SAR439859, a Novel Selective Estrogen Receptor Degrader (SERD), Demonstrates Effective and Broad Antitumor Activity in Wild-Type and Mutant ER-Positive Breast Cancer Models.

Primary treatment for estrogen receptor-positive (ER+) breast cancer is endocrine therapy. However, substantial evidence indicates a continued role for ER signaling in tumor progression. Selective estrogen receptor degraders (SERD), such as fulvestrant, induce effective ER signaling inhibition, although clinical studies with fulvestrant report insufficient blockade of ER signaling, possibly due to suboptimal pharmaceutical properties. Furthermore, activating mutations in the ER have emerged as a resistance mechanism to current endocrine therapies. New oral SERDs with improved drug properties are under clinical investigation, but the biological profile that could translate to improved therapeutic benefit remains unclear. Here, we describe the discovery of SAR439859, a novel, orally bioavailable SERD with potent antagonist and degradation activities against both wild-type and mutant Y537S ER. Driven by its fluoropropyl pyrrolidinyl side chain, SAR439859 has demonstrated broader and superior ER antagonist and degrader activities across a large panel of ER+ cells, compared with other SERDs characterized by a cinnamic acid side chain, including improved inhibition of ER signaling and tumor cell growth. Similarly, in vivo treatment with SAR439859 demonstrated significant tumor regression in ER+ breast cancer models, including MCF7-ESR1 wild-type and mutant-Y537S mouse tumors, and HCI013, a patient-derived tamoxifen-resistant xenograft tumor. These findings indicate that SAR439859 may provide therapeutic benefit to patients with ER+ breast cancer, including those who have resistance to endocrine therapy with both wild-type and mutant ER.

Discovery of 6-(2,4-Dichlorophenyl)-5-[4-[(3S)-1-(3-fluoropropyl)pyrrolidin-3-yl]oxyphenyl]-8,9-dihydro-7H-benzo[7]annulene-2-carboxylic acid (SAR439859), a Potent and Selective Estrogen Receptor Degrader (SERD) for the Treatment of Estrogen-Receptor-Positive Breast Cancer.

More than 75% of breast cancers are estrogen receptor alpha (ERα) positive (ER+), and resistance to current hormone therapies occurs in one-third of ER+ patients. Tumor resistance is still ERα-dependent, but mutations usually confer constitutive activation to the hormone receptor, rendering ERα modulator drugs such as tamoxifen and aromatase inhibitors ineffective. Fulvestrant is a potent selective estrogen receptor degrader (SERD), which degrades the ERα receptor in drug-resistant tumors and has been approved for the treatment of hormone-receptor-positive metastatic breast cancer following antiestrogen therapy. However, fulvestrant shows poor pharmacokinetic properties in human, low solubility, weak permeation, and high metabolism, limiting its administration to inconvenient intramuscular injections. This Drug Annotation describes the identification and optimization of a new series of potent orally available SERDs, which led to the discovery of 6-(2,4-dichlorophenyl)-5-[4-[(3S)-1-(3-fluoropropyl)pyrrolidin-3-yl]oxyphenyl]-8,9-dihydro-7H-benzo[7]annulene-2-carboxylic acid (43d), showing promising antitumor activity in breast cancer mice xenograft models and whose properties warranted clinical evaluation.

Concomitant Inhibition of PI3Kß and BRAF or MEK in PTEN-Deficient/BRAF-Mutant Melanoma Treatment: Preclinical Assessment of SAR260301 Oral PI3Kß-Selective Inhibitor.

