In a single-arm, phase 2 study, inotuzumab ozogamicin, a CD22 monoclonal antibody conjugate, showed potential utility as a monotherapy that may improve the often poor prognosis for patients with refractory or relapsed acute lymphocytic leukemia (ALL; Kantarjian H, et al. Lancet Oncol. 2012;13:403-411).
This study conducted at M.D. Anderson Cancer Center, Houston, initially included adults with refractory or relapsed ALL of B-cell origin; younger patients (aged <16 years) were eligible to participate only after ≥1 course of the study medication was safely used in ≥10 adults. The primary end point was overall response.
A total of 49 patients were treated. Of these patients, 9 had complete response, 19 had marrow complete response, 19 had resistant disease, and 2 died within 4 weeks of treatment onset. The overall response rate was 57%, and the median overall survival was 5.1 months.
The most frequent adverse events (AEs) in the first course of treatment were fever (n = 29), hypotension (n = 13), in creased bilirubin (n = 14), and increased aminotransferase concentration (n = 28). These AEs did not increase in frequency with subsequent treatment courses.
The 57% response rate was much higher than rates reported in previous studies, but it was of short duration. The investigators are exploring a shorter, weekly schedule for the drug, which they hope will improve its efficacy and toxicity profile.
