Discovery of ASP6918, a KRAS G12C inhibitor: Synthesis and structure-activity relationships of 1-{2,7-diazaspiro[3.5]non-2-yl}prop-2-en-1-one derivatives as covalent inhibitors with good potency and oral activity for the treatment of solid tumors.

Although KRAS protein had been classified as an undruggable target, inhibitors of KRAS G12C mutant protein were recently reported to show clinical efficacy in solid tumors. In our previous report, we identified 1-{2,7-diazaspiro[3.5]non-2-yl}prop-2-en-1-one derivative (1) as a KRAS G12C inhibitor that covalently binds to Cys12 of KRAS G12C protein. Compound 1 exhibited potent cellular pERK inhibition and cell growth inhibition against a KRAS G12C mutation-positive cell line and showed an antitumor effect on subcutaneous administration in an NCI-H1373 (KRAS G12C mutation-positive cell line) xenograft mouse model in a dose-dependent manner. In this report, we further optimized the substituents on the quinazoline scaffold based on the structure-based drug design from the co-crystal structure analysis of compound 1 and KRAS G12C to enhance in vitro activity. As a result, ASP6918 was found to exhibit extremely potent in vitro activity and induce dose-dependent tumor regression in an NCI-H1373 xenograft mouse model after oral administration.

Discovery and biological evaluation of 1-{2,7-diazaspiro[3.5]nonan-2-yl}prop-2-en-1-one derivatives as covalent inhibitors of KRAS G12C with favorable metabolic stability and anti-tumor activity.

RAS protein plays a key role in cellular proliferation and differentiation. RAS gene mutation is a known driver of oncogenic alternation in human cancer. RAS inhibition is an effective therapeutic treatment for solid tumors, but RAS protein has been classified as an undruggable target. Recent reports have demonstrated that a covalent binder to KRAS protein at a mutated cysteine residue (G12C) is effective for the treatment of solid tumors. Here, we report a series of 1-{2,7-diazaspiro[3.5]nonan-2-yl}prop-2-en-1-one derivatives as potent covalent inhibitors against KRAS G12C identified throughout structural optimization of an acryloyl amine moiety to improve in vitro inhibitory activity. From an X-ray complex structural analysis, the 1-{2,7-diazaspiro[3.5]nonan-2-yl}prop-2-en-1-one moiety binds in the switch-II pocket of KRAS G12C. Further optimization of the lead compound (5c) led to the successful identification of 1-[7-[6-chloro-8-fluoro-7-(5-methyl-1H-indazol-4-yl)-2-[(1-methylpiperidin-4-yl)amino]quinazolin-4-yl]-2,7-diazaspiro[3.5]nonan-2-yl]prop-2-en-1-one (7b), a potent compound with high metabolic stabilities in human and mouse liver microsomes. Compound 7b showed a dose-dependent antitumor effect on subcutaneous administration in an NCI-H1373 xenograft mouse model.

Characterisation of a novel KRAS G12C inhibitor ASP2453 that shows potent anti-tumour activity in KRAS G12C-mutated preclinical models.

BACKGROUND: KRAS is one of the most frequently mutated oncogenes in various cancers, and several novel KRAS G12C direct inhibitors are now in clinical trials. Here, we characterised the anti-tumour efficacy of ASP2453, a novel KRAS G12C inhibitor, in preclinical models of KRAS G12C-mutated cancer. METHODS: We evaluated the in vitro and in vivo activity of ASP2453, alone or in combination with targeted agents and immune checkpoint inhibitors, in KRAS G12C-mutated cancer cells and xenograft models. We also assessed pharmacological differences between ASP2453 and AMG 510, another KRAS G12C inhibitor, using an SPR assay, washout experiments and an AMG 510-resistant xenograft model. RESULTS: ASP2453 potently and selectively inhibited KRAS G12C-mediated growth, KRAS activation and downstream signalling in vitro and in vivo, and improved the anti-tumour effects of targeted agents and immune checkpoint inhibitors. Further, ASP2453 had more rapid binding kinetics to KRAS G12C protein and showed more potent inhibitory effects on KRAS activation and cell proliferation after washout than AMG 510. ASP2453 also induced tumour regression in an AMG 510-resistant xenograft model. CONCLUSIONS: ASP2453 is a potential therapeutic agent for KRAS G12C-mutated cancer. ASP2453 showed efficacy in AMG 510-resistant tumours, even among compounds with the same mode of action.

