Treatment of acyclovir-unresponsive cutaneous herpes simplex virus infection with topically applied SP-303

Crofelemer, a novel agent for treatment of non-infectious diarrhea in HIV-infected persons

Crofelemer is the first US FDA-approved drug for symptomatic relief in HIV-infected persons on antiretroviral therapy (ART) who have non-infectious diarrhea. With the availability of ART, there is increased survival and decrease in gastrointestinal opportunistic infections. However, diarrhea secondary to ART and HIV enteropathy is common in HIV-infected persons. Crofelemer is manufactured from the red latex sap of the Croton lechleri tree in South America. It has a unique mechanism leading to inhibition of chloride ion secretion by blocking chloride channels in the gastrointestinal lumen. This reduces efflux of sodium and water, which in turn reduces the frequency and consistency of diarrhea. Crofelemer is well tolerated due to minimal systemic absorption and has a good safety profile. The availability of crofelemer will likely have a positive impact on the quality of life in HIV-infected persons and also increase compliance to ART.

Crofelemer for the treatment of secretory diarrhea

Secretory diarrhea is a leading cause of morbidity and mortality worldwide. Crofelemer is a first-in-class antidiarrheal agent that simultaneously targets two distinct channels, the cystic fibrosis conductance regulator and calcium-activated chloride channel, responsible for chloride and fluid secretion in the GI tract. Crofelemer is a novel compound extracted from the stem bark latex of the Croton lechleri tree found in the western Amazonian region of South America. There is little to no systemic absorption of crofelemer when given orally and studies have shown minimal toxicity beyond mild gastrointestinal effects. In studies in diarrheal illness associated with primarily a secretory component, such as cholera, travelers' diarrhea and acute infectious diarrhea, crofelemer has shown improvements in stool consistency and duration of symptoms. Less clear, but interesting, results have been observed in other diarrheal diseases associated with a mixed pathology, including diarrhea in patients with HIV and diarrhea-predominant irritable bowel syndrome.

Crofelemer, a novel agent for treatment of secretory diarrhea

OBJECTIVE

To review the chemistry, pharmacology, pharmacokinetics, efficacy, and safety of crofelemer.

DATA SOURCES

A literature search using the terms SP-303, Provir, and crofelemer was performed with PubMed (up to April 2010), Google Scholar, and selected Ovid bibliography searches. Additional references from the bibliographies of articles included in the search, as well as company and Food and Drug Administration Web sites, were also assessed.

DATA EXTRACTION

English-language in vitro and clinical studies associated with the safety and efficacy of crofelemer were included.

DATA SYNTHESIS

Crofelemer is a first-in-class agent that may be useful for different types of secretory diarrhea, since it prevents chloride and fluid secretion into the bowel by directly inhibiting 2 distinct intestinal chloride channels. Crofelemer significantly brought about faster symptom resolution in patients with traveler's diarrhea, along with lower rates of treatment failure compared to placebo-treated patients. In a post hoc analysis, crofelemer compared to placebo also appears to have reduced abnormal stool weight and frequency in patients with AIDS-associated diarrhea. In a third trial, crofelemer did not offer a significant benefit in improving stool consistency after 12 weeks of treatment in patients with diarrhea-predominant irritable bowel syndrome. However, a significant increase in pain-free days was noted in female patients. Preliminary studies also show that crofelemer may reduce watery stool output in patients with infectious diarrhea such as cholera. Oral crofelemer seemed to be well tolerated in clinical trials, with adverse effect profiles comparable to those with placebo.

CONCLUSIONS

Crofelemer possesses a novel mechanism of action that shows promise in treating secretory diarrhea of several etiologies. However, results from further Phase 3 clinical trials are still needed in order to fully evaluate the efficacy and safety of this agent.

