Epratuzumab Y-90

Prognosis of patients with relapsed or refractory acute lymphoblastic leukaemia is poor and new treatments are needed. We aimed to assess the feasibility, tolerability, dosimetry, and efficacy of yttrium-90-labelled anti-CD22 epratuzumab tetraxetan ((90)Y-DOTA-epratuzumab) radioimmunotherapy in refractory or relapsed CD22-positive B-cell acute lymphoblastic leukaemia in a standard 3 + 3 phase 1 study.

Adults (≥18 years) with relapsed or refractory B-cell acute lymphoblastic leukaemia (with CD22 expression on at least 70% of blast cells) were enrolled at six centres in France. Patients received one cycle of (90)Y-DOTA-epratuzumab on days 1 and 8 (give or take 2 days) successively at one of four dose levels: 2·5 mCi/m(2) (92·5 MBq/m(2); level 1), 5·0 mCi/m(2) (185 MBq/m(2); level 2), 7·5 mCi/m(2) (277·5 MBq/m(2); level 3), and 10·0 mCi/m(2) (370 MBq/m(2); level 4). The primary objective was to identify the maximum tolerated dose of (90)Y-DOTA-epratuzumab. We assessed safety during infusions and regularly after radioimmunotherapy over a 6-month period. Analyses included only patients who received radioimmunotherapy. The trial is closed to inclusion and is registered at ClinicalTrials.gov, NCT01354457.

Between Aug 25, 2011, and June 11, 2014, 17 patients (median age 62 years; range 27-77) were treated (five at level 1, three at level 2, three at level 3, and six at level 4). Radioimmunotherapy infusion was overall well tolerated. One dose-limiting toxic effect (aplasia lasting 8 weeks) occurred at level 4, but the maximum tolerated dose was not reached. The most common grade 3-4 adverse events were pancytopenia (one patient at level 2, one at level 3, and six at level 4) and infections (three at level 1, one at level 2, and five at level 4).

(90)Y-DOTA-epratuzumab radioimmunotherapy is well tolerated. We recommend the dose of 2 × 10·0 mCi/m(2) 1 week apart per cycle for phase 2 studies.

Immunomedics and Direction de la Recherche Clinique of Nantes.

A lingering criticism of radioimmunotherapy in non-Hodgkin lymphoma is the use of cold anti-CD20 antibody along with the radiolabeled anti-CD20 antibody. We instead combined radioimmunotherapy with immunotherapy targeting different B-cell antigens. We evaluated the anti-CD22 (90)Y-epratuzumab tetraxetan with the anti-CD20 veltuzumab in patients with aggressive lymphoma in whom at least one prior standard treatment had failed, but who had not undergone stem cell transplantation. Eighteen patients (median age 73 years, median of 3 prior treatments) received 200 mg/m(2) veltuzumab once-weekly for 4 weeks, with (90)Y-epratuzumab tetraxetan at planned doses in weeks 3 and 4, and (111)In-epratuzumab tetraxetan in week 2 for imaging and dosimetry. Veltuzumab effectively lowered levels of B cells in the blood prior to the radioimmunotherapy doses. No significant immunogenicity or change in pharmacokinetics of either agent occurred in combination. (111)In imaging showed tumor targeting with acceptable radiation dosimetry to normal organs. For (90)Y-epratuzumab tetraxetan, transient myelosuppression was dose-limiting with 6 mCi/m(2) (222 MBq/m(2)) × 2 being the maximal tolerated dose. Of 17 assessable patients, nine (53%) had objective responses according to the 2007 revised treatment response criteria, including three (18%) complete responses (2 relapsing after 11 and 13 months, 1 continuing to be clinically disease-free at 19 months), and six (35%) partial responses (1 relapsing after 14 months, 5 at 3 - 7 months). Responses occurred in patients with different lymphoma histologies, treated at different (90)Y dose levels, and with a predicted risk of poor outcome, most importantly including five of the six patients treated with the maximal tolerated dose (2 of whom achieved durable complete responses). In conclusion, the combination of (90)Y-epratuzumab tetraxetan and veltuzumab was well-tolerated with encouraging therapeutic activity in this difficult-to-treat population.