Abstract
Background:
The combination of low-intensity chemotherapy and inotuzumab ozogamicin (INO), with sequential blinatumomab, is highly effective in older adults with newly diagnosed B-cell acute lymphoblastic leukemia (ALL) and in relapsed or refractory B-cell ALL. Earlier, “dose-dense” administration of blinatumomab could lead to earlier and deeper measurable residual disease (MRD) responses and better outcomes.
Patients and Methods:
We performed a retrospective analysis of the safety and efficacy of a dose-dense regimen of mini-hyper-CVD (mini-hyperfractionated cyclophosphamide, vincristine and dexamethasone alternating with mini-methotrexate and cytarabine), INO and blinatumomab in patients with B-cell ALL.
Results:
Twenty-one patients were treated (frontline, n=9; MRD consolidation, n=4; relapsed/refractory, n=8). In the frontline cohort, all patients achieved CR/CRi and MRD negativity by flow cytometry at the end of cycle 1. Across the frontline and MRD consolidation cohorts, 10/11 patients (91%) achieved next-generation sequencing (NGS) MRD negativity at a sensitivity of 10−6, including 6/10 evaluable patients (60%) who achieved NGS MRD negativity after cycle 1. The CR/CRi rate in the relapsed/refractory cohort was 63%, and all responders achieved MRD negativity by flow cytometry at the end of cycle 1. The 1-year OS rate for the combined cohort of the frontline and MRD-positive patients was 83%. No new safety signals were observed with the dose-dense mini-hyper-CVD, INO and blinatumomab regimen.
Conclusion:
Dose-dense delivery of mini-hyper-CVD, INO and blinatumomab was safe and resulted in rapid and deep MRD negativity in patients with B-cell ALL. This regimen is now being prospectively evaluated in both the frontline and relapsed/refractory settings.
Keywords: chemoimmunotherapy, CD19, CD22, bispecific antibody, antibody-drug conjugate
Micro Abstract:
We retrospectively analyzed the outcomes of patients with B-cell acute lymphoblastic leukemia (ALL) who received a dose-dense regimen of mini-hyper-CVD, inotuzumab ozogamicin and blinatumomab. In newly diagnosed or measurable residual disease (MRD)-positive ALL, 10/11 patients (91%) achieved next-generation sequencing (NGS) MRD negativity at a sensitivity of 10−6, and 6/10 patients (60%) achieved NGS MRD negativity after cycle 1. The regimen was safe and resulted in high rates of deep and rapid MRD negativity, warranting prospective evaluation.
Introduction
The development of novel monoclonal antibodies such as inotuzumab ozogamicin (INO) and blinatumomab, as well as CD19 chimeric antigen receptor (CAR) T-cell therapy, has dramatically improved the outcomes of patients with B-cell acute lymphoblastic leukemia (ALL).1 While these agents are approved as monotherapy, several regimens are being developed where these agents are delivered in sequence or in combinations. Promising results have been reported with a regimen of mini-hyper-fractionated cyclophosphamide, vincristine and dexamethasone, alternating with mini-methotrexate and cytarabine (mini-hyper-CVD regimen), INO and blinatumomab in both relapsed/refractory B-cell ALL and in older adults with newly diagnosed B-cell ALL.2,3 In first salvage, this regimen was associated with a median overall survival (OS) of 31 months and a 3-year OS rate of 49%. In older adults with newly diagnosed B-cell ALL, the median OS was 45 months and the 5-year OS rate was 46%.
In the standard mini-hyper-CVD, INO and blinatumomab regimen, patients receive 4 cycles of low-intensity chemotherapy plus INO, followed by 4 cycles of blinatumomab consolidation, and then maintenance with alternating blocks of POMP (6-mercaptopurine, vincristine, methotrexate and prednisone) and blinatumomab. We hypothesized that earlier administration of blinatumomab—given concurrently with the mini-hyper-CVD and INO cycles in a “dose-dense” fashion—would be safe and would lead to more rapid MRD negativity, a therapeutic endpoint that has been shown to be associated with lower rates of relapse and better long-term survival in several studies.4–6 To evaluate the safety and efficacy of this approach, we performed a retrospective analysis of patients with Philadelphia chromosome-negative B-cell ALL who received dose-dense mini-hyper-CVD + INO + blinatumomab outside of a clinical trial at our institution.
