Nicole Pouli

Purine analogues are important therapeutic tools due to their affinity to enzymes or receptors that are involved in critical biological processes. In this study, new 1,4,6-trisubstituted pyrazolo[3,4-b]pyridines were designed and synthesized, and their cytotoxic potential was been studied. The new derivatives were prepared through suitable arylhydrazines, and upon successive conversion first to aminopyrazoles, they were converted then to 1,6-disubstituted pyrazolo[3,4-b]pyridine-4-ones; this served as the starting point for the synthesis of the target compounds. The cytotoxic activity of the derivatives was evaluated against several human and murine cancer cell lines. Substantial structure activity relationships (SARs) could be extracted, mainly concerning the 4-alkylaminoethyl ethers, which showed potent in vitro antiproliferative activity in the low μM level (0.75–4.15 μΜ) without affecting the proliferation of normal cells. The most potent analogues underwent in vivo evaluation and were found to inhibit tumor growth in vivo in an orthotopic breast cancer mouse model. The novel compounds exhibited no systemic toxicity; they affected only the implanted tumors and did not interfere with the immune system of the animals. Our results revealed a very potent novel compound which could be an ideal lead for the discovery of promising anti-tumor agents, and could also be further explored for combination treatments with immunotherapeutic drugs.

A number of pyrrolo[2,3-c]pyridines, pyrrolo[3,2-d]pyrimidines and pyrazolo[4,3-d]pyrimidines were designed and synthesized as antiproliferative agents. The target compounds possessed selected substituents in analogous positions on the central scaffold that allowed the extraction of interesting SARs. The cytotoxic activity of the new derivatives was evaluated against prostatic (PC-3) and colon (HCT116) cell lines, and the most potent analogues showed IC₅₀ values in the nM to low µM range, while they were found to be non-toxic against normal human fibroblasts (WI-38). Flow cytometric analysis of DNA content revealed that the most promising derivative 14b caused a statistically significant accumulation of PC-3 cells at G₂/M phase and induced apoptosis in PC-3 cells.

Several new amino-substituted aza-acridine derivatives bearing a basic side chain have been designed and synthesized. The antiproliferative activity of the target compounds has been evaluated against three cancer cell lines—namely HCT-116 (colorectal), the uterine sarcoma MES-SA, and its doxorubicin-resistant variant MES-SA/Dx5. A limited number of the new acridines showed marginal cytotoxicity against the tested cell lines; nevertheless, these analogues possessed a similar substitution pattern. The moderate biological activity of these derivatives was attributed to their instability in aqueous media, which has been studied by mass spectrometry and computational chemistry experiments at the density functional level of theory (DFT).

The strong inhibition of Human Cytomegalovirus (HCMV) replication by benzimidazole nucleosides, like Triciribine and Maribavir, has prompted us to expand the structure–activity relationships of the benzimidazole series, using as a central core the imidazo[4,5-b]pyridine scaffold. We have thus synthesized a number of novel amino substituted imidazopyridine nucleoside derivatives, which can be considered as 4-(or 7)-aza-d-isosters of Maribavir and have evaluated their potential antiviral activity. The target compounds were synthesized upon glycosylation of suitably substituted 2-aminoimidazopyridines, which were prepared in six steps starting from 2-amino-6-chloropyridine. Even if the new compounds possessed only a slight structural modification when compared to the original drug, they were not endowed with interesting antiviral activity. Even so, three derivatives showed promising cytotoxic potential.

Cystathionine β-synthase (CBS) is a key enzyme in the production of the signaling molecule hydrogen sulfide, deregulation of which is known to contribute to a range of serious pathological states. Involvement of hydrogen sulfide in pathways of paramount importance for cellular homeostasis renders CBS a promising drug target. An in-house focused library of heteroaromatic compounds was screened for CBS modulators by the methylene blue assay and a pyrazolopyridine derivative with a promising CBS inhibitory potential was discovered. The compound activity was readily comparable to the most potent CBS inhibitor currently known, aminoacetic acid, while a promising specificity over the related cystathionine γ-lyase was identified. To rule out any possibility that the inhibitor may bind the enzyme regulatory domain due to its high structural similarity with cofactor s-adenosylmethionine, differential scanning fluorimetry was employed. A sub-scaffold search guided follow-up screening of related compounds, providing preliminary structure-activity relationships with respect to requisites for efficient CBS inhibition by this group of heterocycles. Subsequently, a hypothesis regarding the exact binding mode of the inhibitor was devised on the basis of the available structure-activity relationships (SAR) and a deep neural networks analysis and further supported by induced-fit docking calculations.

Background: Purine isosteres are often endowed with interesting pharmacological properties, due to their involvement in cellular processes replacing the natural purines. Among these compounds, pyrazolopyridines are under active investigation for potential anticancer properties. Objective: Based on previously discovered substituted pyrazolopyridines with promising antiproliferative activity, we designed and synthesized new, suitably substituted analogues aiming to investigate their potential activity and contribute to SAR studies of this class of bioactive compounds. Methods: The new compounds were synthesized using suitably substituted 2-amino-4-picolines, which upon ring-closure provided substituted pyrazolo[3,4-c] pyridine-5-carbonitriles that served as key intermediates for the preparation of the target 3,5,7 trisubstituted derivatives. The antiproliferative activity of 31 new target derivatives was evaluated against three cancer cell lines (MIA PaCa-2, PC-3 and SCOV3), whereas cell-cycle perturbations of exponentially growing PC-3 cells, using three selected derivatives were also performed. Results: Eight compounds displayed IC50 values in the low μM range, allowing the extraction of interesting SAR’s. Two of the most potent compounds against all cell lines share a common pattern, by accumulating cells at the G0/G1 phase. From this project, a new carboxamidine-substituted hit has emerged. Conclusion: Among the new compounds, those possessing the 3-phenylpyrazolo[3,4-c]pyridine scaffold, proved to be worth investigating and the majority of them showed strong cytotoxic activity against all cell lines, with IC50 values ranging from 0.87-4.3 µM. A carboxamidine analogue that resulted from the synthetic procedure, proved to be highly active against the cancer cells and could be considered as a useful lead for further optimization.