Synthesis of 2H-Imidazo[2',1':2,3] [1,3]thiazolo[4,5-e]isoindol-8-yl-phenylureas with promising therapeutic features for the treatment of acute myeloid leukemia (AML) with FLT3/ITD mutations.

Despite progressive advances in understanding the molecular biology of acute myeloid leukemia (AML), the conventional therapeutic approach has not changed substantially, and the outcome for most patients is poor. Thus, continuous efforts on the discovery of new compounds with improved features are required. Following a multistep sequence, we have identified a new tetracyclic ring system with strong antiproliferative activity towards several haematological cell lines. The new compounds possess structural properties typical of inactive-state-binding kinase inhibitors and are structurally related to quizartinib which is known as type-II tyrosine kinase inhibitor. In particular, the high activity found in two cell lines MOLM-13 and MV4-11, expressing the constitutively activated mutant FLT3/ITD, indicates inhibition of FLT3 kinase and on the basis of structure-activity relationship (SAR) the presence of an ureido moiety demonstrates to play a key role in driving the antiproliferative activity towards these cell lines. Molecular modelling studies supported the mechanism of recognition of the most active compounds within the FLT3 pocket where quizartinib binds. Moreover, Molecular Dynamics simulation (MDs) revealed the formation of a recurrent H-bond with Asp829, which more stabilizes the complex of 9c and the FLT3 inactive state. In MV4-11 cell line compound 9c reduces the phosphorylation of FLT3 (Y591) and some of its downstream targets leading to cell cycle arrest at G1 phase and induction of apoptosis. In an MV4-11 xenograft mouse model, 9c significantly reduces the tumor growth at the dose of 1-3 mg/kg without apparent toxicity.

Evaluation of Fused Pyrrolothiazole Systems as Correctors of Mutant CFTR Protein.

Cystic fibrosis (CF) is a genetic disease caused by mutations that impair the function of the CFTR chloride channel. The most frequent mutation, F508del, causes misfolding and premature degradation of CFTR protein. This defect can be overcome with pharmacological agents named "correctors". So far, at least three different classes of correctors have been identified based on the additive/synergistic effects that are obtained when compounds of different classes are combined together. The development of class 2 correctors has lagged behind that of compounds belonging to the other classes. It was shown that the efficacy of the prototypical class 2 corrector, the bithiazole corr-4a, could be improved by generating conformationally-locked bithiazoles. In the present study, we investigated the effect of tricyclic pyrrolothiazoles as analogues of constrained bithiazoles. Thirty-five compounds were tested using the functional assay based on the halide-sensitive yellow fluorescent protein (HS-YFP) that measured CFTR activity. One compound, having a six atom carbocyle central ring in the tricyclic pyrrolothiazole system and bearing a pivalamide group at the thiazole moiety and a 5-chloro-2-methoxyphenyl carboxamide at the pyrrole ring, significantly increased F508del-CFTR activity. This compound could lead to the synthesis of a novel class of CFTR correctors.

Design, Synthesis, and Biological Evaluation of a Series of Oxazolone Carboxamides as a Novel Class of Acid Ceramidase Inhibitors.

Acid ceramidase (AC) is a cysteine hydrolase that plays a crucial role in the metabolism of lysosomal ceramides, important members of the sphingolipid family, a diversified class of bioactive molecules that mediate many biological processes ranging from cell structural integrity, signaling, and cell proliferation to cell death. In the effort to expand the structural diversity of the existing collection of AC inhibitors, a novel class of substituted oxazol-2-one-3-carboxamides were designed and synthesized. Herein, we present the chemical optimization of our initial hits, 2-oxo-4-phenyl-N-(4-phenylbutyl)oxazole-3-carboxamide 8a and 2-oxo-5-phenyl-N-(4-phenylbutyl)oxazole-3-carboxamide 12a, which resulted in the identification of 5-[4-fluoro-2-(1-methyl-4-piperidyl)phenyl]-2-oxo-N-pentyl-oxazole-3-carboxamide 32b as a potent AC inhibitor with optimal physicochemical and metabolic properties, showing target engagement in human neuroblastoma SH-SY5Y cells and a desirable pharmacokinetic profile in mice, following intravenous and oral administration. 32b enriches the arsenal of promising lead compounds that may therefore act as useful pharmacological tools for investigating the potential therapeutic effects of AC inhibition in relevant sphingolipid-mediated disorders.

Lead Optimization of Benzoxazolone Carboxamides as Orally Bioavailable and CNS Penetrant Acid Ceramidase Inhibitors.

Sphingolipids (SphLs) are a diverse class of molecules that are regulated by a complex network of enzymatic pathways. A disturbance in these pathways leads to lipid accumulation and initiation of several SphL-related disorders. Acid ceramidase is one of the key enzymes that regulate the metabolism of ceramides and glycosphingolipids, which are important members of the SphL family. Herein, we describe the lead optimization studies of benzoxazolone carboxamides resulting in piperidine 22m, where we demonstrated target engagement in two animal models of neuropathic lysosomal storage diseases (LSDs), Gaucher's and Krabbe's diseases. After daily intraperitoneal administration at 90 mg kg-1, 22m significantly reduced the brain levels of the toxic lipids glucosylsphingosine (GluSph) in 4L;C* mice and galactosylsphingosine (GalSph) in Twitcher mice. We believe that 22m is a lead molecule that can be further developed for the correction of severe neurological LSDs where GluSph or GalSph play a significant role in disease pathogenesis.

Pyrrolo[3',2':6,7]cyclohepta[1,2-b]pyridines with potent photo-antiproliferative activity.

Pyrrolo[3',2':6,7]cyclohepta[1,2-b]pyridines were synthesized as a new class of tricyclic system in which the pyridine ring is annelated to a cycloheptapyrrole scaffold, with the aim of obtaining new photosensitizing agents with improved antiproliferative activity and lower undesired toxic effects. A versatile synthetic pathway was approached, which allowed the isolation of derivatives of the title ring system with a good substitution pattern on the pyrrole moiety. Photobiological studies revealed that the majority of the new compounds showed a potent cytotoxic effect upon photoactivation with light of the proper wavelength, especially when decorated with a 2-ethoxycabonyl group and a N-benzyl substituted moiety, with EC50 values reaching the submicromolar level. The mechanism of action was evaluated.

Preclinical Activity of New [1,2]Oxazolo[5,4-e]isoindole Derivatives in Diffuse Malignant Peritoneal Mesothelioma.

A series of 22 derivatives of the [1,2]oxazolo[5,4-e]isoindole system were synthesized through an efficient and versatile procedure that involves the annelation of the [1,2]oxazole moiety to the isoindole ring, producing derivatives with a wide substitution pattern. The structure-activity relationship indicates that the N-4-methoxybenzyl group appears crucial for potent activity. In addition, the presence of a 6-phenyl moiety is important and the best activity is reached with a 3,4,5-trimethoxy substituent. The most active compound, bearing both the structural features, was able to inhibit tumor cell proliferation at nanomolar concentrations when tested against the full NCI human tumor cell line panel. Interestingly, this compound was effective in reducing in vitro and in vivo cell growth, impairing cell cycle progression and inducing apoptosis, as a consequence of the inhibition of tubulin polymerization, in experimental models of diffuse malignant peritoneal mesothelioma (DMPM), a rapidly lethal disease, poorly responsive to conventional therapeutic strategies.