PI3Kδ and mTOR dual inhibitors: Design, synthesis and anticancer evaluation of 3-substituted aminomethylquinoline analogues.

Phosphatidylinositide-3-kinase (PI3K) and the mammalian target of rapamycin (mTOR) have recently been identified as potential cancer targets. In our work, a new family of quinoline analogues was designed, developed, and evaluated as dual inhibitors of PI3Kδ/mTOR. The preliminary biological activity analysis led to the discovery of the lead compounds 5h and 5e. Compounds 5h and 5e exhibited excellent anti-tumor potency with IC50 of 0.26 µM and 0.34 µM against Ramos cells, respectively. Importantly, based on the enzymatic activity assay results, compounds 5h and 5e were identified as dual inhibitors of PI3Kδ and mTOR, with IC50 values of 0.042 µM and 0.056 µM for PI3Kδ and 0.059 µM and 0.073 µM for mTOR, respectively. Furthermore, these compounds showed superior selectivity for blocking PI3Kδ compared to other PI3K isoforms (α, ß, and γ), supporting the concept of developing inhibitors that specifically target PI3Kδ/mTOR. The most effective compound 5h was chosen for additional biological testing. At a low dose of 0.5 µM, a western blot investigation confirmed the anticancer effects by inhibiting the PAM cascade, which in turn reduced downstream biomarkers pAkt (Ser473), pAkt (Thr308), and pRPS6 (Ser235/236). Furthermore, it increased apoptosis at the early (10.03 times) and late (17.95 times) stages in the Annexin-V assay as compared to the standard. In addition, the expression of p53, caspase-3, caspase-9, and the Bax/BCl-2 ratio were all significantly increased by compound 5h in the ELISA assay. Based on these results, it appears that 5h may activate the intrinsic apoptosis pathway, which in turn triggers cell death. Furthermore, the anticancer effects could be attributed to the inhibition of PI3Kδ/mTOR, as shown by docking interactions. Lastly, it demonstrated improved in vitro metabolic stability and passed the in silico ADMET/drug-likeness test. This profile recommends 5h for future in vivo PK-PD and efficacy investigations in animal cancer models.

Discovery of Potent and Selective PI3Kδ Inhibitors for the Treatment of Acute Myeloid Leukemia.

PI3Kδ is an essential target correlated to the occurrence and development of acute myeloid leukemia (AML). Herein, we investigated the pyrazolo[3,4-d]pyrimidine derivatives as potent and selective PI3Kδ inhibitors with high therapeutic efficacy toward AML. There were 44 compounds designed and prepared in a four-round optimization, and the biological evaluation showed that (S)-36 exhibited potent PI3Kδ inhibitory activity, high selectivity, and high antiproliferative activities against MV-4-11 and MOLM-13 cells, coupled with high oral bioavailability (F = 59.6%). In the MOLM-13 subcutaneous xenograft model, (S)-36 could significantly suppress the tumor progression with a TGI of 67.81% at an oral administration dosage of 10 mg/kg without exhibiting obvious toxicity. Mechanistically, (S)-36 could robustly inhibit the PI3K/AKT pathway for significant suppression of cell proliferation and remarkable induction of apoptosis both in vitro and in vivo. Thus, compound (S)-36 represents a promising PI3Kδ inhibitor for the treatment of acute myeloid leukemia with high efficacy.

Computational Design of Phosphatidylinositol 3-Kinase Inhibitors.

One of the most sought-after therapeutic targets for treating human cancers is the phosphoinositide 3-kinase; PI3k is an integral part of the PI3K/protein kinase B signaling arcade. This pathway is frequently activated in malignancies. Drug resistance and dose-limiting adverse effects are currently associated challenges with the existing anticancer chemotherapy. Therefore, in this research, a series of pyrimidine derivatives were designed and evaluated against human PI3K by using molecular docking analysis. The docking results were further verified by molecular dynamic simulation, which analyzed the strength of the macromolecular complex with respect to time. Compounds IV and XIV were found to be the most potent inhibitors of the human PI3K receptor with a high degree of stability within the active site of the target receptor for a timeframe of 50 ns. Thus, both of these compounds could be important drug candidates for the development of PI3K inhibitors as a prospective anticancer agent.

