Novel auristatin E-based albumin-binding prodrugs with superior anticancer efficacy in vivo compared to the parent compound.

Auristatins are a class of highly cytotoxic tubulin-disrupting peptides, which have shown limited therapeutic effect as free agents in clinical trials. In our continuing effort to develop acid-sensitive albumin-binding anticancer drugs exploiting circulating serum albumin as the drug carrier, we investigated the highly toxic drug payload auristatin E to assess whether the corresponding albumin-binding prodrugs were a viable option for achieving significant and concomitant tolerable antitumor activity. To achieve our goal, we developed a new aromatic maleimide-bearing linker (Sulf07) which enhanced both water solubility and stability of the prodrugs. In this study, we describe two auristatin E-based albumin-binding drugs, AE-Keto-Sulf07 and AE-Ester-Sulf07, which were designed to release the active compound at the tumor site in a pH-dependent manner. These prodrugs incorporate an acid-sensitive hydrazone bond, formed by the reaction of a carbonyl-containing auristatin E derivative with the hydrazide group of the water-solubilizing maleimide-bearing linker Sulf07. A panel of patient- and cell-derived human tumor xenograft models (melanoma A375, ovarian carcinoma A2780, non-small-cell lung cancer LXFA737 and LXFE937, and head and neck squamous cell carcinomas) were screened with starting tumor volumes in the range of either 130-150 mm3 (small tumors) or 270-380 mm3 (large tumors). Both albumin-binding prodrugs showed compelling anticancer efficacy compared to the parent drug auristatin E, inducing statistically significant long-term partial and/or complete tumor regressions. AE-Keto-Sulf07 displayed very good antitumor response over a wide dose range, 3.0-6.5 mg/kg (5-8 injections, biweekly). AE-Ester-Sulf07 was highly efficacious between 1.9 and 2.4 mg/kg (8 injections, biweekly) or at 3.8 mg/kg (4 injections, weekly), but caused cumulative skin irritation due to scratching and biting. In contrast at its MTD, auristatin E (0.3 mg/kg, 8 injections, biweekly) was only marginally active. In summary, AE-Keto-Sulf07 and AE-Ester-Sulf07 are novel acid-sensitive albumin-binding prodrugs demonstrating tumor regressions in all of the evaluated human tumor xenograft models thus supporting the stratagem that albumin can be used as an effective drug carrier for the highly potent class of auristatins.

A Versatile Strategy for the Synthesis of 4,5-Dihydroxy-2,3-Pentanedione (DPD) and Related Compounds as Potential Modulators of Bacterial Quorum Sensing.

Resistance to antibiotics is an increasingly serious threat to global public health and its management translates to significant health care costs. The validation of new Gram-negative antibacterial targets as sources for potential new antibiotics remains a challenge for all the scientists working in this field. The interference with bacterial Quorum Sensing (QS) mechanisms represents a potentially interesting approach to control bacterial growth and pursue the next generation of antimicrobials. In this context, our research is focused on the discovery of novel compounds structurally related to (S)-4,5-dihydroxy-2,3-pentanedione, commonly known as (S)-DPD, a small signaling molecule able to modulate bacterial QS in both Gram-negative and Gram-positive bacteria. In this study, a practical and versatile synthesis of racemic DPD is presented. Compared to previously reported syntheses, the proposed strategy is short and robust: it requires only one purification step and avoids the use of expensive or hazardous starting materials as well as the use of specific equipment. It is therefore well suited to the synthesis of derivatives for pharmaceutical research, as demonstrated by four series of novel DPD-related compounds described herein.

Inhibitors to Overcome Secondary Mutations in the Stem Cell Factor Receptor KIT.

