Francesca Musumeci

ATP-Competitive Inhibitors of mTOR: An Update

mTOR (mammalian target of rapamycin) is a serine-threonine kinase belonging to the PI3K/Akt/mTOR signalling pathway that is involved in several cell functions, including growth, proliferation, apoptosis and autophagy. mTOR hyperactivation has been detected in several human cancers, thus representing, together with its upstream effectors, an important target for cancer therapy. mTOR exists in two different complexes in cells, mTORC1 and mTORC2 which could both be targeted by potential anticancer agents. Rapamycin, the selective and allosteric inhibitor of mTOR, inhibits the enzyme in mTORC1, but not in mTORC2. In the last few years a number of mTOR ATP-competitive inhibitors has been reported acting on mTOR in both complexes and possessing a more complete anticancer activity in comparison with that of rapamycin and its derivatives. mTOR shares high sequence homology in the hinge-region with PI3K that is a lipid kinase upstream to mTOR in the same signaling pathway; for this reason some compounds originally developed as PI3K inhibitors later showed to also target mTOR. As indicated by preclinical and clinical studies, compounds acting on more than one target could result in a better biological response and in enhanced therapeutic potential and also dual PI3K/mTOR inhibitors result of great interest as potential antitumor agents. This review mainly reports the recently discovered mTOR ATP-competitive inhibitors in terms of medicinal chemistry, classified by their chemical structures, focusing on SAR and modelling studies that led to the discovery of very potent and selective agents, such as AZD-8055, OSI-027 and INK128, already entered clinical trials, or WYE-132, Torin1 and others in preclinical studies. Also some examples of dual PI3K/mTOR inhibitors, including PI-103, GNE477, WJD008 and GSK2126458 are reported together with their biological and clinical data.

Vascular Endothelial Growth Factor (VEGF) Receptors: Drugs and New Inhibitors

The recent launch onto the market of five VEGFR inhibitors indicates the therapeutic value of these agents and the importance of the research in the field of angiogenesis inhibitors for future oncologic therapy. In this Perspective we briefly report the inhibitors that are in clinical use, while we dedicate two wider sections to the compounds that are in clinical trials and to the new derivatives appearing in the literature. We especially consider the medicinal chemistry aspect of the topic and report the structure-activity relationship studies and the binding mode of some inhibitors as well as the biological data of the compounds discovered in the past 5 years.

Novel dual Src/Abl inhibitors for hematologic and solid malignancies

Importance of the field: c-Src and Bcr-Abl are two non-receptor or cytoplasmic tyrosine kinases (TKs) that play important roles in the development of solid and hematological malignancies. Indeed, Src is overexpressed or hyperactivated in a variety of solid tumors, while Bcr-Abl is the causative agent of chronic myeloid leukemia (CML), where Src is also involved. The two enzymes share significant sequence homology and remarkable structural resemblance. Areas covered in this review: ATP-competitive compounds originally developed as Src inhibitors, showed to be also potent Abl inhibitors. Dasatinib, the first dual Src/Abl inhibitor approved by the US FDA in 2006 for the treatment of imatinib-resistant CML, is currently being tested in several clinical trials for the treatment of different solid tumors. SKI-606 and AZD0530 are two other important dual Src/Abl inhibitors extensively tested in animal models and in clinical trials, but not entered into therapy yet. What the reader will gain: In this review we will report the latest results regarding dasatinib, SKI-606 and AZD0530, but also the knowledge on new compounds that have appeared in the literature in the last few years, including AP24163, AP24534, XL228, DC2036. We will focus on the most recent clinical trials or on preclinical studies that are in progress on these small-molecule TK inhibitors that represent a targeted therapy with high potential against cancer. Take home message: Molecularly targeted therapies, including the inhibition of specific TKs hyperactivated or overexpressed in many human cancers, could be less toxic than the classical non-specific cytotoxic chemotherapeutic agents; they could offer important therapeutic effects, especially if used in association with other agents such as monoclonal antibodies.

Design, synthesis, biological activity, and ADME properties of pyrazolo[3,4-d]pyrimidines active in hypoxic human leukemia cells: a lead optimization study.

A family of dual Src/Abl inhibitors characterized by a substituted pyrazolo[3,4-d]pyrimidine scaffold was previously reported by us and proved to be active against several tumor cell lines. Among these compounds, a promising antileukemia lead (1) has been recently identified, but, unfortunately, it suffers from substandard pharmaceutical properties. Accordingly, an approach for the optimization of the lead 1 is described in the present work. A series of more soluble pyrazolo[3,4-d]pyrimidine derivatives were rationally designed and proved to maintain the dual Src/Abl activity of the lead. Selected compounds showed an interesting activity profile against three different leukemic cells also in hypoxic conditions, which are usually characterized by imatinib-resistance. Finally, in vitro ADME properties (PAMPA permeation, water solubility, microsomal stability) for the most promising inhibitors were also evaluated, thus allowing the identification of a few optimized analogues of lead 1 as promising antileukemia agents.