Virtual clinical trial simulations for a novel KRASG12C inhibitor (ASP2453) in non-small cell lung cancer.

KRAS is a small GTPase family protein that relays extracellular growth signals to cell nucleus. KRASG12C mutations lead to constitutive proliferation signaling and are prevalent across human cancers. ASP2453 is a novel, highly potent, and selective inhibitor of KRASG12C . Although preclinical data suggested impressive efficacy, it remains unclear whether ASP2453 will show more favorable clinical response compared to more advanced competitors, such as AMG 510. Here, we developed a quantitative systems pharmacology (QSP) model linking KRAS signaling to tumor growth in patients with non-small cell lung cancer. The model was parameterized using in vitro ERK1/2 phosphorylation and in vivo xenograft data for ASP2453. Publicly disclosed clinical data for AMG 510 were used to generate a virtual population, and tumor size changes in response to ASP2453 and AMG 510 were simulated. The QSP model predicted ASP2453 exhibits greater clinical response than AMG 510, supporting potential differentiation and critical thinking for clinical trials.

Clinical activity of ASP8273 in Asian patients with non-small-cell lung cancer with EGFR activating and T790M mutations.

Epidermal growth factor receptor (EGFR)-activating mutations confer sensitivity to tyrosine kinase inhibitor (TKI) treatment for non-small-cell lung cancer (NSCLC). ASP8273 is a highly specific, irreversible, once-daily, oral, EGFR TKI that inhibits both activating and resistance mutations. This ASP8273 dose-escalation/dose-expansion study (NCT02192697) was undertaken in two phases. In phase I, Japanese patients (aged ≥20 years) with NSCLC previously treated with ≥1 EGFR TKI received escalating ASP8273 doses (25-600 mg) to assess safety/tolerability and to determine the maximum tolerated dose (MTD) and/or the recommended phase II dose (RP2D) by the Bayesian Continual Reassessment Method. In phase II, adult patients with T790M-positive NSCLC in Japan, Korea, and Taiwan received ASP8273 at RP2D to further assess safety/tolerability and determine antitumor activity, which was evaluated according to Simon's two-stage design (threshold response = 30%, expected response = 50%, α = 0.05, ß = 0.1). Overall, 121 (n = 45 [33W/12M] phase I, n = 76 [48W/28M]) phase 2) patients received ≥1 dose of ASP8273. In phase I, RP2D and MTD were established as 300 and 400 mg, respectively. As 27 of the 63 patients treated with ASP8273 300 mg achieved a clinical response, ASP8273 was determined to have antitumor activity. The overall response rate at week 24 in all patients was 42% (n = 32/76; 95% confidence interval, 30.9-54.0). Median duration of progression-free survival was 8.1 months (95% confidence interval, 5.6, upper bound not reached). The most commonly reported treatment-related adverse event in phase II was diarrhea (57%, n = 43/76). ASP8273 300 mg was generally well tolerated and showed antitumor activity in Asian patients with both EGFR-activating and T790M mutations.

Delayed re-epithelialization in periostin-deficient mice during cutaneous wound healing.

BACKGROUND: Matricellular proteins, including periostin, are important for tissue regeneration. METHODS AND FINDINGS: Presently we investigated the function of periostin in cutaneous wound healing by using periostin-deficient ⁻/⁻ mice. Periostin mRNA was expressed in both the epidermis and hair follicles, and periostin protein was located at the basement membrane in the hair follicles together with fibronectin and laminin γ2. Periostin was associated with laminin γ2, and this association enhanced the proteolytic cleavage of the laminin γ2 long form to produce its short form. To address the role of periostin in wound healing, we employed a wound healing model using WT and periostin⁻/⁻ mice and the scratch wound assay in vitro. We found that the wound closure was delayed in the periostin⁻/⁻ mice coupled with a delay in re-epithelialization and with reduced proliferation of keratinocytes. Furthermore, keratinocyte proliferation was enhanced in periostin-overexpressing HaCaT cells along with up-regulation of phosphorylated NF-κB. CONCLUSION: These results indicate that periostin was essential for keratinocyte proliferation for re-epithelialization during cutaneous wound healing.