Natural Products as a Foundation for Drug Discovery

Natural products have contributed to the development of many drugs for diverse indications. While most U.S. pharmaceutical companies have reduced or eliminated their in-house natural product groups, new paradigms and new enterprises have evolved to carry on a role for natural products in the pharmaceutical industry. Many of the reasons for the decline in popularity of natural products are being addressed by the development of new techniques for screening and production. This overview aims to inform pharmacologists of current strategies and techniques that make natural products a viable strategic choice for inclusion in drug discovery programs.

Proanthocyanidin from blueberry leaves suppresses expression of subgenomic hepatitis C virus RNA

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease such as chronic hepatitis, cirrhosis, and hepatocellular carcinoma. While searching for new natural anti-HCV agents in agricultural products, we found a potent inhibitor of HCV RNA expression in extracts of blueberry leaves when examined in an HCV subgenomic replicon cell culture system. This activity was observed in a methanol extract fraction of blueberry leaves and was purified by repeated fractionations in reversed-phase high-performance liquid chromatography. The final purified fraction showed a 63-fold increase in specific activity compared with the initial methanol extracts and was composed only of carbon, hydrogen, and oxygen. Liquid chromatography/mass-ion trap-time of flight analysis and butanol-HCl hydrolysis analysis of the purified fraction revealed that the blueberry leaf-derived inhibitor was proanthocyanidin. Furthermore, structural analysis using acid thiolysis indicated that the mean degree of polymerization of the purified proanthocyanidin was 7.7, consisting predominantly of epicatechin. Proanthocyanidin with a polymerization degree of 8 to 9 showed the greatest potency at inhibiting the expression of subgenomic HCV RNA. Purified proanthocyanidin showed dose-dependent inhibition of expression of the neomycin-resistant gene and the NS-3 protein gene in the HCV subgenome in replicon cells. While characterizing the mechanism by which proanthocyanidin inhibited HCV subgenome expression, we found that heterogeneous nuclear ribonucleoprotein A2/B1 showed affinity to blueberry leaf-derived proanthocyanidin and was indispensable for HCV subgenome expression in replicon cells. These data suggest that proanthocyanidin isolated from blueberry leaves may have potential usefulness as an anti-HCV compound by inhibiting viral replication.

Current recommendations for the treatment of genital herpes

The incidence of genital herpes continues to increase in epidemic-like fashion. Aciclovir (acyclovir) has been the original gold standard of therapy. The recent addition of famciclovir and valaciclovir as antiherpes drugs has improved convenience as well as the efficacy of treatment. Although aciclovir remains a widely prescribed and reliable drug, its administration schedule falls short of the ease of usage that the newer nucleoside analogues offer, for both episodic and suppressive therapy. Suppression of symptomatic disease and asymptomatic shedding from the genitalia have both become popular approaches, if not the primary targets of antiviral therapy. Knowing that asymptomatic disease leads to most cases of transmission strongly suggests that suppression with antiviral agents could reduce transmission risk in discordant couples. Unfortunately, the role for antivirals in reducing transmission remains to be proven in clinical trials. Neonatal herpes is now successfully treated using aciclovir. Current randomised clinical trials are examining aciclovir and valaciclovir administration, as well as safety and efficacy for post-acute suppressive therapy. Prevention of recurrences in pregnancy is also a topic under investigation, with a view to reducing the medical need for Cesarean section, or alternatively (and far less likely to be accomplished) to protect the neonate. Although resistance is largely limited to the immunocompromised and a change in resistance patterns is not expected, several drugs are available for the treatment of aciclovir-resistant strains of herpes simplex. Foscarnet is the main alternative with proven efficacy in this setting. Unfortunately, administration of foscarnet requires intravenous therapy, although a single anecdote of topical foscarnet efficacy in this setting has been published. Alternatives include cidofovir gel, which is not commercially available but can be formulated locally from the intravenous preparation. Less effective alternatives include trifluridine and interferon. Future possibilities for treatment of genital herpes include a microparticle-based controlled-release formulation of aciclovir and resiquimod (VML-600; R-848). The search for an effective therapeutic vaccine for genital herpes has not been successful to date, although a live virus glycoprotein H-deficient (DISC) vaccine is currently in clinical trials. Recent data suggest that seronegative women are protected (albeit, not fully) by a glycoprotein D recombinant vaccine with adjuvant. Despite the established safety and convenience of current treatment options, better suppressive options and topical treatment options are much needed. Studies using existing agents as potential tools to avoid Cesarean section, or transmission to neonate or partner are ongoing. Both vaccines and antivirals may eventually play a role in prevention of infection.

