Long-Term Follow-up of the Combination of Low-Intensity Chemotherapy Plus Inotuzumab Ozogamicin with or without Blinatumomab in Patients with Relapsed-Refractory Philadelphia Chromosome-Negative Acute Lymphoblastic Leukemia: A Phase 2 Trial

Background: The outcome of patients with relapsed-refractory (R-R) acute lymphoblastic leukemia (ALL) is poor. Inotuzumab ozogamicin and blinatumomab are highly active single agents in R-R ALL. The combination of inotuzumab with low-intensity mini-hyper-CVD chemotherapy showed encouraging results in this patient population. The sequential addition of blinatumomab might optimize the efficacy of the regimen, reduce its toxicities, and further improve outcomes in R-R ALL. The aim of the analysis is to evaluate the efficacy and safety of inotuzumab ozogamicin plus low-intensity chemotherapy with or without blinatumomab in R-R ALL. Methods: Patients with relapsed-refractory Philadelphia chromosome-negative ALL were eligible. The mini-hyper-CVD (cycles 1, 3, 5, 7) were comprised of cyclophosphamide (150 mg/m2 every 12 h on days 1-3), vincristine (2 mg flat dose on days 1 and 8), and dexamethasone (20 mg on days 1-4 and days 11-14) without anthracyclines. Even cycles (cycles 2, 4, 6, 8) were comprised of methotrexate (250 mg/m2 on day 1) and cytarabine (0.5 g/m2 given every 12 h on days 2 and 3). Rituximab and intrathecal chemotherapy were given for the first 4 courses. Inotuzumab ozogamicin was originally given on day 3 of the first four cycles at the dose of 1.3-1.8 mg/m2 at cycle 1, followed by 1.0-1.3 mg/m2 in subsequent cycles. After 67 pts were treated, an amendment was made to incorporate 4 cycles of blinatumomab after 4 cycles of mini-hyper-CVD + inotuzumab ozogamicin. Inotuzumab ozogamicin was given on days 2 and 8 at the dose of 0.6 and 0.3 mg/m2 at cycle 1, respectively, followed by days 2 and 8 at the dose of 0.3 and 0.3 mg/m2 at subsequent cycles; blinatumomab was continuously infused over 28 days every 42-day cycle for 4 cycles. The decision to proceed with allogeneic hematopoietic cell transplantation (HCT) was based on the discretion of the treating physician after discussion with the patient. Results: From 2/2013 to 9/2019, 96 patients were enrolled and treated including 29 patients with mini-hyper-CVD + inotuzumab + blinatumomab. The median follow-up is 36 months (range, 0.1-87.5). Patient characteristics and outcome are summarized in Table 1. The median age was 37 years (range, 17-87), and 20% of patients had received prior HCT. The overall response rate was 80% (CR, 57%, CRp/CRi, 20%). These rates were 91% in salvage(S) 1 (primary refractory, 100%; CR1 duration 12 months, 94%) 61% inS2, and 57% in S3 or higher. A