Preclinical Evaluation of a Novel Small Molecule Inhibitor of LIM Kinases (LIMK) CEL_Amide in Philadelphia-Chromosome Positive (BCR::ABL+) Acute Lymphoblastic Leukemia (ALL).

Ph+ (BCR::ABL+) B-ALL was considered to be high risk, but recent advances in BCR::ABL-targeting TKIs has shown improved outcomes in combination with backbone chemotherapy. Nevertheless, new treatment strategies are needed, including approaches without chemotherapy for elderly patients. LIMK1/2 acts downstream from various signaling pathways, which modifies cytoskeleton dynamics via phosphorylation of cofilin. Upstream of LIMK1/2, ROCK is constitutively activated by BCR::ABL, and upon activation, ROCK leads to the phosphorylation of LIMK1/2, resulting in the inactivation of cofilin by its phosphorylation and subsequently abrogating its apoptosis-promoting activity. Here, we demonstrate the anti-leukemic effects of a novel LIMK1/2 inhibitor (LIMKi) CEL_Amide in vitro and in vivo for BCR::ABL-driven B-ALL. The IC50 value of CEL_Amide was ≤1000 nM in BCR::ABL+ TOM-1 and BV-173 cells and induced dose-dependent apoptosis and cell cycle arrest in these cell lines. LIMK1/2 were expressed in BCR::ABL+ cell lines and patient cells and LIMKi treatment decreased LIMK1 protein expression, whereas LIMK2 expression was unaffected. As expected, CEL_Amide exposure caused specific activating downstream dephosphorylation of cofilin in cell lines and primary cells. Combination experiments with CEL_Amide and BCR::ABL TKIs imatinib, dasatinib, nilotinib, and ponatinib were synergistic for the treatment of both TOM-1 and BV-173 cells. CDKN2Ako/BCR::ABL1+ B-ALL cells were transplanted in mice, which were treated with combinations of CEL_Amide and nilotinib or ponatinib, which significantly prolonged their survival. Altogether, the LIMKi CEL_Amide yields activity in Ph+ ALL models when combined with BCR::ABL-targeting TKIs, showing promising synergy that warrants further investigation.

Biological Effects of BET Inhibition by OTX015 (MK-8628) and JQ1 in NPM1-Mutated (NPM1c) Acute Myeloid Leukemia (AML).

BET inhibitors (BETi) including OTX015 (MK-8628) and JQ1 demonstrated antileukemic activity including NPM1c AML cells. Nevertheless, the biological consequences of BETi in NPM1c AML were not fully investigated. Even if of better prognosis AML patients with NPM1c may relapse and treatment remains difficult. Differentiation-based therapy by all trans retinoic acid (ATRA) combined with arsenic trioxide (ATO) demonstrated activity in NPM1c AML. We found that BETi, similar to ATO + ATRA, induced differentiation and apoptosis which was TP53 independent in the NPM1c cell line OCI-AML3 and primary cells. Furthermore, BETi induced proteasome-dependent degradation of NPM1c. BETi degraded NPM1c in the cytosol while BRD4 is degraded in the nucleus which suggests that restoration of the NPM1/BRD4 equilibrium in the nucleus of NPM1c cells is essential for the efficacy of BETi. While ATO + ATRA had significant biological activity in NPM1c IMS-M2 cell line, those cells were resistant to BETi. Gene profiling revealed that IMS-M2 cells probably resist to BETi by upregulation of LSC pathways independently of the downregulation of a core BET-responsive transcriptional program. ATO + ATRA downregulated a NPM1c specific HOX gene signature while anti-leukemic effects of BETi appear HOX gene independent. Our preclinical results encourage clinical testing of BETi in NPM1c AML patients.

Synergy of FLT3 inhibitors and the small molecule inhibitor of LIM kinase1/2 CEL_Amide in FLT3-ITD mutated Acute Myeloblastic Leukemia (AML) cells.

