Synthesis of guanidino analogues of PMPDAP and their immunobiological activity

Nucleobase Modified Adefovir (PMEA) Analogues as Potent and Selective Inhibitors of Adenylate Cyclases from Bordetella pertussis and Bacillus anthracis

A series of 13 acyclic nucleoside phosphonates (ANPs) as bisamidate prodrugs was prepared. Five compounds were found to be non-cytotoxic and selective inhibitors of Bordetella pertussis adenylate cyclase toxin (ACT) in J774A.1 macrophage cell-based assays. The 8-aza-7-deazapurine derivative of adefovir (PMEA) was found to be the most potent ACT inhibitor in the series (IC50 =16 nm) with substantial selectivity over mammalian adenylate cyclases (mACs). AC inhibitory properties of the most potent analogues were confirmed by direct evaluation of the corresponding phosphonodiphosphates in cell-free assays and were found to be potent inhibitors of both ACT and edema factor (EF) from Bacillus anthracis (IC50 values ranging from 0.5 to 21 nm). Moreover, 7-halo-7-deazapurine analogues of PMEA were discovered to be potent and selective mammalian AC1 inhibitors (no inhibition of AC2 and AC5) with IC50 values ranging from 4.1 to 5.6 μm in HEK293 cell-based assays.

Adenine: an important drug scaffold for the design of antiviral agents

Adenine derivatives, in particular the scaffold bearing the acyclic nucleoside phosphonates (ANPS), possess significant antiviral and cytostatic activity. Till now, several effective adenine derivatives have been marketed for the treatment of HIV, HBV, CMV and other virus-infected diseases. These compounds are represented by tenofovir (PMPA), a medicine for both HIV and HBV, and adefovir as an anti-HBV agent. More than this, other analogs, such as GS9148, GS9131, and GS7340, are also well-known anti-viral agents that have been progressed to the clinical studies for their excellent activity. In general, the structures of these compounds include an adenine nucleobase linked to a phosphonate side chain. Considerable structural modifications on the scaffold itself and the peripheral sections were made. The structure-activity relationships (SARs) of this skeleton will provide valuable clues to identify more effective adenine derivatives as antiviral drugs. Here, we systematically summarized the SARs of the adenine derivatives, and gave important information for further optimizing this template.

Differential effects of acyclic nucleoside phosphonates on nitric oxide and cytokines in rat hepatocytes and macrophages

Acyclic nucleoside phosphonates (ANP) are virostatics effective against viruses like hepatitis B virus and human immunodeficiency virus. Our previous reports indicated immunomodulatory activities of ANP in mouse and human innate immune cells. Recently, evidence has increased that hepatocytes may play an active role in immune regulation of the liver homeostasis or injury. In this study we investigated possible immunomodulatory effects of ANP on rat hepatocytes and macrophages. Nitric oxide (NO) production and secretion of cytokines (IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-10, IL-13, IL-18, IFN-γ, TNF-α and GM-CSF) were analyzed under in vitro conditions. Test compounds included: 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA; adefovir); 9-[2-(phosphonomethoxy)ethyl]-2,6-diaminopurine (PMEDAP); (R)- and (S)-enantiomers of 9-[2-(phosphonomethoxy)propyl]adenine [(R)-PMPA; tenofovir] and [(S)-PMPA]; 9-[2-(phosphonomethoxy)propyl]-2,6-diaminopurine [(R)-PMPDAP] and [(S)-PMPDAP]. The group of test compounds also included their N(6)-substituted derivatives. Some of ANP which are able to induce NO production and cytokine secretion in cultured macrophages possess the same immunobiological activity in isolated hepatocytes. The extent of responses is in range of LPS/IFN-γ stimulation in both types of cells. The effects of active ANP on NO expression and cytokine secretion are dose- and time-dependent. Interestingly, the spectrum of detected cytokines induced by ANP is broader in hepatocytes. The results also confirm immunomodulatory effects of some ANP on rodent macrophages. Moreover, we demonstrate for the first time immunobiological reactivity of primary rat hepatocytes induced by exogenous ANP compounds. The potential of hepatocytes to synthesize cytokines can contribute to better understanding of liver immune function and can serve for pharmacological intervention in liver diseases.