Periostin associates with Notch1 precursor to maintain Notch1 expression under a stress condition in mouse cells.

BACKGROUND: Matricellular proteins, including periostin, modulate cell-matrix interactions and cell functions by acting outside of cells. METHODS AND FINDINGS: In this study, however, we reported that periostin physically associates with the Notch1 precursor at its EGF repeats in the inside of cells. Moreover, by using the periodontal ligament of molar from periostin-deficient adult mice (Pn-/- molar PDL), which is a constitutively mechanically stressed tissue, we found that periostin maintained the site-1 cleaved 120-kDa transmembrane domain of Notch1 (N1) level without regulating Notch1 mRNA expression. N1 maintenance in vitro was also observed under such a stress condition as heat and H(2)O(2) treatment in periostin overexpressed cells. Furthermore, we found that the expression of a downstream effector of Notch signaling, Bcl-xL was decreased in the Pn-/- molar PDL, and in the molar movement, cell death was enhanced in the pressure side of Pn-/- molar PDL. CONCLUSION: These results suggest the possibility that periostin inhibits cell death through up-regulation of Bcl-xL expression by maintaining the Notch1 protein level under the stress condition, which is caused by its physical association with the Notch1 precursor.

Periostin, a novel marker of intramembranous ossification, is expressed in fibrous dysplasia and in c-Fos-overexpressing bone lesions.

Fibrous dysplasia is a benign bone disease caused by a mutation in the gene for the stimulatory guanine nucleotide-binding protein Gs alpha, leading to high cyclic adenosine monophosphate levels. Histologically, fibrous dysplasia is characterized by the production of fibrous tissue accompanied by the deposition of ectopic type I collagen and other bone-associated extracellular matrix proteins, as well as by irregular woven intramembranous bone onto which type I collagen-containing Sharpey fibers are often attached. Fibrous dysplasia is also characterized by high expression of c-Fos/c-Jun, known targets for cyclic adenosine monophosphate signaling. In this study, we examined the expression of the bone-related extracellular matrix protein, periostin, and its known receptor, integrin alpha v beta 3 (CD51/61), in normal bones as well as in fibrous dysplasia. Immunohistochemistry and in situ hybridization studies revealed that periostin was expressed in the extracellular matrix during intramembranous but not endochondral ossification, as well as in the fibrous component of fibrous dysplasia; and all cells adjacent to periostin-positive regions expressed CD51/61. Importantly, periostin was abundantly localized to Sharpey fibers. To investigate the contribution of c-Fos, we examined transgenic mice overexpressing c-fos, which develop sclerotic lesions closely resembling those found in fibrous dysplasia. In all lesions, transformed osteoblasts expressed high levels of periostin, whereas normal osteoblasts did not. Our results show that periostin is a novel marker for intramembranous ossification, and is a good candidate as a diagnostic tool and/or a therapeutic target in fibrous dysplasia. Moreover, the Gs alpha-cyclic adenosine monophosphate-c-Fos pathway might represent one mechanism of periostin up-regulation in fibrous dysplasia, resulting in altered collagen fibrillogenesis characteristic of this disease.

Periostin is expressed in pericryptal fibroblasts and cancer-associated fibroblasts in the colon.

Periostin is a unique extracellular matrix protein, deposition of which is enhanced by mechanical stress and the tissue repair process. Its significance in normal and neoplastic colon has not been fully clarified yet. Using immunohistochemistry and immunoelectron microscopy with a highly specific monoclonal antibody, periostin deposition was observed in close proximity to pericryptal fibroblasts of colonic crypts. The pericryptal pattern of periostin deposition was decreased in adenoma and adenocarcinoma, preceding the decrease of the number of pericryptal fibroblasts. Periostin immunoreactivity appeared again at the invasive front of the carcinoma and increased along the appearance of cancer-associated fibroblasts. ISH showed periostin signals in cancer-associated fibroblasts but not in cancer cells. Ki-67-positive epithelial cells were significantly decreased in the colonic crypts of periostin-/- mice (approximately 0.6-fold) compared with periostin+/+ mice. In three-dimensional co-culture within type I collagen gel, both colony size and number of human colon cancer cell line HCT116 cells were significantly larger ( approximately 1.5-fold) when cultured with fibroblasts derived from periostin+/+ mice or periostin-transfected NIH3T3 cells than with those from periostin-/- mice or periostin-non-producing NIH3T3 cells, respectively. Periostin is secreted by pericryptal and cancer-associated fibroblasts in the colon, both of which support the growth of epithelial components.

