Design, synthesis, and biological evaluation of novel bivalent PI3K inhibitors for the potential treatment of cancer.

Phosphatidylinositol 3-kinase (PI3K) signaling is among the most common alterations in cancer and has become a key target for cancer drug development. Based on a 4-methyl quinazoline scaffold, we designed and synthesized a novel series of bivalent PI3K inhibitors with different linker lengths and types. Bivalent PI3K inhibitor 27 demonstrates improved PI3K potency and antiproliferative cell activity, relative to the corresponding monovalent inhibitor 11. Compound 27 also significantly blocks the PI3K signal pathway, induces cell cycle arrest in G1 phase, and inhibits colony formation and cell migration. Furthermore, compound 27 shows dose-dependent anticancer efficacies in a HGC-27 xenograft mice model. Overall, this work provides a possible strategy to discover novel PI3K inhibitors for the treatment of cancers.

Bioevaluation of a dual PI3K/HDAC inhibitor for the treatment of diffuse large B-cell lymphoma.

The synergistic anti-tumor effect by simultaneous inhibitions of PI3K and HDAC has been verified to provide the rationality of PI3K/HDAC dual inhibitors for cancer treatment. Notably, the outstanding effect of PI3K/HDAC dual inhibitors against DLBCL has been paid much attention, especially for RR-DLBCL. Our previously reported 4-methylquinazoine scaffold based PI3K/HDAC dual inhibitors could suppress the growth of solid tumors and hematologic malignancies both in vitro and in vivo, validating the potential as new therapeutic agents for cancer. In this research, we further investigated the anti-tumor activity of one of our compounds against DLBCL cell lines and in vivo zebrafish xenograft model as well as the underlying mechanism, hoping to provide a novel therapeutic agent for treating DLBCL.

Discovery of a novel photoswitchable PI3K inhibitor toward optically-controlled anticancer activity.

Light has been used increasingly as an external stimulus in drug design. Herein, we report a novel photoswitchable azo-PI3K inhibitor, which bears an azobenzene moiety and can be efficiently converted between trans and cis configuration with changes of anticancer activity upon different light irradiation. Its photochemical properties were characterized by UV, LC-MS and NMR techniques. In biological assessment, trans and cis isomers of the azo-PI3K inhibitor exhibited differential anticancer activity in inhibition of PI3K pathway, cell migratory ability, and colony formation and can be switched at a cellular level upon light irradiation. Moreover, both isomers of the azo-PI3K inhibitor significantly inhibited tumor growth in a zebrafish xenograft model. Together, this photoswitchable azo-PI3K inhibitor may be useful as a valuable tool compound for studying the PI3K pathway and further optimization toward optically-controlled anticancer activity.

Discovery of new thieno[2,3-d]pyrimidine and thiazolo[5,4-d]pyrimidine derivatives as orally active phosphoinositide 3-kinase inhibitors.

As abnormal PI3K signaling is a feature of many types of cancer, the development of orally active PI3K inhibitors is of great significance for targeted cancer therapy. Through integrating strategies of reducing aromatic character/increasing the fraction of sp3 carbons together with scaffold hopping, we designed and synthesized two new series of thieno[2,3-d]pyrimidine and thiazolo[5,4-d]pyrimidine derivatives for use as PI3K inhibitors. Our structure-activity relationship studies led to the identification of thieno[2,3-d]pyrimidine 6a and thiazolo[5,4-d]pyrimidine 7a, which exhibited remarkable nanomolar PI3K potency, good antiproliferative activity, favorable pharmacokinetic properties and significant in vivo anti-cancer efficacy. Notably, thiazolo[5,4-d]pyrimidine 7a had better anti-cancer activity than thieno[2,3-d]pyrimidine 6a and is worthy of further pre-clinical evaluation for its use in cancer treatment.

Identification of Novel Thiazolo[5,4-b]Pyridine Derivatives as Potent Phosphoinositide 3-Kinase Inhibitors.

