P366: Blinatumomab Added to Prephase and Consolidation Therapy in Newly Diagnosed Precursor B-All in Adults. A Phase Ii Hovon Trial

Background: The bispecific antibody blinatumomab (blina) is approved for patients(pts) with relapsed/refractory precursor B-cell ALL (ALL). It has also shown to be highly effective in MRD+ pts in first line treatment. TABLE - Pt characteristics Total, N(%) 71(100%) Age(y), median(range) 53(18-70) Age (y), N(%) ≤40 22(31%) 40-60 29(41%) >60 20(28%) BM blasts (%), N(%) ≤50% 4(6%) >50% 62(87%) Unknown 5(7%) Karyotype, N(%) Ph+ 26/71(37%) KMT2A 2/67(3%) Complex 23/67(34%) Hypodiploidy 5/67(7%) Aims: To evaluate whether blina added in upfront therapy to prephase and after consolidation (cons)-1 would increase MRD negativity measured by qPCR or flowcytometry at a cut-off of 60y 47% SE ± 12%). Overall, 14 (20%) pts died. OS after 2y was 73% SE ± 7% (≤60y 82% SE ± 8% and >60y 52% SE ± 14%) (Figure 1). For pts with Ph+ ALL, 2-y EFS was 88% SE ± 6%and OS also 88% SE ± 7%. For Ph- ALL, 2-y EFS and OS were 53% SE ± 9% and 68% SE ± 9%, resp. Among pts who reached CR on protocol (n=60), 5 (8%) had relapse, 6 (10%) died and 6 (10%) discontinued treatment due to toxicity. Until now, 22 pts proceeded to alloHSCT and 11 with maintenance. Image:Summary/Conclusion: Blina can safely be added to prephase of an intensified pediatric schedule for newly diagnosed ALL up to 70y of age, albeit with dose reductions for PEG-ASP, doxorubicin and dexamethasone. The combination increases CR and MRD negativity rate. The early addition of blina resulted in very early achievement of MRD negativity with 53% after prephase and 91% after blina cons-1. Further reductions of chemotherapy should be explored (especially for Ph+) if these results are maintained with longer follow-up.