1,2-Αnnulated Adamantane Heterocyclic Derivatives as Anti-Influenza Α Virus Agents

In this report we review our results on the development of 1,2-annulated adamantane heterocyclic derivatives and we discuss the structure-activity relationships obtained from their biological evaluation against influenza A virus. We have designed and synthesized numerous potent 1,2-annulated adamantane analogues of amantadine and rimantadine against influenza A targeting M2 protein the last 20 years. For their synthesis we utilized the key intermediates 2-(2-oxoadamantan-1-yl)acetic acid and 3-(2-oxoadamantan-1-yl)propanoic acid, which were obtained by a simple, fast and efficient synthetic protocol. The latter involved the treatment of protoadamantanone with different electrophiles and a carbon-skeleton rearrangement. These ketoesters offered a new pathway to the synthesis of 1,2-disubstituted adamantanes, which constitute starting materials for many molecules with pharmacological potential, such as the 1,2-annulated adamantane heterocyclic derivatives. To obtain additional insight for their binding to M2 protein three structurally similar 1,2-annulated adamantane piperidines, differing in nitrogen position, were studied using molecular dynamics (MD) simulations in palmitoyl-oleoyl-phosphatidyl-choline (POPC) hydrated bilayers. This work is licensed under a Creative Commons Attribution 4.0 International License

Novel Lipophilic Hydroxamates Based on Spirocarbocyclic Hydantoin Scaffolds with Potent Antiviral and Trypanocidal Activity

Flaviviridae infections, such as those caused by hepatitis C (HCV) and dengue viruses (DENVs), represent global health risks. Infected people are in danger of developing chronic liver failure or hemorrhagic fever, both of which can be fatal if not treated. The tropical parasites Trypanosoma brucei and Trypanosoma cruzi cause enormous socioeconomic burdens in Sub-Saharan Africa and Latin America. Anti-HCV chemotherapy has severe adverse effects and is expensive, whereas dengue has no clinically authorized treatment. Antiparasitic medicines are often toxic and difficult to administer, and treatment failures are widely reported. There is an urgent need for new chemotherapies. Based on our previous research, we have undertaken structural modification of lead compound V with the goal of producing derivatives with both antiviral and trypanocidal activity. The novel spirocarbocyclic-substituted hydantoin analogs were designed, synthesized, and tested for antiviral activity against three HCV genotypes (1b, 3a, 4a), DENV, yellow fever virus (YFV), and two trypanosome species (T. brucei, T. cruzi). The optimization was successful and led to compounds with significant antiviral and trypanocidal activity and exceptional selectivity. Several modifications were made to further investigate the structure-activity relationships (SARs) and confirm the critical role of lipophilicity and conformational degrees of freedom

Scaffold hybridization strategy towards potent hydroxamate-based inhibitors of Flaviviridae viruses and Trypanosoma species.

Infections with Flaviviridae viruses, such as hepatitis C virus (HCV) and dengue virus (DENV) pose global health threats. Infected individuals are at risk of developing chronic liver failure or haemorrhagic fever respectively, often with a fatal outcome if left untreated. Diseases caused by tropical parasites of the Trypanosoma species, T. brucei and T. cruzi, constitute significant socioeconomic burden in sub-Saharan Africa and continental Latin America, yet drug development is under-funded. Anti-HCV chemotherapy is associated with severe side effects and high cost, while dengue has no clinically approved therapy and antiparasitic drugs are outdated and difficult to administer. Moreover, drug resistance is an emerging concern. Consequently, the need for new revolutionary chemotherapies is urgent. By utilizing a molecular framework combination approach, we combined two distinct chemical entities with proven antiviral and trypanocidal activity into a novel hybrid scaffold attached by an acetohydroxamic acid group (CH2CONHOH), aiming at derivatives with dual activity. The novel spiro-carbocyclic substituted hydantoin analogues were rationally designed, synthesized and evaluated for their potency against three HCV genotypes (1b, 3a, 4a), DENV and two Trypanosoma species (T. brucei, T. cruzi). They exhibited significant EC50 values and remarkable selectivity indices. Several modifications were undertaken to further explore the structure activity relationships (SARs) and confirm the pivotal role of the acetohydroxamic acid metal binding group

Lipophilic Guanylhydrazone Analogues as Promising Trypanocidal Agents: An Extended SAR Study.

