Stampidine: a selective oculo-genital microbicide

Current antiviral agents against human adenoviruses associated with respiratory infections

Human adenoviruses (HAdVs) are important pathogens responsible for respiratory infections. In children and immunocompromised patients, respiratory infections can cause considerable morbidity and mortality. Currently, there are no approved effective and safe antiviral therapeutics for the clinical treatment of HAdV infections, even those that have undergone preclinical/clinical trials. However, many compounds and molecules with anti-HAdV activity have been explored, and some candidates are undergoing clinical development. Here, we reviewed the reported in vitro and in vivo efficacies, as well as the therapeutic potential of these antiviral compounds, providing an overview and a summary of the current status of anti-HAdV drug development.

Phosphoramidates and phosphonamidates (ProTides) with antiviral activity

Following the first report on the nucleoside phosphoramidate (ProTide) prodrug approach in 1990 by Chris McGuigan, the extensive investigation of ProTide technology has begun in many laboratories. Designed with aim to overcome limitations and the key resistance mechanisms associated with nucleoside analogues used in the clinic (poor cellular uptake, poor conversion to the 5'-monophosphate form), the ProTide approach has been successfully applied to a vast number of nucleoside analogues with antiviral and anticancer activity. ProTides consist of a 5'-nucleoside monophosphate in which the two hydroxyl groups are masked with an amino acid ester and an aryloxy component which once in the cell is enzymatically metabolized to deliver free 5'-monophosphate, which is further transformed to the active 5'-triphosphate form of the nucleoside analogue. In this review, the seminal contribution of Chris McGuigan's research to this field is presented. His technology proved to be extremely successful in drug discovery and has led to two Food and Drug Administration-approved antiviral agents.

Application of Design of Experiment and Simulation Methods to Liquid Chromatography Analysis of Topical HIV Microbicides Stampidine and HI443

This study intended to determine if experimental design and Monte Carlo simulation methods can be utilized to optimize the liquid chromatography (LC) analysis of active molecules. The method was applied for the simultaneous analysis of two topical microbicides, stampidine (STP) and HI443 in bulk and nanoformulations. The Plackett-Burman design was used for screening; whereas, Box-Behnken design was used to evaluate the main and interaction effects of the selected factors on the responses, namely peak area of STP (Y₁), HI443 (Y₂), tailing of STP (Y₃), and HI443 (Y₄). The Monte Carlo simulation was applied to get the minimum defect rate (DR) of the process. The optimized LC conditions were found to be X₁; flow rate: 0.6 mL/min, X₂; injection volume: 18 μL, and X₃; initial gradient acetonitrile ratio: 92% v/v with a minimal DR of 0.077%. The optimized method was applied to determine the percent encapsulation efficiency (%EE) and in vitro release profile of STP and HI443 from solid lipid nanoparticles (SLNs). The %EE of STP and HI443 in SLNs was found to be 30.56 ± 9.44 and 94.80 ± 21.90% w/w, respectively, (n=3). It was observed that the release kinetics of STP followed the first order, whereas, HI443 followed the Peppas kinetic model in SLNs. The LC method was also applied for the estimation of molar extinction coefficients (ε₂₇₀ ) of both drugs for the first time. These values were estimated to be 7,569.03 ± 217.96 and 17,823.67 ± 88.12 L/mol/cm for STP and HI443, respectively, (n=3). The results suggest that experimental design and Monte Carlo simulation can be effectively used to reduce the DR of a process and to optimize the chromatographic conditions for the analysis of bio-active agents as applied in this study.

[Adenovirus infections in immunocompromised patients]

Human adenoviruses function as genetic models and vectors for gene therapy. Upper respiratory, gastrointestinal or ocular infections usually have mild course without any major complication in immunocompetent individuals. However, reactivation from latency in immunocompromised patients may lead to death. Depending on the underlying diseases, different adenovirus serotypes damage different organs. In children with severe combined immunodeficiency syndrome, serotypes of species A and C induce lung, liver or bladder inflammation. Paediatric hematopoietic stem cell transplantation is frequently followed by serotype 31-induced pneumonia, enteritis, cystitis. B serotypes can destroy transplanted organs. In AIDS patients, D and novel F serotypes cause enteritis. Recombinants of B serotypes induce urinary tract infections. Progression of lymphomas, tumours, and systemic lupus erythematosus might be facilitated by immunosuppressive effects of adenoviruses. As far as the diagnostic work-up of adenoviruses, detection of viral DNA and virus copy number is predictive, while serology testing is quite unreliable. For treatment, cidofovir derivates, ribavirin, ganciclovir, vidarabine and microRNA have been used.