Chronic verrucous varicella zoster virus skin lesions: clinical, histological, molecular and therapeutic aspects

The outbreak of HIV infection introduced a new phenomenon in varicella zoster virus (VZV) pathology, namely the long-standing wart-like skin lesions that are frequently associated with resistance to thymidine kinase (TK)-dependent antiviral agents. This paper reviews the clinical, histological, and molecular aspects and the therapeutic management of these verrucous lesions. The majority of lesions are characterized by chronically evolving, unique or multiple wart-like cutaneous lesions. The main histopathological features include hyperkeratosis, verruciform acanthosis and VZV-induced cytopathic changes with scant or absent cytolysis of infected keratinocytes. The mechanism that establishes the chronic nature of the lesions appears to be associated with a particular pattern of VZV gene expression exhibiting reduced or nondetectable gE and gB synthesis. Drug resistance to TK-dependent antiviral agents is a result of nonfunctional or deficient viral TK. This necessitates alternative therapeutic management using antiviral agents that target the viral DNA polymerase.

Approaches and strategies for the treatment of influenza virus infections

Influenza A and B viruses belong to the Orthomyxoviridae family of viruses. These viruses are responsible for severe morbidity and significant excess mortality each year. Infection with influenza viruses usually leads to respiratory involvement and can result in pneumonia and secondary bacterial infections. Vaccine approaches to the prophylaxis of influenza virus infections have been problematic owing to the ability of these viruses to undergo antigenic shift by exchanging genomic segments or by undergoing antigenic drift, consisting of point mutations in the haemagglutinin (HA) and neuraminidase (NA) genes as a result of an error-prone viral polymerase. Historically, antiviral approaches for the therapy of both influenza A and B viruses have been largely unsuccessful until the elucidation of the X-ray crystallographic structure of the viral NA, which has permitted structure-based drug design of inhibitors of this enzyme. In addition, recent advances in the elucidation of the structure and complex function of influenza HA have resulted in the discovery of a number of diverse compounds that target this viral protein. This review article will focus largely on newer antiviral agents including those that inhibit the influenza virus NA and HA. Other novel approaches that have entered clinical trials or been considered for their clinical utility will be mentioned.

Topical treatment of cutaneous herpes simplex virus-1 infection in mice with a specially formulated caffeine gel (Cafon)

Caffeine, although not a nucleoside analog, is known to inhibit the replication of herpes simplex virus-1 (HSV-1) and has been shown to significantly limit the spread of HSV infection in vitro. The therapeutic efficacy of caffeine was examined in a murine cutaneous infection model. The midflanks of 6-week-old BALB/c mice were infected with HSV cutaneously after application of 10% caffeine (Cafon) gel, and was reapplied to the midflank 5 times daily thereafter. Treatment with Cafon gel significantly retarded the development of skin lesions. Both midflanks were cutaneously infected, and a placebo and active gel were applied to the right and left midflanks respectively. Cafon gel significantly retarded the appearance of vesiculation and reduced the number of vesicles compared with the placebo gel. Cafon gel was as effective as 5% acyclovir ointment, and no significant difference was observed in the development of local lesions between these two topical preparations. The efficacy of Cafon gel also corresponded to that of oral treatment with 5 mg/kg or more of acyclovir in our cutaneous infection system. These results suggest that Cafon gel can be useful for the topical treatment of cutaneous HSV infection.