Alternatives to antibiotics-a pipeline portfolio review.

Antibiotics have saved countless lives and enabled the development of modern medicine over the past 70 years. However, it is clear that the success of antibiotics might only have been temporary and we now expect a long-term and perhaps never-ending challenge to find new therapies to combat antibiotic-resistant bacteria. A broader approach to address bacterial infection is needed. In this Review, we discuss alternatives to antibiotics, which we defined as non-compound approaches (products other than classic antibacterial agents) that target bacteria or any approaches that target the host. The most advanced approaches are antibodies, probiotics, and vaccines in phase 2 and phase 3 trials. This first wave of alternatives to antibiotics will probably best serve as adjunctive or preventive therapies, which suggests that conventional antibiotics are still needed. Funding of more than £1·5 billion is needed over 10 years to test and develop these alternatives to antibiotics. Investment needs to be partnered with translational expertise and targeted to support the validation of these approaches in phase 2 trials, which would be a catalyst for active engagement and investment by the pharmaceutical and biotechnology industry. Only a sustained, concerted, and coordinated international effort will provide the solutions needed for the future.

Antibiotics: the changing regulatory and pharmaceutical industry paradigm.

Drug licensing is changing. Previously, regulators prioritized the licensing of innovative drugs that fulfilled a high unmet medical need for a small number of patients, including orphan, cancer and HIV medicines. Alternatives to large and costly prospective, randomized, double-blind clinical trials have led to a more bespoke development, such as adaptive design studies. Regulators have recently agreed to include much-needed narrow-spectrum antibiotics, active against certain MDR bacteria, in this paradigm. The background to why big pharmaceutical companies have largely deserted the antibacterial research arena, and the proposals that are hoped to reinvigorate their interest, are presented.

Introduction to antibiotic resistance.

The inexorable rise in multidrug-resistant Gram-negative bacteria has been widely reported. Multiple modes of resistance often present in a single strain of bacteria, and this may also be combined with an increase in virulence, both of which are leading to a significant increase in morbidity and mortality in patients. Against this background, the absolute number of new antibiotics licensed has declined especially for Gram-negative multidrug-resistant pathogens. The reasons for this failure are presented here: market issues, big pharma changes, regulatory constraints, difficulties in finding drugable targets and, lastly, suitable compounds worthy of full development.

Challenges in developing new antibacterial drugs.

Regulatory guidelines for clinical development of antibacterial drugs have a major impact on decisions regarding research, influencing the degree to which novel targets are pursued, the choice of lead compounds, the spectrum of activity, as well as the dose. It is disconcerting that as pharmaceutical firms abandon antibacterial research and development, and expertise is lost from clinical, regulatory and commercial functions, biotechnology firms focus on easier, Gram-positive targets, which require limited clinical development, and expect pharmaceutical firms that have retreated from antibacterials to in-license compounds with restricted uses. Guidelines and incentives are needed to encourage development of agents targeted against the growing problem of Gram-negative bacterial resistance, as broad-spectrum drugs face even greater hurdles.

Development of a twice daily dosing regimen of amoxicillin/clavulanate.

Amoxicillin/clavulanate was first launched as a three times daily dosage for the treatment of a range of community-acquired infections. A decade later, it became necessary to introduce a twice daily dosage for reasons of convenience, compliance and to remain competitive with other recently launched antibacterials. Twice daily formulations of amoxicillin/clavulanate were developed in which the amount of amoxicillin was increased relative to clavulanate to provide equivalent bacteriological and clinical efficacy with no change in the safety profile. Equivalence of the two dosing regimens was confirmed by randomised clinical trials in adults (in skin and soft tissue, urinary tract and lower respiratory tract infections, sinusitis and recurrent tonsillitis) and paediatrics (in lower respiratory tract infections, otitis media and recurrent tonsillitis). An improvement in the safety profile, specifically gastrointestinal effects, due to the reduced daily dose of clavulanate, was noted for all patients, but particularly in children.

Male tolerance study of 1% C31G.

