletion sample, the “acute” time points represent the sample obtained on days 5 to 15 post CAR T-cell infusion. For sNfL, “pre” represents samples obtained on day 1 and “post” represents samples obtained from days 7 to 10.