Discovery of novel pyrazolo[1,5-a]pyridine-based EP1 receptor antagonists by scaffold hopping: Design, synthesis, and structure-activity relationships.

A scaffold-hopping strategy towards a new pyrazolo[1,5-a]pyridine based core using molecular hybridization of two structurally distinct EP1 antagonists, followed by structure-activity relationship-guided optimization, resulted in the identification of potent EP1 antagonists exemplified by 4c, 4f, and 4j, which were shown to reduce pathological intravesical pressure in rats when administered at 1mg/kg iv.

Novel pyrazolo[1,5-a]pyridines with improved aqueous solubility as p110α-selective PI3 kinase inhibitors.

As part of our investigation into pyrazolo[1,5-a]pyridines as novel p110α selective PI3 kinase inhibitors, we report a range of analogues with improved aqueous solubility by the addition of a basic amine. The compounds demonstrated comparable p110α potency and selectivity to earlier compounds but with up to 1000× greater aqueous solubility, as the hydrochloride salts. The compounds also displayed good activity in a cellular assay of PI3 kinase activity.

Novel pyrazolo[1,5-a]pyridines as orally active EP1 receptor antagonists: Synthesis, structure-activity relationship studies, and biological evaluation.

Novel pyrazolo[1,5-a]pyridine derivatives were designed, synthesized and evaluated as orally active EP1 antagonists for the treatment of overactive bladder. Matched molecular pair analysis (MMPA) allowed the design of a new series of pyrazolo[1,5-a]pyridine derivatives 4-6. Structure-activity relationships (SAR) studies of 4-6 were performed, leading to identification of the nanomolar-level EP1 antagonist 4c, which exhibited good pharmacological effect through intraduodenal (id) administration in a 17-phenyltrinor prostaglandin E2-induced bladder contraction model in rats.

New approach toward the synthesis of deuterated pyrazolo[1,5-a]pyridines and 1,2,4-triazolo[1,5-a]pyridines.

An efficient and operationally simple synthesis of 7-deuteropyrazolo[1,5-a]pyridine and 7-deutero-1,2,4-triazolo[1,5-a]pyridine derivatives using α-H/D exchange of 1-aminopyridinium cations in basic D2O followed by a 1,3-cycloaddition of acetylenes and nitriles is presented. A high regioselectivity and a high degree of deuterium incorporation were achieved. The procedure was applied for several 4-R-1-aminopyridinium cations (R = H, Me, OMe).

Design and synthesis of spirocyclic compounds as HCV replication inhibitors by targeting viral NS4B protein.

Two novel series of spirocyclic piperidine analogs appended to a pyrazolo[1,5-a]pyridine core were designed, synthesized and evaluated for their anti-HCV activity. A series of piperidine ketals afforded dispiro 6p which showed excellent in vitro anti-HCV activities (EC50 of 1.5nM and 1.2nM against genotype 1a and 1b replicons, respectively). A series of piperidine oxazolidinones afforded 27c which showed EC50's of 10.9nM and 6.1nM against 1a and 1b replicons, respectively. Both compounds 6p and 27c bound directly to non-structural NS4B protein in vitro (IC50's=10.2 and 30.4nM, respectively) and exhibited reduced potency in replicons containing resistance mutations encoding changes in the NS4B protein.

Phosphodiesterase inhibitors. Part 6: design, synthesis, and structure-activity relationships of PDE4-inhibitory pyrazolo[1,5-a]pyridines with anti-inflammatory activity.

We previously identified KCA-1490 [(-)-6-(7-methoxy-2-trifluoromethyl-pyrazolo[1,5-a]pyridin-4-yl)-5-methyl-4,5-dihydro-3-(2H)-pyridazinone], a dual PDE3/4 inhibitor. In the present study, we found highly potent selective PDE4 inhibitors derived from the structure of KCA-1490. Among them, N-(3,5-dichloropyridin-4-yl)-7-methoxy-2-(trifluoromethyl)pyrazolo[1,5-a]pyridine-4-carboxamide (2a) had good anti-inflammatory effects in an animal model.

Tetrahydropyrazolo[1,5-a]pyridine-fused steroids and their in vitro biological evaluation in prostate cancer.

The androgen receptor (AR) is a steroid hormone receptor and its high expression and disruption of its regulation are strongly implicated in prostate cancer (PCa) development. One of the current therapies includes application of steroidal antiandrogens leading to blockade of the AR action by the abrogation of AR-mediated signaling. We introduced here novel 4,5,6,7-tetrahydropyrazolo[1,5-a]pyridine-fused steroidal compounds, described their synthesis based on [8π+2π] cycloaddition reactions of diazafulvenium methides with different steroidal scaffolds and showed their biological evaluation in different prostate cancer cell lines in vitro. Our results showed the ability of novel compounds to suppress the expression of known androgen receptor targets, Nkx3.1 and PSA in two prostate cell lines, 22Rv1 and VCaP. Candidate compound diminished the transcription of AR-regulated genes in the reporter cell line in a concentration-dependent manner. Antiproliferative activity of the most promising steroid was studied by clonogenic assay and induction of apoptosis in treated cells was documented by immunoblot detection of cleaved PARP.

A pyrazolo[1,5-a]pyridine-based ratiometric fluorescent probe for sensing Cu2+ in cell.

Ratiometric fluorescent probes based on FRET mechanism have attracted great attention due to their large pseudo-Stokes shifts and built-in correction for environmental effects. However, most donors failed to meet the requirement that the emission of the donor must overlap well with the absorption of the acceptor. Therefore, searching for new fluorophore to construct FRET system is in great need. In this paper, a new fluorescent dye pyrazolo[1,5-a]pyridine was synthesized and used as a donor in the FRET system for ratiometric sensing of Cu2+. The probe is based on FRET and PET mechanism. It shows high selectivity and sensitivity toward Cu2+ (detection limit 30 nM). Furthermore, it was successfully used to detect Cu2+ in Glioma cells.

Pyrazolo[1,5-a]pyridine-3-carboxamide hybrids: Design, synthesis and evaluation of anti-tubercular activity.

A series of pyrazolo[1,5-a]pyridine-3-carboxamide hybrids were designed and evaluated as novel anti-tubercular agents. The representative hybrid 7 exhibited promising in vitro activity against susceptive strain H37Rv and a panel of drug-resistant Mtb strains with MIC values of 0.006 µg/mL and ranged from 0.003 to 0.014 µg/mL, respectively. More importantly, the hybrid 7 also showed very low cytotoxicity, and could significantly reduce the mycobacterial burden in a mouse model infected with autoluminescent H37Ra strain, which may serve as a lead compound for further development of new anti-tubercular agents.

Design, Synthesis, and Biological Evaluation of Pyrazolo[1,5-a]pyridine-3-carboxamides as Novel Antitubercular Agents.

A series of pyrazolo[1,5-a]pyridine-3-carboxamide derivatives were designed and synthesized as new anti-Mycobacterium tuberculosis (Mtb) agents. The compounds exhibit promising in vitro potency with nanomolar MIC values against the drug susceptive H37Rv strain and a panel of clinically isolated multidrug-resistant Mtb (MDR-TB) strains. One of the representative compounds (5k) significantly reduces the bacterial burden in an autoluminescent H37Ra infected mouse model, suggesting its promising potential to be a lead compound for future antitubercular drug discovery.