crenolanib (ARO-002)

Other FLT3 inhibitors, midostaurin, crenolanib, and quizartinib, also reduced FLT3 expression, consistent with the effect of gilteritinib. These findings hold great promise for optimizing gilteritinib treatment in AML patients. However, it is important to recognize that further research is warranted to gain a full understanding of these mechanisms and their clinical implications in the context of FLT3 reduction.

AML patients treated with investigational drugs targeting mutant FLT3, including Quizartinib and Crenolanib, develop resistance to these drugs...We have identified 2 novel nicotinamide-based FLT3 inhibitors (HSN608 and HSN748) that target FLT3 mutations at subnanomolar concentrations and are potently effective against drug-resistant secondary mutations of FLT3. These compounds show antileukemic activity against FLT3ITD in drug-resistant AML, relapsed/refractory AML, and in AML bearing a combination of epigenetic mutations of TET2 along with FLT3ITD. We demonstrate that HSN748 outperformed the FDA-approved FLT3 inhibitor Gilteritinib in terms of inhibitory activity against FLT3ITD in vivo.

We searched and reviewed clinical trial reports on the monotherapy of 13 FLT3 inhibitors, including sorafenib, lestaurtinib, midostaurin, gilteritinib, quizartinib, sunitinib, crenolanib, tandutinib, cabozantinib, pexidartinib, pacritinib, famitinib, and TAK-659 in patients with hematological and solid malignancies before May 31, 2023...The ORRs of FLT3 inhibitors in hematologic malignancies and solid tumors were 40.8% and 18.8%, respectively, indicating FLT3 inhibitors were more effective for hematologic malignancies than for solid tumors. In addition, time to maximum plasma concentration (Tmax) in these FLT3 inhibitors ranged from 0.7-12.0 hours, but the elimination half-life (T1/2) range was highly variable, from 6.8 to 151.8 h. FLT3 inhibitors monotherapy has shown significant anti-tumor effect in clinic, and the effectiveness may be further improved through combination medication.

Crenolanib (a PDGFR inhibitor) inhibited AOFB-01 cell proliferation...Therefore, PDGF-A produced by microvascular proliferations and tumor cells may promote the proliferation of PDGFR-α-expressing tumor cells in canine HGOG. PDGFR-α signaling has potential as a therapeutic target.

P2, N=14, Completed, Arog Pharmaceuticals, Inc. | N=20 --> 14

Crenolanib plus intensive chemotherapy in adults with newly diagnosed FLT3-mutant AML results in high rate of deep responses and long-term survival with acceptable toxicity. A randomized trial of crenolanib versus midostaurin plus chemotherapy in younger patients is ongoing.

P2, N=30, Completed, Arog Pharmaceuticals, Inc. | Active, not recruiting --> Completed | N=48 --> 30

FLT3 tyrosine kinase inhibitors (e. g. , Crenolanib) have the potential to enforce surface expression of FLT3 by impairing its intracellular recycling, thus enhancing CAR-T mediated killing, but their use may be limited by overlapping toxicities on healthy hematopoiesis, in particular in the post-HSCT setting...In conclusion, we believe that epitope edited HSPCs may not only enable safe and effective CAR-T immunotherapies for AML, but also allow their combination with pharmacological blockade of leukemia survival/proliferative pathways to achieve synthetic lethality mechanisms, while still avoiding dose-limiting toxicities. Further exploration of immunotherapy-synergistic combinations will be fundamental to improve the outcomes of difficult-to-treat high-risk AML patients.

85) significantly in favor of quizartinib (Qui) + low dose cytarabine (LDAC) vs. LDAC alone. In two nRCTs (N=63) on unfit patients, Qui + venetoclax (Ven) +Aza/LDAC showed complete response (CR)/overall response (ORR) of 42%/72% and Qui+Aza/LDAC showed CR/ORR of 44%/56%...5% with midostaurin (Mid)+ chemotherapy and chemotherapy, respectively...9% and 73% with Gil+chemotherapy and crenolanib (Cren) + chemotherapy, respectively... Addition of Gil, Qui, Lus, Mid, or Cren to standard therapy was well tolerated by most of the patients with FLT-3 mutation. Addition of Mid or Qui to chemotherapy significantly improved survival and response rates as compared to chemotherapy alone in fit patients with FLT-3 mutation and the results were consistent in both young and old fit patients. In early phase trials, Gil and Cren were effective in combination with chemotherapy in fit patients.

