FLT3 inhibitors in the treatment of acute myeloid leukemia: current status and future perspectives.

Mutations in the FMS-like tyrosine kinase 3 (FLT3) gene arise in 25-30% of all acute myeloid leukemia (AML) patients. These mutations lead to constitutive activation of the protein product and are divided in two broad types: internal tandem duplication (ITD) of the juxtamembrane domain (25% of cases) and point mutations in the tyrosine kinase domain (TKD). Patients with FLT3 ITD mutations have a high relapse risk and inferior cure rates, whereas the role of FLT3 TKD mutations still remains to be clarified. Additionally, growing research indicates that FLT3 status evolves through a disease continuum (clonal evolution), where AML cases can acquire FLT3 mutations at relapse - not present in the moment of diagnosis. Several FLT3 inhibitors have been tested in patients with FLT3-mutated AML. These drugs exhibit different kinase inhibitory profiles, pharmacokinetics and adverse events. First-generation multi-kinase inhibitors (sorafenib, midostaurin, lestaurtinib) are characterized by a broad-spectrum of drug targets, whereas second-generation inhibitors (quizartinib, crenolanib, gilteritinib) show more potent and specific FLT3 inhibition, and are thereby accompanied by less toxic effects. Notwithstanding, all FLT3 inhibitors face primary and acquired mechanisms of resistance, and therefore the combinations with other drugs (standard chemotherapy, hypomethylating agents, checkpoint inhibitors) and its application in different clinical settings (upfront therapy, maintenance, relapsed or refractory disease) are under study in a myriad of clinical trials. This review focuses on the role of FLT3 mutations in AML, pharmacological features of FLT3 inhibitors, known mechanisms of drug resistance and accumulated evidence for the use of FLT3 inhibitors in different clinical settings.

Treatment with daratumumab in patients with relapsed/refractory AL amyloidosis: a multicentric retrospective study and review of the literature.

Management of patients with relapsed or refractory (R/R) AL amyloidosis is complex. Some initial reports have shown positive results with daratumumab in heavily pre-treated AL amyloidosis patients. In this retrospective multicentric study, 38 patients (mean age 64 ± 9 years) with R/R AL amyloidosis treated with daratumumab were included. Cardiac and renal involvement was present in 76 and 74% of patients, and 42% had ≥3 organs involved. Median number of previous lines of therapy was 2 (range 1-8). Overall hematological response was 72%, including 28% complete responses. The median time to first hematological response was 2 weeks. A high-quality response (≥very good partial response) was obtained in 65% of patients who had never achieved such depth of response previously. Hematological responses were more frequent among patients receiving daratumumab as second-line therapy compared to subsequent therapies (92 vs. 61%). Cardiac and renal organ response rates were 37 and 59%. At 12 months, overall and progression-free survival were 59% (95%CI: 0.36-0.77) and 52% (95%CI: 0.29-0.70), respectively. Daratumumab is a safe and effective drug in the treatment of R/R AL amyloidosis and should be considered early in the course of the disease.