In modern cancer therapy, the use of small organic molecules against receptor tyrosine kinases (RTKs) has been shown to be a valuable strategy. The association of cancer cells with dysregulated signaling pathways linked to RTKs represents a key element in targeted cancer therapies. The tyrosine kinase mast/stem cell growth factor receptor KIT is an example of a clinically relevant RTK. KIT is targeted for cancer therapy in gastrointestinal stromal tumors (GISTs) and chronic myelogenous leukemia (CML). However, acquired resistance mutations within the catalytic domain decrease the efficacy of this strategy and are the most common cause of failed therapy. Here, we present the structure-based design and synthesis of novel type II kinase inhibitors to overcome these mutations in KIT. Biochemical and cellular studies revealed promising molecules for the inhibition of mutated KIT.

Total synthesis of dehaloperophoramidine using a highly diastereoselective Hosomi-Sakurai reaction.

The synthesis of dehaloperophoramidine, a non-halogenated derivative of the marine natural product perophoramidine, and its biological activity towards HCT116, HT29 and LoVo colorectal carcinoma cells is reported. A [3,3]-Claisen rearrangement and an epoxide opening/allylsilylation reaction installed the contiguous all-carbon quaternary stereocentres with the required relative stereochemistry.

Design and Synthesis of Fsp(3)-Rich, Bis-Spirocyclic-Based Compound Libraries for Biological Screening.

The exploration of innovative chemical space is a critical step in the early phases of drug discovery. Bis-spirocyclic frameworks occur in natural products and other biologically relevant metabolites and show attractive features, such as molecular compactness, structural complexity, and three-dimensional character. A concise approach to the synthesis of bis-spirocyclic-based compound libraries starting from readily available commercial reagents and robust chemical transformations has been developed. A number of novel bis-spirocyclic scaffold examples, as implemented in the European Lead Factory project, is presented.

DYRK1A inhibition as potential treatment for Alzheimer's disease.

In total, 47,500,000 people worldwide are affected by dementia and this number is estimated to double by 2030 and triple within 2050 resulting in a huge burden on public health. Alzheimer's disease (AD), a progressive neurodegenerative disorder, is the most common cause of dementia, accounting for 60-70% of all the cases. The cause of AD is still poorly understood but several brain abnormalities (e.g., loss of neuronal connections and neuronal death) have been identified in affected patients. In addition to the accumulation of ß-amyloid plaques in the brain tissue, aberrant phosphorylation of tau proteins has proved to increase neuronal death. DYRK1A phosphorylates tau on 11 different Ser/Thr residues, resulting in the formation of aggregates called 'neurofibrillary tangles' which, together with amyloid plaques, could be responsible for dementia, neuronal degeneration and cell death. Small molecule inhibition of DYRK1A could thus represent an interesting approach toward the treatment of Alzheimer's and other neurodegenerative diseases. Herein we review the current progress in the identification and development of DYRK1A inhibitors.

Branching cascades provide access to two amino-oxazoline compound libraries.

An efficient synthetic access to two amino-oxazoline compound libraries was developed employing the branching cascades approach. A common precursor, that is, chromonylidene ß-ketoester was transformed into two different ring-systems, that is, the pyridine and the benzopyrane substituted hydroxyphenones. In further two steps, the ketone moiety in two ring-systems was transformed into an amino-oxazoline ring. The functional groups on the two amino-oxazoline scaffolds were exploited further to generate, a compound collection of ca. 600 amino-oxazolines which are being exposed to various biological screenings within the European Lead Factory consortium.

Exploiting the Divalent Nature of Isonitriles: a novel Pictet-Spengler Amidination process.

An isocyanide-based multicomponent reaction (IMCR) utilized for the rapid assembly of novel, biologically relevant dihydropyrrolo[1,2-a]quinoxalines-amidines is herein presented. Starting from 1-(2-aminophenyl)pyrroles, aldehydes, and isonitriles, the target heterocyclic scaffold is assembled in a one-pot, operationally friendly process. With three points of diversity and formation of three chemical bonds in one step, this strategy proves to be very general. Novel, mild methodology for the generation of amidines from secondary amine anilines and isonitriles is also introduced.

