Weakened APC/C activity at mitotic exit drives cancer vulnerability to KIF18A inhibition

The efficacy of current antimitotic cancer drugs is limited by toxicity in highly proliferative healthy tissues. A cancer-specific dependency on the microtubule motor protein KIF18A therefore makes it an attractive therapeutic target. Not all cancers require KIF18A, however, and the determinants underlying this distinction remain unclear. Here, we show that KIF18A inhibition drives a modest and widespread increase in spindle assembly checkpoint (SAC) signaling from kinetochores which can result in lethal mitotic delays. Whether cells arrest in mitosis depends on the robustness of the metaphase-to-anaphase transition, and cells predisposed with weak basal anaphase-promoting complex/cyclosome (APC/C) activity and/or persistent SAC signaling through metaphase are uniquely sensitive to KIF18A inhibition. KIF18A-dependent cancer cells exhibit hallmarks of this SAC:APC/C imbalance, including a long metaphase-to-anaphase transition, and slow mitosis overall. Together, our data reveal vulnerabilities in the cell division apparatus of cancer cells that can be exploited for therapeutic benefit.

Abstract LB202: Discovery and preclinical characterization of novel small molecule inhibitors of kinesin KIF18A motor protein with potent activity against chromosomally unstable cancers

KIF18A is a mitotic kinesin that localizes to the plus-end tips of kinetochore microtubule (MT) spindle fibers during metaphase, where it regulates chromosome alignment, and promotes the viability of chromosomally unstable cancer cells. KIF18A is overexpressed in a subset of human cancers, and its elevated expression is associated with tumor aggressiveness.

Chromosomal instability (CIN) is a hallmark of human cancers and is caused by persistent errors in chromosome segregation during mitosis. Aggressive types of human cancer such as high-grade serous ovarian cancer (HGSOC) and triple-negative breast cancer (TNBC) have elevated levels of CIN and frequently harbor alterations in TP53 tumor suppressor gene. These two CIN+ cancer subtypes share molecular similarities but have limited treatment options at present. The rationale of pharmacological inhibition of KIF18A motor activity is to selectively target a tumor-specific mitotic spindle vulnerability in CIN+ cancer cells while largely sparing normal diploid dividing somatic cells.

Here, we describe the identification of a novel series of potent and selective small molecule inhibitors of KIF18A MT-ATPase motor activity exemplified by AM-1882, that disrupt the mitotic spindle and selectively kill chromosomally unstable cancer cells. Our KIF18A inhibitors phenocopy genetic ablation of KIF18A and trigger spindle assembly checkpoint activation, multipolarity, and apoptosis in sensitive CIN+ cancer cell lines. The sensitivity profile of AM-1882 is focal-in-nature with cell potency in the low double-digit nanomolar range across a panel of breast and ovarian cancer cell lines, including lines that harbor genetic alterations (e.g., TP53, CCNE1, RB1, BRCA1, whole genome doubling) frequently enriched in CIN+ cancers and in HGSOC and TNBC tumor subtypes. Furthermore, the sensitivity profile of AM-1882 is distinct from comparator test agents ispinesib (Eg5, pan cytotoxic) and palbociclib (CDK4/6, focal cytostatic). The combination of AM-1882 with PARP inhibitor olaparib is synergistic in BRCA1-deficient cancer cell lines, with evidence of increased double-strand DNA breaks (p-H2AX) and apoptosis (cl-PARP). Importantly, KIF18A inhibitors have minimal toxicity on normal dividing somatic cell types in vitro, including proliferating human bone marrow mononuclear cells, distinct from paclitaxel and small molecule inhibitors of essential mitotic kinases and kinesins. In vivo, we demonstrate that administration of KIF18A inhibitors AM-1882 and AM-5308 induce a robust pharmacodynamic response (pH3, mitotic marker) and frank tumor regressions in two TP53 mutant human HGSOC xenograft models (OVCAR-3, OVCAR-8) at well-tolerated doses.

Collectively, our preclinical data provides the first example of a therapeutic strategy to selectively target CIN+ cancers through inhibition of KIF18A motor protein.

Citation Format: Jan Sun, Brain Belmontes, Jodi Moriguchi, Grace Chung, Kui Chen, John D. McCarter, Upendra P. Dahal, Andrew S. Boghossian, Matthew G. Rees, Melissa M. Ronan, Jennifer A. Roth, Sheroy Minocherhomji, Matthew P. Bourbeau, Jennifer R. Allen, Angela Coxon, Paul E. Hughes, Nuria Tamayo, Marc N. Payton. Discovery and preclinical characterization of novel small molecule inhibitors of kinesin KIF18A motor protein with potent activity against chromosomally unstable cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB202.

