Design, synthesis and pharmacological characterization of aminopyrimidine derivatives as BTK/FLT3 dual-target inhibitors against acute myeloid leukemia.

A novel class of aminopyrimidine-based Bruton's tyrosine kinase (BTK) and FMS-like tyrosine kinase 3 (FLT3) dual-target inhibitors based on the BTK inhibitor spebrutinib was designed for the treatment of acute myeloid leukemia. Representative compounds 14d, 14g, 14j and 14m effectively inhibited BTK, FLT3, and FLT3(D835Y) mutant activities with low nanomolar IC50's. These compounds displayed potent antiproliferative activities against leukemia cells with IC50's of 0.29-950 nM. In particular, 14m had IC50 values 101-1045 times lower than those of spebrutinib against all cancer cell lines tested. Compound 14m effectively induced autophagy and apoptosis in MV-4-11 cells through regulating related proteins in a dose-dependent manner. Finally, intraperitoneal administration of 14m at 20 mg/kg significantly repressed the growth of MV-4-11 cells with a TGI value of 95.68% with no apparent toxicity. These BTK/FLT3 dual-target inhibitors represent promising leads for further structural optimization and antitumor mechanism studies.

A Derivative of Piperlongumine and Ligustrazine as a Potential Thioredoxin Reductase Inhibitor in Drug-Resistant Hepatocellular Carcinoma.

The natural products piperlongumine (1) and ligustrazine (2) have been reported to exert antiproliferative effects against various types of cancer cells by up-regulating the level of reactive oxidative species (ROS). However, the moderate activities of 1 and 2 limit their application. To improve their potential antitumor activity, novel piperlongumine/ligustrazine derivatives were designed and prepared, and their potential pharmacological effects were determined in vitro and in vivo. Among the derivatives obtained, 11 exerted more prominent inhibitory activities against proliferation of drug-sensitive/-resistant cancer cells with lower IC50 values than 1. Particularly, the IC50 value of 11 against drug-resistant Bel-7402/5-FU cells was 0.9 µM, which was about 9-fold better than that of 1 (IC50 value of 8.4 µM). Mechanistic studies showed that 11 demonstrated thioredoxin reductase (TrxR) inhibitory activity, increase of ROS levels, decrease of mitochondrial transmembrane potential levels, and occurrence of DNA damage and autophagy, in a dose-dependent manner, via regulation of DNA damage protein H2AX and autophagy-associated proteins LC3, beclin-1, and p62 in drug-resistant Bel-7402/5-FU cells. Finally, compound 11 at 5 mg/kg displayed potent antitumor activity in vivo with tumor suppression of 76% (w/w). Taken together, compound 11 may represent a promising candidate drug for the chemotherapy of drug-resistant hepatocellular carcinoma and warrant more intensive study.

Design and synthesis of novel substituted benzyl pyrrolopyrimidine derivatives as selective BTK inhibitors for treating mantle cell lymphoma.

Ibrutinib, a potent irreversible Bruton's tyrosine kinase (BTK) inhibitor, was approved by the FDA for treating mantle cell lymphoma (MCL). Although ibrutinib exhibited excellent antitumor activity, it was associated with certain adverse reactions, with off-target effects against EGFR, Itk and Src family kinases. Our studies yielded a novel series of substituted benzyl pyrrolopyrimidine derivatives capable of potent inhibition of BTK. Compared with ibrutinib, compound 15c exhibited potent BTK inhibitory activity and enhanced antiproliferative activity, a 12-24-fold increase, against MCL cell lines, with IC50 values lower than 1 µM. Low micromolar doses of 15c inhibited the BCR signaling pathway and strongly induced the apoptosis of Z138 cells. Ibrutinib and 15c induced autophagy in a dose-dependent manner in Z138 cells. Moreover, compound 15c induced the production of reactive oxygen species (ROS), which may be a reason for its potent antiproliferative activity. Importantly, compound 15c showed greater BTK selectivity than ibrutinib, indicating a potentially safer treatment of MCL.

Extensive investigation of benzylic N-containing substituents on the pyrrolopyrimidine skeleton as Akt inhibitors with potent anticancer activity.

