Updated Results from a Phase II Study of Hyper-CVAD, with or without Inotuzumab Ozogamicin, and Sequential Blinatumomab in Patients with Newly Diagnosed B-Cell Acute Lymphoblastic Leukemia

Background

Blinatumomab improves overall survival (OS) compared with chemotherapy in patients (pts) with relapsed/refractory B-cell acute lymphoblastic leukemia (ALL) and is also FDA-approved for eradication of persistent or recurrent measurable residual disease (MRD). Blinatumomab also improves OS when added to standard chemotherapy, irrespective of MRD status, in newly diagnosed Philadelphia chromosome (Ph)-negative B-cell ALL. Inotuzumab ozogamicin (INO) improves OS in the relapsed/refractory setting, and we hypothesized that the addition of INO to hyper-CVAD plus blinatumomab would lead to deeper and more durable responses, reduce relapses, and improve survival.

Methods

In this phase II study, pts age 14-59 with newly diagnosed Ph-negative B-cell ALL, including pts who had received no more than 1 prior cycle of chemotherapy, were eligible. Pts had to have a performance status of ≤3, total bilirubin ≤2 mg/dl, creatinine ≤2 mg/dl, and no significant CNS pathology (except for CNS leukemia). Pts received hyper-CVAD alternating with high-dose methotrexate (MTX) and cytarabine (Ara-C) for up to 4 cycles, followed by 4 cycles of blinatumomab at standard doses. Pts with CD20+ disease (≥1% cells) received 8 doses of ofatumumab (2000 mg) or rituximab (375 mg/m2). Eight doses of prophylactic IT chemotherapy were given. Maintenance was with alternating blocks of POMP (given in maintenance cycles 1-3, 5-7, 9-11, and 13-15) and blinatumomab (given in maintenance cycles 4, 8, and 12). Those with high-risk disease features started blinatumomab after 2 cycles of hyper-CVAD. Beginning with pt #39, INO at a dose of 0.3 mg/m2 on day 1 and 8 was added to the 2 cycles of MTX/Ara-C (which was also dose reduced to 500 mg/m2 of MTX and 1 g/m2 of Ara-C with this amendment) and to 2 cycles of blinatumomab consolidation (4 total cycles with INO).

Results

As of June 2023, 75 pts have been treated (38 without INO and 37 with INO). Pt characteristics are shown in Table 1. The median age across both cohorts was 33 (range, 18-59). 36 pts (48%) had ≥1 high-risk pretreatment characteristic at enrollment (e.g. poor-risk cytogenetics, CRLF2 overexpression by flow and/or TP53 mutation). Sixteen pts were in complete remission (CR) at enrollment after 1-2 cycles of off-protocol therapy, 10 of whom were MRD-negative by 6-color flow cytometry.

All 59 pts (100%) with active disease upon study entry achieved CR, with 50 pts (84%) achieving CR after the first cycle. MRD negativity by flow (sensitivity 10^-4) was achieved in 60 of 65 evaluable pts (92%), with 43 pts (66%) achieving flow MRD negativity after the first cycle. Two of the 5 patients who did not achieve flow MRD negativity had NUP214::ABL1 fusion, 1 had KMT2A rearrangement, and 2 are still early in treatment and have not yet received blinatumomab. Overall, 25 of 36 tested pts (69%) achieved next-generation sequencing-based MRD negativity at a sensitivity of 10^-6.

The median duration of follow-up is 26 months (range, 1-77 months). Overall, 8 pts (11%) relapsed in the absence of SCT, 23 pts (31%) underwent stem cell transplantation (SCT) in first remission (2 of whom relapsed post-SCT), 3 pts (4%) died in CR, and 41 pts (55%) remain in continuous remission without SCT. Among the 10 relapses, 3 were in the CNS, 2 of which were CNS-only. All but one relapse occurred in pts with ≥1 poor-risk feature(s).

Across both cohorts, the estimated 3-year OS was 88% and the 3-year relapse-free survival (RFS) was 79%. The 3-year OS rate for pts without a high-risk baseline feature was 93% vs 83% in pts with ≥1 high-risk feature. In a landmark analysis, there was no difference in outcomes between pts who underwent SCT in first remission versus those who did not (3-year OS: 90% versus 87%). With a median follow-up of 18 months in the INO group, 3 pts (8%) have relapsed, 2 with CNS-only relapses, and none have died. The 18-month RFS in the cohorts with and without INO were 92% vs 76% (p=0.18), and the OS was 100% vs 84% (p=0.04) (Figure 1).

One pt discontinued blinatumomab due to a related adverse event (grade 2 encephalopathy and dysphasia). No pts discontinued INO due to toxicity, and no cases of veno-occlusive disease have been observed.