A series of novel 2-pyridyl, 4-morpholinyl substituted thiazolo[5,4-b]pyridine analogues have been designed and synthesized in this paper. These thiazolo[5,4-b]pyridines were efficiently prepared in seven steps from commercially available substances in moderate to good yields. All of these N-heterocyclic compounds were characterized by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) analysis and tested for phosphoinositide 3-kinase (PI3K) enzymatic assay. The results indicated that these N-heterocyclic compounds showed potent PI3K inhibitory activity, and the IC50 of a representative compound (19a) could reach to 3.6 nm. The structure-activity relationships (SAR) study showed that sulfonamide functionality was important for PI3Kα inhibitory activity, and 2-chloro-4-florophenyl sulfonamide (19b), or 5-chlorothiophene-2-sulfonamide (19c) showed potent inhibitory activity with a nanomolar IC50 value. The pyridyl attached to thiazolo[5,4-b]pyridine was another key structural unit for PI3Kα inhibitory potency, and replacement by phenyl lead to a significant decrease in activity. Enzymatic Inhibition results showed that compound 19a inhibited PI3Kα, PI3Kγ, or PI3Kδ with a nanomolar IC50 value, but its inhibitory activity on PI3Kß was approximately 10-fold reduced. Further docking analysis revealed that the N-heterocyclic core of compound 19a was directly involved in the binding to the kinase through the key hydrogen bonds interaction.

Discovery of new thienopyrimidine derivatives as potent and orally efficacious phosphoinositide 3-kinase inhibitors.

A series of new thienopyrimidine derivatives has been discovered as potent PI3K inhibitors. The systematic SAR studies for these analogues are described. Among them, 8a and 9a exhibit nanomolar enzymatic potencies and sub-micromolar cellular anti-proliferative activities. 8a displays favorable pharmacokinetic profiles, while 9a easily undergoes deacetylation to yield a major metabolite 8a. Furthermore, 8a and 9a potently inhibit tumor growth in a dose-dependent manner in the NCI-H460 xenograft model with an acceptable safety profile.

Synthesis and structure-activity relationships of PI3K/mTOR dual inhibitors from a series of 2-amino-4-methylpyrido[2,3-d]pyrimidine derivatives.

Inhibition of the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway by PI3K/mTOR dual inhibitors provides a promising new approach to the treatment of cancers. In this Letter, we identified structurally novel and potent PI3K/mTOR dual inhibitors from a series of 2-amino-4-methylpyrido[2,3-d]pyrimidine derivatives. Their synthesis and structure-activity relationships are reported.

Identification of novel 7-amino-5-methyl-1,6-naphthyridin-2(1H)-one derivatives as potent PI3K/mTOR dual inhibitors.

Inhibition of the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway is one of the most intensively studied approaches to cancer therapy. Rational design led to the identification of novel 7-amino-5-methyl-1,6-naphthyridin-2(1H)-one derivatives as potent PI3K/mTOR dual inhibitors. Design, synthesis and structure activity relationship are reported.

Rational design and optimization of novel 4-methyl quinazoline derivatives as PI3K/HDAC dual inhibitors with benzamide as zinc binding moiety for the treatment of acute myeloid leukemia.

Simultaneous inhibition of PI3K and HDAC has shown promise for treating various cancers, leading to discovery and development of their dual inhibitors as novel anticancer agents. Herein, we disclose a new series of PI3K/HDAC dual inhibitors bearing a benzamide moiety as the pharmacophore of HDAC inhibition. Based on systematic structure-activity relationship study, compounds 36 and 51 featuring an alkyl and benzoyl linker respectively were identified with favorable potencies against both PI3K and HDAC. In cellular assays, compounds 36 and 51 showed significantly enhanced antiproliferative activities against various cancer cell lines relative to single-target inhibitors. Furthermore, western blotting analysis shows compounds 36 and 51 suppressed AKT phosphorylation and increased H3 acetylation in MV4-11 cells, while flow cytometry analysis reveals both compounds dose-dependently induced cell cycle arrest and cell apoptosis. Supported by pharmacokinetic studies, compounds 36 and 51 were subjected to the in vivo evaluation in a MV4-11 xenograft model, demonstrating significant and dose-dependent anticancer efficacies. Overall, this work provides a promising approach for the treatment of AML by simultaneously inhibiting PI3K and HDAC with a dual inhibitor.