Molecular design of dual inhibitors of PI3K and potential molecular target of cancer for its treatment: A review.

Aberrant activation of the phosphoinositide 3-kinase (PI3K) signaling network is a key event in many human cancers and therefore enormous efforts have been made in the development of PI3K inhibitors. However, due to intrinsic and acquired resistance as well as poor drug tolerance, limited therapeutic efficacy has been achieved with these agents. In view of the fact that PI3K inhibitors can show synergistic antitumor effects with other cancer agents, namely mammalian target of rapamycin (mTOR) inhibitors, histone deacetylase (HDAC) inhibitors and mitogen-activated protein kinase (MEK) inhibitors, dual inhibition of both targets by a single-molecule is regarded as a promising complementary or alternative therapeutic strategy to overcome the drawbacks of just PI3K monotherapy. In this review, we discuss the theoretical foundation for designing PI3K-based dual-target inhibitors and summarize the structure-activity relationships and clinical progress of these dual-binding agents.

Design, synthesis, and biological evaluation of new thieno[2,3-d] pyrimidine derivatives as targeted therapy for PI3K with molecular modelling study.

Cancer is one of the most aggressive diseases characterised by abnormal growth and uncontrolled cell division. PI3K is a lipid kinase involved in cancer progression which makes it fruitful target for cancer control. 28 new morpholine based thieno[2,3-d] pyrimidine derivatives were designed and synthesised as anti-PI3K agents maintaining the common pharmacophoric features of several potent PI3K inhibitors. Their antiproliferative activity on NCI 60 cell lines as well as their enzymatic activity against PI3K isoforms were evaluated. Three compounds revealed good cytotoxic activities against breast cancer cell lines, especially T-47D. Compound VIb exhibited the best enzymatic inhibitory activity (72% & 84% on PI3Kß & PI3Kγ), respectively and good activity on most NCI cell lines especially those with over expressed PI3K. Docking was carried out into PI3K active site which showed comparable binding mode to that of the PI-103 inhibitor. Compound VIb could be optimised to serve as a new chemical entity for discovering new anticancer agents.

Discovery of GSK251: A Highly Potent, Highly Selective, Orally Bioavailable Inhibitor of PI3Kδ with a Novel Binding Mode.

Optimization of a previously reported lead series of PI3Kδ inhibitors with a novel binding mode led to the identification of a clinical candidate compound 31 (GSK251). Removal of an embedded Ames-positive heteroaromatic amine by reversing a sulfonamide followed by locating an interaction with Trp760 led to a highly selective compound 9. Further optimization to avoid glutathione trapping, to enhance potency and selectivity, and to optimize an oral pharmacokinetic profile led to the discovery of compound 31 (GSK215) that had a low predicted daily dose (45 mg, b.i.d) and a rat toxicity profile suitable for further development.

Design, synthesis, and biological evaluation of novel 6-(pyridin-3-yl) quinazolin-4(3H)-one derivatives as potential anticancer agents via PI3K inhibition.

Abnormal activation of the PI3K/Akt pathway is demonstrated in most of human malignant tumors via regulation of proliferation, cell cycle, and apoptosis. Therefore, drug discovery and development of targeting the PI3K/Akt pathway has attracted great interest of researchers in the development of anticancer drugs. In this study, fifteen 6-(pyridin-3-yl) quinazolin-4(3H)-one derivatives were designed and synthesized. Anticancer activities of the synthetic compounds were evaluated and the potential mechanisms were explored. Several compounds showed certain proliferation inhibitory activity against the tested cancer cells including human non-small cell lung cancer (NSCLC) HCC827, human neuroblastoma SH-SY5Y and hepatocellular carcinoma LM3 cells. Among them, compound 7i and 7m showed the best inhibitory activity against all the cancer cell lines and more active against HCC827 cells with IC50 values of 1.12 µM and 1.20 µM, respectively. In addition, 7i and 7m showed lower inhibitory activity against H7702 cells (human normal liver cells) with IC50 values of 8.66 µM and 10.89 µM, respectively, nearly 8-fold lower than that in HCC827 cells. These results suggested that compounds 7i and 7m had certain selectivity to tumor cells, compared to human normal cells. Further biological studies indicated 7i induced G2/M phase arrests and cell apoptosis of HCC827 cells via PI3K/Akt and caspase dependent pathway. Together, these novel 6-(pyridin-3-yl) quinazolin-4(3H)-one derivatives such as compound 7i and 7m might be lead compounds for development of potential anti-cancer drugs.

