Overview of Present Problems Facing Commercialization of Nanomedicines

Abstract

A critical review is attempted to assess the status of nanomedicine entry onto the market.

The emergence of new potential therapeutic entities such as DNA and RNA fragments requires that these new “drugs” will need to be delivered in a cell-and organelle-specific manner. Although efforts have been made over the last 50 years or so to develop such delivery technology, no effective and above all clinically approved protocol for cell-specific drug delivery in humans exists as yet. Various particles, macromolecules, liposomes and most recently “nanomaterials” have been said to “show promise” but none of these promises have so far been “reduced” to human clinical practice.

The focus of this volume is on cancer indication since the majority of published research relates to this application; within that, we focus on solid tumors (solid malignancies). Our aim is to critically evaluate whether nanomaterials, both non-targeted and targeted to specific cells, could be of therapeutic benefit in clinical practice. The emphasis of this volume will be on pharmacokinetics (PK) and pharmacodynamics (PD) in animal and human studies.

Apart from the case of exquisitely specific antibody-based drugs, the development of target-specific drug–carrier delivery systems has not yet been broadly successful at the clinical level. It can be argued that drugs generated using the conventional means of drug development (i.e., relying on facile biodistribution and activity after (preferably) oral administration) are not suitable for a target-specific delivery and would not benefit from such delivery even when a seemingly perfect delivery system is available. Therefore, successful development of site-selective drug delivery systems will need to include not only the development of suitable carriers, but also the development of drug entities that meet the required PK/PD profile.

In general, human clinical studies are approved only after the expected benefits of targeting have been shown in pre-clinical, in vivo animal studies first. Therefore, quantitative data on biodistribution of targeted and non-targeted nanoparticles should be generated as the first step. This should be followed by determining whether an increased presence of nanoparticles in tumors also results in increased concentration of the free drug within the tumor space. Any “promise” for reproducing similar data in human clinical studies should be supported by relevant scaling from the animal model used to humans.

For too long now, the same or similar approaches have been used by researchers without success. We believe that new fundamentally different approaches are needed to make cell-specific drug delivery clinical reality. In this volume we want to focus on (a) how nanoparticles could be redesigned from the material-science point of view (for example, redesigning nanoparticles for long-circulating properties, passive (EPR) and active targeting concept); and (b) on the design and properties of drugs that would benefit from cell-specific targeting (examining why active targeting of drug carrier does not necessarily result in drug accumulation in tumor). Further, we will draw attention to (c) the manner pre-clinical animal data should be translated to humans using appropriate scaling, in particular with reference to the differences between mice and men in terms of differing vascular morphology and immunological background.

Successful development of cell-specific drug-delivery systems requires that reliable quantitative pharmacokinetic/pharmacodynamic (PK/PD) data are collected both in animal and human studies. This volume will include (d) information on improved body imaging technologies and on enabling quantitative tools available.

Finally, we address (e) the issue of diminishing academic funding of animal studies and of (f) the current dismal market and proprietary situation in the area of site-specific drug delivery.