Ross, Kelly

Background: The addition of midostaurin (M), an oral multi-kinase inhibitor, to intensive chemotherapy (IC) prolongs survival in newly diagnosed (ND) FLT3 mutated (m) AML. It is not known if there is a benefit to more potent and selective FLT3 inhibitors. Among these is Gilteritinib (G), now approved as a single agent in relapsed/refractory FLT3m AML. Combined with IC, G also leads to high measurable residual disease (MRD)negative (-) composite complete remission (CRc) in FLT3 Internal Tandem Duplication (ITD)m AML. The aim of the PrECOG 0905 study was to compare FLT3m clearance and CRc rates of G vs M with IC in adults with ND FLT3m AML. Methods: We conducted a randomized, open-label, phase 2 trial comparing G to M in combination with IC during induction and consolidation in ND AML pts with centrally PCR detected FLT3 ITD or TKD mutations. Pts age 18-70 with non M3 AML and no known core binding factor rearrangement were eligible. Pts were stratified by mutation type (TKD only vs. ITD (+/- TKD)), NPM1 mutation status, and FLT3-ITD allelic ratio. Induction consisted of cytarabine 100 mg/m2 by continuous infusion daily, on day (d) 1-7 and daunorubicin 90 mg/m2 IV on d 1-3. G 120 mg daily or M 50 mg twice daily was given orally on d8-21. Consolidation (up to 4 cycles) began within 60 d of induction with Cytarabine (1.5-3 g/m2 IV) X 6 doses and G or M (as per randomization) on d8-21. Pts could proceed to transplant (HCT) at any time. Maintenance was not included. The primary outcome was FLT3m MRD (-) CRc after induction. MRD for TKD mutations was tested by PCR (sensitivity 10-2); ITD MRD was tested by amplicon-based NGS (sensitivity 10-4). Safety and efficacy were analyzed in all eligible pts who received treatment. Secondary endpoints included comparison of CRc, MRD by flow cytometry (sensitivity 10-3), and survival. Results: From 11/2019 to 11/2022, 722 pts were screened at 37 centers, 180 pts randomized, and 177 pts (58% female, 77% white, 8.5% black, 8.5% hispanic) treated on the G (n=90) or M (n=87) arm. Median age was 54, with 27.7% > age 60. FLT3-ITD was present in 80% in the G arm and 78.2% in the M arm. Of those with FLT3-ITD, NPM1 was detected in 56.9% pts in G arm and 58.8% in M arm. 24.4% G and 20.7% M pts had co-occuring FLT3-ITD, NPM1 and DNMT3A mutations. Adverse karyotype was seen in 3.4% G and 9.3% M while 10% G and 13.8% M were ELN 2022 adverse risk. For pts on G arm, 85.6% achieved CRc compared to 72.4% for M (p=0.042). 5 (5.6%) pts on G arm and 6 (6.9%) on M arm received 2 cycles in induction. Post induction, the FLT3m- CRc rate was 40% for G vs 47.1% for M (p=0.366). FLT3-TKD only mutated pts achieved CRc in 88.9 % with G and 63.2% with M and FLT3m- CRc in 72.2% and 63.2% respectively. FLT3-ITDm (+/- TKDm) pts achieved CRc/FLT3m- CRc in 84.7%/31.9% with G and 75%/42.6% with M, respectively. In pts with FLT3-ITD, NPM1 and DNMT3A mutations, 95.5% G and 72.2% M achieved CRc and 50% G vs 33.3% on M achieved FLT3m- CRc. Flow cytometry MRD negative CRc was documented in 64.4% on G arm and 59.8% on M arm after induction (p=0.539). On G arm 67 (74%) patients received at least one cycle of consolidation compared to 53 (61%) pts on M arm. On exploratory analysis, 54 (66%) G and 40 (46%) M were reported to proceed to HCT in first remission. FLT3m testing was done post consolidation cycle 1 in 27 pts in FLT3m+ CRc after induction and 15/18 (83%) on G and 4/9 (44.4%) on M converted to FLT3m-. On multivariate logistic regression analysis for FLT3m-CRc post-induction, FLT3-ITD allelic ratio, NPM1m, WBC and hemoglobin at baseline were significant at the 0.10 two-sided level, while treatment arm, and 2017 ELN risk were not. There were no deaths from treatment-related (TR) adverse events (TRAEs) while grade >=3 TRAE was reported in 73%G vs 70% M during induction and 79%G vs 73%M pts during consolidation. Conclusion: Induction therapy with daunorubicin 90 mg/m2 X 3 days, cytarabine 100 mg/m2 and gilteritinib results in an excellent CRc rate with no TR deaths in pts with ND FLT3m AML up to age 70. Compared to M, G increased the CRc but not the FLT3m- CRc rate after induction. More post induction FLT3m+CRc pts who received G became FLT3m- after consolidation cycle 1 and more G pts succeeded in proceeding to HCT. Future survival data will help evaluate the clinical impact of G and MRD assessments in ND FLT3mAML. Larger studies will be needed to establish most predictive timing of MRD and for definitive comparisons of these drugs in patients with specific mutation profiles ( ie TKD, ITD/NPM1/DNMT3).

PURPOSE Allogeneic hematopoietic cell transplantation (HCT) improves outcomes for patients with AML harboring an internal tandem duplication mutation of FLT3 ( FLT3-ITD) AML. These patients are routinely treated with a FLT3 inhibitor after HCT, but there is limited evidence to support this. Accordingly, we conducted a randomized trial of post-HCT maintenance with the FLT3 inhibitor gilteritinib (ClinicalTrials.gov identifier: NCT02997202 ) to determine if all such patients benefit or if detection of measurable residual disease (MRD) could identify those who might benefit. METHODS Adults with FLT3-ITD AML in first remission underwent HCT and were randomly assigned to placebo or 120 mg once daily gilteritinib for 24 months after HCT. The primary end point was relapse-free survival (RFS). Secondary end points included overall survival (OS) and the effect of MRD pre- and post-HCT on RFS and OS. RESULTS Three hundred fifty-six participants were randomly assigned post-HCT to receive gilteritinib or placebo. Although RFS was higher in the gilteritinib arm, the difference was not statistically significant (hazard ratio [HR], 0.679 [95% CI, 0.459 to 1.005]; two-sided P = .0518). However, 50.5% of participants had MRD detectable pre- or post-HCT, and, in a prespecified subgroup analysis, gilteritinib was beneficial in this population (HR, 0.515 [95% CI, 0.316 to 0.838]; P = .0065). Those without detectable MRD showed no benefit (HR, 1.213 [95% CI, 0.616 to 2.387]; P = .575). CONCLUSION Although the overall improvement in RFS was not statistically significant, RFS was higher for participants with detectable FLT3-ITD MRD pre- or post-HCT who received gilteritinib treatment. To our knowledge, these data are among the first to support the effectiveness of MRD-based post-HCT therapy.