Byrd, Kenneth

Abstract In a real-world analysis of brexucabtagene autoleucel recipients with relapsed/refractory B-cell acute lymphoblastic leukemia (N = 278), lack of response to prior blinatumomab correlates with significantly worse following chimeric antigen receptor T-cell therapy outcomes.

7006 Background: Older adult patients (pts) with Philadelphia-chromosome-negative (Ph-) acute lymphoblastic leukemia (ALL) have poor survival with chemotherapy. The α-CD22 Ab-drug conjugate inotuzumab ozogamicin (InO) and α-CD19/CD3 T-cell engager blinatumomab (blina) were each superior to chemotherapy in Phase III studies in relapsed/refractory B-ALL. Because InO induces high CR rates and blina can induce durable remissions in low burden disease, we conducted a Phase II trial of induction InO then blina for older adults with newly-diagnosed (ND), Ph-, B-ALL. Methods: Eligible were pts ≥60 years old with ND, Ph-, CD22+ (≥20% of blasts) B-ALL without plan for allogeneic HCT (alloHCT). Pts with CNS leukemia or liver disease were excluded. Induction IA was InO 0.8 mg/m 2 day (d) 1, 0.5 mg/m 2 d8, d15 IV on a 21d cycle. Pts with adequate cytoreduction (marrow blasts by ≥50% or cellularity ≤20%) after IA went to IB if in CR/CRi (InO 0.5 mg/m 2 d1, d8, d15 IV; 28d cycle) or IC if no CR/CRi (InO 0.8 mg/m 2 on d1 and 0.5 mg/m 2 on d8 and d15 IV; 28d cycle). Those without cytoreduction to IA started course II blina. Pts without events in IA/B/C received course II blina CIV (9 mcg/d x 7d then 28 mcg/d x 21d; 14d break; 28 mcg/d x28d). Pts with CR/CRi to InO received 2 more 28d cycles of blina, others received 3 more. CNS prophylaxis was methotrexate 15 mg intrathecal x 8. The primary endpoint was 1-yr event-free survival (EFS) with a lower limit of a 90% CI for 1-yr EFS >10% defined as success. EFS was the time from therapy start to failure to achieve CR/CRh/CRi by end Course II, progression, relapse, or death, whichever occurred first. Results: Thirty-three eligible pts were treated (1 ineligible, 2 nd malignancy). The median age was 71 years (range 60-84). Median WBC count was 3,200/mcl (range 6-38,000). Median CD22 expression was 92% (range 21-100%). Eight pts had therapy-related ALL. The cumulative CR rates through Course IA/B/C and Course II were 85% and 97%, respectively (Table). With median follow up of 22 mo, the 1-yr EFS was 75% (95% CI 61-92%). The 2-sided 90% CI was 63-89% for 1-yr EFS with lower bound above 10% indicating regimen success. Twelve pts had events: 9 relapses, 2 deaths in remission (1 after alloHCT), and 1 death without remission from respiratory failure with sinusoidal occlusion syndrome of liver. The 1-yr OS was 84% (95% CI 72-98%). Nine pts have died, 6 after relapse. Conclusions: InO induction then blina consolidation is highly active for ND, Ph-, CD22+ B-ALL. The regimen is an option for older adults and a comparator regimen for future studies. Support: U10CA180821, U10CA180882, U10CA180820 https://acknowledgments.alliancefound.org . Clinical trial information: NCT03739814 . N=33 I A/B/C II Composite CR* 28 ( 85%) 32 ( 97%) CR 15 (45%) 19 (58%) CRh 11 (33%) 12 (36%) CRi 2 (6%) 1 (3%) Refractory 3 (9%) † - 1-yr EFS 75% (95% CI 61-92%) 1-yr OS 84% (95% CI 72-92%) *CR+CRh+CRi † 1 completed IA only