Mucosal safety of PHI-443 and stampidine as a combination microbicide to prevent genital transmission of HIV-1

OBJECTIVE

To investigate the in vitro and in vivo mucosal safety of a nonnucleoside reverse transcriptase (RT) inhibitor (PHI-443) and a nucleoside analogue RT inhibitor (stampidine)-based anti-HIV microbicide either alone or in combination.

DESIGN

In vitro and in vivo studies using three-dimensional vaginal epithelia integrating Langerhans cells and 16 New Zealand White rabbits, respectively.

SETTING

Research laboratory.

INTERVENTION(S)

Rabbits in groups of four were exposed intravaginally to a gel with and without 1% PHI-443, 1% stampidine, or 1% PHI-443 plus 1% stampidine for 14 days. Cytokine/chemokine release by three-dimensional co-cultures in the presence and absence of PHI-443 or stampidine.

MAIN OUTCOME MEASURES(S)

Histologic scoring of vaginal tissue for mucosal toxicity at 24 hours after dosing. Simultaneous evaluation of levels of 10 cytokines (granulocyte-macrophage colony-stimulating factor, interleukin-1 alpha, interleukin-13, macrophage inflammatory protein-1 beta, granulocyte colony-stimulating factor, interleukin-18, tumor necrosis factor-alpha, interleukin-6, interleukin-1 beta, and interferon-gamma) and 6 chemokines (epithelial neutrophil-activating peptide-78, interleukin-8, monocyte/macrophage chemoattractant protein-1, macrophage inflammatory protein-3 alpha, interferon-inducible protein-10, and regulated upon activation of normal T-cell expressed and secreted) in culture media by a multiplexed chemiluminescence-based immunoassay.

RESULT(S)

In the rabbit model, repeated intravaginal administration of PHI-443 plus stampidine via a gel formulation at concentrations nearly 2,000 and 10,000 times higher than their respective in vitro anti-HIV IC(50) values did not result in vaginal irritation. The levels of proinflammatory cytokines/chemokines secreted by multilayered human genital epithelia integrating Langerhans cells were unaffected by prolonged exposure to PHI-443 or stampidine.

CONCLUSION(S)

The combination of PHI-443 and stampidine was noncytotoxic to vaginal epithelial cells, nonirritating to vaginal mucosa, and did not induce the secretion of proinflammatory cytokines and chemokines by co-cultures of human genital epithelia and Langerhans cells. These attributes are particularly useful for the clinical development of PHI-443 and stampidine as a combination microbicide and as a prophylactic anti-HIV agent to curb genital transmission of HIV-1 by semen.

Anti-adenoviral effect of anti-HIV agents in vitro in serotypes inducing keratoconjunctivitis

BACKGROUND

Around one million people are affected by adenoviral keratoconjunctivitis a year in Japan, and it is recognized as one of the major pathogens of ophthalmological nosocomial infection worldwide. Although cidofovir can be used systemically for immunocompromised patients with disseminated adenoviral infection, no specific anti-adenoviral agent has been established for the treatment of adenoviral infection. We evaluated the anti-adenoviral effect of anti-HIV (human immunodeficiency virus) agents in this study.

METHODS

Five anti-HIV agents (zalcitabine, stavudine, nevirapine, indinavir and amprenavir) were subjected to in vitro evaluation. A549 cells were used for viral cell culture, and adenovirus serotypes 3, 4, 8, 19 and 37 were used. After calculating CC(50) (50% cytotoxic concentration) of each agent by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) method, we cultured adenovirus with the agents for seven days and quantitatively measured extracted adenoviral DNA by real-time PCR.

RESULTS

Among the anti-HIV drugs, zalcitabine and stavudine, both nucleoside reverse transcriptase inhibitors, showed significant anti-adenoviral activity. In contrast, nevirapine, a non-nucleoside reverse transcriptase inhibitor, and indinavir and amprenavir, which are both protease inhibitors, were ineffective against adenovirus.

CONCLUSIONS

These results indicate that zalcitabine and stavudine are possible candidates for the local and systemic treatment of adenoviral infection, and the anti-adenoviral effect might depend on the pharmacological properties of anti-HIV agents. The chemical properties on the clinical safety for systemic and local application need to be determined in order to for these drugs to be accepted for the treatment of adenovirus in clinical settings.