Methods
Study design and participants
This is a retrospective analysis of patients with Philadelphia chromosome-negative B-cell ALL who received at least one cycle of dose-dense mini-hyper-CVD + INO + blinatumomab outside of a clinical trial at our institution. Patients of all ages (including both children and adults) were eligible for this analysis. The hyper-CVD + INO backbone was administered as previously described2,3, although it could be modified as needed per the physician’s discretion. Rituximab was administrated to patients with CD20-positive ALL. To be evaluable for this analysis, blinatumomab must have been started by cycle 1, day 21. Patients were included if they received this regimen for 1.) frontline induction, 2.) consolidation for MRD-positive disease, or 3.) salvage therapy for relapsed/refractory disease. An example of this regimen (first 4 cycles only) is shown in Figure 1; this dosing schedule is currently being evaluated in an ongoing clinical trial (clinicaltrials.gov identifier: NCT01371630). While not all patients received the exact dosing schedule shown, this provides a visual representation of a treatment schema that is similar to one used for the patients in this analysis.
Figure 1. Example treatment schema of the dose-dense mini-hyper-CVD, inotuzumab ozogamicin and blinatumomab regimen.
Only the first 4 cycles are shown. Note that this is an example of the regimen used in this cohort, although variations to dosing and timing of some agents were implemented in some patients.
Response and outcome definitions
MRD was assessed by 6-color multiparameter flow cytometry (MFC) with a sensitivity of 10−4 and/or next-generation sequencing (NGS) for immunoglobin or T-cell receptor gene rearrangements with a sensitivity of 10−6, as described previously.5,7 Overall survival (OS) was calculated from the time of treatment initiation until death from any cause, censored if the patient was alive at last follow-up.
Statistical methods
Patient characteristics were summarized using median (range) for continuous variables and frequencies (percentages) for categorical variables. The Kaplan-Meier method was used to estimate the probabilities for OS. All statistical analyses were performed using GraphPad Prism 9.
Results
Patient characteristics
Between July 2020 and January 2023, 21 patients were treated with this regimen (Table 1). The median age was 48 years (range, 6–74 years); 3 patients were <18 years of age (all in the relapsed/refractory cohort). Nine patients (43%) were treated as frontline therapy, 4 (19%) for treatment of MRD (3 for MFC MRD and 1 for persistent FISH for t[4;11]), and 8 (38%) for relapsed/refractory disease. Of the 19 patients with evaluable immunophenotyping prior to treatment, all were positive for CD19 and CD22. In the MRD cohort, 3 patients were in first remission and 1 was in second remission. In those with MRD positive by MFC, the levels of MRD were 0.01%, 0.02% and 0.34%. In the relapsed/refractory cohort, patients were heavily pretreated, with a median of 3 prior therapies (range, 1–7); 2 patients had received prior INO, 3 had received prior blinatumomab, 3 had received prior CD19 CAR T-cell therapy, and 3 had undergone prior allogeneic stem cell transplantation (alloSCT). Specifically, 2 patients in the relapsed/refractory cohort previously received blinatumomab, CD19 CAR T-cells and alloSCT; 2 patients had received prior INO only, and 1 patient each had received prior blinatumomab only, prior CD19 CAR T-cells only and prior alloSCT only. Three patients had extramedullary disease (all in the relapsed/refractory cohort), 1 with central nervous system (CNS) leukemia and bone marrow MRD-positivity by MFC and 2 with non-CNS extramedullary disease without bone marrow involvement.
Table 1.
