Newly-diagnosed Low Risk Pediatric B-cell ALL Protocol

All LR-B-ALL patients will be treated with 14 days of blinatumomab (Blina-14) as early intensification to replace CAT+ (historically given in LR-B-AL with MRD19>0.1% in the 2020 protocol).

Two courses of HD-MTX will be administered as consolidation phase, maintaining the same dose of 3 g/m².

Second 14 days of blinatumomab will be given after completion of HDMTX consolidation treatment .

Adding IgH rearrangement NGS MRD as an evaluation indicator. Reinduction-2 will be omitted for patients with NGS-MRD46<10-6 who have receive the second course of Blina-14. (Reinduction-2 should be given regardless of NGS-MRD 46 status in patients who did not receive the second course of binatumomab).

A total of four repeating courses will be applied in Maintenance 1 (in contrast to 5 courses in 2020 protocol). Additionally, one-week rest period will be implemented after each course to ensure safety and optimal efficacy.

Patients with FCM-MRD19<0.01% and IgH rearrangement NGS MRD 46<10-6 will receive chemo-light maintenance-2 with 4 cyles of 8-week course of MTX + 6MP (totally 32 weeks). The other patients with higher levels of MRD by FCM MRD or NGS MRD will receive maintenance-2 with 9 cycles of 8-week course of MTX + 6MP for a total of 72 weeks (same as CCCG-ALL2020)

Bone Marrow Aspiration Assessment (BMA): One additional bone marrow puncture at the end of 1st Blina-14 course (Day60 MRD) will be performed at early intensification phase. This results in a total of 4 BMAs in the CCCG2025-LR protocol, in contrast to 3 BMAs in 2020 protocol.

Triple Intrathecal Therapy (TIT)：In the HDMTX consolidation phase, there will be two TITs in contrast to four treatments in the CCCG2020 protocol. To compensate for this reduction, two additional TIT treatments will be administrated before the 1st and 2nd Blina-14 courses. Additionally, two intrathecal treatments will be added during Reinduction 1 and Reinduction 2 to further enhance CNS control. Meanwhile, one TIT will be reduced in the Maintenance-1 phase compared to 2020 protocol. This results in a total of 16 or 17 TITs, depending on whether the second Blina-14 course is applied This is similar to the CCCG2020, where 16 or 17 TITs are administrated depending on whether CAT+ was given).

Adding pharmacotyping study for LR B-ALL.

Treatment duration: The treatment duration for the CCCG-LR-ALL-2020 protocol is 121/124 weeks (depending on if CAT+ was given). In the CCCG-LR-ALL-2025 protocol:

• For patients with NGS MRD46 ≥10-6, the total treatment duration is 123 weeks. Key changes include: 2 weeks of Blina-14 replacing 3 weeks of CAT+, 2 courses of HDMTX reduction (4 weeks), and an additional 2 weeks for the 2nd blina-14 course added following HDMTX;

• For patients with MRD19≥ 0.01% and NGS MRD46 < 10-6 who subsequently receive 2nd Blina-14, Reinduction-2 is omitted, shortening the total duration by 3 weeks. (120 weeks in total). If the 2nd Blina-14 is not administrated, Reinduction -2 will still be included, resulting in a total duration of 121 weeks.

• For patients with MRD19 < 0.01% and NGS MRD46 < 10-6, who subsequently receive 2nd Blina-14, both the Reinduction-2 (3 weeks) and the subsequent 5 cycles of Maintenance-2 (40 weeks) are omitted. This results in a total treatment duration of 80 weeks (81 weeks if 2nd Blina-14 is not applied).