Chemoimmunotherapy Combining Vincristine, Dexamethasone and Epratuzumab (hLL2) As Salvage Regimen for Older Relapsed/Refractory, CD22⁺ B-Acute Lymphoblastic Leukemia (B-ALL) Patients: Results of the French Non-Intensive Phase 2 Prospective Cheprall Study

Purpose: Best supportive care is generally offered to older patients presenting with refractory/relapsed acute lymphoblastic leukemia (ALL). There is clearly a need for new therapeutic approaches in these older patients for whom aggressive chemotherapies cannot be administered.

Materials and Methods: The present study evaluated the addition of epratuzumab (hLL2), a humanized monoclonal therapeutic antibody against CD22, to the combination of vincristine and dexamethasone in older patients (>55 years) with relapsed/refractory CD22+ B-ALL. The salvage regimen consisted of epratuzumab 360 mg/m²/d iv days 1, 8, 15, and 22, vincristine 2 mg iv days 1, 8, 15 and 22, and dexamethasone 40 mg/d po days 1, 8, 15, and 22. Morphologic and phenotypic minimal residual disease (MRD) responses were determined between 4 and 6 weeks from day 1.

Results: Between November 2010 and December 2013, 26 patients from six French centers were enrolled in the study. One case was excluded because of progression before receiving the treatment, while 2 younger patients were inappropriately included (49-year old female in fourth relapse and 32-year old female with refractory second relapse). Among the 25 patients considered for analyses, there were 13 males and the median age was 65 years. Eighteen, 4, 1, and 1 patients were in first, second, third, and fourth relapse, respectively, and one case had refractory B-ALL. Median percentage of blasts in bone marrow was 72%. Karyotypes were as follow: normal n=8; Ph⁺ n=6, complex n=1, MLL rearrangement n=1, hyperdiploidy n=2, hypodiploidy n=2, 17p duplication n=1, del9p n=1, t(1;19) n=1, t(13;14) n=1, 14 abnormality n=1. Median interval between diagnosis and salvage regimen was 16 months. Three patients were previously allotransplanted. Two patients died of progression during treatment. Salvage regimen was overall well tolerated, since the large majority of grade 3/4 toxicities were expected pancytopenia. One grade 3 toxicity was related to the first epratuzumab infusion, but the patient received the three other infusions without events. One grade 3 renal injury and one grade 4 hypertriglyceridemia of unclear etiology also were documented.

The overall response rate was 40% (n=10), including 4 complete responses (CR) and 1 CR with incomplete platelet recovery (CRp) (20%), and 5 partial responses (PR) (20%). Two patients in CR/CRp were documented with negative MRD. All patients in CR/CRp and 1 patient in PR received a second cycle as consolidation. All patients died of disease progression, except two non-responder cases. Median OS was 4 months (range: 0.5-43). Median DFS for those achieving CR/CRp was 4 months (range: 1-8).

Conclusion: Non-intensive chemoimmunotherapy combining vincristine/dexamethasone/epratuzumab provides encouraging results in this very high-risk, refractory/relapsed, older population. These results pave the way for integrating epratuzumab within first-line chemotherapies in older CD22+ B-ALL patients. This trial is registered at http://clinicaltrials.gov/ct no.NCT01219816.