Continuous optimization of benzylic substituents on 1-(4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)piperazin-1-yl)-2-phenylethan-1-one structure as Akt inhibitors was described in this paper. Particularly, compounds 8 and 14g exhibited high enzymatic potency against all Akt isoforms and antiproliferative effects in mantle cell lymphoma cell lines, as well as favorable cytotoxicities in patient primary cancer cells. Low micromolar doses of both 8 and 14g dose-dependently induced cell apoptosis and G2/M cell cycle arrest, also suppressed the phosphorylation level of Akt downstream targets GSK3ß and S6.

Design and synthesis of novel 1-substituted 3-(6-phenoxypyridin-3-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine analogs as selective BTK inhibitors for the treatment of mantle cell lymphoma.

Ibrutinib (IBN), a first-in-class BTK-inhibitor, was approved by the FDA for the treatment of mantle cell lymphoma (MCL). Although IBN shows excellent performance as an anti-lymphoma agent, it has some undesirable side effects due to its off-target activities. Our studies yielded a novel series of 3-(6-phenoxypyridin-3-yl)-4-amine-1H-pyrazolo[3,4-d]pyrimidine derivatives capable of potent inhibition of Bruton's tyrosine kinase (BTK). Notably, compound 13e explained potent BTK inhibitory activity and could completely inhibit the phosphorylation of BTK and PLCγ2 in Z138 cells at low micromolar concentration. Compared with IBN, compound 13e improved anti-proliferative activities 3-40 folds in MCL cell lines with IC50 values lower than 1 µM. Low micromolar doses of 13e could induce strong cell apoptosis in Jeko-1 and Z138 cells. In addition, compound 13e showed greater BTK selectivity and higher stability in human liver microsomes than IBN and potential safety improvement for the treatment of MCL.

Discovery of novel pyrazole derivatives as potential anticancer agents in MCL.

Mantle cell lymphoma (MCL) is characterized by the translocation t(11;14) (q13;q32), resulting in the overexpression of cyclin-D1. The progression of MCL is an interaction of multitarget and multilink regulation. It has been proven that Bruton's tyrosine kinase (BTK) is commonly overexpressed in MCL, which makes it a focus of targeted therapy for MCL. Irreversible inhibitors usually have great potency, rapid onset of inhibition and long duration of drug action. Herein, structural modification via an open-loop strategy based on lead compound ibrutinib (IBN) was performed, leading to a series of pyrazole derivatives. Compounds 19c, 19'c, 21c and 21'c showed potent effect in MCL cells with IC50 values lower than 1 µM, and a more than 3-28-fold increase in antiproliferative activity compared with IBN.

Discovery of pyrazolopyrimidine derivatives as potent BTK inhibitors with effective anticancer activity in MCL.

Bruton's tyrosine kinase (BTK) is a key regulator of B-cell receptor (BCR) signaling pathway and takes effect in the regulation of B-cell activation, survival, proliferation and differentiation. It has been proved that BTK is commonly overexpressed in mantle cell lymphoma (MCL), which makes it a focus of targeted therapy for MCL. Our studies yielded a novel series of pyrazolopyrimidine derivatives capable of potent inhibition of BTK. Notably, 12a showed higher selectivity against BTK and exhibited robust antiproliferative effects in both mantle cell lymphoma cell lines and primary patient tumor cells. Low micromolar doses of 12a induced strong cell apoptosis in Jeko-1 and Z138 cells.

Targeting Bruton's tyrosine kinase for the treatment of B cell associated malignancies and autoimmune diseases: Preclinical and clinical developments of small molecule inhibitors.

B cell receptor (BCR) signaling plays a key role in B cell development and function. Aberrant BCR signaling has been confirmed as a central driver for the pathogenesis of various B cell malignancies. Bruton's tyrosine kinase (BTK) is a vital component of BCR signaling and exhibits overexpression in various B cell leukemias and lymphomas. Inhibiting BTK has been proved as an efficient way for B cell malignancy intervention. Remarkable achievements have been made in the pursuit of selective BTK inhibitors, represented by the success of the irreversible BTK inhibitors, ibrutinib and acalabrutinib. Constantly emerging agents exhibiting superior efficacy and safety in preclinical and clinical studies provide promising therapeutics for the treatment of B cell malignancies.

