Chronic myeloid leukaemia (CML) is driven by the activity of the BCR-ABL1 fusion oncoprotein. ABL1 kinase inhibitors have improved the clinical outcomes for patients with CML, with over 80% of patients treated with imatinib surviving for more than 10 years. Second-generation ABL1 kinase inhibitors induce more potent molecular responses in both previously untreated and imatinib-resistant patients with CML. Studies in patients with chronic-phase CML have shown that around 50% of patients who achieve and maintain undetectable BCR-ABL1 transcript levels for at least 2 years remain disease-free after the withdrawal of treatment. Here we characterize ABL001 (asciminib), a potent and selective allosteric ABL1 inhibitor that is undergoing clinical development testing in patients with CML and Philadelphia chromosome-positive (Ph) acute lymphoblastic leukaemia. In contrast to catalytic-site ABL1 kinase inhibitors, ABL001 binds to the myristoyl pocket of ABL1 and induces the formation of an inactive kinase conformation. ABL001 and second-generation catalytic inhibitors have similar cellular potencies but distinct patterns of resistance mutations, with genetic barcoding studies revealing pre-existing clonal populations with no shared resistance between ABL001 and the catalytic inhibitor nilotinib. Consistent with this profile, acquired resistance was observed with single-agent therapy in mice; however, the combination of ABL001 and nilotinib led to complete disease control and eradicated CML xenograft tumours without recurrence after the cessation of treatment.
Type III phosphatidylinositol-4-kinase beta (PI4KIII) was previously implicated in hepatitis C virus (HCV) replication by small interfering RNA (siRNA) depletion and was therefore proposed as a novel cellular target for the treatment of hepatitis C. Medicinal chemistry efforts identified highly selective PI4KIII inhibitors that potently inhibited the replication of genotype 1a and 1b HCV replicons and genotype 2a virus in vitro. Replicon cells required more than 5 weeks to reach low levels of 3-to 5-fold resistance, suggesting a high resistance barrier to these cellular targets. Extensive in vitro profiling of the compounds revealed a role of PI4KIII in lymphocyte proliferation. Previously proposed functions of PI4KIII in insulin secretion and the regulation of several ion channels were not perturbed with these inhibitors. Moreover, PI4KIII inhibitors were not generally cytotoxic as demonstrated across hundreds of cell lines and primary cells. However, an unexpected antiproliferative effect in lymphocytes precluded their further development for the treatment of hepatitis C. C hronic hepatitis C virus (HCV) infection, a major cause of chronic hepatitis, cirrhosis, and hepatocellular carcinoma, afflicts approximately 3% of the world's population (24). The current standard of care for treating hepatitis C is pegylated interferon and ribavirin, which shows poor tolerability and is capable of achieving a sustained viral response in only half of genotype 1 patients (7). Two NS3 protease inhibitors, telaprevir and boceprevir, have been approved recently, and additional direct-acting antivirals are in clinical development. While triple therapy with interferon, ribavirin, and a protease inhibitor increases the percentage of patients showing a sustained viral response to 75% and can shorten the treatment time, it still has limitations: only genotype 1 patients are responsive, side effects (such as anemia) prevent the use in transplant patients, and the inconvenient dosing schedule (three times a day) might cause noncompliance. Development of viruses resistant to direct antivirals occurs very rapidly and leads to relapse and viral breakthrough. A possible exception might be nucleoside inhibitors, since viruses with resistance mutations are not viable. We therefore executed high-throughput small interfering RNA (siRNA) screens in order to identify novel cellular targets for the treatment of HCV. Type III phosphatidylinositol-4-kinases (PI4KIIIs) were identified from these studies and in screens performed in other laboratories (3,4,(20)(21)(22).Mammalian cells express a large number of lipid kinases, including four enzymes that phosphorylate phosphatidylinositol at position four of the inositol ring, the phosphatidylinositol-4-kinases (PI4Ks). Lipid kinases are involved in multiple functions of the cell, of which phosphatidylinositol 3,4,5-trisphosphate (PIP 3 ) signaling is the most thoroughly investigated process. The four PI4Ks (type II ␣ and  and type III ␣ and ) are localized to different sites in the cell by pro...