Periostin is essential for cardiac healing after acute myocardial infarction.

Acute myocardial infarction (AMI) is a common and lethal heart disease, and the recruitment of fibroblastic cells to the infarct region is essential for the cardiac healing process. Although stiffness of the extracellular matrix in the infarct myocardium is associated with cardiac healing, the molecular mechanism of cardiac healing is not fully understood. We show that periostin, which is a matricellular protein, is important for the cardiac healing process after AMI. The expression of periostin protein was abundant in the infarct border of human and mouse hearts with AMI. We generated periostin(-/-) mice and found no morphologically abnormal cardiomyocyte phenotypes; however, after AMI, cardiac healing was impaired in these mice, resulting in cardiac rupture as a consequence of reduced myocardial stiffness caused by a reduced number of alpha smooth muscle actin-positive cells, impaired collagen fibril formation, and decreased phosphorylation of FAK. These phenotypes were rescued by gene transfer of a spliced form of periostin. Moreover, the inhibition of FAK or alphav-integrin, which blocked the periostin-promoted cell migration, revealed that alphav-integrin, FAK, and Akt are involved in periostin signaling. Our novel findings show the effects of periostin on recruitment of activated fibroblasts through FAK-integrin signaling and on their collagen fibril formation specific to healing after AMI.

Impaired capsule formation of tumors in periostin-null mice.

Being a secreted protein, periostin is a multifunctional matricellular glycoprotein. In vitro, periostin has the ability to promote the proliferation and migration of fibroblasts. Previously, it was demonstrated that periostin is mainly produced by cancer-associated fibroblasts or tumor stromal cells. In the present study, we show that periostin regulates capsule formation in a positive manner and inhibits tumor growth. Consistent with a previous finding, several tumor cell lines did not exhibit expression of periostin in vitro or in vivo; and the growth of tumors that had been allografted into periostin -/- mice was significantly accelerated compared with that of the same kind of tumors grafted into periostin +/+ mice. Immunostaining and biochemical analyses revealed that mature collagen was detected abundantly in the capsules and interstitium of the wild-type-grafted tumors but not in those of the periostin -/- grafted tumors. Moreover, the number of activated tumor stromal cells was decreased significantly in the periostin -/- grafted tumors. Our studies suggest that host-derived periostin negatively regulates tumor growth by promoting capsule formation and by mediating changes in the deposition and organization of the tumor microenvironment coordinated by periostin-producing stromal cells.

GFP transgenic mice reveal active canonical Wnt signal in neonatal brain and in adult liver and spleen.

In the past decades, the function of the Wnt canonical pathway during embryogenesis has been intensively investigated; however, little survey of neonatal and adult tissues has been made, and the role of this pathway remains largely unknown. To investigate its role in mature tissues, we generated two new reporter transgenic mouse lines, ins-TOPEGFP and ins-TOPGAL, that drive EGFP and beta-galactosidase expression under TCF/beta-catenin, respectively. To obtain the accurate expression pattern, we flanked these transgenes with the HS4 insulator to reduce chromosomal positional effects. Analysis of embryos showed that the reporter genes were activated in regions where canonical Wnt activity has been implicated. Furthermore, their expression patterns were consistent in both lines, indicating the accuracy of the reporter signal. In the neonatal brain, the reporter signal was detected in the mesencephalon and hippocampus. In the adult mice, the reporter signal was found in the mature pericenteral hepatocytes in the normal liver. Furthermore, during inflammation the number of T cells expressing the reporter gene increased in the adult spleen. Thus, in this research, we identified two organs, i.e., the liver and spleen, as novel organs in which the Wnt canonical signal is in motion in the adult. These transgenic lines will provide us broader opportunities to investigate the function of the Wnt canonical pathway in vivo.