BACKGROUND: C31G is being studied as a vaginal contraceptive and microbicide. This study was conducted to ensure that male partners of the women in future trials of C31G will not be subjected to an undue risk of penile irritation. METHODS: This was a randomized, double-blinded, single-center Phase I study in circumcised and uncircumcised men to assess penile irritation, safety and acceptability of seven consecutive daily doses of 1.0% C31G compared with a marketed spermicide, Extra Strength Gynol II(R) (3% nonoxynol-9) (ES Gynol II). Each participant was instructed to apply the study product to his penis at bedtime, to wash it off 6-10 h later, and to record any symptoms on a diary card. At the follow-up visit, a genital examination was performed and participants were again asked about adverse events and to complete an acceptability questionnaire. RESULTS: Of the 36 men enrolled, 12.5% of C31G users and 16.7% of Extra Strength Gynol II users reported product-related adverse events (AEs). All product-related AEs were considered mild by the investigator, except for one in the ES Gynol II group. Both products were acceptable. CONCLUSION: The manner in which the products were used in this study is not the route by which men will be exposed to such products in actual use, and results should be considered in this light. Based on the observations in this study, C31G appears to be at least as safe and acceptable for male penile exposure as the marketed product ES Gynol II.

A phase I comparative postcoital testing study of three concentrations of C31G.

BACKGROUND: C31G is a broad-spectrum antibacterial agent that shows contraceptive properties in vitro. This postcoital testing study evaluated the ability of three C31G concentrations, 0.5%, 1.0% and 1.7%, administered as a 3.5-mL dose of a vaginal gel to prevent sperm from entering mid-cycle cervical mucus. Irritation of the genitalia and acceptability were also assessed. METHOD: At baseline, a mid-cycle cervical mucus test and a postcoital test were performed within 24 h of each other without use of any study products to establish normal mid-cycle cervical mucus and sperm penetration. Subjects then completed up to three test cycles using one of the three concentrations of study product during intercourse. RESULTS: Twenty-two of the 61 women enrolled completed a baseline cycle and at least one test cycle. An average of 14.6 progressively motile sperm per high power field was seen at baseline. This was reduced to 0.3 after use of 0.5% C31G, 0.5 after use of 1.0% C31G, and 0.4 after use of 1.7% C31G. There was no significant difference between test products (p >/= 1.000) but each test product was significantly different from baseline (p < 0.002). Very little genital irritation was observed. There were more reports of leakage and messiness with increasing C31G concentration. CONCLUSION: This study suggests that all three concentrations of C31G are likely to give reasonable results in a contraceptive effectiveness trial. Based on the results of this and other trials, the 1.0% concentration has been selected for further development, including Phase III trials of contraceptive effectiveness.

A randomized Phase I vaginal safety study of three concentrations of C31G vs. Extra Strength Gynol II.

BACKGROUND: C31G is an antimicrobial and spermicidal agent that contains two surface-active compounds, cetyl betaine and myristamine oxide. It is being developed as a vaginal microbicide and contraceptive. METHOD: Three C31G concentrations (0.5%, 1.0% and 1.7%) were tested and compared with Extra Strength Gynol II(R), a marketed spermicide containing 3% nonoxynol-9 (N-9), in a randomized, double-blinded, Phase I, dose-escalation study to assess genital irritation (by subject report, visual examination at pelvic examination and colposcopy), plasma and vaginal lavage levels of C31G, product leakage, systemic safety and acceptability. Women were randomized to use 3.5 mL of one of the three C31G products or the N-9 gel at night for 7 days then twice daily for another 7 days. Pelvic and colposcopic evaluations were performed after 7 and 14 days of product use. RESULTS: The percent of women experiencing irritation in the 0.5% and 1.0% C31G groups in the study were similar to each other and were lower than the percent experiencing irritation in the 1.7% and N-9 groups, which were also similar to each other. Differences were statistically significant between 1.0% C31G vs. N-9 at 7 days and between 0.5% C31G and 1.0% C31G vs. N-9 at 14 days. There was no significant difference between groups in leakage or acceptability. No C31G was detected in the plasma of any volunteer. CONCLUSIONS: These results suggest that 0.5% and 1.0% C31G are less irritating to the female genital tract than 1.7% C31G or Extra Strength Gynol II.

The future challenges facing the development of new antimicrobial drugs.

The emergence of resistance to antibacterial agents is a pressing concern for human health. New drugs to combat this problem are therefore in great demand, but as past experience indicates, the time for resistance to new drugs to develop is often short. Conventionally, antibacterial drugs have been developed on the basis of their ability to inhibit bacterial multiplication, and this remains at the core of most approaches to discover new antibacterial drugs. Here, we focus primarily on an alternative novel strategy for antibacterial drug development that could potentially alleviate the current situation of drug resistance--targeting non-multiplying latent bacteria, which prolong the duration of antimicrobial chemotherapy and so might increase the rate of development of resistance.