Guillaume Mata

Selective KIT inhibition is an effective strategy for treating mast cell-driven diseases, but highly conserved ATP-binding sites in class III RTKs hinder selective inhibitor design. We employed structure-guided medicinal chemistry to optimize a series of potent, selective KIT inhibitors. An initial triazolopyridine hinge-binding motif enabled potent KIT inhibition with high selectivity and, after central linker optimization, led to a “reverse” arylacetamide series with further improved potency and pharmacokinetic properties. Incorporation of a pyrazole-based linker and modification of the hinge-binding motif led to improved potency in the presence of human serum. Further tuning of the terminal aryl substituent mitigated cytochrome P450 time-dependent inhibition and improved kinome selectivity. Crystallography revealed key elements of KIT inhibition and showed that subtle modulation of linker stereoelectronic effects in the gatekeeper region can drive selectivity. These efforts yielded an optimized lead inhibitor with low-nanomolar cellular potency, high KIT selectivity, and properties favorable for chronic therapy.

Mast cells play critical roles in the pathogenesis of many allergic and inflammatory diseases. KIT, a receptor tyrosine kinase, is a crucial regulator of mast cells and, in consequence, the modulation of mast cells through KIT inhibition presents a promising therapeutic approach for treating a range of chronic diseases. Clinical applications of small-molecule KIT inhibitors have been limited to oncology due to adverse effects associated with poor kinome selectivity. Here, we describe a highly selective small-molecule KIT inhibitor (7) that exhibits excellent broad kinome selectivity, with a selectivity score of S(50%) = 0.003. Data-driven investigations of structure–activity relationships and careful modulation of physicochemical properties yielded improvements in potency, selectivity, and metabolic stability. Compound 7 demonstrated promising in vivo therapeutic efficacy in an SCF-driven acute cutaneous anaphylaxis model in rodents.

Hypoxia-inducible factor 2α (HIF-2α) is recognized as a key oncogenic driver in clear cell renal cell carcinoma (ccRCC), the most prevalent type of kidney cancer. Here, we describe the discovery of a highly potent and selective tetralin-based HIF-2α inhibitor, casdatifan (61), originating from previously identified tetrahydroquinolines reported in the Part 1 companion manuscript. Casdatifan demonstrates a potentially best-in-class clinical profile. In a healthy volunteer study (NCT05117554), casdatifan exhibited a favorable pharmacokinetic profile, with an approximate 24-h half-life suitable for once-daily oral administration. Casdatifan has shown promising clinical activity in the ARC-20 ccRCC platform study, both as monotherapy and in combination with the VEGFR tyrosine kinase inhibitor (TKI) cabozantinib. Currently, casdatifan is being evaluated in a Phase 3 trial in combination with cabozantinib (NCT07011719) in patients with advanced ccRCC.

Disruption of hypoxia-inducible factor (HIF) signaling is implicated in multiple diseases, including clear cell renal cell carcinoma (ccRCC), where HIF-2α functions as a key oncogenic driver. Here, we report the design and structure-activity relationships of a novel class of N-aryl-substituted tetrahydroquinolines that bind the HIF-2α PAS-B domain with high affinity. Structural and biophysical studies revealed that ligand binding induces localized conformational perturbations at the dimerization interface between HIF-2α and HIF-1β. Notably, incorporation of cis-vicinal difluorination was critical for productive engagement of the lipophilic pocket, with hyperconjugative effects contributing to improved binding efficiency and facial polarization enhancing physicochemical properties. These features translated into improved biochemical and cellular activity, including inhibition of hypoxia-regulated gene expression. Insights from this campaign ultimately informed the discovery of casdatifan, a clinical-stage HIF-2α inhibitor, underscoring the translational potential of this novel chemotype.

We disclose a stereodivergent strategy to prepare vicinal difluorinated tetralins from γ-substituted tetralones via a combination of catalyst-controlled transfer hydrogenation and substrate-controlled fluorinations. This process is easily scalable and amenable to highly functionalized substrates, as demonstrated here in the late-stage synthesis of casdatifan, a clinical-stage inhibitor of hypoxia-inducible factor-2α. Analysis of the physicochemical properties of casdatifan, which features a cis-vicinal difluoride, revealed a higher level of facial polarization compared to its trans-vicinal difluoride isomers.

Phosphoinositide-3-kinase γ (PI3Kγ) is highly expressed in immune cells and promotes the production and migration of inflammatory mediators. The inhibition of PI3Kγ has been shown to repolarize the tumor immune microenvironment to a more inflammatory phenotype, thereby controlling immune suppression in cancer. Herein, we report the structure-based optimization of an early lead series of pyrazolopyrimidine isoindolinones, which culminated in the discovery of highly potent and isoform-selective PI3Kγ inhibitors with favorable drug-like properties. X-ray cocrystal structure analysis, molecular docking studies, and detailed structure–activity relationship investigations resulted in the identification of the optimal amide and isoindolinone substituents to achieve a desirable combination of potency, selectivity, and metabolic stability. Preliminary in vitro studies indicate that inhibition of PI3Kγ with compound 56 results in a significant immune response by increasing pro-inflammatory cytokine gene expression in M1 macrophages.

The successful application of immunotherapy in the treatment of cancer relies on effective engagement of immune cells in the tumor microenvironment. Phosphoinositide 3-kinase γ (PI3Kγ) is highly expressed in tumor-associated macrophages, and its expression levels are associated with tumor immunosuppression and growth. Selective inhibition of PI3Kγ offers a promising strategy in immuno-oncology, which has led to the development of numerous potent PI3Kγ inhibitors with variable selectivity profiles. To facilitate further investigation of the therapeutic potential of PI3Kγ inhibition, we required a potent and PI3Kγ-selective tool compound with sufficient metabolic stability for use in future in vivo studies. Herein, we describe some of our efforts to realize this goal through the systematic study of SARs within a series of 7-azaindole-based PI3Kγ inhibitors. The large volume of data generated from this study helped guide our subsequent lead optimization efforts and will inform further development of PI3Kγ-selective inhibitors for use in immunomodulation.