Bioisosteric replacements of the indole moiety for the development of a potent and selective PI3Kδ inhibitor: Design, synthesis and biological evaluation.

Based on indole scaffold, a potent and selective phosphoinositide 3-kinase delta (PI3Kδ) inhibitor, namely FD223, was developed by the bioisosteric replacement drug discovery approach and studied for the treatment of acute myeloid leukemia (AML). In vitro studies revealed that FD223 displays high potency (IC50 = 1 nM) and selectivity (29-51 fold over other PI3K isoforms) against PI3Kδ, and exhibits efficient inhibition of the proliferation of AML cell lines (MOLM-16, HL-60, EOL-1 and KG-1) by suppressing p-AKT Ser473 thus causing G1 phase arrest during the cell cycle. Further given the favorable pharmacokinetic (PK) profiles of FD223, in vivo studies were evaluated using xenograft model in nude mice, confirming its significant antitumor efficacy meanwhile with no observable toxicity. All these results are comparable to the positive group of Idelalisib (CAL-101), indicating that FD223 has potential for further development as a promising PI3Kδ inhibitor for the treatment of leukemia such as AML.

Synthesis and biological evaluation of novel purinyl quinazolinone derivatives as PI3Kδ-specific inhibitors for the treatment of hematologic malignancies.

Phosphatidylinositol 3-kinases (PI3Ks) mediate intracellular signal transduction. Aberrant PI3K signaling is associated with oncogenesis and disease progression in solid tumors and hematologic malignancies. Idelalisib (1), a first-in-class PI3Kδ inhibitor for the treatment of hematologic malignancies, was developed, but its sales were limited by black box warnings due to unexpected adverse effects. Therefore, to overcome these adverse events, various quinazolinone derivatives were synthesized and evaluated in vitro based on their inhibitory activity against the PI3K enzyme and the viability of cell lines such as MOLT and SUDHL. Among them, 6f (IC50 = 0.39 nM) and 6m (IC50 = 0.09 nM) showed excellent enzyme activity, and 6m displayed an approximately four-fold higher selectivity for PI3Kγ/δ compared with Idelalisib (1). Furthermore, in vivo PK experiments with 6f and 6m revealed that 6f (AUClast = 81.04 h*ng/mL, Cmax = 18.34 ng/mL, Tmax = 0.5 h, t1/2 = 10.2 h in 1 mpk dose) had improved PK compared with 1. Finally, further experiments will be conducted with 6f selected as a candidate, and the potential for it to be developed as a treatment with good efficacy for hematologic malignancies will be determined.

Discovery of cinnoline derivatives as potent PI3K inhibitors with antiproliferative activity.

Cinnoline is a potential pharmacophore which has rarely been reported for uses as PI3K inhibitors. In this study, a series of cinnoline derivatives were developed as PI3K inhibitors and evaluated for enzymatic and cellular activities. Most compounds displayed nanomolar inhibitory activities against PI3Ks, among which 25 displayed high LLE and micromolar inhibitory potency against three human tumor cell lines (IC50 = 0.264 µM, 2.04 µM, 1.14 µM).

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.

Discovery of a new series of PI3K-δ inhibitors from Virtual Screening.

PI3K-δ mediates key immune cell signaling pathways and is a target of interest for treatment of oncological and immunological disorders. Here we describe the discovery and optimization of a novel series of PI3K-δ selective inhibitors. We first identified hits containing an isoindolinone scaffold using a combined ligand- and receptor-based virtual screening workflow, and then improved potency and selectivity guided by structural data and modeling. Careful optimization of molecular properties led to compounds with improved permeability and pharmacokinetic profile, and high potency in a whole blood assay.

Multitarget Inhibition of Histone Deacetylase (HDAC) and Phosphatidylinositol-3-kinase (PI3K): Current and Future Prospects.

