Sequential Combination of Inotuzumab Ozogamicin (InO) with Low-Intensity Chemotherapy (mini-hyper-CVD) with or without Blinatumomab (Blina) As Salvage Therapy for Patients (Pts) with Acute Lymphoblastic Leukemia (ALL) in First Relapse

Background:

The combination of low intensity therapy with InO improved outcome compared to intensive chemotherapy and to single agent InO in Salvage 1. The sequential addition of blina may allow the administration of weekly lower dose of InO and distancing allogeneic stem cell transplant (ASCT) from the last dose of InO, while deepening the minimal residual disease response. This will lead to less veno-occlusive disease (VOD) and better long-term efficacy. The aim of this study is to evaluate the outcome of pts in first relapse treated with this combination.

Methods:

The mini-hyper-CVD (cycles 1, 3, 5, 7) comprised 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 anthracycline. Even cycles (cycles 2, 4, 6, 8) comprised 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 first 4 courses. InO 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 38 pts were treated, an amendment was made to incorporate 4 cycles of blina after 4 cycles of mini-hyper-CVD + InO. InO 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; blina was continuously infused over 28 days every 42-day cycle for 4 cycles. The decision to proceed with ASCT was based on the discretion of the treating physician after discussion with the pt.

Results:

From 2/2013 to 9/2019, 65 pts were enrolled and received first salvage therapy including 27 pts with mini-hyper-CVD + InO + blina. Patient characteristics and outcome are summarized in Table 1. The median age at diagnosis was 39 years (range, 18-87). Among 65 pts, 8 (12%) pts had primary refractory disease; 25 (38%), CR1 duration less than 12 months. 7 (11%) pts had prior history of ASCT. The overall response rate was 91% (CR, 66%, CRp/CRi, 25%). These rates were 100% in pts with primary refractory disease (CR 100%); 84 % in pts with CR1 duration <12 months (CR 60%, CRp/CRi 24%); and 94% in pts with CR1 duration >12 months (CR 63%, CRi/CRp 31%) (Table 2). Among 56 evaluable pts for minimal residual disease (MRD) assessment at morphologic response and 57 overall, 57% of pts achieved negative MRD by multicolor flow cytometry at response and 88% overall. Among 59 who achieved remission, 26 (44%) relapsed, 35 (59%) underwent allogeneic SCT in CR2, and 6 (9%) died in CR/CRp. Overall, 6 pts (9%) developed VOD; 4 after subsequent ASCT. The rate of VOD was 5/38 (13%) in pts who did not receive blina. In contrast, only 1 case of VOD was observed among the 27 pts (4%) who received the weekly lower dose of InO and sequential addition of blina; this pt had VOD post ASCT in CR2. With a median follow-up of 36 months (range, 1-87 months), 27 pts (42%) were alive, 21 of whom (32%) were in CR and MRD negative status. The median CR duration (CRD) and overall survival (OS) were 13 and 16.5 months, respectively. The estimated 3-year CRD and OS rates were 25% and 42%, respectively. Using the IPTW analysis, compared to a similar historical cohort of pts treated with standard salvage chemotherapy (n=77), the mini-hyper-CVD + InO with or without blina (n=58) resulted in significantly improved survival (P<0.001). The 3-year OS rates were 54% (median not reached) and 32% (median 16 months), respectively (P=0.002).

Conclusion:

The combination of InO with mini-hyper-CVD with or without blina is highly effective and shows improved outcome compared to intensive chemotherapy in pts with ALL in first relapse, with 3-year OS rate of 42%. The risk of VOD can be minimized with fractionated lower dose InO and sequential combination of blina.