The Lancet Oncology has featured a phase II study evaluating inotuzumab ozogamicin, a CD22 monoclonal antibody conjugated to the toxin calecheamicin, for the treatment of patients with refractory and relapsed acute lymphocytic leukaemia (ALL).

The study involved 49 adults and children with refractory and relapsed ALL with CD22 expressed in more than 50% of blasts in all the patients. The median age of the patients was 36 years (range 6 to 80). Patients were given 1.8 mg/m2 inotuzumab ozogamicin intravenously over 1 hour every 3—4 weeks (the first three adults and three children received 1.3 mg/m2 in the first course). The median number of courses was two (range one to five) and the median time between courses was 3 weeks (range 3—6).The primary endpoint was overall response (complete response or marrow complete response with no recovery of platelet count or incomplete recovery of neutrophil and platelet counts).

The following results were reported:

• Nine (18%) patients had complete response, 19 (39%) had marrow complete response, 19 (39%) had resistant disease, and two (4%) died within 4 weeks of starting treatment.

• The overall response rate was 57% (95% CI 42—71).

• The most frequent adverse events during course one of treatment were fever (grade 1—2 in 20 patients, grade 3—4 in nine), hypotension (grade 1—2 in 12 patients, grade 3 in one), and liver-related toxic effects (bilirubin: grade 1—2 in 12 patients, grade 3 in two; raised aminotransferase concentration: grade 1—2 in 27 patients, grade 3 in one).

The researchers conclude that inotuzumab ozogamicin shows promise as a treatment option for refractory and relapsed ALL.