Synthesis of diverse nitrogen-enriched heterocyclic scaffolds using a suite of tunable one-pot multicomponent reactions.

Five elegant and switchable three-component reactions which enable access to a new series of nitrogen-containing heterocycles are reported. A novel one-step addition of an isocyanide to a hydrazine derived Schiff base affords unique six-membered pyridotriazine scaffolds (A and E). With slight modification of reaction conditions and replacement of the nucleophilic isocyanide moiety with different electrophiles (i.e., isocyanates, isothiocyanates, cyclic anhydrides, and acyl chlorides) five-membered triazolopyridine scaffolds (B, D, F, G) are generated in a single step. Furthermore, the use of phenyl hydrazine enables access to dihydroindazole-carboxamides, devoid of a bridge-head nitrogen (C). All protocols are robust and tolerate a diverse collection of reactants, and as such, it is expected that the new scaffolds and associated chemistry will garner high interest from medicinal chemists involved in either file enhancement or specific target-related drug discovery campaigns.

3-(4-Bromo-phen-yl)-1-butyl-5-[1-(2-chloro-6-methyl-phen-yl)-1H-tetra-zol-5-yl]imidazolidine-2,4-dione.

In the title mol-ecule, C21H20BrClN6O2, the chloro-substituted benzene ring forms a dihedral angle of 77.84 (7)° with the tetra-zole ring and the bromo-substituted ring forms a dihedral angle of 43.95 (6)° with the imidazole ring. The dihedral angle between the tetra-zole and imidazole rings is 67.42 (8)°. The terminal methyl group of the butyl substituent is disordered over two sets of sites, with refined occupancies 0.67 (3) and 0.33 (3). In the crystal, there is a short Br⋯N contact of 3.183 (2) Å.

Synthesis and biological activity of aminophthalazines and aminopyridazines as novel inhibitors of PGE2 production in cells.

This Letter reports the synthesis and biological evaluation of a collection of aminophthalazines as a novel class of compounds capable of reducing production of PGE(2) in HCA-7 human adenocarcinoma cells. A total of 28 analogs were synthesized, assayed for PGE(2) reduction, and selected active compounds were evaluated for inhibitory activity against COX-2 in a cell free assay. Compound 2xxiv (R(1)=H, R(2)=p-CH(3)O) exhibited the most potent activity in cells (EC(50)=0.02 µM) and minimal inhibition of COX-2 activity (3% at 5 µM). Furthermore, the anti-tumor activity of analog 2vii was analyzed in xenograft mouse models exhibiting good anti-cancer activity.

Recent advances in the design, synthesis, and biological evaluation of selective DYRK1A inhibitors: a new avenue for a disease modifying treatment of Alzheimer's?

With 24.3 million people affected in 2005 and an estimated rise to 42.3 million in 2020, dementia is currently a leading unmet medical need and costly burden on public health. Seventy percent of these cases have been attributed to Alzheimer's disease (AD), a neurodegenerative pathology whose most evident symptom is a progressive decline in cognitive functions. Dual specificity tyrosine phosphorylation regulated kinase-1A (DYRK1A) is important in neuronal development and plays a variety of functional roles within the adult central nervous system. The DYRK1A gene is located within the Down syndrome critical region (DSCR) on human chromosome 21 and current research suggests that overexpression of DYRK1A may be a significant factor leading to cognitive deficits in people with Alzheimer's disease (AD) and Down syndrome (DS). Currently, treatment options for cognitive deficiencies associated with Down syndrome, as well as Alzheimer's disease, are extremely limited and represent a major unmet therapeutic need. Small molecule inhibition of DYRK1A activity in the brain may provide an avenue for pharmaceutical intervention of mental impairment associated with AD and other neurodegenerative diseases. We herein review the current state of the art in the development of DYRK1A inhibitors.

Synthesis and biological activity of 2-aminothiazoles as novel inhibitors of PGE2 production in cells.

