Identification of potent and selective MTH1 inhibitors.

Structure based design of a novel class of aminopyrimidine MTH1 (MutT homolog 1) inhibitors is described. Optimization led to identification of IACS-4759 (compound 5), a sub-nanomolar inhibitor of MTH1 with excellent cell permeability and good metabolic stability in microsomes. This compound robustly inhibited MTH1 activity in cells and proved to be an excellent tool for interrogation of the utility of MTH1 inhibition in the context of oncology.

Multisite Verification of a Targeted CFTR Polymerase Chain Reaction/Capillary Electrophoresis Assay That Evaluates Pathogenic Variants Across Diverse Ethnic and Ancestral Groups.

CONTEXT.­: Existing targeted cystic fibrosis screening assays miss important pathogenic CFTR variants in the ethnically diverse US population. OBJECTIVE.­: To evaluate the analytic performance of a multiplex polymerase chain reaction (PCR)/capillary electrophoresis (CE) CFTR assay panel that simultaneously interrogates primary pathogenic variants of different ethnic/ancestral groups. DESIGN.­: Performance characteristic assessment and variant coverage comparison of the panel with a focus on ethnicity-specific CFTR variants were performed. Sample DNA was primarily from whole blood or cell lines. Detection of CFTR carriers was compared across several commercially available CFTR kits and recommended variant sets based on panel content. RESULTS.­: The panel interrogated 65 pathogenic CFTR variants representing 92% coverage from a recent genomic sequencing survey of the US population, including 4 variants with top 5 frequency in African or Asian populations not reflected in other targeted panels. In simulation studies, the panel represented 95% of carriers across the global population, resulting in a 6.9% to 19.0% higher carrier detection rate compared with 10 targeted panels or variant sets. Precision and sensitivity/specificity were 100% concordant. Multisite sample-level genotyping accuracy was 99.2%. Across PCR and CE instruments, sample-level genotyping accuracy was 97.1%, with greater than 99% agreement for all variant-level metrics. CONCLUSIONS.­: The CFTR assay achieves 92% or higher coverage of CFTR variants in diverse populations and provides improved pan-ethnic coverage of minority subgroups of the US populace. The assay can be completed within 5 hours from DNA sample to genotype, and performance data exceed acceptance criteria for analytic metrics. This assay panel content may help address gaps in ancestry-specific CFTR genotypes while providing a streamlined procedure with rapidly generated results.

Discovery of IACS-9779 and IACS-70465 as Potent Inhibitors Targeting Indoleamine 2,3-Dioxygenase 1 (IDO1) Apoenzyme.

Indoleamine 2,3-dioxygenase 1 (IDO1), a heme-containing enzyme that mediates the rate-limiting step in the metabolism of l-tryptophan to kynurenine, has been widely explored as a potential immunotherapeutic target in oncology. We developed a class of inhibitors with a conformationally constrained bicyclo[3.1.0]hexane core. These potently inhibited IDO1 in a cellular context by binding to the apoenzyme, as elucidated by biochemical characterization and X-ray crystallography. A SKOV3 tumor model was instrumental in differentiating compounds, leading to the identification of IACS-9779 (62) and IACS-70465 (71). IACS-70465 has excellent cellular potency, a robust pharmacodynamic response, and in a human whole blood assay was more potent than linrodostat (BMS-986205). IACS-9779 with a predicted human efficacious once daily dose below 1 mg/kg to sustain >90% inhibition of IDO1 displayed an acceptable safety margin in rodent toxicology and dog cardiovascular studies to support advancement into preclinical safety evaluation for human development.

Discovery of 6-[(3S,4S)-4-Amino-3-methyl-2-oxa-8-azaspiro[4.5]decan-8-yl]-3-(2,3-dichlorophenyl)-2-methyl-3,4-dihydropyrimidin-4-one (IACS-15414), a Potent and Orally Bioavailable SHP2 Inhibitor.