Design, Synthesis, and Bioevaluation of Novel Reversibly Photoswitchable PI3K Inhibitors Based on Phenylazopyridine Derivatives toward Light-Controlled Cancer Treatment.

Photopharmacology is an emerging approach for achieving light-controlled drug activity. Herein, we design and synthesize a novel series of photoswitchable PI3K inhibitors by replacing a sulfonamide moiety with an azo group in a 4-methylquinazoline-based scaffold. Through structure-activity relationship studies, compound 6g is identified to be effectively switched between its trans- and cis-configuration under irradiation with proper wavelengths. Molecular docking studies show the cis-isomer of 6g is favorable to bind to the PI3K target, supporting compound 6g in the PSS365 (cis-isomer enriched) was more potent than that in the PSSdark (trans-isomer dominated) in PI3K enzymatic assay, cell antiproliferative assay, Western blotting analysis on PI3K downstream effectors, cell cycle analysis, colony formation assay, and wound-healing assay. Relative to the cis-isomer, the trans-isomer is more metabolically stable and shows good pharmacokinetic properties in mice. Moreover, compound 6g inhibits tumor growth in nude mice and a zebrafish HGC-27 xenograft model.

Discovery of a Novel Photocaged PI3K Inhibitor Capable of Real-Time Reporting of Drug Release.

A novel photocaged PI3K inhibitor 2 was designed and synthesized by introducing a cascade photocaging group to block its key interaction with the kinase. Upon UV light irradiation, the photocaged compound released a highly potent PI3K inhibitor to recover its anticancer properties and a fluorescent dye for real-time reporting of drug release, providing a new approach for studying the PI3K signaling transduction pathway as well as developing precisely controlled cancer therapeutics.

S-72, a Novel Orally Available Tubulin Inhibitor, Overcomes Paclitaxel Resistance via Inactivation of the STING Pathway in Breast Cancer.

Microtubule-targeting agents are widely used as active anticancer drugs. However, drug resistance always emerges after their long-term use, especially in the case of paclitaxel, which is the cornerstone of all subtypes of breast cancer treatment. Hence, the development of novel agents to overcome this resistance is vital. This study reports on a novel, potent, and orally bioavailable tubulin inhibitor called S-72 and evaluated its preclinical efficacy in combating paclitaxel resistance in breast cancer and the molecular mechanisms behind it. We found that S-72 suppresses the proliferation, invasion and migration of paclitaxel-resistant breast cancer cells in vitro and displays desirable antitumor activities against xenografts in vivo. As a characterized tubulin inhibitor, S-72 typically inhibits tubulin polymerization and further triggers mitosis-phase cell cycle arrest and cell apoptosis, in addition to suppressing STAT3 signaling. Further studies showed that STING signaling is involved in paclitaxel resistance, and S-72 blocks STING activation in paclitaxel-resistant breast cancer cells. This effect further restores multipolar spindle formation and causes deadly chromosomal instability in cells. Our study offers a promising novel microtubule-destabilizing agent for paclitaxel-resistant breast cancer treatment as well as a potential strategy that can be used to improve paclitaxel sensitivity.

Design and Optimization of Thienopyrimidine Derivatives as Potent and Selective PI3Kδ Inhibitors for the Treatment of B-Cell Malignancies.

