Discovery of new piperaquine hybrid analogs linked by triazolopyrimidine and pyrazolopyrimidine scaffolds with antiplasmodial and transmission blocking activities.

The World Health Organization (WHO) estimated that there were 247 million malaria cases in 2021 worldwide, representing an increase in 2 million cases compared to 2020. The urgent need for the development of new antimalarials is underscored by specific criteria, including the requirement of new modes of action that avoid cross-drug resistance, the ability to provide single-dose cures, and efficacy against both assexual and sexual blood stages. Motivated by the promising results obtained from our research group with [1,2,4]triazolo[1,5-a]pyrimidine and pyrazolo[1,5-a]pyrimidine derivatives, we selected these molecular scaffolds as the foundation for designing two new series of piperaquine analogs as potential antimalarial candidates. The initial series of hybrids was designed by substituting one quinolinic ring of piperaquine with the 1,2,4-triazolo[1,5-a]pyrimidine or pyrazolo[1,5-a]pyrimidine nucleus. To connect the heterocyclic systems, spacers with 3, 4, or 7 methylene carbons were introduced at the 4 position of the quinoline. In the second series, we used piperazine as a spacer to link the 1,2,4-triazolo[1,5-a]pyrimidine or pyrazolo[1,5-a]pyrimidine group to the quinoline core, effectively merging both pharmacophoric groups via a rigid spacer. Our research efforts yielded promising compounds characterized by low cytotoxicity and selectivity indices exceeding 1570. These compounds displayed potent in vitro inhibitory activity in the low nanomolar range against the erythrocytic form of the parasite, encompassing both susceptible and resistant strains. Notably, these compounds did not show cross-resistance with either chloroquine or established P. falciparum inhibitors. Even though they share a pyrazolo- or triazolo-pyrimidine core, enzymatic inhibition assays revealed that these compounds had minimal inhibitory effects on PfDHODH, indicating a distinct mode of action unrelated to targeting this enzyme. We further assessed the compounds' potential to interfere with gametocyte and ookinete infectivity using mature P. falciparum gametocytes cultured in vitro. Four compounds demonstrated significant gametocyte inhibition ranging from 58 % to 86 %, suggesting potential transmission blocking activity. Finally, we evaluated the druggability of these new compounds using in silico methods, and the results indicated that these analogs had favorable physicochemical and ADME (absorption, distribution, metabolism, and excretion) properties. In summary, our research has successfully identified and characterized new piperaquine analogs based on [1,2,4]triazolo[1,5-a]pyrimidine and pyrazolo[1,5-a]pyrimidine scaffolds and has demonstrated their potential as promising candidates for the development of antimalarial drugs with distinct mechanisms of action, considerable selectivity, and P. falciparum transmission blocking activity.

Antimalarial and anti-inflammatory activities of new chloroquine and primaquine hybrids: Targeting the blockade of malaria parasite transmission.

Malaria is a disease that requires new drugs not only to fight Plasmodium but also to reduce symptoms of infection such as fever and inflammation. A series of 21 hybrid compounds were designed from chloroquine (CQ) and primaquine (PQ) linked to the pharmacophoric group present in phenylacetic anti-inflammatory drugs. These compounds were designed to have dual activity: namely, to be capable of killing Plasmodium and still act on the inflammatory process caused by malaria infection. The compounds were assayed with nine different biological methods. The carbonylated CQ derivative 6 (n = 3; R1 = Cl) was more potent than CQ in vitro, and 8 (n = 4; R1 = H) reduced P. berghei parasitemia up to 37% on day 7. The carbonylated PQ derivative 17 (R = Br) was slightly less potent than PQ. The gem-difluoro PQ derivative 20 (R = Cl) exhibited high transmission blockade of the malaria sporogonic cycle in mosquitoes. Compounds 6 and 20 dose-dependently reduced nitric oxide (NO) production and inhibited TNFα production by LPS-stimulated J774A.1 macrophages. Our results indicate a viable and interesting approach in planning new chemical entities that act as transmission-blocking drugs for treating malaria caused by P. falciparum and P. vivax and the anti-inflammatory process related to this disease.

TP53 gene expression levels and tumor aggressiveness in canine mammary carcinomas.

The protein p53 is considered to be one of the most important tumor suppressor factors. Despite this importance, a potential association between TP53 messenger (m)RNA levels and tumor aggressiveness has not been well defined in animal cancer. We assessed and correlated TP53 gene expression in 40 canine mammary carcinomas with histologic grade, tumor size, and aggressiveness. The tumors were subjected to histologic analysis and the TP53 mRNA levels determined by RT-rtPCR. Statistical analysis revealed no correlation between levels of TP53 mRNA and tumor aggressiveness ( r = 0.00) or tumor growth ( r = 0.06). Histologic grades ( r = 0.17) and mitosis count ( r = 0.12) showed a weak correlation with TP53 mRNA expression levels. These findings are consistent with molecular studies that revealed heterogeneous expression of TP53 in canine and human mammary tumors. Hence, TP53 gene expression alone cannot be considered a marker for tumor aggressiveness in canine mammary carcinomas.

Different intra- and inter-molecular hydrogen-bonding patterns in (3S,4aS,8aS)-2-[(2R,3S)-3-(2,5-X2-benzamido)-2-(2,5-X2-benzo-yloxy)-4-phenyl-butyl]-N-tert-butyldeca-hydro-iso-quinoline-3-carboxamides (X = H or Cl): compounds with moderate aspartyl protease inhibition activity.