Most FLT3 inhibitors (FLT3i) identified to date, including approved drugs such as gilteritinib, midostaurin, ponatinib, quizartinib, and FLT3i in clinical trials, such as quizartinib and crenolanib, also inhibit closely-related kinases that are important for immune (c-KIT), cardiovascular (KDR/VEGFR2, FGFR, PDGFR) or kidney (RET) functions. Here, we report the identification of new FLT3i compounds that have low activities against kinases that have traditionally been difficult to differentiate from FLT3 inhibition, such as KDR/VEGFR, FGFR, PGFR, c-KIT, and RET. These selective compounds could be valuable chemical probes for studying FLT3 biology in the context of chronic pain and/or may represent good starting points to develop well-tolerated FLT3 therapeutics for non-oncology indications or for maintenance therapy for AML.

To evaluate the effect of FLT3 inhibitors in ALL, we treated ex vivo primary leukemic cells of 6 adult ALL patients (FLT3 mut n=4; FLT3 wt n=2) with increasing concentrations of Gilteritinib, Midostaurin, Crenolanib, Sorafenib and Quizartibin for 24, 48 and 72h. AIRC IG 2019 (Project Code: 23810). Figure 1.

Of 137 with FLT3 ITD or D835 mutations, 54 who were treated with FLT3I (Sorafenib=22, Quizartinib=11, Midostaurine=6, Gilteritinib=4 and Crenolanib=1) combined with other agents (Hypomethylating agents (HMA)=23, HMA+Venetoclax (VTX)=5, Idarrubicin+Cytarabine (AraC)+Purine Analogs (IA+Pur)=19, IA+Pur+VTX=2, AraC=3, Fludarabine+AraC (FA)=1, none=1) were selected for analyses. Protein profiling identified cohorts of FLT3 mutant patients that achieved the highest benefit from FLT3I addition, regardless of all other clinical or molecular characteristics. We identified targetable proteins that are elevated in adverse signatures, and hypothesized that these may be targets for modulation to improve FLT3I response. Moreover, a small set of 6 proteins accurately classifies patients and could be used clinically to triage patients for treatment recommendation.

We demonstrated that the addition of the PDGFR inhibitor, crenolanib, to TTFields further reduced cell growth in comparison to either treatment alone. Collectively, our data suggest the efficacy of TTFields in vitro and identify common signaling responses to TTFields in TMZ-sensitive and -resistant populations, which may support more personalized medicine approaches.

A class of drugs, tyrosine-kinase inhibitors (TKI), targeting mutated FLT3, is already available with 1 and 2 generation molecules, but only midostaurin and gilteritinib are currently approved...Indeed, FLT3 inhibitors have significantly contributed to reducing the negative impact of FLT3 mutations on the prognosis of AML patients who are no longer considered at high risk by the European LeukemiaNet (ELN) 2022. Finally, several ongoing efforts to overcome resistance to FLT3-inhibitors will be presented: new generation FLT3 inhibitors in monotherapy or combined with standard chemotherapy, hypomethylating drugs, or IDH1/2 inhibitors, Bcl2 inhibitors; novel anti-human FLT3 monoclonal antibodies (e.g., FLT3/CD3 bispecific antibodies); FLT3-CAR T-cells; CDK4/6 kinase inhibitor (e.g., palbociclib).

We compared the abilities of five clinically used FLT3-ITD inhibitors, namely, midostaurin, crenolanib, gilteritinib, quizartinib, and sorafenib, to induce apoptosis...Homoharringtonine decreases the protein levels of Mcl-1, FLT3-ITD, and Axl. Moreover, it synergistically induces apoptosis with gilteritinib in vitro and prolongs survival of MOLM-13/sor xenografts. The GSK3β/Mcl-1 axis works as the hub of FLT3-ITD inhibitors and plays a critical role in resistance against FLT3-ITD AML-targeted therapy.

There are therefore risks in the management of FLT3i DDIs (i.e., sorafenib, ponatinib, crenolanib, midostaurin, quizartinib, and gilteritinib) and ignoring them can compromise therapeutic success in acute myeloid leukemia (AML) treatment, in complex patients and secondary pathologies. FLT3i will be combined with other therapeutic agents (supportive care, doublet, or triplet therapy) and in different clinical settings, which means a greater chance of controlling and even eradicating the disease effectively, but also an increased risk to patients due to potential DDIs. Healthcare professionals should be aware of the potential interactions that may occur and be vigilant in monitoring those patients who are receiving any potentially interacting drug.