The discovery of histone deacetylase (HDAC) inhibitors is a hot topic in the medicinal chemistry community regarding cancer research. This is related primarily to two factors: success in the clinic, e. g., the four FDA-approved HDAC inhibitors, and strong versatility to combine their pharmacophoric features to design new hybrid compounds with multitarget profiles. Thus, the selection of adequate pharmacophores to combine, i. e., combining targets that can result in a synergistic effect, is desirable, as it increases the probability of discovering a new useful therapeutic strategy. In this work, we highlight the design of multitarget HDAC/PI3K inhibitors. Although this approach is still in its early stages, many significant works have described the design and pharmacological evaluation of this new promising class of multitarget inhibitors, where compound CUDC-907, which is already in clinical trials, stands out. Therefore, the question emerges of whether there still space for the design and evaluation of new multitarget HDAC/PI3K inhibitors. When considering the selectivity profile of the described multitarget compounds, the answer appears to be in the affirmative, especially since the first examples of compounds with a certain selectivity profile only recently appeared in 2020.

Docking Studies and Antiproliferative Activities of 6-(3-aryl-2-propenoyl)-2(3H)- benzoxazolone Derivatives as Novel Inhibitors of Phosphatidylinositol 3-Kinase (PI3Kα).

BACKGROUND: Cancer is a life-threatening group of diseases and universally, the second main cause of death. The design and development of new scaffolds targeting selective cancer cells are considered a promising goal for cancer treatment. AIMS AND OBJECTIVE: Chalcone derivatives; 6-(3-aryl-2-propenoyl)-2(3H)-benzoxazolone, were previously prepared and evaluated against the oral cavity squamous cell carcinoma cell line, HSC-2, and were reported to have remarkably high tumor selectivity. The aim of this study was to further investigate the anticancer activities of the chalcone derivatives against human colon cancer cells with a possible elucidation of their mechanism of action. METHODS: Computational studies were conducted to explore the potential interaction of the synthesized molecules with the phosphatidylinositol-4,5-bisphosphate 3-kinaseα (PI3Kα). Biological evaluation of the antiproliferative activities associated with compounds 1-23 was carried out against the colon cancer cell line, HCT116. Lactate Dehydrogenase (LDH) activity was measured to study necrosis, while the caspase-3 activation and DNA measurements were used to evaluate apoptosis in the treated cells. RESULTS: Glide studies against PI3Kα kinase domain demonstrated that the 6-(3-aryl-2-propenoyl)-2(3H)- benzoxazolone scaffold forms H-bond with K802, Y836, E849, V851, N853, Q859, and D933, and it fits the fingerprint of PI3Kα active inhibitors. Biological evaluation of the reported compounds in HCT116 cell line confirmed that the series inhibited PI3Kα activity and induced apoptosis via activation of caspase-3 and reduction of DNA content. CONCLUSION: The recently developed compounds might be employed as lead structures for the design of new antitumor drugs targeting PI3Kα.

Identification of methyl (5-(6-((4-(methylsulfonyl)piperazin-1-yl)methyl)-4-morpholinopyrrolo[2,1-f][1,2,4]triazin-2-yl)-4-(trifluoromethyl)pyridin-2-yl)carbamate (CYH33) as an orally bioavailable, highly potent, PI3K alpha inhibitor for the treatment of advanced solid tumors.

In various human cancers, PI3Ks pathway is ubiquitously dysregulated and thus become a promising anti-cancer target. To discover new potent and selective PI3K inhibitors as potential anticancer drugs, new pyrrolo[2,1-f][1,2,4]triazines were designed, leading to the discovery of compound 37 (CYH33), a selective PI3Kα inhibitor (IC50 = 5.9 nM, ß/α, δ/α,γ/α = 101-, 13-, 38-fold). Western blot analysis confirmed that compound 37 could inhibit phosphorylation of AKT in human cancer cells to modulate the cellular PI3K/AKT/mTOR pathway. And further evaluation in vivo against SKOV-3 xenograft models demonstrated that a dose-dependent antitumor efficacy was achieved.

Structure-Based Drug Design and Synthesis of PI3Kα-Selective Inhibitor (PF-06843195).

The phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling pathway is a frequently dysregulated pathway in human cancer, and PI3Kα is one of the most frequently mutated kinases in human cancer. A PI3Kα-selective inhibitor may provide the opportunity to spare patients the side effects associated with broader inhibition of the class I PI3K family. Here, we describe our efforts to discover a PI3Kα-selective inhibitor by applying structure-based drug design (SBDD) and computational analysis. A novel series of compounds, exemplified by 2,2-difluoroethyl (3S)-3-{[2'-amino-5-fluoro-2-(morpholin-4-yl)-4,5'-bipyrimidin-6-yl]amino}-3-(hydroxymethyl)pyrrolidine-1-carboxylate (1) (PF-06843195), with high PI3Kα potency and unique PI3K isoform and mTOR selectivity were discovered. We describe here the details of the design and synthesis program that lead to the discovery of 1.

Discovery of novel PARP/PI3K dual inhibitors with high efficiency against BRCA-proficient triple negative breast cancer.

Co-targeting PARP and PI3K by PARP/PI3K dual inhibitors has been recognized as a promising chemotherapeutic strategy for the treatment of triple negative breast cancer (TNBC) in our previous work. To further explore novel and more potent PARP/PI3K dual inhibitors, a series of compounds were designed, synthesized and evaluated for their pharmacological properties, resulting in the candidate compound 12, a potent and highly selective PARP/PI3K dual inhibitor. Compared to Olaparib, compound 12 exhibits a superior antiproliferative profile against BRCA-proficient MDA-MB-468 cells. In MDA-MB-468 cell-derived xenograft model, compound 12 displayed excellent antitumor efficacy at a dose of 50 mg/kg, which is considerably more efficacious than the single administration of Olaparib or BKM120. Furthermore, compound 12 displayed good metabolic stability and high safety. Taken together, these results suggest that compound 12 as a novel PARP/PI3K dual inhibitor is worthy for further study.

Discovery of 2-(5-(quinolin-6-yl)-1,3,4-oxadiazol-2-yl)acetamide derivatives as novel PI3Kα inhibitors via docking-based virtual screening.

PI3Kα is an attractive target for PIK3CA mutated malignant tumor and searching for lead compounds with novel scaffold is important for the development of PI3Kα inhibitors. Therefore, the strategy of docking-based virtual screening was performed to discovery potent inhibitors. The 4L2Y_A PI3Kα crystal structure was used as the model protein receptor due to its high docking reliability. After the multistep virtual screening protocol and biological evaluation, three hits were picked up and further similarity searching led to more potent 2-(5-(quinolin-6-yl)-1,3,4-oxadiazol-2-yl)acetamide derivatives ES-25 and ES-27. In addition, the primary SAR of these novel derivatives was discussed, which provide a basis for the further structural modification.

Discovery of a Potent and Selective PI3Kδ Inhibitor (S)-2,4-Diamino-6-((1-(7-fluoro-1-(4-fluorophenyl)-4-oxo-3-phenyl-4H-quinolizin-2-yl)ethyl)amino)pyrimidine-5-carbonitrile with Improved Pharmacokinetic Profile and Superior Efficacy in Hematological Cancer Models.

PI3Kδ inhibitors have been approved for B-cell malignancies like CLL, small lymphocytic lymphoma, and so forth. However, currently available PI3Kδ inhibitors are nonoptimal, showing weakness against at least one of the several important properties: potency, isoform selectivity, and/or pharmacokinetic profile. To come up with a PI3Kδ inhibitor that overcomes all these deficiencies, a pharmacophoric expansion strategy was employed. Herein, we describe a systematic transformation of a "three-blade propeller" shaped lead, 2,3-disubstituted quinolizinone 11, through a 1,2-disubstituted quinolizinone 20 to a novel "four-blade propeller" shaped 1,2,3-trisubstituted quinolizinone 34. Compound 34 has excellent potency, isoform selectivity, metabolic stability across species, and exhibited a favorable pharmacokinetic profile. Compound 34 also demonstrated a differentiated efficacy profile in human germinal center B and activated B cell-DLBCL cell lines and xenograft models. Compound 34 qualifies for further evaluation as a candidate for monotherapy or in combination with other targeted agents in DLBCLs and other forms of iNHL.

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.