Background: Chronic myelogenous leukemia (CML) and a subset of acute lymphoblastic leukemia (ALL) are caused by the t(9;22)(q34;q11.2) chromosome translocation, resulting in fusion of the BCR and ABL1 genes on the Philadelphia chromosome to encode constitutively active ABL1 kinase. Despite the dramatic progress made over the past decade with tyrosine kinase inhibitors (TKIs) in the treatment of CML, allogeneic stem cell transplant is considered the only proven curative therapy. To achieve cure or benefit from treatment-free remissions with pharmacologically-based therapies, it is estimated that patients will likely need to achieve a sustained reduction in tumor burden of 4 logs (MR4) or deeper (MR4.5). Currently, only 39% and 18% of patients achieve MR4 by 24 months of treatment with single agent nilotinib or imatinib, respectively. Furthermore, for a subset of CML patients and the majority of Ph+ ALL patients, resistance develops to current TKI’s as a result of emergence of point mutations in the ATP site of the kinase domain. ABL001 is a potent, selective BCR-ABL inhibitor that maintains activity across most mutations, including T315I, with a distinct, allosteric mechanism of action which recently entered Phase I development for the treatment of patients with CML and Ph+ ALL. ABL001 was developed to be dosed in combination with nilotinib to provide greater pharmacological coverage of BCR-ABL disease and prevent the emergence of resistance. Methods: Based on X-ray crystallography, NMR and molecular modeling, ABL001 is the result of a structure-guided medicinal chemistry program targeting the myristoyl pocket of the ABL1 kinase. In vitro cell based assays were performed using the Ba/F3 isogenic cell system and a panel of over 300 cell lines. KCL-22 cells were used to develop an in vivo xenograft model to assess the efficacy of ABL001 and the PD marker, pSTAT5, was used to monitor the inhibition of BCR-ABL signaling. Results: In contrast to TKIs that bind to the ATP-site of the ABL1 kinase domain, NMR and X-Ray crystallography studies confirmed that ABL001 binds to a pocket on the BCR-ABL kinase domain that is normally occupied by the myristoylated N-terminus of ABL1. Upon fusion with BCR, this myristoylated N-terminus that serves to autoregulate ABL1 activity is lost. ABL001 functionally mimics the role of the myristoylated N-terminus by occupying its vacant binding site and restores the negative regulation of the kinase activity. Cell proliferation studies demonstrate that ABL001 selectively inhibited the growth of CML and Ph+ ALL cells with potencies ranging from 1-10nM range. In contrast, BCR-ABL-negative cell lines remained unaffected at concentrations 1000-fold higher. With resistance emerging in the clinic to current TKI’s as a result of point mutations in the ATP-site, ABL001 was tested for activity against clinically observed mutations and found to be active in the low nM range. In the KCL-22 mouse xenograft model, ABL001 displayed potent anti-tumor activity with complete tumor regression observed and a clear dose-dependent correlation with pSTAT5 inhibition. The KCL-22 xenograft model was also used to compare the dosing of ABL001 and nilotinib as single agents to dosing a combination of ABL001 and nilotinib. Single agent dosing regimens led to tumor regressions; however, despite continuous dosing, all tumors relapsed within 30-60 days with evidence of point mutations in the resistant tumors. In contrast, animals treated with the combination of ABL001 and nilotinib achieved sustained tumor regression with no evidence of disease relapse either during the 70 days of treatment or for > 150 days after treatment stopped. Conclusion: ABL001 selectively inhibited the proliferation of cells expressing the BCR-ABL fusion gene and was active against clinically important mutations that arise with current TKI therapy in CML. In an in vivo model of CML, the combination of ABL001 and nilotinib resulted in complete and sustained tumor regression with no evidence of disease relapse. These results provide proof-of-principle that simultaneous targeting of the myristoyl pocket and ATP-pocket by ABL001 and nilotinib, respectively, promotes a more sustained overall efficacy and prevents the emergence of resistance via acquisition of point mutations in the respective binding sites. ABL001 is currently being evaluated in a Phase 1 study in patients with CML and Ph+ ALL. Disclosures Wylie: Novartis Institutes for Biomedical Research, Inc: Employment. Schoepfer:Novartis Institutes for Biomedical Research: Employment. Berellini:Novartis Institutes for Biomedical Research: Employment. Cai:Novartis Institutes for Biomedical Research: Employment. Caravatti:Novartis Institutes for Biomedical Research: Employment. Cotesta:Novartis Institues for Biomedical Research: Employment. Dodd:Novartis Institutes for Biomedical Research: Employment. Donovan:Novartis Institutes for Biomedical Research: Employment. Erb:Novartis Institutes for Biomedical Research: Employment. Furet:Novartis Institutes for Biomedical Research: Employment. Gangal:Novartis Institutes for Biomedical Research: Employment. Grotzfeld:Novartis Institutes for Biomedical Research: Employment. Hassan:Novartis Institutes for Biomedical Research: Employment. Hood:Novartis Institutes for Biomedical Research: Employment. Iyer:Novartis Institutes for Biomedical Research: Employment. Jacob:Novartis Institutes for Biomedical Research: Employment. Jahnke:Novartis Institutes for Biomedical Research: Employment. Lombardo:Novartis Institutes for Biomedical Research: Employment. Loo:Novartis Institutes for Biomedical Research: Employment. Manley:Novartis Institutes for Biomedical Research: Employment. Marzinzik:Novartis Institutes for Biomedical Research: Employment. Palmer:Novartis Institutes for Biomedical Research: Employment. Pelle:Novartis Institutes for Biomedical Research: Employment. Salem:Novartis Institutes for Biomedical Research: Employment. Sharma:Novartis Institutes for Biomedical Research: Employment. Thohan:Novartis Institutes for Biomedical Research: Employment. Zhu:Novartis Institutes for Biomedical Research: Employment. Keen:Novartis Institutes for Biomedical Research: Employment. Petruzzelli:Novartis Institutes for Biomedical Research: Employment. Vanasse:Novartis: Employment, Equity Ownership. Sellers:Novartis: Employment.
Mealtime pramlintide (PRAM) and insulin (INS) reduce postprandial glucose excursions, mimics natural pancreas physiology and improves glycemic control. Due to differences in physico-chemical characteristics of PRAM and INS, mixing these two products can cause precipitation. Xeris has developed novel room temperature stable co-formulations to overcome precipitation, simplify dose administration and reduce injection burden. Streptozotocin (65 mg/kg) treated SD rats were given co-formulations of PRAM and Regular Insulin (RI) or Lispro Insulin (LISPRO) as a single injection and compared with dual injection of commercial Symlin, Humulin, or Humalog. Blood samples were evaluated for plasma glucose and PK. A sparse sampling PK scheme resulted in ∼30% CV for glucose values. Mean glucose profiles with reductions in glucose AUC by treatment (efficacy). PRAM-INS single injection co-formulations showed comparable efficacy and PK profiles to two injection commercial products. Consistent with PRAM's known pharmacological action, there was no glucose lowering with PRAM alone. These results support clinical development of room temperature stable PRAM-INS co-formulations. Disclosure S. Thohan: None. W.T. Hu: None. M.J. Donovan: None. S.J. Prestrelski: Employee; Self; Xeris Pharmaceuticals, Inc. M.S. Choi: None. D.M. Hester: None.
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