In this report, we extend the SAR analysis of a number of lipophilic guanylhydrazone analogues with respect to in vitro growth inhibition of Trypanosoma brucei and Trypanosoma cruzi. Sleeping sickness and Chagas disease, caused by the tropical parasites T. brucei and T. cruzi, constitute a significant socioeconomic burden in low-income countries of sub-Saharan Africa and Latin America, respectively. Drug development is underfunded. Moreover, current treatments are outdated and difficult to administer, while drug resistance is an emerging concern. The synthesis of adamantane-based compounds that have potential as antitrypanosomal agents is extensively reviewed. The critical role of the adamantane ring was further investigated by synthesizing and testing a number of novel lipophilic guanylhydrazones. The introduction of hydrophobic bulky substituents onto the adamantane ring generated the most active analogues, illustrating the synergistic effect of the lipophilic character of the C1 side chain and guanylhydrazone moiety on trypanocidal activity. The n-decyl C1-substituted compound G8 proved to be the most potent adamantane derivative against T. brucei with activity in the nanomolar range (EC50=90 nM). Molecular simulations were also performed to better understand the structure-activity relationships between the studied guanylhydrazone analogues and their potential enzyme target

Novel heterocyclic chelating agents with antiviral and antiparasitic activity

The present doctoral dissertation describes the design, synthesis and biological evaluation of new compounds, bearing a bidental metal chelating functional group, which can act as potent metalloenzyme inhibitors. The present work is divided into two parts. The first part comprises a series of 48 hydantoin analogues which are substituted with the carbohydroxamic acid group, and they exhibit antitrypanosomal activity against T. brucei and T. cruzi. The design of these compounds was based on previous data and publications of our research group, which showed that the introduction of the acetohydroxamic acid moiety on the imidic nitrogen atom of lipophilic spirocarbocyclic 2,6-diketopiperazines, leads to derivatives with significant trypanocidal activity. More specifically, in the present thesis, spirocarbocyclic and disubstituted hydantoin analogues bearing the acetohydroxamic acid moiety on the imidic nitrogen were synthesized. In addition, acetohydroxamic acid analogues bearing a N-methyl or a N-benzyl substitution on the amidic nitrogen atom of the hydantoin ring were synthesized, as well as a class of spirocarbocyclic glycine hydroxamic and proline hydroxamic acids. Considering the approach to further exploit compounds that act by bind metal ions in more than one microorganism and the fact that several metal chelating agents with anti-HCV activity have been reported in the literature, the novel synthesized analogues were tested for their antiviral activity against HCV replication and other re-emerging Flaviviruses of the Flaviviridae family. The new analogues exhibited highly potent antitrypanosomal activity against T. brucei with EC50 values ranging from nanomolar to low micromolar range and remarkable selectivity indices. Some acetohydroxamic acid derivatives are also active against T. cruzi with EC50 values at submicromolar to micromolar levels. Moreover, most compounds display potent activity in nanomolar to low micromolar range against two different HCV genotypes, and some of them are active against one or more Flaviviruses. The second part refers to the synthesis of 19 N-hydroxypyridinediones (HPDs), as HBV RNaseH inhibitors. The idea was based on the ability of certain compounds, bearing the N-hydroxyimidic moiety, to inhibit HBV replication. In particular, HPDs conjugated to arylamines, alkylamines and aryl-alkyl-amines were synthesized. The compounds were tested for their activity against HBV replication, and most of them are active with submicromolar to low micromolar EC50 values. By synthesizing these new HPDs, an improvement in the therapeutic index of the lead compound was achieved, with no simultaneous suppression of the human enzyme, huRNaseH1.Στην παρούσα διδακτορική διατριβή περιγράφονται ο σχεδιασμός, η σύνθεση και η αξιολόγηση της βιολογικής δράσης νέων ενώσεων, που φέρουν δισχιδή χηλικό υποκαταστάτη συμπλοκοποίησης μετάλλων και μπορούν να δράσουν ως ισχυροί αναστολείς μεταλλοενζύμων. Η παρούσα εργασία χωρίζεται σε δύο μέρη. Το πρώτο μέρος περιλαμβάνει μια σειρά 48 υδαντοϊνικών αναλόγων τα οποία είναι υποκατεστημένα με την καρβοϋδροξαμική ομάδα και επιδεικνύουν αντιτρυπανοσωμιακή δράση έναντι των Τ. brucei και T. cruzi. Ο σχεδιασμός αυτών των ενώσεων βασίστηκε σε προηγούμενα δεδομένα και δημοσιεύσεις της ερευνητικής μας ομάδας, σύμφωνα με τα οποία η εισαγωγή της ακετοϋδροξαμικής ομάδας στο ιμιδικό άτομο αζώτου λιπόφιλων σπειροκαρβοκυκλικών 2,6-δικετοπιπεραζινών οδηγεί σε ανάλογα με σημαντική αντιτρυπανοσωμιακή δράση. Πιο συγκεκριμένα, στην παρούσα διατριβή συντέθηκαν σπειροκαρβοκυκλικά και δισυποκατεστημένα υδαντοϊνικά ανάλογα που φέρουν στο ιμιδικό άζωτο την ακετοϋδροξαμική ομάδα. Επιπλέον συντέθηκαν ακετοϋδροξαμικά ανάλογα που φέρουν Ν-μεθυλο ή Ν-βενζυλο υποκατάσταση στο αμιδικό άζωτο του υδαντοϊνικού δακτυλίου καθώς επίσης και μια κατηγορία σπειροκαρβοκυκλικών γλυκινοϋδροξαμικών και προλινοϋδροξαμικών οξέων. Λαμβάνοντας υπόψη την προσέγγιση για περαιτέρω εκμετάλλευση ενώσεων που δρουν δεσμεύοντας μεταλλικά ιόντα σε περισσότερους από έναν μικροοργανισμούς, και το γεγονός ότι αρκετοί χηλικοί παράγοντες με αντι-HCV δράση έχουν αναφερθεί στη βιβλιογραφία, τα νεοσυντεθειμένα ανάλογα εξετάστηκαν για την αντιική τους δράση έναντι της αντιγραφής του HCV και επανεμφανιζόμενων Φλαβοϊών της οικογένειας Flaviviridae. Τα νέα ανάλογα επέδειξαν πολύ ισχυρή αντιτρυπανοσωμιακή δράση έναντι του Τ. brucei με τιμές EC50 που κυμαίνονται από τη νανομοριακή μέχρι τη χαμηλή μικρομοριακή κλίμακα και αξιοσημείωτους δείκτες εκλεκτικότητας. Ορισμένα ακετοϋδροξαμικά παράγωγα είναι επίσης δραστικά έναντι του T. cruzi με τιμές EC50 σε υπομικρομοριακά έως μικρομοριακά επίπεδα. Επιπλέον, οι περισσότερες ενώσεις εμφανίζουν ισχυρή δράση σε νανομοριακή και χαμηλή μικρομοριακή κλίμακα έναντι δύο διαφορετικών γονοτύπων του HCV και ορισμένες είναι δραστικές έναντι ενός ή περισσότερων Φλαβοϊών. Το δεύτερο μέρος αναφέρεται στη σύνθεση 19 N-υδροξυπυριδινοδιονών (HPDs), ως αναστολείς της HBV RNaseH. Η ιδέα προήλθε βάσει της ικανότητας ορισμένων ενώσεων, που φέρουν την Ν-υδροξυιμιδική ομάδα, να αναστέλλουν την αντιγραφή του HBV. Συγκεκριμένα, συντέθηκαν HPDs συζευγμένες με αρυλαμίνες, αλκυλαμίνες και αρυλ- αλκυλ- αμίνες. Οι ενώσεις ελέγχθηκαν για τη δράση τους έναντι της αντιγραφής του HBV, και οι περισσότερες από αυτές είναι δραστικές με υπομικρομοριακές έως χαμηλές μικρομοριακές τιμές EC50. Με τη σύνθεση αυτών των νέων HPDs επιτεύχθηκε βελτίωση του θεραπευτικού δείκτη της ένωσης-οδηγού, χωρίς ταυτόχρονη καταστολή του ανθρώπινου ενζύμου, huRNaseH1

