Upfront azacitidine (AZA) in juvenile myelomonocytic leukemia (JMML): Interim analysis of the prospective AZA-JMML-001 study.

Abstract

10031 Background: Hematopoietic stem cell transplantation (HSCT) is the only curative therapy for JMML patients (pts). Novel therapies controlling the disorder prior to HSCT are urgently needed. A phase 2, multicenter, open-label study was conducted to evaluate safety and anti-leukemia activity of AZA monotherapy prior to HSCT in pts with newly diagnosed (ND) JMML. Methods: AZA (75 mg/m2 IV) was administered once daily on days 1–7 of each 28-day cycle (C). Primary endpoint was number of pts with clinical complete remission or clinical partial remission (cPR) at C3 day (D) 28 (C3D28). Results: 18 JMML pts (13 PTPN11-, 3 NRAS-, 1 KRAS-, 1 NF1-mutated) were enrolled from 09/2015 to 11/2017. Median (range) white blood cell and platelet (Plt) counts were 19.7 (4.3–59.0) × 109/L and 28 (7–85) × 109/L, respectively. DNA methylation class (MC) was high, intermediate (int), or low in 11, 5, and 2 pts, respectively. 16 pts completed C3 and 5 pts C6. 2 pts discontinued treatment (Tx) pre-C3D28 due to disease progression (PD). 6 pts (33%) had ≥ 1 grade (Gr) 3–4 manageable adverse event (AE) related to AZA. Most common Gr 3–4 AEs related to AZA were neutropenia (2) and anemia (2). 11 pts (61%) were in cPR at C3D28; 7 had PD at C3D28 or prior. All 7 pts of the int/low MC and 4/11 in high MC achieved cPR. 17 pts received HSCT at median of 58 days (37–518) from last AZA dose; 14 were leukemia-free at a median follow-up of 15.7 months (0.1–31.7) after HSCT. 2 pts (high MC) given HSCT relapsed after allograft. 16/18 pts were alive at a median follow-up of 19.8 months (2.6–37.3) from diagnosis. 1 pt discontinuing Tx prior to C3 died from PD; 1 non-responder died from transplant-related causes. Plt response in pts with cPR prompted retrospective comparison of Plt counts at time of HSCT with a historical registry control cohort. Pts with NF1-mutated JMML with higher Plt counts versus other genetic subtypes were excluded. While 7/16 (44%) study pts had Plt counts ≥ 100 × 109/L at HSCT, only 10/58 (17%) historical cohort pts reached this cutoff ( P < 0.01). Conclusions: This study shows that AZA monotherapy was well tolerated in pts with ND JMML. Although the long-term advantage of AZA Tx remains to be fully assessed, responses show it was effective in JMML and provided clinical benefit to pts in this study. Clinical trial information: NCT02447666.