Src homology 2 (SH2) domain-containing phosphatase 2 (SHP2) plays a role in receptor tyrosine kinase (RTK), neurofibromin-1 (NF-1), and Kirsten rat sarcoma virus (KRAS) mutant-driven cancers, as well as in RTK-mediated resistance, making the identification of small-molecule therapeutics that interfere with its function of high interest. Our quest to identify potent, orally bioavailable, and safe SHP2 inhibitors led to the discovery of a promising series of pyrazolopyrimidinones that displayed excellent potency but had a suboptimal in vivo pharmacokinetic (PK) profile. Hypothesis-driven scaffold optimization led us to a series of pyrazolopyrazines with excellent PK properties across species but a narrow human Ether-à-go-go-Related Gene (hERG) window. Subsequent optimization of properties led to the discovery of the pyrimidinone series, in which multiple members possessed excellent potency, optimal in vivo PK across species, and no off-target activities including no hERG liability up to 100 µM. Importantly, compound 30 (IACS-15414) potently suppressed the mitogen-activated protein kinase (MAPK) pathway signaling and tumor growth in RTK-activated and KRASmut xenograft models in vivo.

Discovery of IACS-9439, a Potent, Exquisitely Selective, and Orally Bioavailable Inhibitor of CSF1R.

Tumor-associated macrophages (TAMs) have a significant presence in the tumor stroma across multiple human malignancies and are believed to be beneficial to tumor growth. Targeting CSF1R has been proposed as a potential therapy to reduce TAMs, especially the protumor, immune-suppressive M2 TAMs. Additionally, the high expression of CSF1R on tumor cells has been associated with poor survival in certain cancers, suggesting tumor dependency and therefore a potential therapeutic target. The CSF1-CSF1R signaling pathway modulates the production, differentiation, and function of TAMs; however, the discovery of selective CSF1R inhibitors devoid of type III kinase activity has proven to be challenging. We discovered a potent, highly selective, and orally bioavailable CSF1R inhibitor, IACS-9439 (1). Treatment with 1 led to a dose-dependent reduction in macrophages, promoted macrophage polarization toward the M1 phenotype, and led to tumor growth inhibition in MC38 and PANC02 syngeneic tumor models.

Allosteric SHP2 Inhibitor, IACS-13909, Overcomes EGFR-Dependent and EGFR-Independent Resistance Mechanisms toward Osimertinib.

Src homology 2 domain-containing phosphatase (SHP2) is a phosphatase that mediates signaling downstream of multiple receptor tyrosine kinases (RTK) and is required for full activation of the MAPK pathway. SHP2 inhibition has demonstrated tumor growth inhibition in RTK-activated cancers in preclinical studies. The long-term effectiveness of tyrosine kinase inhibitors such as the EGFR inhibitor (EGFRi), osimertinib, in non-small cell lung cancer (NSCLC) is limited by acquired resistance. Multiple clinically identified mechanisms underlie resistance to osimertinib, including mutations in EGFR that preclude drug binding as well as EGFR-independent activation of the MAPK pathway through alternate RTK (RTK-bypass). It has also been noted that frequently a tumor from a single patient harbors more than one resistance mechanism, and the plasticity between multiple resistance mechanisms could restrict the effectiveness of therapies targeting a single node of the oncogenic signaling network. Here, we report the discovery of IACS-13909, a specific and potent allosteric inhibitor of SHP2, that suppresses signaling through the MAPK pathway. IACS-13909 potently impeded proliferation of tumors harboring a broad spectrum of activated RTKs as the oncogenic driver. In EGFR-mutant osimertinib-resistant NSCLC models with EGFR-dependent and EGFR-independent resistance mechanisms, IACS-13909, administered as a single agent or in combination with osimertinib, potently suppressed tumor cell proliferation in vitro and caused tumor regression in vivo. Together, our findings provide preclinical evidence for using a SHP2 inhibitor as a therapeutic strategy in acquired EGFRi-resistant NSCLC. SIGNIFICANCE: These findings highlight the discovery of IACS-13909 as a potent, selective inhibitor of SHP2 with drug-like properties, and targeting SHP2 may serve as a therapeutic strategy to overcome tumor resistance to osimertinib.