Phosphoinositide 3-kinase δ (PI3Kδ) plays a critical role in B lymphocyte (B-cell) development and activation and has been a validated target for the treatment of B-cell malignancies. Herein, we report a series of thienopyrimidine derivatives as novel potent and selective PI3Kδ inhibitors based on a scaffold hopping design strategy. Among them, compound 6 exhibited nanomolar PI3Kδ potency and a favorable selectivity profile compared to other class I PI3K isoforms. In cellular assays, compound 6 showed antiproliferative activity against a panel of B-cell lymphoma cell lines in a low micromolar range, caused cell cycle arrest, and induced apoptosis in Pfeiffer and SU-DHL-6 cells. Further, compound 6 inhibited the activation of mouse B-cells. With support from in vivo pharmacokinetic studies, compound 6 demonstrated significant anticancer efficacy in a Pfeiffer xenograft mouse model. Overall, compound 6 is a promising PI3Kδ inhibitor worthy of further preclinical investigation for the treatment of B-cell malignancies.

A novel PI3K inhibitor XH30 suppresses orthotopic glioblastoma and brain metastasis in mice models.

Glioblastoma is carcinogenesis of glial cells in central nervous system and has the highest incidence among primary brain tumors. Brain metastasis, such as breast cancer and lung cancer, also leads to high mortality. The available medicines are limited due to blood-brain barrier. Abnormal activation of phosphatidylinositol 3-kinases (PI3K) signaling pathway is prevalent in glioblastoma and metastatic tumors. Here, we characterized a 2-amino-4-methylquinazoline derivative XH30 as a potent PI3K inhibitor with excellent anti-tumor activity against human glioblastoma. XH30 significantly repressed the proliferation of various brain cancer cells and decreased the phosphorylation of key proteins of PI3K signaling pathway, induced cell cycle arrest in G1 phase as well. Additionally, XH30 inhibited the migration of glioma cells and blocked the activation of PI3K pathway by interleukin-17A (IL-17A), which increased the migration of U87MG. Oral administration of XH30 significantly suppressed the tumor growth in both subcutaneous and orthotopic tumor models. XH30 also repressed tumor growth in brain metastasis models of lung cancers. Moreover, XH30 reduced IL-17A and its receptor IL-17RA in vivo. These results indicate that XH30 might be a potential therapeutic drug candidate for glioblastoma migration and brain metastasis.

Optimization of Benzamide Derivatives as Potent and Orally Active Tubulin Inhibitors Targeting the Colchicine Binding Site.

Targeting the colchicine binding site on tubulin is a promising strategy to develop cancer therapeutics. Herein, we describe our systematic structure-activity relationship studies of benzamide derivatives that lead to an identification of a potent and orally active tubulin inhibitor 48, which occupied all three zones of the colchicine binding site in the X-ray co-crystal structure, inhibited tubulin polymerization, promoted mitotic blockade and apoptosis, and exhibited significant antiproliferative activities against various cancer cell lines. Compound 48 demonstrated favorable pharmacokinetic profiles, robust in vivo antitumor efficacies, and acceptable safety profiles. Furthermore, 48 overcame drug resistance in the paclitaxel-resistant A549 xenograft model. Collectively, 48 has been advanced into further preclinical evaluation for the development of next-generation microtubule-targeting drugs.

Synthesis and structure-analgesic activity relationships of a novel series of monospirocyclopiperazinium salts (MSPZ).

A series of monospirocyclopiperazinium salts were designed and synthesized to search for a peripherally-acting analgesic drug with low side effects. Extensive SAR studies revealed that a suitable NR(2)R(3) was critical for the analgesic activity, which might be beneficial to expose the cationic nitrogen to bind to the receptor, and possibly interact with the receptor via π-π interaction. Introduction of substituting group on the N(4)-phenyl ring could improve the activity, and the best position was the 4-position. Compound 14n showed more potent analgesic activity (63%, 20 µM/kg, sc) and holds promise for development as a mechanically new analgesic drug.

The PI3K Inhibitor XH30 Enhances Response to Temozolomide in Drug-Resistant Glioblastoma via the Noncanonical Hedgehog Signaling Pathway.