Recent Advances in Hepatitis B Treatment

Hepatitis B virus infection affects over 250 million chronic carriers, causing more than 800,000 deaths annually, although a safe and effective vaccine is available. Currently used antiviral agents, pegylated interferon and nucleos(t)ide analogues, have major drawbacks and fail to completely eradicate the virus from infected cells. Thus, achieving a “functional cure” of the infection remains a real challenge. Recent findings concerning the viral replication cycle have led to development of novel therapeutic approaches including viral entry inhibitors, epigenetic control of cccDNA, immune modulators, RNA interference techniques, ribonuclease H inhibitors, and capsid assembly modulators. Promising preclinical results have been obtained, and the leading molecules under development have entered clinical evaluation. This review summarizes the key steps of the HBV life cycle, examines the currently approved anti-HBV drugs, and analyzes novel HBV treatment regimens

Antiviral effect of compounds on bunyavirus replication.

Vero cells were infected with either RVFV ZH501 (A) or LACV (B) then treated with decreasing concentrations of antiviral compound. Viral growth was measured by FFA. Data represents three independent experiments completed with biological replicates. Error bars represent standard deviation.</p

EC₅₀ against LACV and ZIKV replication.

EC50 against LACV and ZIKV replication.</p

Representative structures of RFVF inhibitors.

(A) Inactive and active troponoid natural products, illustrating preference for oxygen triad, along with common nuclease inhibition mode for αHTs. (B) Synthetic αHTs with activity under 10 μM against RVFV, demonstrating broad substitution tolerance. (C) Representative examples of alternative scaffolds with activity against RFVF.</p