Thesis title: SMALL MOLECULES AS ENABLING TOOLS TO COMBAT VIRAL INFECTIONS AND TO BLOCK TRANSMISSION OF MALARIA
Nowadays, discovering and then bringing new drugs for the treatment and eradication of infectious diseases to market is a formidable challenge, this thesis addresses to these hurdles with the investigation and exploration of new specific antiviral compounds and innovative interventions to overcome the spread of malaria.
Every year, enteroviruses infect millions of humans, and there is not a specific treatment for this infection due to non-selective compounds available. Therefore, more antiviral strategies and new molecules need to be explored. Lately, the mortality and morbidity rates in neonatal and immune-compromised populations have been increasing suggesting that new interventions are strictly required. These reasons led us to perform a cell-based screening selectively against CVA9 serotype, which allowed the identification of a class of N-phenyl benzamides with promising activity values. Two hit compounds, CL212 and CL213, were investigated to understand their mechanism of action. Compounds seem to inhibit the uncoating of the viruses. New derivatives were synthesized to enlarge the series and define the SAR of this new class of antiviral compounds. Among all the compounds, N-phenyl benzamines performed the best inhibition values. Thereby, they were selected to identify some critical drug-like properties, such as kinetic solubility and lipophilicity (LogD). Aim of this study is the design and optimization of new derivatives with a high antiviral activity against the enterovirus infection.
Malaria is still a global public burden, indeed infections caused by the most virulent Plasmodium falciparum (Pf) cause over 300,000 deaths each year. Although the observed reduction between 2000 and 2015, the World Health Assembly planned to reduce malaria burden a further 90% by 2030. The spread of Pf resistance to antimalarial drugs, which commonly target ABSs, notably has been reducing the efficacy of available pharmacological treatments. Moreover, novel resistance mechanisms, developed by Anopheles, have been decreasing the efficacy of vector-control strategies. Hence, transmission-blocking candidates (TCP-5) represent the new promising frontier to abrogate parasite development both in humans and mosquitoes. Primaquine is the only FDA approved drug, which targets the bottleneck population of gametocytes, responsible for the transmission between humans and vectors. Product development partnerships (PDPs) join efforts to reprofile existing drugs as either TCP-5 or a combination of TCP-1 and TCP-5, and to identify novel candidates through parallel HTSs. An example is the discovery of MMV1580843, by Reader et al., which displays moderate activity against asexual blood stages and owns the features to be profiled as transmission blocker. Previously, we started a hit-to-lead campaign around MMV1580843 scaffold, and we found that positions N1, C3 and C5 of the main scaffold, are amenable to chemical modifications to improve both the potency and physiochemical properties. Hence, aim of this PhD thesis project is the design of novel pyrazoles, to enrich the SAR analysis of this class of potent gametocytocidal compounds.
In parallel, we carried out phenotypic screening on pyrazole- and pyrrole- based compounds of our library. In detail, aim of this study is the investigation of the activity of selected compounds, on multiple stages of Plasmodium falciparum, as following: (i) according to the work of Paton et al. topical exposure is performed to assess gametocidal activity; (ii) gametocytocidal activity, previously observed in vitro, is validated through iSMFA; (iii) target identification is carried out for the potent pyrazole 17, which displays high potency in killing asexual blood stages of P. falciparum.