Recent Developments in Androgen Receptor Antagonists.

The androgen receptor (AR), a ligand-dependent transcription factor that regulates the expression of a series of downstream target genes after the binding of androgens, has been a target for the discovery of drugs used to treat prostate cancer. Prostate cancer always progresses to castration-resistant prostate cancer after a period of androgen deprivation therapy. Thus, developing potent androgen receptor antagonists for the therapy of castration-resistant prostate cancer possesses great significance. This review summarizes the preclinical development of androgen receptor antagonists, conventional androgen receptor antagonists that competitively bind to the ligand binding domain of the androgen receptor and coactivator antagonists of the androgen receptor, including both activation function-2 antagonists and binding function-3 antagonists. We hope that this review can help other researchers find new scaffolds and sites for the treatment of prostate cancer.

Development of novel hydrazidoarylaminopyrimidine-based BTK/FLT3 dual inhibitors with potent in vivo anti-hematological malignancies effects.

Computer-aided drug design and structure-based drug design techniques were used to find 18 novel hydrazidoarylaminopyrimidine-based BTK/FLT3 dual inhibitors. At 1 µM and 0.05 µM, the majority of the target compounds inhibited BTK and FLT3 by more than 80%, respectively. Among these, compound RSH-7 inhibited BTK and FLT3 most effectively, with IC50 values of 47 and 12 nM, respectively, which were superior to spebrutinib (BTK IC50 = 54 nM) and sorafenib (FLT3 IC50 = 33 nM). RSH-7 effectively inhibited the proliferation of multiple hematological malignancy cells with IC50 values ranging from 3 to 17 nM, which were 81-133 folds lower than spebrutinib. Furthermore, RSH-7 strongly inhibited BTK and FLT3 signaling and induced apoptosis in jeko-1 cells by upregulating pro-apoptotic proteins and downregulating Bcl-2 levels. RSH-7 showed moderate in vitro ADME properties. Importantly, RSH-7 demonstrated highly efficacious and well-tolerated in jeko-1 (50 mg/kg, TGI = 79.78%) and MV4-11 (20 mg/kg, TGI = 94.84%) xenograft models. These findings indicated that RSH-7 may be a promising lead compound for the treatment of hematological malignancies.

Review of the development of BTK inhibitors in overcoming the clinical limitations of ibrutinib.

Bruton's tyrosine kinase (BTK) regulates multiple important signaling pathways and plays a key role in the proliferation, survival, and differentiation of B-lineage cells and myeloid cells. BTK is a promising target for the treatment of hematologic malignancies. Ibrutinib, the first-generation BTK inhibitor, was approved to treat several B-cell malignancies. Despite the remarkable potency and efficacy of ibrutinib against various lymphomas and leukemias in the clinics, there are also some clinical limitations, such as off-target toxicities and primary/acquired drug resistance. As strategies to overcome these challenges, second- and third-generation BTK inhibitors, BTK-PROTACs, as well as combination therapies have been explored. In this review, we summarize clinical developments of the first-, second- and third-generation BTK inhibitors, as well as recent advances in BTK-PROTACs and ibrutinib-based combination therapies.

Recent development of BTK-based dual inhibitors in the treatment of cancers.

Bruton's tyrosine kinase (BTK) is a promising target in the treatment of various cancers. Despite the early success of BTK inhibitors in the clinic, these single-target drug therapies have limitations in their clinical applications, such as drug resistance. Several alternative strategies have been developed, including the use of dual inhibitors, to maximize the therapeutic potential of anticancer drugs. In this review, we highlight the scientific background and theoretical basis for developing BTK-based dual inhibitors, as well as the status of these agents in preclinical and clinical studies, and discuss further options in this field. We posit that these advances in BTK-based dual inhibitors confirm their feasibility for the treatment of refractory tumors, including those with drug resistance, and provide a framework for future drug design in this field. Accordingly, we anticipate increasingly rapid progress in the development of novel potent dual inhibitors and advanced clinical research on BTK-based dual inhibitors.

