The Impact of Prior Immunotherapy on Composition of Apheresis Material for CAR T-cell Therapy in Patients with B-Cell Acute Lymphocytic Leukemia (B-ALL)

Background & Aim

CAR T-cell functionality relies on the composition of the apheresis product used for manufacturing, with higher total nucleated cell (TNC) yield and balanced CD4/CD8 ratios associated with improved disease response. The impact of prior immunotherapy on apheresis composition has not been established. As targeted agents like blinatumomab and inotuzumab are increasingly used for leukemia therapy, an understanding of how these agents affect apheresis composition will be important for treatment planning.

Our aim was to describe the relationship between blinatumomab and inotuzumab exposure and apheresis composition in patients with relapsed/refractory B-ALL.

Methodology

Data from children and young adults with relapsed or refractory B-ALL who underwent apheresis collection for CAR T-cell therapy trials (NCT05442515, NCT03448393, NCT02315612) were analyzed retrospectively. Independent variables included exposure to blinatumomab and/or inotuzumab therapies and timing between immunotherapy and apheresis. Patients who had hematopoietic stem cell transplant following immunotherapy were excluded. Patients who received both blinatumomab and inotuzumab were grouped based on the most proximal therapy (Fig 1). Primary outcomes were TNC yield per patient weight in kilograms, CD3%, and CD4/CD8 ratios as measured by flow cytometry. Outcomes were compared using Mann Whitney U tests.

Results

A total of 114 patients with a median age of 18 years (range 4-38), 5 prior lines of therapy (range 2-13), and baseline disease burden of 1% blasts (range 0 to 97%) in bone marrow were evaluated. 29 (25%) patients had blinatumomab exposure at a median of 5.1 months (range 1-58). 22 (19%) had prior inotuzumab at a median of 3.4 months (range 1-30 mo) prior to apheresis.

Exposure to and timing of blinatumomab were not associated with differences in apheresis composition. In contrast, inotuzumab exposure at any time prior to apheresis was associated with a lower CD4/CD8 ratio (0.77 for those exposed vs 1.11 for those not exposed, p = 0.0047) (Fig 2). The timing of inotuzumab did not impact apheresis composition. TNC yield and CD3% did not differ with blinatumomab or inotuzumab exposure.

Conclusion

Inotuzumab exposure may alter CD4 and CD8 proportions in apheresis products, leading to decreased CD4/CD8 ratios, while the same effect was not observed with blinatumomab. More detailed characterization of T-cell phenotypes and fitness after immunotherapy will help guide apheresis timing.