Use of FLT3 inhibitors in acute myeloid leukemia remission induction or salvage therapy: systematic review and meta-analysis

FLT3 inhibitors in acute myeloid leukaemia: assessment of clinical effectiveness, adverse events and future research-a systematic review and meta-analysis

BACKGROUND

FMS-like tyrosine kinase 3 (FLT3) is the most frequent mutation in AML. With two FLT3 inhibitors recently approved by the FDA (midostaurin and gilteritinib), there is a need to evaluate these targeted agents.

PURPOSE

To assess the clinical effectiveness of FLT3 inhibitors in AML patients.

METHODS

Standard systematic review methods were utilised. Searches were conducted to July 2020 for completed and in-progress randomised controlled trials of FLT3 inhibitors in AML. A fixed-effect meta-analysis was undertaken.

RESULTS

Eight completed trials involving 2656 patients and assessing five different FLT3 inhibitors (sorafenib, lestaurtinib, midostaurin, gilteritinib and quizartinib) were included. The pooled results were as follows (FLT3 inhibitor/control): overall survival hazard ratio (HR) = 0.83 (95% confidence interval [CI] 0.75 to 0.92, p = 0.0005), event-free survival HR = 0.85 (95% CI 0.77 to 0.94, p = 0.002), relapse-free survival HR = 0.76 (95% CI 0.64 to 0.90, p = 0.001), complete remission relative risk (RR) = 1.11 (95% CI 1.00 to 1.22. p = 0.05) and 60-day mortality RR = 1.04 (95% CI 0.77 to 1.40, p = 0.79). Relative risk of grade 3 and above vascular, dermatological, respiratory and hepatobiliary adverse events were found to be statistically significantly higher in the FLT3 inhibitor group compared to control, but the actual numbers of events were relatively small. Nineteen ongoing trials are still in progress, only one of which specifically targets older patients with AML.

CONCLUSIONS

There is evidence to support the use of FLT3 inhibitors in patients with AML, but more data is needed to verify the optimum use of the drugs regarding type of inhibitor, disease stage and patient characteristics, not only in relation to disease control, but adverse events and quality of life. There are a large number of ongoing trials; therefore, the results of this review are not a fait accompli; thus, is it recommended that the review be updated in a couple of years' time. Given the challenges in extracting the complete data set required to assess clinical effectiveness, it is highly recommended that ongoing and future trials improve transparency and consistency of reporting of all trial outcomes, particularly disease control and adverse events, to enable a global clinical effectiveness assessment.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42017055581.

Inhibition of ubiquitin-specific protease 7 sensitizes acute myeloid leukemia to chemotherapy

Resistance of acute myeloid leukemia (AML) to therapeutic agents is frequent. Consequently, the mechanisms leading to this resistance must be understood and addressed. In this paper, we demonstrate that inhibition of deubiquitinylase USP7 significantly reduces cell proliferation in vitro and in vivo, blocks DNA replication progression and increases cell death in AML. Transcriptomic dataset analyses reveal that a USP7 gene signature is highly enriched in cells from AML patients at relapse, as well as in residual blasts from patient-derived xenograft (PDX) models treated with clinically relevant doses of cytarabine, which indicates a relationship between USP7 expression and resistance to therapy. Accordingly, single-cell analysis of AML patient samples at relapse versus at diagnosis showed that a gene signature of the pre-existing subpopulation responsible for relapse is enriched in transcriptomes of patients with a high USP7 level. Furthermore, we found that USP7 interacts and modulates CHK1 protein levels and functions in AML. Finally, we demonstrated that USP7 inhibition acts in synergy with cytarabine to kill AML cell lines and primary cells of patients with high USP7 levels. Altogether, these data demonstrate that USP7 is both a marker of resistance to chemotherapy and a potential therapeutic target in overcoming resistance to treatment.