Patients with FLT3-ITD mutated (FLT3-ITD+) Acute Myeloid Leukemia (AML), have frequently relapsed or refractory disease and FLT3-ITD+ inhibitors have limited efficacy. Rho kinases (ROCK) are constitutively activated by FLT3-ITD+ in AML via PI3 kinase and Rho GTPase. Upon activation by ROCK, LIM kinases (LIMK) inactivate cofilin by phosphorylation which affects cytoskeleton dynamics, cell growth and apoptosis. LIMK inhibition leads to cofilin activation via dephosphorylation and activated cofilin localizes to mitochondria inducing apoptosis. Thus, we investigated the therapeutic potential of the LIMK1/2 inhibitor CEL_Amide (LIMKi) in FLT3-ITD+ AML. Expression of LIMK1/2 in FLT3-ITD+ cell lines MOLM-13 and MV-4-11 cells could be detected by RT-qPCR and at the protein level. IC50 after LIMKi monotherapy was 440 nM in MOLM-13 cells and 420 nM in MV4-11 cells. Treatment with LIMKi decreased LIMK1 protein levels and repression of inactivating phosphorylation of cofilin in FLT3-ITD+ cells. Combination experiments with LIMKi and FLT3 inhibitors including midostaurin, crenolanib and gilteritinib were synergistic for treatment of MOLM-13 cells while combinations with quizartinib were additive. Combinations of LIMKi and the hypomethylating agent azacitidine or the ROCK inhibitor fasudil were additive. In NOD-SCID mice engrafted with MOLM13-LUC cells, the FLT3 inhibitor midostaurin and LIMKi delayed MOLM13-LUC engraftment as detected by in vivo bioluminescence imaging and the LIMKi and midostaurin combination prolonged significantly survival of leukemic mice. LIMK1/2 inhibition by the small molecule CEL_Amide seems to have promising activity in combination with FLT3 inhibitors in vitro as well as in vivo and may constitute a novel treatment strategy for FLT3-ITD+ AML.

Successful Use of Recombinant Activated Factor VII to Reverse Ticagrelor-Induced Bleeding Risk: A Case Report.

Management of ticagrelor-associated bleeding is challenging, especially in neurosurgery. Platelet transfusion is inefficient and no antidote is currently available. We report here the first case of recombinant activated factor VII (rFVIIa) use to bypass ticagrelor-induced platelet inhibition. A woman treated with ticagrelor and requiring emergent neurosurgery for an intracranial hematoma received preoperative high-dose platelet transfusion and 60 µg/kg rFVIIa. Laboratory monitoring demonstrated that platelet transfusion failed to reverse ticagrelor-induced platelet inhibition while rFVIIa improved hemostasis by shortening the thromboelastometric clotting time. Neurosurgery occurred without any bleeding event but the patient presented with a postoperative pulmonary embolism. In conclusion, rFVIIa may decrease ticagrelor-induced bleeding risk but careful assessment of the benefit-risk balance is warranted before using rFVIIa to reverse ticagrelor effects.

BET inhibitor OTX015 targets BRD2 and BRD4 and decreases c-MYC in acute leukemia cells.

The bromodomain (BRD) and extraterminal (BET) proteins including BRD2, BRD3 and BRD4 have been identified as key targets for leukemia maintenance. A novel oral inhibitor of BRD2/3/4, the thienotriazolodiazepine compound OTX015, suitable for human use, is available. Here we report its biological effects in AML and ALL cell lines and leukemic samples. Exposure to OTX015 lead to cell growth inhibition, cell cycle arrest and apoptosis at submicromolar concentrations in acute leukemia cell lines and patient-derived leukemic cells, as described with the canonical JQ1 BET inhibitor. Treatment with JQ1 and OTX15 induces similar gene expression profiles in sensitive cell lines, including a c-MYC decrease and an HEXIM1 increase. OTX015 exposure also induced a strong decrease of BRD2, BRD4 and c-MYC and increase of HEXIM1 proteins, while BRD3 expression was unchanged. c-MYC, BRD2, BRD3, BRD4 and HEXIM1 mRNA levels did not correlate however with viability following exposure to OTX015. Sequential combinations of OTX015 with other epigenetic modifying drugs, panobinostat and azacitidine have a synergic effect on growth of the KASUMI cell line. Our results indicate that OTX015 and JQ1 have similar biological effects in leukemic cells, supporting OTX015 evaluation in a Phase Ib trial in relapsed/refractory leukemia patients.

Molecular exploration of the α(1A)-adrenoceptor orthosteric site: binding site definition for epinephrine, HEAT and prazosin.

Despite the physiological and pharmacological importance of the α1A-adrenoreceptor, the mode of interactions of classical agonists and radioactive ligands with this receptor is not yet clearly defined. Here, we used mutagenesis studies and binding experiments to evaluate the importance of 11 receptor sites for the binding of (125)I-HEAT, (3)H-prazosin and epinephrine. Only one residue (F312) commonly interacts with the three molecules, and, surprisingly, D106 interacts only with epinephrine in a moderate way. Our docking model shows that prazosin and HEAT are almost superimposed into the orthosteric pocket with their tetralone and quinazoline rings close to the phenyl ring of the agonist.