Benzothiadiazine dioxide acyclonucleosides as lead compounds for the development of new agents against human cytomegalovirus and varicella-zoster virus infections

Benzothiadiazine dioxide human cytomegalovirus inhibitors: synthesis and antiviral evaluation of main heterocycle modified derivatives

The benzothiadiazine dioxide derivatives are potent non-nucleoside human cytomegalovirus (HCMV) inhibitors. As part of our comprehensive structure-activity relationship (SAR) study of these compounds, we have now proposed structural modifications on the heterocyclic moiety both on the number and the nature of the fused heterocycle and on the kind of heteroatoms present on it. Synthesis of these new compounds (benzyl derivatives of thiadiazines, thienothiadiazines, benzothienothiadiazines and quinazolines) and the antiviral evaluation against HCMV has been performed. SAR investigation on this class of compounds has defined the structural requirements for potency and toxicity. They have revealed two important clues: i) a fused ring to the thiadiazine framework is necessary to maintain the anti-HCMV action, and ii) the sulfamido moiety in the main heterocycle is crucial to avoid cytotoxicity.

Anti-HIV-1 activity of benzothiadiazine dioxide

Antiviral assays carried out on the potent benzothiadiazine dioxide (BTD) human cytomegalovirus (HCMV) inhibitors have led us to find marginal but selective anti-HIV-1 activity. Specific pharmacological studies, such as time of addition experiments and assays on specific viral strains with mutations on its reverse transcriptase, have indicated that BTD compounds act as non-nucleoside reverse transcriptase inhibitors. Theoretical calculations showed a butterfly conformation for the active derivatives that are compatible with their mechanism of action. Therefore, BTD derivatives can be considered as potential lead compounds for the treatment of opportunistic HCMV infections in immunocompromised individuals such as AIDS patients.

Recent strategies in the development of new human cytomegalovirus inhibitors

Human cytomegalovirus (HCMV) is one of the most common opportunistic infections in immunucompromised individuals, such as AIDS patients and organ transplant recipients, and is the most frequent congenital viral infection in humans. Despite a reduction of the incidence of AIDS-related opportunistic infections in patients under highly active antiretroviral treatment, attention should be paid to the HCMV risk factor in these individuals. Furthermore, HCMV may have an important role in atherosclerosis. Existing antiviral treatments for the HCMV infection suffer from poor bioavailability, toxicity, and limited effectiveness, mainly due to the development of drug resistance. Fortunately there are novel and potentially very effective new compounds undergoing pre-clinical and clinical evaluation. This review provides an overview in the last five years of new HCMV inhibitors (chemical structures, SAR, and new mechanisms of action) with the aim to provide new clues for the development of future drugs against this opportunistic virus.

Thienothiadiazine 2,2-dioxide acyclonucleosides: synthesis and antiviral activity

The synthesis of acyclonucleosides derived from thieno[3,2-c] and thieno[2,3-c][1,2,6]thiadiazine 2,2-dioxides was achieved following the silylation method. Lipase-mediated methodology was employed for deprotection of the acyclic moieties. The antiviral effects were determined against a broad spectrum of viruses, including cytomegalovirus (CMV) and varicella zoster virus (VZV). Only minor antiviral activity against VZV was observed for those acyclonucleosides carrying a benzyl group.

Chlorophenylmethyl benzothiadiazine dioxides derivatives: potent human cytomegalovirus inhibitors

Modifications of our previously reported lead compounds, acyclonucleosides derived from 2,1,3-benzothiadiazine dioxides, in the search for inhibitors of human cytomegalovirus (HCMV), lead us to identify the chlorophenylmethyl benzothiadiazine dioxides derivatives as potent HCMV inhibitors. The synthesis and antiviral data of this second-generation of benzothiadiazine dioxide compounds are reported.

Imidazothiadiazine dioxides: synthesis and antiviral activity

A new series of imidazothiadiazine dioxides, including the first acyclonucleosides derived from this heterocycle moiety, has been synthesized. A wide-spectrum antiviral screening was performed. Some of the N-1 benzyl imidazothiadiazines and the new acyclonucleosides showed interesting anti-CMV or anti-HIV activity. These structures could be considered as new lead compounds for antiviral drug research.