Frontline Consolidation with Blinatumomab for High-Risk Philadelphia-Negative Acute Lymphoblastic Adult Patients. Early Results from the Graall-2014-QUEST Phase 2

Introduction: Philadelphia chromosome (Ph)-negative acute lymphoblastic leukemia (ALL) with high-risk genetics and/or measurable residual disease (MRD) are at high-risk of disease recurrence. In the previous GRAALL-2005 study, we identified KMT2A rearrangements (KMT2A-r), IKZF1 intragenic deletion (IKZF1del) and post-induction (TP1, week 6) MRD ≥ 0.01% as independent factors to predict relapse in Ph-negative B-cell precursor (BCP) ALL (Beldjord K, Blood 2014). In the GRAALL-2014 trial, high-risk (HR) patients were thus defined by the presence of at least one of these three factors. Among them, only those with higher MRD levels defined as TP1-MRD ≥ 0.1% and/or week 12 (TP2) MRD ≥ 0.01% were considered at very high risk (VHR) and proposed allogeneic hematopoietic stem cell transplant (alloSCT) in first remission (Dhedin et al., Blood 2015). Since October 2018, all these patients were eligible to be included in the GRAALL-2014-QUEST phase 2 study to receive blinatumomab as part of consolidation and maintenance phases or as a bridge to transplant.

Methods: From October 2018 to December 2020, 95 patients with high-risk Ph-negative BCP-ALL without central nervous system involvement at diagnosis and in continuous complete remission after induction and consolidation 1, were prospectively included to start blinatumomab at week 12. One patient was excluded because of T-ALL phenotype (with CD19 aberrant expression). Patients with alloSCT indication and a stem cell source received blinatumomab 28 microg/d administered by continuous intravenous infusion (cIV) until transplant. A minimum of 4 weeks blinatumomab was recommended before proceeding to transplantation. All other patients received 5 cycles of blinatumomab 28 microg/day cIV (for 28 days), during consolidation 2 and 3 and at months 1/3/5 of the maintenance phase respectively. The primary objective was disease-free survival (DFS). Secondary objectives included post-blinatumomab MRD response at TP3 (after consolidation 2 or before alloSCT), overall survival (OS), and safety. Early results are reported here.

Results: Median age was 35 years old (range, 18-60). Median white blood cell count (WBC) at diagnosis was 12 G/L (range, 1-449). Oncogenetic analyses allowed classifying ALL as Ph-like (18%), KMT2A-r (17%), DUX4/ERGdel (13%), ZNF384-r (11%), low hypodiploidy/near triploidy (7%), B-other (26%) or unknown (9%). An IKZF1del was found in 37/93 (40%). A TP1-MRD ≥ 0.01% was found in 46/94 patients (49%). Final risk group was HR for 45 patients and VHR for 49 patients. Last pre-blinatumomab MRD was <0.01% in 49/88 (56%) of evaluable patients. A total of 40 patients (42%) received an alloSCT. The median number of blinatumomab cycles received in patients not proceeding to alloSCT was 4 cycles (range, 1-5). Thirty-nine severe adverse events (SAEs) were reported: 1 CRS (grade 2), 8 neurotoxicities (1 grade 2, 3 grade 3, 3 grade 4, 1 grade 5), 19 infections, and 11 others. The only grade 5 SAE occurred after alloSCT (seizures). After blinatumomab, a complete MRD response (with at least 0.01% sensitivity) was achieved in 61/82 (74%) evaluable patients and in evaluable patients with pre-blinatumomab detectable MRD. MRD response to blinatumomab was lower in patients with high pre-blinatumomab MRD level, while not impacted by age, WBC, or oncogenic subgroup. With a median follow-up of 20 months, 18-month DFS and OS was 78.8% (95% CI [66.9-86.8]) and 92.1% (95% CI [83.2-96.4]) respectively (Figure 1). Patients with VHR diseases had a worse DFS (68.8%, 95% CI [51.1-81.2]) as compared to other patients (90.6%, 95% CI [72.1-97.1]); p=0.018). This difference of DFS was abrogated by censoring patients at transplant (VHR 88.1%, 95% CI [65.5-96.3] versus others 90.6%, 95% CI [72.1-97.1%], p=0.10). Other factors significantly associated with better DFS were DUX4/ERGdel subgroup, low pre-blinatumomab MRD, and complete MRD response after blinatumomab.

Conclusion. In patients wih high-risk BCP-ALL, blinatumomab added to consolidation is safe and gives promising results. A comparison to similar patients treated in the same GRAALL-2014 study before October 2018 is planned with a longer follow-up.