Development of Pilosebaceous Unit-Targeted Drug Products

The present chapter outlines the rationale, advances, methods, and product development processes of pilosebaceous unit (PSU)-targeted topical drug products. Since the anatomic structure of the pilosebaceous unit provides a possible pathway for targeted drug delivery into hair follicles and sebaceous glands, significant progress has been made in the area of PSU-targeted drug delivery over past 20 years. Discovery of new chemical entities (NCEs) targeting the PSU is being explored in part because the physical/chemical properties of NCEs are not ameniable for transepidermal penetration. As a formulation approach, micro-/nanoparticulate systems, micro-/nanovesicular systems, and excipients enhancing follicular delivery have been widely investigated for PSU-targeted drug delivery. Several dermal products with these micro-/nanostructures are commercialized for possible enhancement of follicular delivery. Product development process pathways are illustrated using a stage-dependent approach. Considering the complexity, rate of success, cost, and time, product development strategy for NCEs are significantly different from that for an existing drug molecule. The methods for the characterization, testing, quality control of dermal products, and in vitro and in vivo models for nonclinical development are also summarized in the present chapter. Despite substantial advances in the science and technology, it is still challenging to develop commercial prescription (Rx) products based on PSU-targeted mechanisms.