Gilteritinib as Post-Transplant Maintenance for AML With Internal Tandem Duplication Mutation of FLT3.

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.

A phase II study assessing the safety and efficacy of ASP1650 in male patients with relapsed refractory germ cell tumors.

Claudin6(CLDN6) is a tight junction protein of claudin-tetraspanin family and is of the earliest molecules expressed in embryonic epithelium. CLDN6 is frequently aberrantly expressed in testicular germ-cell tumors(GCT). ASP1650 is a chimeric-mouse/human-IgG1 antibody directed against CLDN6. Two-part, open-label, phase-II trial investigating ASP1650 in patients with relapsed/refractory GCT and no curable options. Part1 was a safety lead-in to establish the recommended-phase-II-dose(RP2D). Part2 was a phase-II study designed to evaluate the antitumor effects of ASP1650. CLDN6 expression was centrally assessed on archival tumor tissue using immunohistochemistry. The primary objectives were to establish the RP2D(safety lead-in) and the antitumor activity(phase-II) of ASP1650. Nineteen male patients were enrolled: 6 patients in 1000 mg/m2 safety lead-in group, and 13 in 1500 mg/m2 group. Median age 37.2 years(range,20-58). Histology was non-seminoma in 17/19 patients. Median number of previous chemotherapy regimens was 3. Thirteen patients had prior high-dose chemotherapy. No dose-limiting toxicity events were reported at any study drug dose. A RP2D of 1500 mg/m2 every 2 weeks was established. No partial or complete responses were observed. The study was stopped at the end of Simon Stage-I due to lack of efficacy. 15/16 subjects with available tissue had CLDN6 positive staining. The mean percent membrane staining was 71.6% and the mean membrane H score was 152.6(SD 76). ASP1650 did not appear to have clinically meaningful single-agent activity in relapsed/refractory GCT. CLDN6 expression seems ubiquitous in all elements of GCT and is worthy of investigation as a diagnostic biomarker and therapeutic target. (Clinical trial information: NCT03760081).

Molecular profile of FLT3-mutated relapsed/refractory patients with AML in the phase 3 ADMIRAL study of gilteritinib.

The phase 3 Study of ASP2215 Versus Salvage Chemotherapy in Patients With Relapsed or Refractory Acute Myeloid Leukemia (AML) With FMS-like Tyrosine Kinase (FLT3) Mutation (ADMIRAL) trial demonstrated the superiority of the FLT3 inhibitor, gilteritinib, to salvage chemotherapy (SC) in patients with FLT3-mutated relapsed or refractory (R/R) AML. Baseline comutations, FLT3-internal tandem duplication (ITD) allelic ratio and length, and treatment-emergent mutations were analyzed in patients in the ADMIRAL trial. Baseline comutations were grouped according to gene subgroups (DNA methylation/hydroxymethylation, transcription, chromatin-spliceosome, receptor tyrosine kinase-Ras signaling, TP53-aneuploidy, NPM1, DNMT3A, DNMT3A/NPM1, WT-1, and IDH1/IDH2). Across all but 1 gene subgroup (TP53-aneuploidy), higher pretransplant response rates and a trend toward longer overall survival were observed with gilteritinib vs SC. Patients with DNMT3A/NPM1 comutations who received gilteritinib had the most favorable outcomes of any molecular subgroup analyzed. Survival outcomes with gilteritinib were not adversely affected by FLT3-ITD allelic ratio, FLT3-ITD length, or multiple FLT3-ITD mutations. Among patients who relapsed on gilteritinib, Ras/mitogen-activated protein kinase (MAPK) pathway and FLT3 F691L gene mutations were the most common mutational events associated with treatment resistance. However, the occurrence of Ras/MAPK pathway gene mutations at baseline did not preclude a clinical benefit from gilteritinib. Acquisition of multiple Ras/MAPK pathway gene mutations at relapse suggests a high level of pathway reactivation is needed to overcome the gilteritinib treatment effect. These findings provide insight into the R/R AML molecular profile and the impact of FLT3 inhibitors on mutational evolution associated with treatment resistance and benefit of gilteritinib across a wide spectrum of molecular and genetic subgroups in FLT3-mutated R/R AML. This trial was registered at www.clinicaltrials.gov as #NCT02421939.

The impact of FLT3 mutation clearance and treatment response after gilteritinib therapy on overall survival in patients with FLT3 mutation-positive relapsed/refractory acute myeloid leukemia.

The FLT3 inhibitor gilteritinib has clinical activity in patients with FLT3-mutated (FLT3mut+ ) relapsed/refractory (R/R) acute myeloid leukemia (AML). The impact of FLT3 mutation clearance and the achievement of composite complete remission (CRc) and complete remission/complete remission with partial hematologic recovery (CR/CRh) on overall survival (OS) in patients with FLT3mut+ R/R AML treated with single-agent gilteritinib in a phase 1/2 trial were evaluated. Using next-generation sequencing, a FLT3-ITD variant allele frequency of ≤10-4 was used to define FLT3-ITD clearance in patients with no morphologic leukemia (ie, CRc). A total of 108 patients with FLT3-ITD-positive (FLT3-ITD+) R/R AML were analyzed; 95 of these patients had received ≥80-mg/day gilteritinib. Ten of the 95 patients had FLT3-ITD clearance; eight of these 10 patients achieved CRc and were considered negative for measurable residual disease. There was a trend toward longer OS in patients who attained CRc with FLT3-ITD clearance (131.4 weeks) versus those who achieved CRc and did not have FLT3-ITD clearance (n = 41; 43.3 weeks; HR = 0.416; p = 0.066). Among patients treated with ≥80-mg/day gilteritinib who achieved CR/CRh (n = 24), seven had FLT3-ITD clearance. Among patients who received 120-mg/day gilteritinib, those who achieved CR/CRh had a longer median OS (70.6 weeks) and higher 52-week survival probability (66.7%) than patients who did not achieve CR/CRh (n = 71; median OS, 41.7 weeks; 52-week survival probability, 20.2%). Overall, these data suggest that gilteritinib can induce deep molecular responses in patients with FLT3-ITD+ R/R AML, and in the setting of CRc or CR/CRh, these responses may be associated with prolonged survival.