Baseline Characteristics
| Characteristic N (%); median [range] |
Frontline (N=9) | MRD-positive consolidation (N=4) | Relapsed/refractory (N=8) |
|---|---|---|---|
| Age (years) | 45 [20–74] | 30 [19–42] | 24 [6–61] |
| Inadequate sample | 0 | 0 | 1 (13) |
| Bone marrow blasts (%) | 83 [33–95] | ---- | 62 [4–97] |
| Ph-like ALL | 3 (33) | 1 (25) | 1 (13) |
| TP53 mutation | 2 (22) | 0 | 3 (38) |
| CD19 positive (%) | 99 [91–99.9] | 99 [99–99] | 99 [2.8–99.9] |
| CD22 positive (%) | 97.7 [63.7–99.9] | 89.5 [80–99] | 98.3 [31–99.9] |
| CD20 positive ≥20% | 6 (67) | 1/3 (33) | 4/7 (57) |
| Extramedullary disease | 0 | 0 | 3 (38) |
| Number of prior therapies | ---- | 1 [1–1] | 3 [1–7] |
| Prior INO | ---- | 1 (25) | 2 (25) |
| Prior blinatumomab | ---- | 0 | 3 (38) |
| Prior alloSCT | ---- | 1 (25) | 3 (38) |
| Prior CAR T-cells | ---- | 0 | 3 (38) |
Regimen characteristics
Patients received a median of 2 cycles (range, 1–5) of the dose-dense regimen. Twenty of the patients (95%) received 0.9 mg/m2 of INO in cycle 1; 1 patient in the relapsed/refractory cohort received 0.6 mg/m2. The median cumulative dose of INO received as part of the dose regimen was 1.2 mg/m2 (range, 0.6–2.7 mg/m2). The median day of blinatumomab start was day 4 (range, day 4–17); in 16 patients (76%) blinatumomab was started by day 7. Eighteen of the patients (86%) received rituximab as part of the dose dense regimen
Response and MRD outcomes
In the frontline cohort, all patients achieved complete remission (CR) or CR with incomplete hematologic recovery (CRi) (CR in 8 patients and CRi in 1 patients), all after cycle 1 (Table 2). All patients in the frontline cohort achieved MFC MRD negativity after 1 cycle of therapy. Among 7 frontline patients who were tested for NGS MRD, all achieved NGS MRD negativity, with 4 of 6 tested patients (67%) achieving NGS MRD negativity after cycle 1. In the MRD cohort, all 3 patients who were MRD positive by MFC became MRD negative after cycle 1; the patient with positive FISH for t(4;11) became FISH-negative after cycle 2. Three of the 4 patients in the MRD cohort became NGS MRD negative, two of them after 1 cycle. Overall, 5 of the 8 patients (63%) in the relapsed/refractory cohort achieved CR/CRi. Among the 5 responders in the relapsed/refractory cohort (including the patient with CNS disease + MRD-positive bone marrow), all achieved MFC MRD-negativity after 1 cycle of therapy, including one patient who had received prior blinatumomab, CD19 CAR T-cells and alloSCT, one who had received prior blinatumomab, and one who had received (and was refractory to) prior CD19 CAR T-cells. Across all 3 cohorts, all responding patients achieved MFC MRD negativity, all after 1 cycle of therapy. Across the frontline and MRD consolidation cohorts, 10 of 11 patients (91%) achieved NGS MRD negativity at a sensitivity of 10−6, with 6 of 10 evaluable patients (60%) achieving NGS MRD negativity after cycle 1.
Table 2.