Class IA PI3K pathway activation resulting from PTEN deficiency has been associated with lack of sensitivity of melanoma to BRAF kinase inhibitors. Although previous studies have shown synergistic activity when pan-PI3K inhibitors were combined with MAPK inhibitors in the treatment of melanoma exhibiting concurrent genetic abnormalities, overlapping adverse events in patients limit optimal dosing and clinical application. With the aim of specifically targeting PTEN-deficient cancers and minimizing the potential for on-target toxicity when inhibiting multiple PI3K isoforms, we developed a program to discover PI3Kß-selective kinase inhibitors and identified SAR260301 as a potent PI3Kß-selective, orally available compound, which is now in clinical development. Herein, we provide a detailed biological characterization of SAR260301, and show that this compound has outstanding biochemical and cellular selectivity for the PI3Kß isoform versus the α, δ, and γ isoforms and a large panel of protein and lipid kinases. We demonstrate that SAR260301 blocks PI3K pathway signaling preferentially in PTEN-deficient human tumor models, and has synergistic antitumor activity when combined with vemurafenib (BRAF inhibitor) or selumetinib (MEK inhibitor) in PTEN-deficient/BRAF-mutated human melanoma tumor models. Combination treatments were very well tolerated, suggesting the potential for a superior safety profile at optimal dosing using selective compounds to inhibit multiple signaling pathways. Together, these experiments provide a preclinical proof-of-concept for safely combining inhibitors of PI3Kß and BRAF or MEK kinase modulators to improve antitumor activity in PTEN-deficient/BRAF-mutant melanoma, and support the evaluation of SAR260301-based combinations in clinical studies. Mol Cancer Ther; 15(7); 1460-71. ©2016 AACR.

Differential Water Thermodynamics Determine PI3K-Beta/Delta Selectivity for Solvent-Exposed Ligand Modifications.

Phosphoinositide 3-kinases (PI3Ks) are involved in important cellular functions and represent desirable targets for drug discovery efforts, especially related to oncology; however, the four PI3K subtypes (α, ß, γ, and δ) have highly similar binding sites, making the design of selective inhibitors challenging. A series of inhibitors with selectivity toward the ß subtype over δ resulted in compound 3(S), which has entered a phase I/Ib clinical trial for patients with advanced PTEN-deficient cancer. Interestingly, X-ray crystallography revealed that the modifications making inhibitor 3(S) and related compounds selective toward the ß-isoform do not interact directly with either PI3Kß or PI3Kδ, thereby confounding rationalization of the SAR. Here, we apply explicit solvent molecular dynamics and solvent thermodynamic analysis using WaterMap in an effort to understand the unusual affinity and selectivity trends. We find that differences in solvent energetics and water networks, which are modulated upon binding of different ligands, explain the experimental affinity and selectivity trends. This study highlights the critical role of water molecules in molecular recognition and the importance of considering water networks in drug discovery efforts to rationalize and improve selectivity.

Preparation and optimization of pyrazolo[1,5-a]pyrimidines as new potent PDE4 inhibitors.

A new series of pyrazolo[1,5-a]pyrimidines exemplified by compound 1, has been identified with moderate activity (IC50=165nM), following GSK256066 rescaffolding. Compound 1 optimization at positions 2, 3, 6 and 7 gave compound 10 with high in vitro activity (IC50=0.7nM). Modeling studies based on the PDB structure 3GWT with compound 5 showed the expected overlay with the carboxamide, the aryl moiety and the sulfone. Cyclisation of the primary amide to the 5 position of the pyrazolo[1,5-a]pyrimidines scaffold afforded compounds 15 and 16 with 200-fold enhancement in activity and cellular potency.

Preparation and optimization of new 4-(2-(indolin-1-yl)-2-oxoethyl)-2-morpholinothiazole-5-carboxylic acid and amide derivatives as potent and selective PI3Kß inhibitors.

In our continuous efforts to identify and develop novel targeted cancer treatments, a new morpholino-thiazole scaffold active against PI3Kß has been identified. This Letter reports the optimization of this compound class to develop PI3Kß isoform-selective inhibitors with suitable pharmacological properties.

Discovery and optimization of pyrimidone indoline amide PI3Kß inhibitors for the treatment of phosphatase and tensin homologue (PTEN)-deficient cancers.

