Donald P. Waller

Cytochrome P450 variations in different ethnic populations

Introduction: Variability of drug response is an important consideration in clinical medicine. A major determinant of drug response variability is hepatic cytochrome P450 oxidase (CYP450)-mediated drug metabolism. Advances in genetics permits genotyping large numbers of patients to identify single nucleotide polymorphisms (SNPs) which may result in variant CYP450 enzyme expression and/or activity. New SNPs with functional impacts are constantly being identified which further explain variability in CYP450 phenotype. Areas covered: The racial/ethnic distribution of selected CYP450 (CYP1A2, P2C8/9/19, 2D6 and 3A4/5) SNPs are reviewed with an emphasis on the agreement between genotype and phenotype. The reader will gain insight into the SNP distribution by racial/ethnic group and the corresponding relationship between important, highly prevalent, SNPs and their impact on metabolic phenotype. Expert opinion: Racial/ethnic differences in metabolic phenotype can be explained by differences in SNP distribution. However, overlap in substrate specificity, linkage disequilibrium and previously unidentified SNPs have made phenotypic characterization difficult for CYP3A4/5 and 2C8/9. Studies utilizing newly identified, highly prevalent, racially stratified SNPs and their impact on CYP isoform-specific metabolism will provide new answers.

Properties of a new acid-buffering bioadhesive vaginal formulation (ACIDFORM) ☆

Vaginal prophylactic methodology may prevent heterosexual transmission of the HIV and other sexually transmitted disease-causing organisms as well as unplanned pregnancies. A new delivery system (ACIDFORM) was designed with acid-buffering, bioadhesive, and viscosity-retaining properties to (1) maintain the acidic vaginal milieu (the low pH inactivates many pathogens and spermatozoa), (2) form a protective layer over the vaginal/cervical epithelium (minimizing contact with pathogenic organisms), and (3) provide long-term vaginal retention. A Phase I clinical study with ACIDFORM provided initial information about its safety and showed the formation of a layer over the vaginal/cervical epithelium [1; Amaral et al., Contraception 1999;60:361-6]. To study the properties of the gel (without active ingredient) in more detail, ACIDFORMs acid-buffering, bioadhesive, viscosity-retaining, and spermicidal properties were compared in vitro to marketed formulations, and its long-term stability was assessed. ACIDFORM, either when titrated with NaOH or when mixed directly with semen, is highly acid buffering and much more effective than Aci-Jel, a commercial acid-buffering vaginal product. ACIDFORM adheres well to two model membranes (excised sheep vagina and cellophane) and is more bioadhesive than Conceptrol, Advantage S, Replens, Aci-Jel, and K-Y jelly. On dilution, ACIDFORM also retains its viscosity better than these marketed products. ACIDFORM is spermicidal and is stable for at least 2 years. These results suggest that ACIDFORM has advantages over presently marketed vaginal delivery systems. The gel may either be useful by itself as an antimicrobial contraceptive product or as a formulation vehicle for an active ingredient with antimicrobial and/or contraceptive properties.

Candidate Sulfonated and Sulfated Topical Microbicides: Comparison of Anti-Human Immunodeficiency Virus Activities and Mechanisms of Action

ABSTRACT Poly(styrene 4-sulfonate), cellulose sulfate, polymethylenehydroquinone, and PRO 2000 are sulfated or sulfonated polymers (SPs) under development as topical microbicides. They are presumed to work through similar mechanisms of action, although to date there has been no extensive comparison of their anti-human immunodeficiency virus activities. To determine whether any of these candidate microbicides offers a potential advantage, their in vitro activities, mechanisms of action, stabilities in biological secretions, and toxicities were compared. All four compounds were found to be active against X4, R5, and dualtropic primary isolates and against X4 and R5 laboratory-adapted strains in CD4+ T cells, macrophages, and single-coreceptor cell lines. Our single-cycle experiments using pseudotyped virus suggest that all four SPs function at the binding and entry stages of the viral life cycle but differ in degree of postentry effect. Surface plasmon resonance analyses demonstrate that SPs bind to X4 and R5 monomeric glycoprotein 120 with similar high binding affinities. When mixed with cervicovaginal lavage fluid, SPs maintain inhibitory activity at concentrations achievable in formulations.

Candidate Topical Microbicides Bind Herpes Simplex Virus Glycoprotein B and Prevent Viral Entry and Cell-to-Cell Spread

ABSTRACT Topical microbicides designed to prevent acquisition of sexually transmitted infections are urgently needed. Nonoxynol-9, the only commercially available spermicide, damages epithelium and may enhance human immunodeficiency virus transmission. The observation that herpes simplex virus (HSV) and human immunodeficiency virus bind heparan sulfate provided the rationale for the development of sulfated or sulfonated polymers as topical agents. Although several of the polymers have advanced to clinical trials, the spectrum and mechanism of anti-HSV activity and the effects on soluble mediators of inflammation have not been evaluated. The present studies address these gaps. The results indicate that PRO 2000, polystyrene sulfonate, cellulose sulfate, and polymethylenehydroquinone sulfonate inhibit HSV infection 10,000-fold and are active against clinical isolates, including an acyclovir-resistant variant. The compounds formed stable complexes with glycoprotein B and inhibit viral binding, entry, and cell-to-cell spread. The effects may be long lasting due to the high affinity and stability of the sulfated compound-virus complex, as evidenced by surface plasmon resonance studies. The candidate microbicides retained their antiviral activities in the presence of cervical secretions and over a broad pH range. There was little reduction in cell viability following repeated exposure of human endocervical cells to these compounds, although a reduction in secretory leukocyte protease inhibitor levels was observed. These studies support further development and rigorous evaluation of these candidate microbicides.