Development of UHPLC-MS/MS Method for Indirubin-3'-Oxime Derivative as a Novel FLT3 Inhibitor and Pharmacokinetic Study in Rats

This study aimed to develop and validate a sensitive liquid chromatography-coupled tandem mass spectrometry method for the quantification of LDD-2614, an indirubin derivative and novel FLT3 inhibitor, in rat plasma. In addition, the developed analytical method was applied to observe the pharmacokinetic properties of LDD-2614. Chromatographic separation was achieved on a Luna omega C₁₈ column using a mixture of water and acetonitrile, both containing 0.1% formic acid. Quantitation was performed using positive electrospray ionization in a multiple reaction monitoring (MRM) mode. The MRM transitions were optimized as m/z 426.2→113.1 for LDD-2614 and m/z 390.2→113.1 for LDD-2633 (internal standard), and the lower limit of quantification (LLOQ) for LDD-2614 was determined as 0.1 ng/mL. Including the LLOQ, the nine-point calibration curve was linear with a correlation coefficient greater than 0.9991. Inter- and intraday accuracies (RE) ranged from -3.19% to 8.72%, and the precision was within 9.02%. All validation results (accuracy, precision, matrix effect, recovery, stability, and dilution integrity) met the acceptance criteria of the U.S. Food and Drug Administration and the Korea Ministry of Food and Drug Safety guidelines. The proposed method was validated and demonstrated to be suitable for the quantification of LDD-2614 for pharmacokinetics studies.

Gilteritinib induces PUMA-dependent apoptotic cell death via AKT/GSK-3β/NF-κB pathway in colorectal cancer cells

As a highly potent and highly selective oral inhibitor of FLT3/AXL, gilteritinib showed activity against FLT3D835 and FLT3‐ITD mutations in pre‐clinical testing, although its role on colorectal cancer (CRC) cells is not yet fully elucidated. We examined the activity of gilteritinib in suppressing growth of CRC and its enhancing effect on other drugs used in chemotherapy. In this study, we observed that, regardless of p53 status, treatment using gilteritinib induces PUMA in CRC cells via the NF‐κB pathway after inhibition of AKT and activation of glycogen synthase kinase 3β (GSK‐3β). PUMA was observed to be vital for apoptosis in CRC cells through treatment of gilteritinib. Moreover, enhancing induction of PUMA through different pathways could mediate chemosensitization by using gilteritinib. Furthermore, PUMA deficiency revoked the antitumour role of gilteritinib in vivo. Thus, our results indicate that PUMA mediates the antitumour activity of gilteritinib in CRC cells. These observations are critical for the therapeutic role of gilteritinib in CRC.

A Novel T-Cell Engaging Bi-specific Antibody Targeting the Leukemia Antigen PR1/HLA-A2

Despite substantial advances in the treatment of acute myeloid leukemia (AML), only 30% of patients survive more than 5 years. Therefore, new therapeutics are much needed. Here, we present a novel therapeutic strategy targeting PR1, an HLA-A2 restricted myeloid leukemia antigen. Previously, we have developed and characterized a novel T-cell receptor-like monoclonal antibody (8F4) that targets PR1/HLA-A2 and eliminates AML xenografts by antibody-dependent cellular cytotoxicity (ADCC). To improve the potency of 8F4, we adopted a strategy to link T-cell cytotoxicity with a bi-specific T-cell-engaging antibody that binds PR1/HLA-A2 on leukemia and CD3 on neighboring T-cells. The 8F4 bi-specific antibody maintained high affinity and specific binding to PR1/HLA-A2 comparable to parent 8F4 antibody, shown by flow cytometry and Bio-Layer Interferometry. In addition, 8F4 bi-specific antibody activated donor T-cells in the presence of HLA-A2⁺ primary AML blasts and cell lines in a dose dependent manner. Importantly, activated T-cells lysed HLA-A2⁺ primary AML blasts and cell lines after addition of 8F4 bi-specific antibody. In conclusion, our studies demonstrate the therapeutic potential of a novel bi-specific antibody targeting the PR1/HLA-A2 leukemia-associated antigen, justifying further clinical development of this strategy.