Blinatumomab Therapy for Low Level Minimal Residual Disease Detected By Next-Generation Sequencing in Adult B-Cell Acute Lymphoblastic Leukemia

Introduction: Blinatumomab, a bi-specific T-cell engager, has shown clinical benefit in patients with relapsed-refractory and hematologic complete remission with minimal residual disease (MRD)-positive Acute Lymphoblastic Leukemia (ALL). The BLAST trial (Gökbuget N et al., Blood. 2018) demonstrated improved overall survival (OS) and disease-free survival (DFS) in patients with MRD-positive disease (≥0.1%) who achieved MRD response with Blinatumomab. We sought to evaluate the utility of Blinatumomab in low levels of MRD (<0.1%) using clonoSEQ with a sensitivity of (0.0001%).

Methods: Adult (18+) B- ALL patients that underwent treatment for B-cell ALL at Norris Comprehensive Cancer Center (NCCC) between 2016 and 2022 who had residual disease tracked using the Next Generation Sequencing (NGS)-based clonoSEQ assay (Adaptive Biotechnologies, Seattle, WA) were included. Patients who received Blinatumomab for MRD positivity were included only if they had a tracked clonoSEQ sequence within one month before starting treatment. Patients who didn't receive Blinatumomab were included if they had an MRD-positive clonoSEQ report. Those who were relapse/refractory when found to be MRD positive were excluded.

Cumulative incidence of relapse (CIR) was evaluated using competing risk regression (Fine-Gray method), with death as a competing outcome. At the same time, OS and DFS were analyzed using Cox proportional hazards model. The start time was set to the date of the MRD report, and patients were censored until the last follow-up. Confounder-adjusted KM curves were calculated using direct standardization.

Results: 47 patients were included with a median age at diagnosis of 45 years (range: 21-70). Most were Hispanic (N = 33, 70.2%), and the median follow-up time was 12 months. The 3-year OS, DFS, and CIR were 95.4% (95% CI 89.3-100%), 75.1% (95% CI 60.4-93.5%), and 20.3% (95% CI 7.2-38.0%).

Twenty-six patients were treated with Blinatumomab (median two cycles, range 1-9), with most (N= 14, 53.8%) having low levels of MRD (<0.1%). Fourteen patients (53.8%) achieved MRD negativity with a median time to MRD negativity of 3.1 months. There were no relapses or death in patients who achieved MRD negativity in the treated group. However, non-responders with Blinatumomab had one death and two relapses. All patients continued Maintenance therapy after receiving Blinatumomab and did not proceed with the transplant.

The patients who received Blinatumomab were more likely to be MRD positive on multiparameter flow cytometry (MFC) (60.0% vs. 28.6%, P = 0.042) but had a similar distribution of patient age, treatment type, and receipt of transplant. Additionally, there was a trend toward increased median percent residual cells on clonoSEQ (0.018% vs. 0.003% P =0.244) and flow (0.02% vs 0% P =0.066) in the Blinatumomab treatment group.

On univariate analysis, significant predictors of CIR and DFS were flow percent (DFS: HR = 1.54; 95% CI 1.07-2.23; P = 0.019; CIR: HR = 1.83; 95% CI 1.38-2.41; P<0.001) and clonoSEQ residual cell count(DFS: HR = 1.58; 95% CI 1.04-2.41; P = 0.031, CIR: HR = 1.88; 95% CI 1.18-2.97 P=0.008). When controlling for the number of residual cells on close, patients who received Blinatumomab had significantly better CIR(HR = 0.11; 95% CI 0.02-0.69; P = 0.019) and a trend towards improved DFS(HR = 0.21; 95% CI 0.04-1.28; P = 0.092), but no difference in OS.

On subgroup analysis of the 31 patients with low levels of MRD (<0.1%), there was no improvement in DFS for patients who were treated with Blinatumomab (HR = 0.41; 95% CI 0.04-3.91; P = 0.44). Of those with low levels of MRD, only two relapsed, and both did not receive Blinatumomab.

Conclusions:

In B cell ALL, Blinatumomab may offer a CIR benefit to patients with low levels of MRD as detected on clonoSEQ.