A Phase 1 Trial of Inotuzumab in Combination with CVP (Cyclophosphamide, Vincristine, Prednisone) for Relapsed/ Refractory CD22+ Acute Leukemia (SWOG 1312)

The prognosis of patients (pts) with relapsed/ refractory acute lymphoblastic leukemia (ALL) remains poor and novel therapies are needed. The anti-CD22 immunoconjugate inotuzumab ozogamicin (INO) has demonstrated promising results in both phase 2 and 3 trials (Kantarjian et al. Lancet Oncology 2012; 13(4): 403-11). Pre-clinical studies have demonstrated superior anti-tumor activity when INO is co-administered with cyclophosphamide (C), vincristine (V), and prednisone (P). In this study, SWOG 1312, we assess the safety of INO in combination with CVP and determine the maximum tolerated dose (MTD) of INO in this regimen for patients with relapsed or refractory (R/R) CD22+ acute leukemia (B-ALL, mixed phenotype, and Burkitts). Here, we present our toxicity results.

Methods: Pts were treated at limited SWOG institutions from Apr 2014 to present. INO was supplied by Pfizer and an IND was approved by the FDA. The protocol was reviewed and approved by each institutional review board. Eligibility criteria included: age > 18 years (yrs), > 20% blasts expressing CD22, R/R CD22+ acute leukemia (B-ALL, mixed phenotype, or Burkitts), and adequate organ function. All pts received treatment with C (750 mg/m²) intravenous (IV) Day 1, V (1.4 mg/m²) (max 2 mg) IV Day 1, P (100 mg) orally Days 1-5 and IO (dose escalated as in Table 1) IV Days 1, 8, and 15. Each cycle was 28 days, and a maximum of 6 cycles could be administered. Dose escalation was performed using a standard 3x3 design; with the plan to treat 12 pts once the MTD was defined. Dose limiting toxicities (DLTs) were considered: (1) > Grade 4 non-hematologic toxicities with the exception of nausea, vomiting and toxicities secondary to neutropenia and sepsis; (2) prolonged myelosuppression [absolute neutrophil count (ANC) < 500/ uL or platelet count < 25,000/uL] in a bone marrow with < 5% blasts and no evidence of leukemia that lasts > 35 days beyond the most recent dose of IO; (3) any grade 3 non-hematologic toxicity (excluding peripheral neuropathy, hyperglycemia, and toxicities secondary to neutropenia, thrombocytopenia, and sepsis) that does not resolve to Grade 2 or better by 7 days beyond the most recent dose of IO; (4) any > Grade 3 elevation in SGOT/ SGPT or bilirubin lasting ≥ 7 days; (5) any IO-related toxicity resulting in permanent discontinuation of IO.

Results: As of 7/14/2016, 24 pts have been enrolled: 2 pts were ineligible and 3 pts are currently receiving treatment and are not evaluable for toxicity. Of the 19 evaluable pts, the median age was 49 yrs (range 21-75), 10 (53%) were male, and the median WBC at registration was 9.4 K/uL (range 0.9-59.6). All pts had B-ALL. The median time from initial diagnosis to registration was 774 days. Five pts were in 1^st relapse, 8 in 2^nd relapse, 3 in 3^rd relapse, 1 in 4^th relapse, and 2 pts were primary refractory. Five pts had received prior allogeneic hematopoietic stem cell transplant (AHSCT); 7 pts had poor risk cytogenetics (Ph+, -7, +8, complex, or hypodiploid). One death occurred during treatment and was attributed to pneumonia. Grade 3-4 hematologic toxicity related to treatment was common: neutropenia (11 pts), thrombocytopenia (7 pts), and anemia (6 pts). Grade 3-4 non-hematologic toxicities were almost exclusively febrile neutropenia. One DLT occurred at Dose Level 3: prolonged myelosuppression. No cases of hepatic veno-occlusive disease (VOD) occurred during treatment, and 1 pt experienced Grade 3 alkaline phosphatase at Dose Level 1. Three pts proceeded to AHSCT after study treatment; 1 pt developed VOD post AHSCT however, this fully resolved. Currently, 3 pts have been enrolled to Dose Level 4.

Conclusion: The combination of CVP/IO is well tolerated and only 1 significant hepatic event (which subsequently resolved) was observed despite a heavily pre-treated group of patients. Further toxicity results and dose escalation will be presented at the meeting. Response data will also be presented if enrollment is complete.

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