Abstract 1807: The discovery and preclinical characterization of the MTA cooperative PRMT5 inhibitor AM-9747

Homozygous deletion of the tumor suppressor gene CDKN2A and the neighboring MTAP gene located at chr9p21 occurs in 10-15% of human cancers. Deletion of MTAP, an enzyme in methionine and adenine salvage pathways, results in accumulation of its substrate MTA, which is structurally similar to SAM, the substrate methyl donor for the type II methyltransferase PRMT5. In MTAP deleted cells, MTA competes with SAM for binding to PRMT5, placing PRMT5 in a partially inhibited or hypormorphic state. Multiple studies using shRNAi knockdown have shown that tumor cell lines harboring MTAP deletions are vulnerable to PRMT5 inhibition. PRMT5 inhibitors that have advanced to clinical studies do not selectively target the MTA-bound form of PRMT5, and the preclinical activity of these molecules is not enriched in MTAP-deleted tumor cells lines. Moreover, the therapeutic window of these molecules is narrow, presumably due to the inhibition of PRMT5 in normal cells. We set out to identify PRMT5 inhibitors that bind cooperatively with MTA, with the goal of selectively targeting PRMT5 in MTAP-deleted tumors. A DNA encoded library screen was conducted to identify small molecules that preferentially bind to PRMT5 in the presence of MTA. The subsequent optimization of screening hits to improve potency, MTA-cooperativity, and pharmacokinetic properties led to the identification of AM-9747. The nature of the MTA cooperativity of AM-9747 was interrogated by multiple biophysical methods and structural biology experiments. Following treatment with AM-9747, the levels of SDMA marks were lower in HCT116 MTAP-deleted cells (IC50 = 0.0002 μM) compared to HCT116 MTAP-WT cells (IC50 = 0.050 μM). AM-9747 selectively inhibited the proliferation of HCT116 MTAP-deleted cells (IC50 = 0.027 μM) compared to HCT116 MTAP-WT cells (IC50 = 0.63 μM). The profiling of AM-9747 in an expanded panel of tumor cell lines demonstrated that AM-9747 inhibited the proliferation of most MTAP-deleted cells, with minimal effects on MTAP-WT cells. In vitro mechanism of action studies demonstrated that treatment with AM-9747 induces DNA damage, as illustrated by increased phosphorylation of H2AX, and an arrest in the G2/M phase of the cell cycle in MTAP-deleted cells. In vivo, oral administration of AM-9747 selectively inhibits SDMA and tumor growth in HCT116 MTAP-deleted tumor xenografts, compared to HCT116 MTAP-WT xenografts. Furthermore, treatment with AM-9747 inhibits the growth of multiple MTAP-deleted tumor xenograft models, including BXPC3 (PDAC) and DOHH2 (DLBCL). AM-9747 was profiled against a panel of over twenty PDX models, with greater than 50% tumor growth inhibition observed in the majority of PDX models harboring deletion of the MTAP gene. Our data with AM-9747 indicates that PRMT5 inhibitors that selectively target PRMT5 in cooperation with MTA may represent a novel and compelling therapeutic strategy for the treatment of MTAP-deleted cancers.

Citation Format: Brian Belmontes, Antonia Policheni, Siyuan Liu, Katherine Slemmons, Jodi Moriguchi, Hayley Ma, Daniel Aiello, Yajing Yang, Mikkel Vestergaard, Sanne Cowland, Jan Anderson, Ian Sarvary, Nuria Tamayo, Liping Pettus, Susmith Mukund, Leszek Pope, Jennifer R. Allen, Sanne Glad, Matthew Bourbeau, Paul E. Hughes. The discovery and preclinical characterization of the MTA cooperative PRMT5 inhibitor AM-9747 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1807.

