2-Heptyl-4-hydroxyquinoline (HHQ) and Pseudomonas quinolone signal (PQS) are involved in the regulation of virulence factor production and biofilm formation in Pseudomonas aeruginosa. PqsD is a key enzyme in the biosynthesis of these signal molecules. Using a ligand-based approach, we have identified the first class of PqsD inhibitors. Simplification and rigidization led to fragments with high ligand efficiencies. These small molecules repress HHQ and PQS production and biofilm formation in P. aeruginosa. This validates PqsD as a target for the development of anti-infectives.

This paper summarises the proceedings of a recent workshop which brought together pharmaceutical scientists and dermatologists from academia, industry and regulatory agencies to discuss current regulatory issues and industry practices for establishing therapeutic bioequivalence (BE) of dermatologic topical products. The methods currently available for assessment of BE were reviewed as well as alternatives and the advantages and disadvantages of each method were considered. Guidance on quality and performance of topical products was reviewed and a framework to categorise existing and alternative methods for evaluation of BE was discussed. The outcome of the workshop emphasized both a need for greater attention to quality, possibly, via a Quality-By-Design (QBD) approach and a need to develop a "whole toolkit" approach towards the problem of determination of rate and extent in the assessment of topical bioavailability. The discussion on the BE and clinical equivalence of topical products revealed considerable concerns about the variability present in the current methodologies utilized by the industry and regulatory agencies. It was proposed that academicians, researchers, the pharmaceutical industry and regulators work together to evaluate and validate alternative methods that are based on both the underlying science and are adapted to the drug product itself instead of single "universal" method.

In order to improve the therapeutic index of adapalene, a new drug under development for the treatment of acne, site-specific delivery to the hair follicles using 50:50 poly(DL-lactic-co-glycolic acid) microspheres as particulate carriers was investigated in vitro and in vivo. The percutaneous penetration pathway of the microspheres was shown to be dependent on their mean diameter. Thus, after topical application onto hairless rat or human skin, adapalene-loaded microspheres (5-microns diameter) were specifically targeted to the follicular ducts and did not penetrate via the stratum corneum. The in vitro release of adapalene from the microspheres into artificial sebum at 37 degrees C was controlled and faster than the in vivo sebum excretion in humans. Aiming to reduce either the applied dose of drug or the frequency of administration, different formulations of adapalene-loaded microspheres were evaluated in vivo in the rhino mouse model. A dose-related comedolytic activity of topical formulations of adapalene-loaded microspheres was observed in this model. Furthermore, by applying a site-specific drug delivery system (0.1% adapalene) every other day or by administering a 10-fold less concentrated targeted formulation (0.01%) every day, a pharmacological activity equivalent to a daily application of an aqueous gel containing drug crystals (0.1% adapalene) was observed. Since an aqueous gel containing 10% adapalene-loaded microspheres was not irritating in a rabbit skin irritancy test, this formulation was applied onto forearms of human volunteers. Site-specific drug delivery was further evidenced by follicular biopsy. Since an aqueous gel containing 10% adapalene-loaded microspheres was not irritating in a rabbit skin irritancy test, this formulation was applied onto forearms of human volunteers. Site-specific drug delivery was further evidenced by follicular biopsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Trifarotene is a new drug with retinoic acid receptor activity and selectivity for retinoic acid receptor-γ. The reported studies aimed at assessing the clinical pharmacology and safety of trifarotene. The clinical pharmacology of topical trifarotene up to 100 µg/g was extensively investigated through 2 maximal usage pharmacokinetic trials (MUsT) conducted in adult (ࣙ18 years) and pediatric patients (9-17 years) with moderate to severe acne and two studies conducted in healthy volunteers: 1 thorough QT C study and 1 drug-drug interaction study with concomitantly administered oral levonorgestrel (0.15 mg)/ethinyl estradiol (0.03 mg). Safety assessments included adverse event reporting and assessment of erythema, scaling, dryness, and stinging/burning using a scale from 0 = none to 4 = severe, as well as the evaluation of the systemic safety of trifarotene through routine laboratory testing. Systemic absorption of trifarotene was generally unquantifiable in the target population, especially when applied at 50 µg/g. QT C investigations did not show any risk of cardiovascular health issues; trifarotene did not reduce the systemic exposure to oral contraceptives such as levonorgestrel/ethinyl estradiol. Safety analyses did not show local or systemic safety concerns with trifarotene up 100 µg/g, a dose twice as high as the intended market dose. Results showed that trifarotene 50 µg/g cream is well tolerated and safe, even when applied under maximized conditions in adults and pediatric acne patients presenting with severe acne. Daily use of trifarotene 50 µg/g cream was not associated with cardiovascular effects and did not result in drug-drug interaction in women of childbearing potential using oral contraception.