Responses and Subsequent Consolidation
| Response N (%) |
Frontline (N=9) | MRD-positive consolidation (N=4) | Relapsed/refractory (N=8) |
|---|---|---|---|
| CR/CRi rate # | 9 (100) | ----- | 5 (63) |
| At any time | 9 (100) | 3/3 (100) | 5/5 (100) |
| At any time | 7/7 (100) | 3 (75) | |
| CAR T-cell consolidation | 0 | 1 (25) | 0 |
| AlloSCT consolidation | 0 | 2 (50) | 5 (63) |
Abbreviations: MRD, measurable residual disease; Ph, Philadelphia chromosome; ALL, acute lymphoblastic leukemia; INO, inotuzumab ozogamicin; AlloSCT, allogeneic hematopoietic stem cell transplant; CAR, chimeric antigen receptor; CR, complete remission; CRi, complete remission with incomplete count recovery
Including only patients with baseline morphological marrow or extramedullary disease
Including only responding patients with baseline flow-detectable marrow disease
Relapse and survival outcomes
With a median follow-up of 13.4 months (range, 0.5–20.6 months), 7 patients (33%) underwent consolidative alloSCT (2 in the MRD cohort and all 5 responders in the relapsed/refractory cohort). One patient in the MRD cohort received CAR-T cell consolidation. Six patients (29%) have died (1 in the frontline cohort, 1 in the MRD cohort and 4 in the relapsed/refractory cohort). Three deaths were due to complications of alloSCT (1 in the MRD cohort and 2 in the relapsed/refractory cohort), 2 of which were from veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS); 2 deaths were due to infection and sepsis (1 in the setting of refractory ALL and 1 in MRD-negative CR during cycle 4 of the dose-dense regimen), and 1 from unknown cause in the setting of refractory ALL. Among 18 responding patients, only 1 patient relapsed. This patients had FISH MRD positivity for t(4;11), achieved FISH negativity with mini-hyper-CVD + INO + blinatumomab, underwent alloSCT and relapsed 4.5 months later. The median OS for the relapsed/refractory cohort was 5.8 months and was not reached for the frontline or MRD cohorts. The 1-year OS rate for the combined cohort of the frontline and MRD-positive patients was 83% (Figure 1).
Safety
No new safety signals were observed with the dose-dense delivery of these agents. One patient developed grade 1 cytokine release syndrome (MRD cohort), and 2 patients developed grade 1 tremor (one in the MRD cohort and one in the frontline cohort). No patients experienced grade 2 or higher blinatumomab-related toxicity. During cycle 1, 5 patients (24%) had infection, 3 of which were grade 3 (all pneumonia) and 1 that was grade 5 (occurring on cycle 1, day 7 in a patient in the relapsed/refractory cohort). Two additional patients (10%) had neutropenic fever. The 30-day and 60-day mortality were both 5%. Two patients developed VOD/SOS after alloSCT. One patient was in the relapsed/refractory cohort, had undegone prior alloSCT, received cumulative INO dose of 2.1 mg/m2 and died on day +25. The other patient was in the MRD cohort, received cumulative INO dose of 2.7 mg/m2 and died on day +58.
Discussion
In this retrospective analysis, we observed that the dose-dense regimen of mini-hyper-CVD, INO and blinatumomab could be delivered safely and was associated with very rapid MRD clearance. All responding patients achieved MFC MRD negativity after 1 cycle of therapy and 6 of 10 evaluable patients (60%) achieved NGS MRD negativity at a sensitivity of 10−6 after 1 cycle. These rates of MRD clearance compare favorably to historical expectations with the conventional chemotherapy such as hyper-CVAD where the MFC MRD negativity rate after the first cycle of therapy is approximately 60–75%.7–9
Early MRD negativity is an important endpoint in ALL associated with superior outcomes.4–6 In one retrospective analysis of adults with ALL undergoing frontline intensive chemotherapy, remission duration and survival were superior in those who achieved MFC MRD negativity after cycle 1 versus those who achieved MFC MRD negativity later in consolidation (3-year OS 76% versus 58%; P=0.001).6 Outcomes are even better for patients who achieve early MRD negativity using more sensitive assays such as NGS-based MRD. In one report, no relapses were observed in the cohort of patients who achieved NGS MRD negativity at a sensitivity of 10−6 after 1 cycle of induction with either conventional hyper-CVAD or mini-hyper-CVD, which translated into a 5-year OS rate of 90%.5 In this previous analysis, only 23% of patients achieved NGS MRD negativity after 1 cycle of therapy; in contrast, we observed a 60% rate of NGS MRD negativity with the dose-dense mini-hyper-CVD, INO and blinatumomab regimen. Acknowledging the relatively short follow-up of our cohort, the 1-year OS rate of 83% in the combined cohort of the frontline and MRD-positive patients is encouraging, with the only relapse occurring in a high-risk patient with t(4;11).