Biologically Driven Synthesis of Pyrazolo[3,4-d]pyrimidines As Protein Kinase Inhibitors: An Old Scaffold As a New Tool for Medicinal Chemistry and Chemical Biology Studies

Protein Kinase Inhibitors: An Old Scaffold As a New Tool for Medicinal Chemistry and Chemical Biology Studies Silvia Schenone,*,† Marco Radi,‡ Francesca Musumeci,† Chiara Brullo,† and Maurizio Botta †Dipartimento di Farmacia, Universita ̀ degli Studi di Genova Viale Benedetto XV, 3, 16132 Genova, Italy ‡Dipartimento di Farmacia, Universita ̀ degli Studi di Parma Viale delle Scienze, 27/A, 43124 Parma, Italy Dipartimento di Biotecnologie, Chimica e Farmacia, Universita ̀ degli Studi di Siena Via Aldo Moro, 2, 53100 Siena, Italy Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, BioLife Science Building, Suite 333, 1900 N 12th Street, Philadelphia, Pennsylvania 19122, United States

Fyn Kinase in Brain Diseases and Cancer: The Search for Inhibitors

Fyn is a non-receptor tyrosine kinase belonging to the Src family kinases. It has been shown to play important roles in neuronal functions, including myelination and oligodendrocytes formation, and in inflammatory processes. It has also demonstrated its involvement in signaling pathways that lead to severe brain pathologies, such as Alzheimers and Parkinsons diseases. Moreover, Fyn is upregulated in some malignancies. Experimental studies demonstrated that Fyn inhibition could be useful in the disruption of metabolic processes involved in cancer neurodegenerative diseases. Unfortunately, no specific Fyn inhibitor has been discovered till today, active compounds on other members of Src family or on different tyrosine kinases have also been reported. However, multitargeted inhibitors might be endowed with therapeutic potential. Indeed, as increasingly reported, also a not completely selective inhibitor of a specific protein could be therapeutically useful, affecting a number of cell pathways involved especially in cancer development. In this review, we report some examples of small molecule tyrosine kinase inhibitors for which data on Fyn inhibition, both in enzymatic and in cell assays, have been reported, with the aim of giving information as starting point for the researchers working in this field.

An update on dual Src/Abl inhibitors.

c-Src and Bcr-Abl are two cytoplasmatic tyrosine kinases (TKs) involved in the development of malignancies. In particular, Bcr-Abl is the etiologic agent of chronic myeloid leukemia, where Src is also involved; the latter is hyperactivated in several solid tumors. Because of the structural homology between Src and Abl, several compounds originally synthesized as Src inhibitors have also been shown to be Abl inhibitors, useful in overcoming the onset of some types of chronic myeloid leukemia resistances, which frequently appear in the advanced phases of pathology. In recent years, the development of such compounds has been promoted by both excellent preclinical and clinical results, and by the theory that dual or multi-targeted inhibitors might be more effective than selective inhibitors. This review is an update on the most important dual inhibitors already in clinical trials and includes information regarding compounds that have appeared in the literature in recent years.

Identification of potent c-Src inhibitors strongly affecting the proliferation of human neuroblastoma cells

Neuroblastoma (NB) represents the most common extracranial paediatric solid tumor for which no specific FDA-approved treatment is currently available. The tyrosine kinase c-Src has been reported to play an important role in the differentiation, cell-adhesion and survival of NB cells. Starting from dual Src/Abl inhibitors previously found active in NB cell lines (1-3), small modification of the original structures almost abolished the Abl activity with a contemporary improvement of affinity and specificity for c-Src. Among the synthesized compounds, the most potent c-Src inhibitor (10a) showed a very interesting antiproliferative activity in SH-SY5Y cells with an IC(50) of 80 nM and a favourable ADME profile. A 3D SAR analysis was also attempted and may guide the design of more potent c-Src inhibitors as potential agents for NB treatment.

Design, synthesis, and biological evaluation of pyrazolo[3,4-d]pyrimidines active in vivo on the Bcr-Abl T315I mutant

Starting from our in-house library of pyrazolo[3,4-d]pyrimidines, a cross-docking simulation was conducted on Bcr-Abl T315I mutant. Among the selected compounds (2a-e), the 4-bromo derivative 2b showed the best activity against the Bcr-Abl T315I mutant. Deeper computational studies highlighted the importance of the bromine atom in the para position of the N1 side chain phenyl ring for the interaction with the T315I mutant. A series of 4-bromo derivatives was thus synthesized and biologically evaluated. Compound 2j showed a good balance of different ADME properties, high activity in cell-free assays, and a submicromolar potency against T315I Bcr-Abl expressing cells. In addition, it was converted into a water-soluble formulation by liposome encapsulation, preserving a good activity on leukemic T315I cells and avoiding the use of DMSO as solubilizing agent. In vivo studies on mice inoculated with 32D-T315I cells and treated with 2j showed a more than 50% reduction in tumor volumes.

SI113, a Specific Inhibitor of the Sgk1 Kinase Activity that Counteracts Cancer Cell Proliferation

Background/Aims: Published observations on serum and glucocorticoid regulated kinase 1 (Sgk1) knockout murine models and Sgk1-specific RNA silencing in the RKO human colon carcinoma cell line point to this kinase as a central player in colon carcinogenesis and in resistance to taxanes. Methods: By in vitro kinase activity inhibition assays, cell cycle and viability analysis in human cancer model systems, we describe the biologic effects of a recently identified kinase inhibitor, SI113, characterized by a substituted pyrazolo[3,4-d]pyrimidine scaffold, that shows specificity for Sgk1. Results: SI113 was able to inhibit in vitro cell growth in cancer cells derived from tumors with different origins. In RKO cells, this kinase inhibitor blocked insulin-dependent phosphorylation of the Sgk1 substrate Mdm2, the main regulator of p53 protein stability, and induced necrosis and apoptosis when used as a single agent. Finally, SI113 potentiated the effects of paclitaxel on cell viability. Conclusion: Since SI113 appears to be effective in inducing cell death in RKO cells, potentiating paclitaxel sensitivity, we believe that this new molecule could be efficiently employed, alone or in combination with paclitaxel, in colon cancer chemotherapy.