Phase 2 study of inotuzumab ozogamicin for measurable residual disease in acute lymphoblastic leukemia in remission.

ABSTRACT: The detection of measurable residual disease (MRD) is the strongest predictor of relapse in acute lymphoblastic leukemia (ALL). Using inotuzumab ozogamicin in the setting of MRD may improve outcomes. Patients with ALL in first complete remission (CR1) or beyond (CR2+) with MRD ≥ 1 × 10-4 were enrolled in this phase 2 trial. Inotuzumab was administered at 0.6 mg/m2 on day 1 and 0.3 mg/m2 on day 8 of cycle 1, then at 0.3 mg/m2 on days 1 and 8 of cycles 2-6. Twenty-six consecutive patients with a median age of 46 years (range, 19-70 years) were treated. Nineteen (73%) were in CR1 and seven (27%) in CR2+; 16 (62%) had Philadelphia chromosome-positive ALL. Fifteen (58%) had baseline MRD ≥ 1 × 10-3. A median of 3 cycles (range, 1-6) were administered. Eighteen (69%) patients responded and achieved MRD negativity. After a median follow-up of 24 months (range, 9-43), the 2-year relapse-free survival rate was 54% and the 2-year overall survival rate was 60% in the entire cohort. Most adverse events were low grade; sinusoidal obstruction syndrome was noted in 2 patients (8%). In summary, inotuzumab ozogamicin resulted in favorable survival, MRD negativity rates, and safety profiles for patients with ALL and MRD-positive status. This study was registered at www.ClinicalTrials.gov as #NCT03441061.

Genomic determinants of response and resistance to inotuzumab ozogamicin in B-cell ALL.

Inotuzumab ozogamicin (InO) is an antibody-drug conjugate that delivers calicheamicin to CD22-expressing cells. In a retrospective cohort of InO treated patients with B-cell acute lymphoblastic leukemia, we sought to understand the genomic determinants of response to InO. Acquired CD22 mutations were observed in 11% (3/27) of post-InO relapsed tumor samples. There were multiple CD22 mutations per sample and the mechanisms of CD22 escape included protein truncation, protein destabilization, and epitope alteration. Hypermutation by error-prone DNA damage repair (alternative end-joining, mismatch repair deficiency) drove CD22 escape. Acquired loss-of-function mutations in TP53 , ATM and CDKN2A were observed, suggesting compromise of the G1/S DNA damage checkpoint as a mechanism of evading InO-induced apoptosis. In conclusion, genetic alterations modulating CD22 expression and DNA damage response influence InO efficacy. The escape strategies within and beyond antigen loss to CD22-targeted therapy elucidated in this study provide insights into improving therapeutic approaches and overcoming resistance. KEY POINTS: We identified multiple mechanisms of CD22 antigen escape from inotuzumab ozogamicin, including protein truncation, protein destabilization, and epitope alteration.Hypermutation caused by error-prone DNA damage repair was a driver of CD22 mutation and escape.

Hyper-CVAD plus ponatinib versus hyper-CVAD plus dasatinib as frontline therapy for patients with Philadelphia chromosome-positive acute lymphoblastic leukemia: A propensity score analysis.

BACKGROUND: The clinical efficacy of hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone (HCVAD) plus ponatinib has not been compared with that of HCVAD plus dasatinib in patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) in a randomized clinical trial. METHODS: The authors analyzed 110 patients with newly diagnosed Ph+ ALL who were enrolled in 2 consecutive, prospective, phase 2 clinical trials of frontline HCVAD with either dasatinib (63 patients) or ponatinib (47 patients). Propensity score analysis with 1:1 matching with the nearest neighbor matching method and inverse probability of treatment weighting (IPTW) analysis based on the propensity scores were performed to assess response rates, event-free survival (EFS), and overall survival (OS) between the cohorts. RESULTS: Propensity score matching identified 41 patients in each cohort. With propensity score matching, the 3-year EFS rates for patients treated with HCVAD plus ponatinib and HCVAD plus dasatinib were 69% and 46%, respectively (P =.04), and the 3-year OS rates were 83% and 56%, respectively (P =.03). IPTW analysis using prematching cohorts demonstrated that patients treated with HCVAD plus ponatinib had significantly higher rates of minimal residual disease negativity by flow cytometry on day 21, complete cytogenetic response at complete response, major molecular response at complete response and at 3 months, and complete molecular response at 3 months. IPTW confirmed that treatment with HCVAD plus ponatinib was associated with longer EFS (P =.003) and OS (P =.001) compared with treatment with HCVAD plus dasatinib. CONCLUSIONS: The clinical outcome of patients treated with HCVAD plus ponatinib appears to be superior to that of patients treated with HCVAD plus dasatinib among individuals with Ph+ ALL. Cancer 2016;122:3650-6. © 2016 American Cancer Society.