Future prospects and perspectives on microbicides.

As 'proof of concept' has now been well validated for topical microbicides, the progress has, appropriately, refined the questions of who, how, when and at what risk and cost. These are welcome challenges requiring intensified, cross-disciplinary responses. This is especially true in the areas of adherence and pharmacokinetic/pharmacodynamics (PK/PD) sampling and modeling to optimize preventive trials measuring "efficacy", which is well known to reduce when measured as "effectiveness" in real-world use. Intensified exploratory and Phase 1 safety trials to investigate acceptability, adherence, PK and ex vivo efficacy with drug-exposed tissue biopsies/compartment fluids even though they are complex in design, management, assays and monitoring are moving forward As well, great strides in recent efforts in a variety of delivery formulations are promising. These current and future efforts will provide potential insights earlier that at Phase IIb or III in the development pipeline.