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2824 Short-Term Blinatumomab Combined with Early Chemotherapy for Newly Diagnosed Pediatric Patients with B-Cell Acute Lymphoblastic Leukemia

Program: Oral and Poster Abstracts
Session: 613. Acute Lymphoblastic Leukemias: Therapies Excluding Allogeneic Transplantation: Poster II
Hematology Disease Topics & Pathways:
Research, Clinical trials, Lymphoid Leukemias, ALL, Combination therapy, Clinical Research, Diseases, Therapy sequence, Treatment Considerations, Lymphoid Malignancies, Adverse Events, Measurable Residual Disease
Sunday, December 8, 2024, 6:00 PM-8:00 PM

Changwen Xue1,2*, Yingjin Zhang1,3*, Chao Wu1,3*, Wenyu Yang1,3*, Yao Zou1,4*, Ye Guo1,5*, Yumei Chen1,5*, Xiaojuan Chen, MD1,5*, Yueshen Ma1,3*, Xiaofan Zhu, MD1,4 and Li Zhang1,3*

1Tianjin Institutes of Health Science, Tianjin, China
2State Key Laboratory of Experimental Hematology, National Clinical Research Cent, Tianjin, China
3State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Haihe Laboratory of Cell Ecosystem, Institute of Hematology& Blood Diseases Hospital, Chinese Academy of Medical Sciences& Peking Union Medical College, Tianjin, China
4State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Haihe Laboratory of Cell Ecosystem, Institute of Hematology & Blood Diseases Hospital, CAMS & PUMC, Tianjin, China
5Department of Pediatric Hematology and Oncology, State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Haihe Laboratory of Cell Ecosystem, Institute of Hematology& Blood Diseases Hospital, Chinese Academy of Medical Sciences& Peking Union Medical College, Tianjin, China

More treatment options are available for pediatric patients (pts) with newly diagnosed measurable residual disease positive (MRD-pos) B-ALL. As the efficacy of blinatumomab (Blin) has been confirmed in adult pts, early chemotherapy combined with immunotherapy has become a new focus in the treatment of pediatric B-ALL. The conventional single course of Blin lasts 4 weeks and is associated with a high risk of CRS. Therefore, we developed a prospective trial to evaluate short-term Blin in sequence with chemotherapy in this pts population (ChiCTR2100053318).

Pts aged 1 month (mo) to 18 years (yrs) with CD19-positive, Day46 MRD-pos B-cell ALL were eligible. Blin was administered before consolidation therapy by continuous intravenous infusion over 14 days (Blin-14d), at a dose of 15ug/m2/d (weight ≤45kg) or 28ug/d (weight >45kg). The chemotherapy protocol was continued after Blin-14d therapy. Signed informed consent was obtained from each patient’s guardian. The primary endpoint was MRD complete remission (CR) response rate to Blin-14d. Secondary objectives include safety of Blin-14d and comparison of long-term efficacy between Blin-14d and Non-Blin-14d. MRD was assessed using droplet digtial quantitative polymerase chain reaction (ddPCR) and multiparameter flow cytometry (MFC). The pharmacodynamics of Blin-14d, including changes in lymphocyte subpopulation and cytokine levels, was assessed by MFC-based analyses. The toxicity was graded by CTCAE 5.0.

Between June 2022 and March 2024, 56 eligible pts were included, of which 30 (54%) received Blin-14d, constituting the Blin-14d group (pt#1 to 30), while the remaining constituted the Non-Blin-14d group (pt#N1 to 26). For Blin-14d group, the median age of pts was 6.38 (1.58-15.43) yrs old. The median percentage of pre-treatment MRD was 0.09% (0.01-2.50%). For Non-Blin-14d group, the median age was 10.45 (2.25-17.00) yrs old. The median MRD at Day46 was 0.025% (0.01-17.69%).

During the Blin-14d infusion, 14 (47%) pts were dose escalated and 16 (53%) pts received full dose. The median level of IL-6 at day2 was 17.78 pg/ml vs 57.29 pg/ml (p=0.0130) and the incidence of adverse events (AEs) was 57% vs 94% (p=0.0309). In general, 23 (77%) pts experienced AEs of any grade, with 2 (8%) experiencing grade 3 AEs, including severe numbness of limbs and ALT increasing. No grade 4 or higher event related to Blin was observed. The most frequent manifestation of AEs was fever, particularly a moderate fever of >38.3℃. Prior to the Blin-14d therapy, 23 (77%) pts received induction therapy and 7 (23%) received induction plus early intensification therapy (EIT). The median total T-cell count was 1287/ul vs 1308/ul (p>0.10) at the end of Blin-14d infusion and 1961/ul vs 1165/ul (p=0.0127) one week later, suggesting the possibility of premature T-cell exhaustion caused by EIT. All of pts (100%) were in MFC-MRD-neg remission and 29 (97%) achieved molecular complete remission (mCR) one week after the end of Blin-14d.

The final follow-up was on July 1, 2024. The median time to first detection of MRD-neg in bone marrow was significantly earlier in Blin-14d group compared to Non-Blin-14d [3.0 (2.4-4.4) mos vs 3.3 (0.66-11.0) mos, p=0.0199]. The median follow-up after initiation of induction treatment was 14.1 (3.6-27.5) mos in Blin-14d group and 14.4 (3.3-28.2) mos in Non-Blin-14d group, with similar EFS in the two groups (92.3% vs 84.7%, p=0.2206).

In Blin-14d group, pt#3 MFC-MRD relapsed 14.9 mos after Blin-14d, then received a higher dose of chemotherapy and reached MFC-MRD-CR2 at the last follow-up (23.3 mos after Blin-14d). Pt#9 ddPCR-MRD relapsed 5.2 mos after Blin-14d and underwent allo-HSCT and is alive now (19.4 mos). In Non-Blin-14d group, 13 (50%) pts had treatment deviations, among whom 2 pts received Blin-14d after consolidation therapy and 3 received Blin-28d for persistent MRD>0.01%, and 3 pts underwent CAR-T for D46 MRD>5%. Two pts (#N9 and #N20) had bone marrow relapse and pt#N13 MFC-MRD relapsed. Pt#N9 was lost to follow-up. Pt#N13 and pt#N20 underwent allo-HSCT and are alive.

Preliminary data from this prospective study showed encouraging clinical activity and manageable safety profile for Blin-14d therapy, which also demonstrated earlier responses and therapeutic consistency compared to Non-Blin-14d group. For newly diagnosed pediatric B-ALL patients with MRD-pos, early chemotherapy followed by short-term blinatumomab would be a promising option.

Disclosures: No relevant conflicts of interest to declare.

*signifies non-member of ASH