This Letter presents the synthesis and biological evaluation of a collection of 2-aminothiazoles as a novel class of compounds with the capability to reduce the production of PGE(2) in HCA-7 human adenocarcinoma cells. A total of 36 analogs were synthesized and assayed for PGE(2) reduction, and those with potent cellular activity were counter screened for inhibitory activity against COX-2 in a cell free assay. In general, analogs bearing a 4-phenoxyphenyl substituent in the R(2) position were highly active in cells while maintaining negligible COX-2 inhibition. Specifically, compound 5l (R(1)=Me, R(2)=4-OPh-Ph, R(3)=CH(OH)Me) exhibited the most potent cellular PGE(2) reducing activity of the entire series (EC(50)=90 nM) with an IC(50) value for COX-2 inhibition of >5 µM in vitro. Furthermore, the anti-tumor activity of analog 1a was analyzed in xenograft mouse models exhibiting promising anti-cancer activity.

Facile and rapid route for the synthesis of novel conformationally constrained norstatine analogs via PADAM-cyclization methodology.

The following report describes novel methodology for the rapid synthesis of unique conformationally constrained norstatine analogs of potential biological relevance. A PADAM (Passerini reaction - Amine Deprotection - Acyl Migration reaction) sequence is followed by a TFA-mediated microwave-assisted cyclization to generate the final benzimidazole isostere of the norstatine scaffold in moderate to good yields. The applicability of this solution phase methodology to the preparation of a small collection of compounds is discussed.

Novel cambinol analogs as sirtuin inhibitors: synthesis, biological evaluation, and rationalization of activity.

The tenovins and cambinol are two classes of sirtuin inhibitor that exhibit antitumor activity in preclinical models. This report describes modifications to the core structure of cambinol, in particular by incorporation of substituents at the N1-position, which lead to increased potency and modified selectivity. These improvements have been rationalized using molecular modeling techniques. The expected functional selectivity in cells was also observed for both a SIRT1 and a SIRT2 selective analog.

Gonadotropin-releasing hormone receptor levels and cell context affect tumor cell responses to agonist in vitro and in vivo.

Activation of gonadotropin-releasing hormone (GnRH) receptors inhibits proliferation of transformed cells derived from reproductive tissues and in transfected cell lines. Hence, GnRH receptors represent a therapeutic target for direct action of GnRH analogues on certain proliferating cells. However, more cell biological data are required to develop this particular application of GnRH analogues. Therefore, we compared the effects of GnRH receptor activation in transfected HEK293 cells (HEK293([SCL60])) with transfected human ovarian cancer cell lines SKOV3 and EFO21, human hepatoblastoma HepG2 cells, and rat neuroblastoma B35 cells. Marked differences in receptor levels, magnitude of inositol phosphate generation, and dynamics of inositol phosphate turnover occurred in the different cells. Activation of GnRH receptors, expressed at high or moderate levels, inhibited the growth of HEK293([SCL60]) and B35 cells, respectively. Western blotting detected markers of apoptosis [cleaved poly(ADP-ribose) polymerase, caspase-9] in HEK293([SCL60]) and B35 following treatment with 100 nmol/L d-Trp(6)-GnRH-I. Cell growth inhibition was partially or completely rescued with inhibitor Q-VD-OPh or Ro32-0432. Low levels of GnRH receptor expression in transfected SKOV3, EFO21, or HepG2 activated intracellular signaling but did not induce apoptosis or significantly affect cell proliferation. Tumor xenografts prepared from HEK293([SCL60]) regressed during treatment with d-Trp(6)-GnRH-I and growth of xenografts derived from transfected B35 was slowed. SKOV3 xenografts were not growth inhibited. Therefore, differences in levels of GnRH receptor and signaling differentially affect the apoptotic machinery within cell lines and contribute to the cell type-specific effects of GnRH on growth. Further studies should exploit the growth-inhibitory potential of GnRH receptor activation in abnormal cells in diseased human tissues.