In vitro spermicidal activity of gossypol

The in vitro spermicidal effect of gossypol, gossypol acetic acid and gossypol-polyvinylpyrrol idone was investigated. Gossypol-polyvinylmulations. Thus, gossypol in an appropriate chemical form may be useful as a spermicide.

Poly(Sodium 4-Styrene Sulfonate): An Effective Candidate Topical Antimicrobial for the Prevention of Sexually Transmitted Diseases

Presently marketed vaginal barrier agents are cytotoxic and damage the vaginal epithelium and natural vaginal flora with frequent use. Novel noncytotoxic agents are needed to protect women from sexually transmitted diseases. One candidate compound is a high-molecular-mass form of soluble poly(sodium 4-styrene sulfonate) (T-PSS). The antimicrobial activity of T-PSS was evaluated in primary culture systems and in a genital herpes murine model. Results obtained indicate that T-PSS is highly effective against herpes simplex viruses, Neisseria gonorrhoeae, and Chlamydia trachomatis in vitro. A 5% T-PSS gel protected 15 of 16 mice from vaginal herpes, compared with 2 of 16 mice treated with a placebo gel. Moreover, T-PSS exhibited little or no cytotoxicity and has an excellent selectivity index. T-PSS is an excellent candidate topical antimicrobial that blocks adherence of herpes simplex virus at low concentrations, inactivates virus at higher concentrations, and exhibits a broad spectrum of antimicrobial activity.

Efficacy and Safety of a New Vaginal Contraceptive Antimicrobial Formulation Containing High Molecular Weight Poly(Sodium 4-Styrenesulfonate)

Abstract Host cell infection by sexually transmitted disease (STD)-causing microbes and fertilization by spermatozoa may have some mechanisms in common. If so, certain noncytotoxic agents could inhibit the functional activity of both organisms. High molecular mass poly(sodium 4-styrenesulfonate) (T-PSS) may be one of these compounds. T-PSS alone (1 mg/ml) or in a gel (2% or 5% T-PSS) completely prevented conception in the rabbit. Contraception was not due to sperm cytotoxicity or to an effect on sperm migration. However, T-PSS inhibited sperm hyaluronidase (IC50 = 5.3 μg/ml) and acrosin (IC50 = 0.3 μg/ml) and caused the loss of acrosomes from spermatozoa (85% maximal loss by 0.5 μg/ml). T-PSS (5% in gel) also reduced sperm penetration into bovine cervical mucus (73% inhibition by 1 mg gel/ml). T-PSS (5% in gel) inhibited human immunodeficiency virus (HIV; IC50= 16 μg gel/ml) and herpes simplex viruses (HSV-1 and HSV-2; IC50 = 1.3 and 1.0 μg gel/ml, respectively). The drug showed high efficacy against a number of clinical isolates and laboratory strains. T-PSS (5% in gel) also inhibited Neisseria gonorrhea (IC50 < 1.0 gel/ml) and Chlamydia trachomatis (IC50 = 1.2 μg gel/ml) but had no effect on lactobacilli. These results imply that T-PSS is an effective functional inhibitor of both spermatozoa and certain STD-causing microbes. The noncytotoxic nature should make T-PSS safe for vaginal use. T-PSS was nonmutagenic in vitro and possessed an acute oral toxicity of >5 g/kg (rat). Gel with 10% T-PSS did not irritate the skin or penile mucosa (rabbit) and caused no dermal sensitization (guinea pig). Vaginal administration of the 5% T-PSS gel to the rabbit for 14 consecutive days caused no systemic toxicity and only mild (acceptable) vaginal irritation. T-PSS in gel form is worthy of clinical evaluation as a vaginal contraceptive HIV/STD preventative.

Methods in ethnopharmacology

A variety of pharmacological models are utilized in the evaluation of ethnomedicine. Most investigations are focused on developing new leads for therapeutic agents. However, there should be more efforts focused on the development of ethnomedicines because of their accessibility and acceptability in areas where modern medicine is not readily available. Testing methods to identify the active agents must be carefully selected utilizing information from ethnoanthropology, ethnobotany, phytochemistry, toxicology and pharmacology. New pharmacological models focused on cellular and molecular mechanisms can be used for ethnomedical evaluations but with great caution since they are based on known mechanisms of actions and limited by knowledge of the disease state.

Two Novel Vaginal Microbicides (Polystyrene Sulfonate and Cellulose Sulfate) Inhibit Gardnerella vaginalis and Anaerobes Commonly Associated with Bacterial Vaginosis

ABSTRACT This is the first report demonstrating the in vitro inhibitory activity of two novel microbicides (cellulose sulfate and polystyrene sulfonate) against bacterial vaginosis (BV)-associated bacteria. Vaginal application of these microbicides not only may reduce the risk of acquisition of human immunodeficiency virus and other sexually transmitted infection-causing organisms but may also decrease the incidence of BV.

Comparative in vitro spermicidal effects of (+)-gossypol, (+)-gossypol, (−)-gossypol and gossypolone

The comparative in vitro spermicidal effects of (+)-gossypol, (-)-gossypol and (+/-)-gossypol were evaluated on the spermatozoa of human, monkey, rabbit, mouse, rat and hamster. The spermicidal effects of gossypol isomers were also compared with those of gossypolone, which is a proposed major metabolite of gossypol. Gossypol isomers and gossypolone were all spermicidal. (+)- and (-)-Gossypol demonstrated spermicidal activities at the same concentration at which (+/-)-gossypol shows spermicidal effects on the spermatozoa of all species tested. However, gossypolone was less potent than the gossypol isomers. The spermicidal action of gossypol may be a nonspecific effect unrelated to the antifertility mechanism of orally administered gossypol, since (+)-gossypol which is not an effective male antifertility agent also showed the equivalent spermicidal effect to that of (+/-)-gossypol.