Pyrimido[4,5-e][1,4]diazepines acting as inhibitors of adenylyl cyclase of G. lamblia: Synthesis, Bioassays y Molecular Modelling Studies

ESTEBAN G. VEGA HISSI; ADOLFO ZURITA; DANIEL RICARDO ENRIZ; MANUEL NOGUERAS; JOSÉ M DE LA TORRE; JUSTO COBO

Santiago de Compostela

Congreso; XX National Meeting of the Spanish Society of Medicinal Chemistry; 2022

Sociedad Española de Química Terapéutica (SEQT)

Giardia lamblia (G. lamblia) (also known as Giardia intestinalis or Giardia duodenalis) is an anaerobic protozoan parasite that inhabits in the small intestine of humans and other higher animals. This parasite is the cause of giardiasis, a parasitosis of great epidemiological and clinical importance due to its high prevalence and pathogenicity. In previous works we demonstrated the importance of cAMP synthesis and degradation on the growth and differentiation processes of the intestinal parasite G. lamblia: i) cAMP increases significantly during the encysting process of trophozoites incubated in vitro1; ii) The addition to the culture medium of the non-hydrolyzable analog of cAMP, dbAMPc, increases the replication rate of the parasite.2 In this context, and through an analysis of the G. lamblia genome, we found the complete sequence of two nucleotidyl cyclase enzymes (gNC1 and gNC2) and a phosphodiesterase enzyme (gPDE), which would be responsible for the synthesis and degradation of cAMP in this parasite.1 In addition, we have recently reported a structural model of sAC for G. lamblia through an exhaustive molecular modeling study applying homology techniques.2 Taking advantage of the information obtained in our previous article, in this work, we report a series of pyrimido[4,5-e][1,4]diazepine derivatives IV3 (See figure 1a) as a new inhibitors for adenylyl cyclase of Giardia lamblia. Such compounds have been arisen as potential candidates from a study using structural data of the nucleotidyl cyclase 1 (gNC1) of this parasite. For this study, we used an own model for this specific enzyme by using homology techniques, which is the first model reported for gNC1 of G.2 Our simulations indicate that these ligands are located at the base of the ATP binding pocket, and that complexes are stabilized mainly through interactions with residues Thr 125, Phe 204, Phe 116, Leu 213 and Ile 127. Our results suggest that these new inhibitors follow a competitive mechanism of action against this enzyme. 2-Hydroxyestradiol was used as the reference compound for comparative studies. Results in this work are important from two points of view. On the one hand, an experimentally corroborated model for gNC1 of G. lamblia obtained by molecular modelling is validated further; on the other hand, new inhibitors possessing a new structural scaffold are excellent starting structures for the development of new metabolic inhibitors for G. lamblia.