The Impact of Leukapheresis Collection on Patients Undergoing Chimeric Antigen T-Cell Receptor Therapy with Tisagenlecleucel

Introduction

Autologous chimeric antigen receptor T-cell therapy (CAR-T) has revolutionized the treatment of acute lymphoblastic leukemia (ALL) in children and young adolescents, with an impressive overall remission rate of 81% in patients with relapsed or refractory (r/r) disease ¹. Approved by the US FDA, tisagenlecleucel (Kymriah ®) is now approved for patients up to 25 years of age with pre B -cell ALL that is refractory or in second or later relapse as well as adult patients with r/r non-Hodgkin lymphoma (NHL) including diffuse large B cell lymphoma (DLBCL) after two or more lines of systemic therapy ². Apheresis is the first step of CAR-T cell manufacturing with the recommended collection goal of ≥1.0x10 ⁹ CD3 cells or ≥2.0x10 ⁹ total nucleated cells (TNC) ³. However, this crucial process can be affected by technical and patient specific factors, including heavily pre-treated patients, resulting in CAR T-cell manufacture failure rates of 1-14% in clinical trials ^{4, 5, 6, 7}. The clinical impact of CD3+ count in peripheral blood at the time of leukapheresis and optimal apheresis collection parameters remain to be established.

Methods:

This is a retrospective study of patients 0-88 years with r/r DLBCL or ALL who underwent leukapheresis between August 31 ^st 2017 to August 1 ^st, 2022 for tisagenlecleucel therapy. Spearman correlation was conducted to evaluate the association between absolute lymphocyte count (ALC) and cell counts prior to leukapheresis. The Kaplan-Meier method was employed to evaluate overall survival (OS) and event-free survival (EFS) from date of CAR-T. Cox proportional hazards regression analysis was utilized to examine the associations between OS or EFS and measures of interest, including white blood cell count (WBC), ALC, CD3+ cells from leukapheresis, CD3+%, cell viability, viable T cells %, total cell count, IFNγ CD19, maximum cytokine release syndrome (CRS) score (Max CRS), maximum immune effector cell-associated neurotoxicity syndrome (ICANS) score (Max ICANS), duration of CRS, duration of ICANS, and post-CART transplantation.

Results:

Forty patients were included, 22 (55%) patients were male, and the median age at apheresis was 50 years (5-88 years). There were significant positive correlations between ALC and the CD3+ cells from leukapheresis (Correlation: 0.62 [0.33 - 0.83], p-value <0.001) and CD3+ % (Correlation: 0.46 [0.001 - 0.78], p-value 0.020). For the 39 patients with data available, the median OS was 94.2 months (95% CI: 55.3 - 129.1). For EFS from date of CAR-T, the median survival from the date of diagnosis until the date of first recurrence event (relapse, secondary malignancy, and death) or the last follow-up date was 75.1 months (95% CI: 34.7 - 104.5). Based on univariate survival analysis results, there was no significant association observed between OS or EFS and the variables of interest.

The median IFNγ reported on certificate of analysis from manufacturer was 162 (13-818) with 14 (36%) patients maximum grade CRS equal to 0, and 27 (69%) maximum grade ICANS equal to 0. For those who experienced any grade of CRS, there was a significant correlation with CD3+ cells (p-value 0.007) but not significant when compared to IFNγ (p-value 0.51). There was no significant correlation between those who experienced ICANS compared to CD3+ cells (p-value 0.17) or IFNγ (p-value 0.1). There was no significant positive correlations between IFNγ and the duration CRS (Correlation: 00.292 [-0.045, 0.554], p-value 0.07) or duration of ICANS (Correlation: 0-0.241 [-0.531, 0.064], p-value 0.16).

Of note, we had one patient who had a manufacturing failure and unfortunately passed away before second round of apheresis. For this patient, WBC on apheresis was 4.3k/microL, ALC was 560 and CD3+ cells was 84.4%.

Conclusion:

A significant positive correlation was observed between ALC and the CD3+ cells as well as its percentage from leukapheresis for pediatric and adult patients undergoing tisagenlecleucel CAR-T. However, no significant effects were found when detecting the association between ALC with OS or EFS. In addition, there were no significant findings between IFNγ and the duration of CRS or ICANS.

Funding: This work was supported in part by the NIH/NCI Cancer Center Support Grant (award number P30 CA016672) and used the Biostatistics Resource Group.