Glioblastoma multiforme (GBM) is the most common malignant tumor of the central nervous system. Temozolomide (TMZ)-based adjuvant treatment has improved overall survival, but clinical outcomes remain poor; TMZ resistance is one of the main reasons for this. Here, we report a new phosphatidylinositide 3-kinase inhibitor, XH30; this study aimed to assess the antitumor activity of this compound against TMZ-resistant GBM. XH30 inhibited cell proliferation in TMZ-resistant GBM cells (U251/TMZ and T98G) and induced cell cycle arrest in the G1 phase. In an orthotopic mouse model, XH30 suppressed TMZ-resistant tumor growth. XH30 was also shown to enhance TMZ cytotoxicity both in vitro and in vivo. Mechanistically, the synergistic effect of XH30 may be attributed to its repression of the key transcription factor GLI1 via the noncanonical hedgehog signaling pathway. XH30 reversed sonic hedgehog-triggered GLI1 activation and decreased GLI1 activation by insulin-like growth factor 1 via the noncanonical hedgehog signaling pathway. These results indicate that XH30 may represent a novel therapeutic option for TMZ-resistant GBM.

Design, Synthesis, and Biological Evaluation of a Novel Photocaged PI3K Inhibitor toward Precise Cancer Treatment.

Aberrant activation of the PI3K pathway has been intensively targeted for cancer therapeutics for decades, leading to more than 40 PI3K inhibitors advanced into clinical trials. However, it is increasingly noticed that PI3K inhibitors often showed limited efficacy as well as a number of serious on-target adverse effects during the clinical development. In this work, we designed and synthesized a novel photocaged PI3K inhibitor 1, which could be readily activated by UV irradiation to release a highly potent PI3K inhibitor 2. Upon UV irradiation, the photocaged inhibitor 1 demonstrated remarkably enhanced antiproliferative activity against multiple cancer cell lines and significant efficacy in the patient-derived tumor organoid model. Furthermore, 1 also showed favorable anticancer activity in an in vivo zebrafish xenograft model. Taken together, the photocaged PI3K inhibitor 1 represents a promising avenue for novel therapeutics toward precise cancer treatment.

A novel orally active microtubule destabilizing agent S-40 targets the colchicine-binding site and shows potent antitumor activity.

The tubulin colchicine binding site has been recognized as an attractive drug target to combat cancer, but none of the candidate drugs have been approved for medical treatment. We recently identified a structurally distinct small molecule S-40 as an oral potent tubulin destabilizing agent. Crystal structure analysis of S-40 in a complex with tubulin at a resolution of 2.4 Å indicated that S-40 occupies all 3 zones in the colchicine pocket with interactions different from known microtubule inhibitors, presenting unique effects on assembly and curvature of tubulin dimers. S-40 overcomes paclitaxel resistance and lacks neurotoxicity, which are the main obstacles limiting clinical applications of paclitaxel. Moreover, S-40 harbors the ability to inhibit growth of cancer cell lines as well as patient-derived organoids, induce mitotic arrest and cell apoptosis. Xenograft mouse models of human prostate cancer DU145, non-small cell lung cancer NCI-H1299 and paclitaxel-resistant A549 were strongly restrained without apparent side effects by S-40 oral administration once daily. These findings provide evidence for the development of S-40 as the next generation of orally effective microtubule inhibitors for cancer therapy.

Switching the site-selectivity of C-H activation in aryl sulfonamides containing strongly coordinating N-heterocycles.

The limitations of arene C-H functionalization of aryl sulfonamides containing strongly coordinating N-heterocycles were overcome using a Rh(iii) catalyst. The site-selectivity of C-H carbenoid functionalization at the ortho position relative to either the sulfonamide or N-heterocycle directing groups was elegantly switched using solvents of different polarities and different additive concentrations. Importantly, sulfonamide-group-directed ortho-C-H carbenoid functionalization tolerated strongly coordinating N-heterocycles, including pyridine, pyrrole, thiazole, pyrimidine, and pyrazine. Density functional theory (DFT) calculations were performed to rationalize the reaction mechanisms and the influence of reaction polarity.