First- and second-generation inhibitors classify FLT3 inhibitors according to FLT3 specificity: first-generation FLT3 inhibitors include sorafenib and midostaurin and second-generation inhibitors are represented by quizartinib, gilteritinib and crenolanib, among others...The results of published randomized studies support the use of sorafenib in a post-transplant setting (SORMAIN trial), midostaurin in combination with ICT based (RATIFY trial) and gilteritinib for R/R AML (ADMIRAL trial). Gilteritinib in combination with hypomethylating agent as well as quizartinib are not supported by solid randomized trial results for their use in FLT3-mutated AML patients.

PDAC-PDX tumors with lower expression of LINC00460 showed a better response to gemcitabine plus crenolanib treatment. Our finding supported the application of LINC00460 in precision medicine that uses gemcitabine plus crenolanib to treat PDAC with low-expression of LINC00460.

FLT3 inhibitors are divided into first generation multi-kinase inhibitors (such as sorafenib, lestaurtinib, midostaurin) and next generation inhibitors (such as quizartinib, crenolanib, gilteritinib) or based on their specificity of FLT3 inhibition [type I inhibitors (midostaurin, gilteritinib) inhibit FLT3 ITD and TKD mutations whereas type II inhibitors (sorafenib, quizartinib) have only FLT3 ITD activity]. Type II FLT3 TKIs had worse cardiac safety profile in our cohort and an increased risk of cardiac toxicity, particularly in patients with prior reduced ejection fraction or A-fib. A careful cardiac history and management of predisposing conditions to serious cardiac events could help improve drug tolerance, morbidity, and mortality. Further studies are required to elucidate the precise mechanisms of increased incidence of cardiac arrythmias and ways to mitigate them.

Luxeptinib suppresses additional signaling pathways in AML cells (CSF1R, PDGFRα, TRK, SYK, BTK, LYN, AKT, ERK, MAPK), kills primary AML cells insensitive to other FLT3 inhibitors at pM and low nM concentrations, and shows enhanced activity in combination with venetoclax...At 450 mg BID, one heavily pretreated AML patient (received 8 prior regimens including alloSCT and FLT3 inhibitors gilteritinib and crenolanib) had a 99% reduction in peripheral blasts (6.4x103/µL at C1D1 to 0.1x103/µL at C1D15), though the blast proportion increased during Cycle 2... As of July 8, 2022, luxeptinib is well tolerated at dose levels of 450, 600, 750, and 900 mg BID over multiple cycles without evidence of having reached the MTD. Luxeptinib in heavily pretreated relapsed FLT3-ITD AML patients has shown anti-tumor activity including a durable, MRD negative CR. Enrollment of patients with R/R AML is ongoing and updated clinical data with the G3 formulation will be presented at the meeting.

The main effective inhibitors of PDGFRA are ripretinib, avapritinib, and crenolanib, and their mechanisms and efficacy in GIST (as confirmed in clinical trials) are described in this review. This review focuses on PDGFRA-mutated GISTs, introduces their clinical characteristics, downstream molecular signaling pathways, and existing resistance mechanisms. We focus on the most recent literature that describes the development of PDGFRA inhibitors and their use in clinical trials, as well as the potential benefits from different combination therapy strategies.

Knowledge of tumor escape pathways has helped in the identification of new targeted drugs to overcome resistance. Immunotherapy and combination or sequential use of BCL2 inhibitors and experimental drugs including aurora kinases, menin and JAK2 inhibitors will be the goal of present and future clinical trials, especially in patients with FLT3-mutated (FLT3mut) AML who are not eligible for allogeneic transplantation.

In April 2017, midostaurin became both the first FLT3 inhibitor and the first targeted therapy of any kind in AML to be approved by the US FDA. The use of FLT3 inhibitors has continued to grow as clinical trials continue to demonstrate the efficacy of this class of agents, with an expanding number available for use as both experimental standard-of-care usage. This review examines the biology of FLT3 and its downstream pathways, the mechanism of FLT3 inhibition, the development of the FLT3 inhibitors as a class and uses of the agents currently available clinically, and the mechanisms by which resistance to FLT3 inhibition may both develop and be overcome.