Discovery of ( R)-8-(6-Methyl-4-oxo-1,4,5,6-tetrahydropyrrolo[3,4- b]pyrrol-2-yl)-3-(1-methylcyclopropyl)-2-((1-methylcyclopropyl)amino)quinazolin-4(3 H)-one, a Potent and Selective Pim-1/2 Kinase Inhibitor for Hematological Malignancies

Pim kinases are a family of constitutively active serine/threonine kinases that are partially redundant and regulate multiple pathways important for cell growth and survival. In human disease, high expression of the three Pim isoforms has been implicated in the progression of hematopoietic and solid tumor cancers, which suggests that Pim kinase inhibitors could provide patients with therapeutic benefit. Herein, we describe the structure-guided optimization of a series of quinazolinone-pyrrolodihydropyrrolone analogs leading to the identification of potent pan-Pim inhibitor 28 with improved potency, solubility, and drug-like properties. Compound 28 demonstrated on-target Pim activity in an in vivo pharmacodynamic assay with significant inhibition of BAD phosphorylation in KMS-12-BM multiple myeloma tumors for 16 h postdose. In a 2-week mouse xenograft model, daily dosing of compound 28 resulted in 33% tumor regression at 100 mg/kg.

Small molecule disruptors of the glucokinase-glucokinase regulatory protein interaction: 2. Leveraging structure-based drug design to identify analogues with improved pharmacokinetic profiles

In the previous report , we described the discovery and optimization of novel small molecule disruptors of the GK-GKRP interaction culminating in the identification of 1 (AMG-1694). Although this analogue possessed excellent in vitro potency and was a useful tool compound in initial proof-of-concept experiments, high metabolic turnover limited its advancement. Guided by a combination of metabolite identification and structure-based design, we have successfully discovered a potent and metabolically stable GK-GKRP disruptor (27, AMG-3969). When administered to db/db mice, this compound demonstrated a robust pharmacodynamic response (GK translocation) as well as statistically significant dose-dependent reductions in fed blood glucose levels.

Structure-activity relationships of phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) dual inhibitors: investigations of various 6,5-heterocycles to improve metabolic stability

N-(6-(6-Chloro-5-(4-fluorophenylsulfonamido)pyridin-3-yl)benzo[d]thiazol-2-yl)acetamide (1) is a potent and efficacious inhibitor of PI3Kα and mTOR in vitro and in vivo. However, in hepatocyte and in vivo metabolism studies, 1 was found to undergo deacetylation on the 2-amino substituent of the benzothiazole. As an approach to reduce or eliminate this metabolic deacetylation, a variety of 6,5-heterocyclic analogues were examined as an alternative to the benzothiazole ring. Imidazopyridazine 10 was found to have similar in vitro potency and in vivo efficacy relative to 1, while only minimal amounts of the corresponding deacetylated metabolite of 10 were observed in hepatocytes.

Phospshoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) dual inhibitors: discovery and structure-activity relationships of a series of quinoline and quinoxaline derivatives

The phosphoinositide 3-kinase (PI3K) family catalyzes the ATP-dependent phosphorylation of the 3'-hydroxyl group of phosphatidylinositols and plays an important role in cell growth and survival. There is abundant evidence demonstrating that PI3K signaling is dysregulated in many human cancers, suggesting that therapeutics targeting the PI3K pathway may have utility for the treatment of cancer. Our efforts to identify potent, efficacious, and orally available PI3K/mammalian target of rapamycin (mTOR) dual inhibitors resulted in the discovery of a series of substituted quinolines and quinoxalines derivatives. In this report, we describe the structure-activity relationships, selectivity, and pharmacokinetic data of this series and illustrate the in vivo pharmacodynamic and efficacy data for a representative compound.

High-Content Screening Analysis of the p38 Pathway: Profiling of Structurally Related p38α Kinase Inhibitors Using Cell-Based Assays

The complexity of the p38 mitogen-activated protein kinase (MAPK) signaling pathway presents challenges to understanding the efficacy of p38 inhibitors. Biochemical recombinant kinase assays and tumor necrosis factor alpha (TNFalpha) secretion assays are typically used to evaluate p38alpha inhibitors, but they do not provide insight into proximal intracellular events. Stimulation of the pathway evokes a cascade of phosphorylation events, accompanied by movement of molecules to different cellular compartments. Herein, we describe the profiling and potency comparison of a large set of p38alpha inhibitors with a pyrimidinone, imidazopyrimidine, or triazolopyrimidine core against biochemical recombinant p38alpha kinase activity, lipopolysaccharide (LPS)-mediated TNFalpha secretion by THP-1 cells, and a set of cellular imaging assays in SW1353 chondrocytes and baby hamster kidney cells. These pathway assays included p38 phosphorylation, MAPK-activated protein kinase 2 translocation, and heat shock protein (HSP) 27 phosphorylation. We established that HSP27 phosphorylation correlates well with LPS-induced TNFalpha secretion, validating our cellular imaging assays. We also found that the choice of cells and inducer can profoundly affect cellular potency results. High-content analysis may reveal signaling details, enriching our understanding of the mechanism of action of p38alpha inhibitors.