Redox-Activatable Theranostic Co-Prodrug for Precise Tumor Diagnosis and Selective Combination Chemotherapy.

A novel theranostic co-prodrug SCB has been designed by combining a co-prodrug from CDDO-Me and SAHA with a biotin-coupled near-infrared (NIR) probe hemicyanine via redox-responsive linker thiolactate to enhance the tumor theranostic efficacy and reduce the toxic side effects using both active and passive targeting strategies. SCB displayed reactive oxygen species (ROS)- and glutathione (GSH)-dependent release of NIR fluorescence and two parent drugs. Furthermore, the administration of SCB caused selective illumination of the tumor tissues for >24 h, thereby guiding precise removal of a tumor from intraoperative mice. Importantly, SCB exhibited highly efficient tumor inhibition, exerted selective combination therapy through prodrug mode, and minimized the adverse effects. Finally, SCB induced mitochondrial depolarization, DNA damage, and cell apoptosis through ROS generation and downregulation of HDAC6 protein, as verified by H2AX, Bax, cleaved-PARP, and Mcl-1 proteins. Thus, we suggest that SCB can provide a new platform for both precise diagnosis-guided tumor removal and selective combination therapy with high safety.

TME-targeting theranostic agent uses NIR tracking for tumor diagnosis and surgical resection and acts as chemotherapeutic showing enhanced efficiency and minimal toxicity.

Rationale: Precise diagnosis and effective therapy of the tumor microenvironment (TME) remains a challenge. Fluorescence tracers for monitoring primary tumors are currently reported; however, they face challenges in accurately delineating tumors in real-time during surgery, including interference from the background and insufficient accumulation of imaging reagents at tumor sites. Additionally, although the natural product podophyllotoxin (PPT) had potent and broad anti-tumor activity, the poor tumor target specificity and high toxicity of PPT extremely limited its clinical application. Methods: In the current study, a novel theranostic agent PBB was designed and synthesized by coupling the natural chemotherapeutic drug PPT with a near-infrared (NIR) fluorescence probe hemicyanine (CyOH) via redox-responsive thiolactate linker and introducing biotin to CyOH to enhance the active target ability. The activation mechanism of PBB was characterized by absorption spectra, fluorescence spectra, and HPLC. Subsequently, we investigated its imaging action, anti-tumor activity, and toxicity in vitro and in vivo. Results:In vitro experiments, PBB was verified to possess a ROS/GSH-responsive molecular switch, impelling PBB to release a fluorescent fragment and active drug PPT and selectively lighting up tumor cells but not the normal cells. As such, PBB was demonstrated to selectively inhibit the growth of tumor cells by inducing intracellular accumulation of ROS and MMP depolarization. More importantly, PBB significantly suppressed hepatic tumor growth and minimized the adverse effects caused by PPT, including acute toxicity and impaired liver function. Finally, the NIR fluorescence accumulated in the tumor tissue and stayed continuous for over 24h, and PBB provided precise visualization and highly selective fluorescence diagnosis to guide tumor resection. Conclusions: Therefore, the multilevel targeting theranostic agent provided a novel tool for precise diagnosis, real-time monitoring, and efficient tumor chemotherapy with high safety.

Overview of piperlongumine analogues and their therapeutic potential.

Natural products have long been an important source for discovery of new drugs to treat human diseases. Piperlongumine (PL) is an amide alkaloid isolated from Piper longum L. (long piper) and other piper plants and has received widespread attention because of its diverse biological activities. A large number of PL derivatives have been designed, synthesized and assessed in many pharmacological functions, including antiplatelet aggregation, neuroprotective activities, anti-diabetic activities, anti-inflammatory activities, anti-senolytic activities, immune activities, and antitumor activities. Among them, the anti-tumor effects and application of PL and its derivatives are most extensively studied. We herein summarize the development of PL derivatives, the structure and activity relationships (SARs), and their therapeutic potential on the treatments of various diseases, especially against cancer. We also discussed the challenges and future directions associated with PL and its derivatives in these indications.