The crystal structures of (3S,4aS,8aS)-2-[(2R,3S)-3-benzamido-2-benzo-yloxy-4-phenyl-but-yl]-N-tert-butyldeca-hydro-iso-quinoline-3-carboxamide, C38H47N3O4, (I), and (3S,4aS,8aS)-2-[(2R,3S)-3-(2,5-di-chloro-benzamido)-2-(2,5-di-chloro-benzo-yloxy)-4-phenyl-but-yl]-N-tert-butyldeca-hydro-iso-quinoline-3-carboxamide, C38H43Cl4N3O4, (II), are described. Despite their chemical similarity, they adopt different conformations in the solid state: (I) features a bifurcated intra-molecular N-H⋯(N,O) hydrogen bond from the tert-butylamide NH group to the piperidine N atom and the benzoate O atom, whereas (II) has an intra-molecular N-H⋯O link from the benzamide NH group to the tert-butyl-amide O atom. In the crystal of (I), mol-ecules are linked by C(4) amide N-H⋯O hydrogen bonds into chains propagating in the [010] direction, with both donor and acceptor parts of the benzamide group. In the extended structure of (II), C(11) N-H⋯O chains propagating in the [010] direction arise, with the donor being the tert-butylamide NH group and the acceptor being the O atom of the benzamide group.

Design, synthesis and anti-P. falciparum activity of pyrazolopyridine-sulfonamide derivatives.

Ten 1-phenyl-1H-pyrazolo[3,4-b]pyridine derivatives connected by a linker group to benzenesulfonamide moieties with different substituents in the 4-position were synthesized and assayed against Plasmodium falciparum. These ten compounds exhibited activity in vitro against the chloroquine-resistant clone W2 with IC50 values ranging from 3.46 to 9.30µM. The most active derivatives with substituent R2=Cl or CH3 at the benzenesulfonamide moiety exhibited the lowest IC50. Compounds with an R1=CO2Et substituent at the 5-position of the 1H-pyrazolo[3,4-b]pyridine ring presented lower activity than those with a CN substituent. The 1H-pyrazolo[3,4-b]pyridine system appears to be promising for further studies as an antimalarial for overcoming the burden of resistance in P. falciparum.

Anti-Plasmodium falciparum activity of quinoline-sulfonamide hybrids.

Fifteen quinoline-sulfonamide hybrids, with a 7-chloroquinoline moiety connected by a linker group to arylsulfonamide moieties with different substituents in the 4-position were synthesized and assayed against Plasmodium falciparum. The compounds displayed high schizonticidal blood activity in vitro, with IC50 values ranging from 0.05 to 1.63 µM, in the anti-HPR2 assay against clone W2-chloroquine-resistant; ten of them showed an IC50 (ranging from 0.05 to 0.40 µM) lower than that of chloroquine and sulfadoxine. Among them, two compounds inhibited Plasmodium berghei parasitemia by 47% and 49% on day 5 after mice inoculation. The most active, in vivo, hybrid 13 is considered to be a new prototype for the development of an antimalarial drug against chloroquine-resistant parasites.

New compounds hybrids 1h-1,2,3-triazole-quinoline against Plasmodium falciparum.

Malaria is one of the most prevalent parasitic diseases in the world. The global importance of this disease, current vector control limitations, and the absence of an effective vaccine make the use of therapeutic antimalarial drugs the main strategy to control malaria. Chloroquine is a cost-effective antimalarial drug with a relatively robust safety profile, or therapeutic index. However, chloroquine is no longer used alone to treat patients with Plasmodium falciparum due to the emergence and spread of chloroquine-resistant strains, which have also been reported for Plasmodium vivax. However, the activity of 1,2,3-triazole derivatives against chloroquine-sensitive and chloroquine-resistant strains of P. falciparum has been reported in the literature. To enhance the anti-P. falciparum activity of quinoline derivatives, we synthesized 11 new quinoline-1H-1,2,3-triazole hybrids with different substituents in the 4-positions of the 1H-1,2,3-triazole ring, which were assayed against the W2-chloroquine-resistant P. falciparum clone. Six compounds exhibited activity against the P. falciparum W2 clone, chloroquine-resistant, with IC50 values ranging from 1.4 to 46 µm. None of these compounds was toxic to a normal monkey kidney cell line, thus exhibiting good selectivity indexes, as high 351 for one compound (11).

[1-(3-Chloro-phen-yl)-1H-1,2,3-triazol-4-yl]methanol hemihydrate.

The asymmetric unit of the title hydrate, C(9)H(8)ClN(3)O·0.5H(2)O, comprises two independent 1,2,3-triazole mol-ecules and a water mol-ecule of crystallization. The dihedral angles between the six- and five-membered rings in the 1,2,3-triazole mol-ecules are 12.71 (19) and 17.3 (2)°. The most significant different between them is found in the relative orientations of the terminal CH(2)OH groups with one being close to perpendicular to the five-membered ring [N-C-C-O torsion angle = 82.2 (5)°], while in the other mol-ecule, a notable deviation from a perpendicular disposition is found [torsion angle = -60.3 (5)°]. Supra-molecular chains feature in the crystal packing sustained by O-H⋯(O,N) inter-actions along the a-axis direction. The chains are connected via C-H⋯N inter-actions and the resultant layers stack along the b axis.