Ilaria Manca

Novel pyrazole derivatives as neutral CB1 antagonists with significant activity towards food intake

In spite of rimonabants withdrawal from the European market due to its adverse effects, interest in the development of drugs based on CB1 antagonists is revamping on the basis of the peculiar properties of this class of compounds. In particular, new strategies have been proposed for the treatment of obesity and/or related risk factors through CB1 antagonists, i.e. by the development of selectively peripherally acting agents or by the identification of neutral CB1 antagonists. New compounds based on the lead CB1 antagonist/inverse agonist rimonabant have been synthesized with focus on obtaining neutral CB1 antagonists. Amongst the new derivatives described in this paper, the mixture of the two enantiomers (±)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-3-(2-cyclohexyl-1-hydroxyethyl)-4-methyl-1H-pyrazole ((±)-5), and compound 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-3-[(Z)-2-cyclohexyl-1-fluorovinyl]-4-methyl-1H-pyrazole ((Z)-6), showed interesting pharmacological profiles. According to the preliminary pharmacological evaluation, these novel pyrazole derivatives showed in fact both neutral CB1 antagonism behaviour and significant in vivo activity towards food intake.

Weight loss induced by rimonabant is associated with an altered leptin expression and hypothalamic leptin signaling in diet-induced obese mice.

This study investigates the molecular mechanisms and the center-periphery cross talk underlying the anti-obesity effect of the cannabinoid receptor 1 (CB(1)) antagonist/inverse agonist rimonabant in diet-induced obese (DIO) mice exposed to a 31 days chronic treatment with the drug. Present data showed a significant and stable weight loss both in animals treated with rimonabant 10mg/kg by oral gavage exposed to a high fat diet (SRFD) and in vehicle treated mice switched to a regular chow (VEND) with respect to vehicle fat diet fed mice (VEFD). Caloric intake was significantly lowered in SRFD and VEND during the first two and four days, respectively, then reaching the VEFD consume throughout the treatment. The drop of body weight was accompanied by leptin mRNA decrease in visceral fat tissue both in VEND and SRFD, as revealed by Real time PCR analysis. No difference in CB(1) mRNA receptor expression in hypothalamus and in visceral fat tissue among groups was observed. Leptin receptors were decreased in the hypothalamus of SRFD but not of VEND mice. Moreover, in SRFD and VEND mice the expression of orexigenic genes Neuropeptide Y and Agouti Related Protein (AGRP) was increased, while anorexigenic ones, Pro-OpioMelanoCortin (POMC) and Cocaine-and-Amphetamine-Regulated Transcript (CART) displayed no alteration in any group. This data contribute to clarify the molecular basis of the anti-obesity properties of rimonabant, underlying the role of the peripheral modulators which affect central circuits involved in the regulation of food intake and energy homeostasis.

Synthesis and biological evaluation of novel delta (δ)opioid receptor ligands with diazatricyclodecane skeletons

Considering the interesting pharmacological profile of the delta (δ) selective opioid agonist compound SNC-80, conformationally constrained analogs containing two diazatricyclodecane ring systems in place of dimethylpiperazine core motif were synthesized. The compounds showed subnanomolar or low nanomolar δ opioid receptor binding affinity. Depending upon the substituents on the diazatricyclodecane ring, these compounds displayed varying selectivity for δ opioid receptor over μ and κ receptors. Amongst the novel compounds, 1Aa showed the more interesting biological profile, with higher δ affinity and selectivity compared to SNC-80. The δ receptor agonist profile and antinociceptive activity of 1Aa were confirmed using ex-vivo (isolated mouse vas deferens) and in vivo (tail flick) assays.

Novel diazabicycloalkane delta opioid agonists.

Here we report the investigation of diazabicycloalkane cores as potential new scaffolds for the development of novel analogues of the previously reported diazatricyclodecane selective delta (δ) opioid agonists, as conformationally constrained homologues of the reference δ agonist (+)-4-[(αR)-α((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC80). In particular, we have simplified the diazatricyclodecane motif of δ opioid agonist prototype 1a with bridged bicyclic cores. 3,6-diazabicyclo[3.1.1]heptane, 3,8-diazabicyclo[3.2.1]octane, 3,9-diazabicyclo[3.3.1]nonane, 3,9-diazabicyclo[4.2.1]nonane, and 3,10-diazabicyclo[4.3.1]decane were adopted as core motifs of the novel derivatives. The compounds were synthesized and biologically assayed as racemic (3-5) or diastereoisomeric (6,7) mixtures. All the novel compounds 3-7 showed δ agonism behaviour and remarkable affinity to δ receptors. Amongst the novel derivatives, 3,8-diazabicyclo[3.2.1]octane based compound 4 evidenced improved δ affinity and selectivity relative to SNC80.

Novel pyrrolocycloalkylpyrazole analogues as CB1 ligands

Novel 1,4‐dihydropyrazolo[3,4‐a]pyrrolizine‐, 4,5‐dihydro‐1H‐pyrazolo[4,3‐g]indolizine‐ and 1,4,5,6‐tetrahydropyrazolo[3,4‐c]pyrrolo[1,2‐a]azepine‐3‐carboxamide‐based compounds were designed and synthesized for cannabinoid CB1 and CB2 receptor interactions. Any of the new synthesized compounds showed high affinity for CB2 receptor with Ki values superior to 314 nm, whereas some of them showed moderate affinity for CB1 receptor with Ki values inferior to 400 nm. 7‐Chloro‐1‐(2,4‐dichlorophenyl)‐N‐(homopiperidin‐1‐yl)‐4,5‐dihydro‐1H‐pyrazolo[4,3‐g]indolizine‐3‐carboxamide (2j) exhibited good affinity for CB1 receptor (KiCB1 = 81 nm) and the highest CB2/CB1 selectively ratio (>12). Docking studies carried out on such compounds were performed using the hCB1 X‐ray in complex with the close pyrazole analogue AM6538 and disclosed specific pattern of interactions related to the tricyclic pyrrolopyrazole scaffolds as CB1 ligands.

Synthesis and Superpotent Anticancer Activity of Tubulysins Carrying Non-hydrolysable N-Substituents on Tubuvaline

Synthetic tubulysins 24 a-m, containing non-hydrolysable N-substituents on tubuvaline (Tuv), were obtained in high purity and good overall yields using a multistep synthesis. A key step was the formation of differently N-substituted Ile-Tuv fragments 10 by using an aza-Michael reaction of azido-Ile derivatives 8 with the α,β-unsaturated oxo-thiazole 5. A structure-activity relationship study using a panel of human tumour cell lines showed strong anti-proliferative activity for all compounds 24 a-m, with IC50 values in the sub-nanomolar range, which were distinctly lower than those of tubulysin A, vinorelbine and paclitaxel. Furthermore, 24 a-m were able to overcome cross-resistance to paclitaxel and vinorelbine in two tumour cell lines with acquired resistance to doxorubicin. Compounds 24 e and 24 g were selected as leads to evaluate their mechanism of action. In vitro assays showed that both 24 e and 24 g interfere with tubulin polymerization in a vinca alkaloid-like manner and prevent paclitaxel-induced assembly of tubulin polymers. Both compounds exerted antimitotic activity and induced apoptosis in cancer cells at very low concentrations. Compound 24 e also exhibited potent antitumor activity at well tolerated doses on in vivo models of diffuse malignant peritoneal mesothelioma, such as MESOII peritoneal mesothelioma xenografts, the growth of which was not significantly affected by vinorelbine. These results indicate that synthetic tubulysins 24 could be used as standalone chemotherapeutic agents in difficult-to-treat cancers.