The regimen was delivered safely with no new toxicity signals identified. Although blinatumomab is administered as early as day 4 of cycle 1 in this dose-dense regimen, the rate of blinatumomab-associated toxicities was low, and these events were all mild (grade 1). The relatively low rate of these adverse events may be driven by the use of effective cytoreductive therapy (i.e. hyper-CVD and INO) immediately prior to delivery of blinatumomab. It is notable that this regimen utilizes low-dose fractionated INO with a maximum cumulative dose of 2.7 mg/m2, a dosing strategy that has been employed in the conventional mini-hyper-CVD, INO and blinatumomab regimen, and which has been associated with a lower rate of VOD/SOS since it was implemented (only 2% in the last report of this regimen in the salvage setting).3 We observed 2 cases of VOD/SOS (10% of the cohort), although one of these was in a patient with undergoing a second alloSCT, which significantly increases the risk of VOD/SOS, independently of INO administration.10
This study is limited by its retrospective nature at a single institution and the heterogeneity of the treated patients (including both frontline and relapsed/refractory). This regimen was typically used in patients who were not eligible for our other clinical trials due to out-of-range laboratory values or financial/logistical considerations that could impact their ability to follow-up longitudinally. In this respect, there could be some selection bias for use of this off-protocol regimen. However, for patients with newly diagnosed ALL, it is important to note that we do not typically wait for full cytomolecular results (except for BCR::ABL1 status) before starting frontline therapy; therefore, there was unlikely a selection bias with respect to genomic features.
Conclusion
The dose-dense mini-hyper-CVD, INO and blinatumomab regimen was associated with high rates of early and deep MRD negativity that compare favorably to historical expectations. This regimen is now being assessed prospectively at our institution in children and adults with relapsed/refractory B-cell ALL and in older adults with newly diagnosed B-cell ALL (NCT05645718 and NCT01371630).
Figure 2.
Overall survival of the frontline and MRD consolidation cohorts
Clinical Practice Points.
Low-intensity chemotherapy and inotuzumab ozogamicin (INO), with sequential blinatumomab, is highly effective in older adults with newly diagnosed B-cell acute lymphoblastic leukemia (ALL) and in relapsed or refractory B-cell ALL.
Earlier, “dose-dense” administration of blinatumomab could lead to earlier and deeper measurable residual disease (MRD) responses and better outcomes, but the safety and efficacy of this approach is unknown.
We performed a retrospective analysis of the safety and efficacy of a dose-dense regimen of mini-hyper-CVD, INO and blinatumomab in patients with B-cell ALL.
Among 13 patients with newly diagnosed or MRD-positive ALL, all achieved complete remission (CR) or CR with incomplete hematological recovery (CRi), and all achieved MRD negativity by flow cytometry after the first cycle.
In newly diagnosed or MRD-positive ALL, 10/11 patients (91%) achieved next-generation sequencing (NGS) MRD negativity at a sensitivity of 10−6, and 6/10 patients (60%) achieved NGS MRD negativity after cycle 1.
In the relapsed/refractory cohort, the CR/CRi rate was 63%, and all responders achieved MRD negativity by flow cytometry at the end of cycle 1.
There were no new safety concerns observed with the dose-dense administration of these agents.
Dose-dense mini-hyper-CVD, INO and blinatumomab was safe and resulted in rapid and deep MRD negativity in patients with B-cell ALL, warranting evaluation of this regimen in prospective clinical trials.
Funding source:
This research is supported in part by the MD Anderson Cancer Center Leukemia SPORE CA100632, and the NIH/NCI Cancer Center Support Grant P30 CA016672.
Footnotes
Conflict of interest statement: N.J.S, E.J. and H.K. have received research funding and honoraria from Amgen and Pfizer Inc. The rest of the authors have no relevant conflicts to disclose.
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