Quality of Life, Tryptophan Metabolites, and Neurotoxicity Assessments of Patients with Relapsed or Refractory B Cell Malignancies Undergoing CAR 20/19 - T Cell Therapy

Introduction

Chimeric antigen receptor (CAR) T cell immunotherapy represents a novel and increasingly used treatment modality for patients with relapsed and/or refractory B cell malignancies. Acute neurological toxicities of CAR-T cell therapy (e.g. immune effector cell-associated neurotoxicity syndrome) are well described, though delayed cognitive and emotional functioning and quality of life (QOL) are less well studied, with mechanisms of all incompletely understood. Given the known bidirectional relationship between neuroinflammation and depression, and the role of kynurenine (Kyn) metabolism in both, we studied QOL through patient-reported outcomes (PROs) and neurotoxicity and their relationship to Kyn metabolites.

Methods

Patients with relapsed refractory B-cell non-Hodgkin lymphoma and chronic lymphocytic leukemia treated with CAR-20/19-T cells on our Phase I/Ib clinical trial (NCT03019055) (N=16) were included. Patients were excluded if they had a history of previous allogeneic hematopoietic stem cell transplantation. Study subjects provided serum and PROs through self-report surveys at the following time points: baseline/ apheresis, Day-14 (D14), D28, and D90 post-intervention. The following scales were used to assess QOL: Inventory of Depression and Anxiety Symptoms (IDAS), Brief Pain Inventory (BPI), Fatigue Severity Index (FSI), and Pittsburgh Sleep Quality Index (PSQI). Tryptophan and its metabolites (kynurenine (Kyn), 3-Hydroxy-anthranilic Acid (3-HAA), 3-Hydroxykynurenine (3-HK), quinolinic acid (QA), kynurenic acid (KA)) and neurotoxicity grades were measured for all 16 subjects. Patients were evaluated for neurotoxicity with the CTCAE 5.0. The measurements were log-transformed to stabilize the variances and allow modeling of the expected multiplicative effects. A mixed effects longitudinal model was used for all eligible patients to evaluate the impact of time on all PRO variables over the 4 timepoints through 90 days post CAR-T infusion. Neurotoxicity was evaluated two ways: as a categorical variable with 5 levels (0 to -4) and as a continuous variable.

Results

Depression symptoms improved over time with the lowest value at Day 90, though the changes were not statistically significant (P = .072). Remaining QOL PRO variables did not show statistically significant changes, tending to improve or remain stable over time (Table 1 & Figure 1). Mean Kyn levels significantly changed over time (P = .028; Table 2). This effect is most pronounced in patients with Grade 3/4 neurotoxicity where Kyn levels rise at Day 14 and Day 28 followed by a decrease by Day 90 (Figure 2). Among patients who exhibited neurotoxicities, baseline levels of 3-HAA and 3-HK before CAR-T therapy were elevated; though nonsignificant, similar trends were not observed in the other metabolites (Figure 2). These observations however were significant when neurotoxicity was evaluated as a continuous variable (Table 2) with 3-HAA and 3-HK higher in patients with higher grade neurotoxicities (P = .015 and .070).

Conclusions

Our findings suggest that CAR-T therapy does not impair QOL and may in fact result in improved mood in the early months following cell infusion, adding to recent literature about long-term QOL in CAR-T survivors. Here, we also identify elevated baseline 3-HAA and 3-HK levels as well as increased Kyn levels following CAR-T therapy, with the first two associated with worse neurotoxicity. Most interestingly, we find higher levels of 3-HAA and 3-HK in patients who experience neurotoxicities. Correlational studies will be needed to confirm potential relationships between PROs and metabolites.