Doucette, Kimberley

Abstract Background: Older adults with newly diagnosed ALL treated with conventional chemotherapy have poor survival due to high rates of toxic death and disease relapse. The Alliance A041703 trial (NCT0373981) tested chemotherapy-free treatment with the anti-CD22 antibody-drug conjugate inotuzumab ozogamicin (InO) followed by the anti-CD19-CD3 bifunctional T-cell engager blinatumomab (blina) without maintenance in older adults to reduce toxicity and increase efficacy of therapy for this patient (pt) population. We previously reported with 22-month (mo) median follow-up that the study met its primary endpoint with a 1-year (yr) event-free survival (EFS) of 75% (90% confidence interval [CI] 63-89% lower bound exceeding null rate of 10%; JCO 2023 41, 7006). Here we report secondary outcomes with 45-mo median follow-up: 3-yr EFS, 3-yr overall survival (OS), response, and relapse characteristics. Methods: Eligible pts were ≥60 yrs old with newly diagnosed, Ph-negative, CD22-positive (≥20% of blasts) B-cell ALL without planned allogeneic HCT (alloHCT), liver disease, or CNS involvement at enrollment. Induction IA was InO 0.8 mg/m2 day (d) 1, 0.5 mg/m2 d8, d15 IV on a 21d cycle. Pts with adequate cytoreduction (marrow blasts reduced ≥50% or marrow cellularity ≤20%) after IA went to IB if in CR/CRi (InO 0.5 mg/m2 d1, d8, d15 IV; 28d cycle) or IC if no CR/CRi (InO 0.8 mg/m2 on d1 and 0.5 mg/m2 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 continuous IV (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 doses. EFS was time from therapy start to failure to achieve CR/CRh/CRi by the end of course II, progression, relapse, or death, whichever occurred first, censored at last follow up. OS was time from registration to death from any cause censored at the last known alive date. Results: The median age of the 33 treated pts was 71 yrs (range 60-84). Eight pts had prior therapy for alternate malignancy in CR for >2 yrs prior to enrollment (6 multiple myeloma, 1 non-Hodgkin lymphoma, 1 breast cancer). Median CD22 expression was 92% (range 21-100%) and 49% had NCCN poor-risk genetics. Five pts underwent alloHCT in first CR/CRi and 2 pts received POMP maintenance after early discontinuation of blina (1 toxicity, 1 physician choice). The CR/CRi rate after InO was 85% (1 early death/refractory, 2 refractory, 2 undetermined due to low marrow cellularity on remission assessment marrow) with CR/CRi rate of 97% by completion of course II blina. With 45 mo median follow-up, the estimated 3-yr EFS was 48% (95% CI 33-70%) with a median EFS of 31 mo (95% CI 17.4-not reached [NR]) and no events after 31 mo. Sixteen events occurred: 12 relapses, 1early death, and 3 deaths in remission (1 encephalopathy, 1 relapse of multiple myeloma, 1 pulmonary complications after alloHCT). No isolated CNS relapse has been reported. Among relapses, 10 had immunophenotyping. Four (40%) were CD19-negative, one of which was also CD22-negative. Among CD19-negative relapses, genetics were hypodiploid (2), Pax5alt (1), and ZNF384-like (1, also CD22-negative). TP53 mutation or loss was observed in 5/12 (42%) relapses. Thirteen pts died. The estimated 3-yr OS was 59% (95% CI 44-79%) with median OS NR (95% CI 32-NR) with no deaths after 36 mo. In univariate analysis, EFS and OS were not impacted by age, gender, genetic risk (NCCN), prior therapy for alternate malignancy, or alloHCT in first remission. EFS was better with higher CD22 expression at diagnosis (≥90% vs <90%, 3-yr EFS 60% vs 25%, P=0.044). EFS and OS were worse for detectable minimal residual disease (MRD) at any timepoint by ASO-PCR. Undetectable MRD after course IA (1 cycle InO induction) was associated with EFS with a 3-yr EFS of 52% vs 0% for detectable MRD (median NR vs 8 mo, hazard ratio [HR] 0.07, P=0.004) and a 3-yr OS of 100% vs 0% for detectable MRD (median NR vs 20 mo, HR 0.00, P=0.0014). Conclusions: Longer follow-up of chemotherapy-free treatment with InO and blina for older pts with newly diagnosed, Ph-negative, CD22-positive, B-cell ALL reveals durable remissions and survival. The A041703 regimen is a compelling option for first-line treatment of this pt population. Support: U10CA180821, U10CA18088; https://acknowledgments.alliancefound.org.

PURPOSE Older patients with ALL receiving conventional chemotherapy have poor survival due to toxic death and relapse. We hypothesized that a chemotherapy-free, targeted regimen using the anti-CD22 antibody-calicheamicin conjugate inotuzumab ozogamicin followed by the bispecific anti-CD19/CD3 T-cell engager blinatumomab would reduce toxic death and yield high rates of prolonged remission and survival. METHODS Eligible patients were age 60 years and older with untreated, Philadelphia chromosome (Ph)–negative, CD22-positive, B-cell ALL. Patients received up to two cycles of inotuzumab ozogamicin followed by four or five cycles of blinatumomab with intrathecal methotrexate CNS prophylaxis. The primary end point was 1-year event-free survival (EFS). RESULTS The 33 eligible patients had a median age of 71 years (range, 60-84) and a median CD22 expression of 92% (range, 21%-100%). Eight (24%) had previous chemotherapy or radiation for other cancers, six for multiple myeloma. The composite complete remission rate was 85% after two cycles of inotuzumab ozogamicin and 97% by the end of two cycles of blinatumomab. At a median follow-up of 30 months, the 1-year EFS and overall survival were 75% (95% CI, 61 to 92) and 85% (95% CI, 73 to 98), respectively. EFS was shorter with lower CD22 expression or detectable measurable residual disease at any time point. CONCLUSION Inotuzumab ozogamicin then blinatumomab without maintenance chemotherapy in older patients with untreated, Ph-negative, CD22-positive, B-cell ALL yields a high remission rate and excellent EFS. Given the lack of standard, safe, and effective therapies in this population, the regimen should be considered a standard treatment option.

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