p38 MAP kinase inhibitors: many are made, but few are chosen

The mitogen-activated protein kinase (MAPK) p38 is a Ser/Thr kinase, originally isolated from lipopolysaccharide-stimulated monocytes. There are four isoforms of the enzyme (p38alpha, p38beta, p38gamma and p38delta), which differ in tissue distribution, regulation of kinase activation and subsequent phosphorylation of downstream substrates. These enzymes also differ in sensitivity to p38 MAPK inhibitors. The most thoroughly studied isoform is p38alpha, for which activation has been observed in many hematopoietic and non-hematopoietic cell types upon appropriate stimuli. p38alpha kinase is involved in the biosynthesis of the cytokines tumor necrosis factor-alpha and interleukin-1beta at the translational and transcriptional level. MAPK p38alpha represents a point of convergence for multiple signaling processes that are activated during inflammation, making it a key potential target for the modulation of cytokine production. The discovery and publication of p38alpha and a pyridinyl-imidazole-based p38alpha inhibitor initiated a huge effort by many companies to develop p38alpha inhibitors as potential treatments for inflammatory diseases. Herein, a brief overview is provided of the discovery and development of AMG-548 (Amgen Inc), a selective and efficacious p38alpha inhibitor, and its pharmacodynamic effects in a first-in-human study. Data from a phase I multidose clinical trial are also included. In addition, other p38alpha inhibitors that have advanced to clinical trials over the last three years are discussed, such as BIRB-796 (Boehringer Ingelheim Pharmaceuticals Inc), SCIO-469 and SCIO-323 (Scios Inc), and VX-702 (Vertex Pharmaceuticals Inc/Kissei Pharmaceutical Co).

Design and synthesis of potent pyridazine inhibitors of p38 MAP kinase

Novel potent trisubstituted pyridazine inhibitors of p38 MAP (mitogen activated protein) kinase are described that have activity in both cell-based assays of cytokine release and animal models of rheumatoid arthritis. They demonstrated potent inhibition of LPS-induced TNF-alpha production in mice and exhibited good efficacy in the rat collagen induced arthritis model.

Melanocortin subtype-4 receptor agonists containing a piperazine core with substituted aryl sulfonamides

The biological activity for a set of melanocortin-4 receptor (MC4R) agonists containing a piperazine core with an ortho-substituted aryl sulfonamide is described. Compounds from this set had binding and functional activities at MC4R less than 30 nM. The most selective compound in this series was >25,000-fold more potent at MC4R than MC3R, and 490-fold more potent at MC4R than MC5R. This compound also reduced food intake after oral dosing at 25, 50, and 100 mg kg(-1) in fasted mice.

Pheochromocytoma: a twenty year experience at the University Hospital

During the past 20 years (1970-90), we had 24 patients with pheochromocytoma: 19 diagnosed clinically and 5 post-mortem. Their ages ranged from 17 to 74 (mean, 43.2 years). Males (n = 14) outnumbered females (n = 10), a 1.41:1 M:F ratio. A majority were symptomatic (95%), with a typical triad of headaches, palpitations and diaphoresis. Most frequent finding was hypertension (95%). It was sustained in 60% and paroxysmal in 35%. In 6 patients (25%) pheochromocytomas were bilateral, all familial. Fifteen were solitary adrenal tumors (63%); 3 (12.5%) were extra-adrenal: 2 intra-abdominal, and 1 cardiac paraganglioma of right atrium. Of 6 familial cases, 4 were associated to Von Hippel-Lindau (VHL) disease, while 2 were multiple endocrine neoplasia (MEN-II) patients. All familial cases were bilateral and in the adrenals. There were no malignancies. Among the 19 clinical cases pre-operative Dx was made by positive urine VMA or catecholamines urine levels: (95 and 100% sensitivity respectively). Preoperative visualization by CT or MRI was done in 62% of the most recent patients. In 5 earlier cases the diagnosis was made post mortem: 3 died of cerebral hemorrhage, 1 with a pons infarct and 1 with congestive heart failure (CHF). There were 2 post-operative deaths and another died 13 years later from thyroid medullary carcinoma. Of the 19 operated, 13 (68%) were cured. Thus pheochromocytomas retain considerable morbidity and some mortality. These rare tumors constitute a clinical diagnostic challenge yet a rewarding therapeutic experience for the alert physician.