Compelling molecular biology publications have reported the implication of phosphoinositide kinase PI3Kß in PTEN-deficient cell line growth and proliferation. These findings supported a scientific rationale for the development of PI3Kß-specific inhibitors for the treatment of PTEN-deficient cancers. This paper describes the discovery of 2-[2-(2,3-dihydro-indol-1-yl)-2-oxo-ethyl]-6-morpholin-4-yl-3H-pyrimidin-4-one (7) and the optimization of this new series of active and selective pyrimidone indoline amide PI3Kß inhibitors. 2-[2-(2-Methyl-2,3-dihydro-indol-1-yl)-2-oxo-ethyl]-6-morpholin-4-yl-3H-pyrimidin-4-one (28), identified following a carefully designed methyl scan, displayed improved physicochemical and in vitro pharmacokinetic properties. Structural biology efforts enabled the acquisition of the first X-ray cocrystal structure of p110ß with the selective inhibitor compound 28 bound to the ATP site. The nonplanar binding mode described herein is consistent with observed structure-activity relationship for the series. Compound 28 demonstrated significant in vivo activity in a UACC-62 xenograft model in mice, warranting further preclinical investigation. Following successful development, compound 28 entered phase I/Ib clinical trial in patients with advanced cancer.

Preparation and optimization of new 4-(morpholin-4-yl)-(6-oxo-1,6-dihydropyrimidin-2-yl)amide derivatives as PI3Kß inhibitors.

From a HTS campaign, a new series of pyrimidone anilides exemplified by compound 1 has been identified with good inhibitory activity for the PI3Kß isoform. The structure of compound 1 in PI3Kγ was solved revealing a binding mode in agreement with the SAR observed on PI3Kß. These compounds displayed inhibition in the nanomolar range in the biochemical assay and were also potent p-Akt inhibitors in a PTEN-deficient PC3 prostate cancer cell line. Optimization of in vitro pharmocokinetic properties led to compound 25 exhibiting 52% bioavailability in mice and target engagement in an acute PK/PD study.

Discovery and optimization of new benzimidazole- and benzoxazole-pyrimidone selective PI3Kß inhibitors for the treatment of phosphatase and TENsin homologue (PTEN)-deficient cancers.

Most of the phosphoinositide-3 kinase (PI3K) kinase inhibitors currently in clinical trials for cancer treatment exhibit pan PI3K isoform profiles. Single PI3K isoforms differentially control tumorigenesis, and PI3Kß has emerged as the isoform involved in the tumorigenicity of PTEN-deficient tumors. Herein we describe the discovery and optimization of a new series of benzimidazole- and benzoxazole-pyrimidones as small molecular mass PI3Kß-selective inhibitors. Starting with compound 5 obtained from a one-pot reaction via a novel intermediate 1, medicinal chemistry optimization led to the discovery of compound 8, which showed a significant activity and selectivity for PI3Kß and adequate in vitro pharmacokinetic properties. The X-ray costructure of compound 8 in PI3Kδ showed key interactions and structural features supporting the observed PI3Kß isoform selectivity. Compound 8 achieved sustained target modulation and tumor growth delay at well tolerated doses when administered orally to SCID mice implanted with PTEN-deficient human tumor xenografts.

Design of potent and selective GSK3beta inhibitors with acceptable safety profile and pharmacokinetics.

From potent and selective inhibitors of GSK3beta displaying CYP1A2 inhibition and poor PK properties, mostly linked to metabolic instability and in vivo hydrolysis of the amide bond, we were able to obtain safe and orally available inhibitors with good half lives.

Rational design of potent GSK3beta inhibitors with selectivity for Cdk1 and Cdk2.

From an HTS hit, a series of potent and selective inhibitors of GSK3beta have been designed based on a Cdk2-homology model and with the help of several crystal structures of the compounds within Cdk2.

An algorithm-directed two-component library synthesized via solid-phase methodology yielding potent and orally bioavailable p38 MAP kinase inhibitors.

Previously we reported the identification of RPR200765A, a potent orally bioavailable pyridine-imidazole inhibitor of p38 mitogen-activated protein (MAP) kinase which suppressed paw swelling and joint pathology in streptococcal cell wall-induced arthritis. Herein, we report the use of solid-phase combinatorial organic synthesis for the parallel processing of a related pyrimidine-imidazole-based library with two points of structural variability. We report also that the application of a computer algorithm, the Monte Carlo Monomer Selection, maximized both the combinatorial synthetic efficiency and the bioavailability of the final compounds. In conjunction with the synthetic protocols, the polymer-supported quench technique was applied to the purification of the final compounds. Through rapid evaluation of the library using a p38 kinase assay and permeability assays, it was possible to identify a number of potent and orally bioavailable p38 MAP kinase inhibitors suitable for further biological investigation.