The combination of crenolanib and sorafenib was tolerable with antileukemic activities and rare emergence of FLT3-TKD mutations, which warrants further investigation.

To understand how clonal evolution contributes to the tumor's invasive spread, we performed exome sequencing and SNP array profiling on 49 multi-region autopsy samples from 11 patients with pontine DMG-H3 K27-a enrolled in a phase I clinical trial of PDGFR inhibitor crenolanib...Subclones harboring a PDGFRA amplicon, including one that amplified a PDGRFA mutant allele, were detected in four patients; their presence in extrapontine tumor and normal brain samples imply their involvement in extrapontine invasion. Our study expands the current knowledge on tumor invasion patterns in DMG-H3 K27-a, which may inform the design of future clinical trials.

Results The median age was 62 years (range 25; 81) and 56% were women.   Most  patients presented ITD FLT3 (80%), 56% were refractory  and 44% were relapsed  (CR1 duration ≥6 months in 60%).  The 1 st line therapy was intensive chemotherapy (78%, 38% with midostaurin) or  HMA (22%).  A total of 13/27 patients (48%) had previously received a  FLT3 inhibitor (midostaurin=6, sorafenib=2, quizartinib=2, midostaurin + crenolanib vs placebo=2 and midostaurin + quizartinib=1).   Seventy percent of the patients received >1 line of treatment prior to Gilteritinib/Quizartinib (the most frequent was FLAG-IDA).  Compared with diagnosis, patients in R/R had poorer functional status (ECOG<2 88% vs. 73%) but lower leukocyte counts, LDH level and FLT3 ITD ratio  (21.5 x10 9 /L vs 4.7x10 9 /L, 563 U/L vs 330 U/L and 0.60 vs 0.42, respectively). One patient died of toxicity attributed to Gilteritinib (febrile neutropenia). Conclusion Treatment with Gilteritinib and Quizartinib as monotherapy is an effective and tolerable option for patients with R/R FLT3-mutated AML in real-life, with similar response rates and toxicity  to those reported in  Phase 3 trials, despite the fact that the study population from our series  was more heterogeneous.

Pts (≥ 18 yrs) with newly diagnosed FLT3-AML received 7+3 induction with cytarabine 100 mg/m2/d for 7 days and daunorubicin (DNR) (<60 yrs: 90 mg/m2; ≥60 yrs: 60 mg/m2) or idarubicin (IDA 12 mg/m2) for 3 days. Long-term outcomes of a phase 2 trial of crenolanib combined with 7+3 induction and consolidation in adults with newly diagnosed FLT3 mutant AML demonstrate high response rates (CRc 86%). With a median follow-up of 45 mos, median OS has not been reached. A phase 3 trial (NCT03258931) randomizing pts with newly diagnosed FLT3 mutant AML to crenolanib vs midostaurin with 7+3 is ongoing.

The protein-inhibitor interactions displayed that the motions of PHE-830 influenced that of sorafenib, but not to crenolanib. These findings indicated that the structural impact brought by D835V mutation should be considered in designing novel drugs to overcome resistance to FLT3-D835V.

Midostaurin, quizartinib, and gilteritinib have been approved in the last years for the treatment of AML, and more Tyrosine Kinase Inhibitors (TKIs) targeting FLT3 are being developed such as crenolanib. Although several aspects may challenge the use of FLT3 inhibitors in AML (resistance mechanisms, on- and off-target toxicities or drug-drug interactions), these drugs are generally well tolerated, particularly if we compare their safety profile with classical chemotherapy agents or even with newer immunotherapies, thus enabling their use in fit and unfit AML patients, alone or combined. As AML is a polyclonal disease and FLT3 mutations are a late leukemogenic event, combinations of these FLT3 inhibitors with other antileukemic agents (like venetoclax or hypomethylating agents) seem a necessary research pathway.

Here we report the development of appropriate chromatographic conditions to detect and quantitate crenolanib and an internal standard, tyrphostin AG-1478, on an HPLC-UV system. Chromatographic parameters were determined for the quantitation of crenolanib in brain, lung, liver and serum of crenolanib-treated mice.

Children tolerate crenolanib well at doses slightly higher than the established MTD in adults, with a toxicity spectrum generally similar to that in adults. Studies evaluating intratumoral PDGFR pathway inhibition in biomarker-enriched patients are needed to evaluate further the clinical utility of crenolanib in this population.

Midostaurin is approved in the U.S. and Europe for newly diagnosed FLT3 mutated AML in combination with standard induction and consolidation chemotherapy based on data from the RATIFY study. Gilteritinib is approved for relapsed or refractory FLT3 mutated AML as monotherapy based on the ADMIRAL study...Several drug resistance mechanisms have been identified, including clonal selection, stromal protection, FLT3-associated mutations, and off-target mutations. The benefit of FLT3 inhibitor maintenance therapy, either post-chemotherapy or post-transplant, remains controversial, although several studies are ongoing.

We found that combined inhibition of both EGFR and PDGFRA using FDA-approved EGFR-targeted agents (Erlotinib, Gefitinib, Dacomitinib, Neratinib, and Osimertinib) and Crenolanib, respectively, leads to synergistic cytotoxicity in vitro . These pathways are targetable with FDA-approved agents that could be used in patients with GBM with Chr. 7 gain.

Based on these results, the combination activity of CC-90009 with venetoclax (VEN)/azacitidine (AZA) is being evaluated in a phase 1/2 trial in patients with AML (NCT04336982)...Synergy between the isocitrate dehydrogenase 2 (IDH2) inhibitor enasidenib and CC-90009 was evaluated in a TF‑1 erythroleukemia cell line overexpressing IDH2 R140Q mutant, and an IDH2 R140Q PDX model, AM7577...FLT3 inhibitors, including sunitinib, pexidartinib, midostaurin, lestaurtinib, crenolanib, and gilteritinib, synergized with CC-90009 to reduce viability in FLT3-ITD AML cell lines MV4-11 and MOLM-13...The FLT3 inhibitor quizartinib significantly prolonged survival when combined with CC‑90009 compared with either agent alone ( P < 0.001)... Using a high-throughput combination screen, we identified rational combination partners that synergize with CC-90009 in in vitro and in vivo AML models. Collectively, these results support the clinical evaluation of CC-90009 in combination with FLT3, BCL2, and IDH2 inhibitors to further improve treatment outcomes for patients with AML.

Luxeptinib simultaneously suppresses additional signaling pathways in AML cells (CSF1R, PDGFRα, TRK, SYK, BTK, LYN, AKT, ERK, MAPK), kills primary AML cells insensitive to other FLT3 inhibitors at pM and low nM concentrations, and shows enhanced activity in combination with venetoclax...One heavily pretreated AML patient (8 prior regimens including alloSCT and FLT3 inhibitors gilteritinib and crenolanib) had 99% reduction of blasts in peripheral blood (from 6.38x10 3 /µL at C1D1 to 0.09x10 3 /µL at C1D15), though the decrease in blasts reversed during Cycle 2...MRD-negative complete remission (CR) was confirmed in one FLT3-ITD AML patient (6 prior regimens including 2 alloSCT and FLT3 inhibitor sorafenib) at Cycle 5 of treatment evidenced by reduction of FLT3-ITD VAF and blasts in bone marrow to below limit of detection (LOD) of PCR-based FLT3-ITD assay and high-sensitivity flow cytometry (LOD < 0.1%), respectively... As of June 7, 2021, luxeptinib is well tolerated at dose levels of 450 and 600 mg BID over multiple cycles and escalated to 750 mg BID (Cohort 3). Pharmacodynamic studies documented inhibition of FLT3 signaling, and anti-leukemic activity has been observed in heavily pretreated relapsed FLT3-ITD AML patients as evidenced by significant reduction of FLT3-ITD VAF and blasts in bone marrow and / or peripheral blood. One FLT3-ITD AML patient has had confirmed MRD negative CR and continues treatment.

4T1 cells expressed mRNA for platelet-derived growth factor (PDGF)-a, b and c, and the PDGF receptor inhibitor crenolanib almost completely inhibited 4T1-sup-induced MCP-1 production by fibroblasts...Thus, although cancer cells have the capacity to crosstalk with fibroblasts via PDGFs, this crosstalk does not play a major role in MCP-1 production or cancer progression in this model. Unraveling complex crosstalk between cancer cells and stromal cells will help us identify new targets to help treat breast cancer patients.