Molecular platforms for targeted drug delivery.

The targeted delivery of bioactive molecules to the appropriate site of action, one of the critical focuses of pharmaceutical research, improves therapeutic outcomes and increases safety at the same time; a concept envisaged by Ehrlich over 100 years ago when he described the "magic bullet" model. In the following decades, a considerable amount of research effort combined with enormous investment has carried selective drug targeting into clinical practice via the advent of monoclonal antibodies (mAbs) and antibody-drug conjugates derivatives. Additionally, a deeper understanding of physiopathological conditions of disease has permitted the tailored design of targeted drug delivery platforms that carry drugs, many copies of the same drug, and different drugs in combination to the appropriate site of action least selectively or preferentially. The acquired know-how has provided the field with the design rationale to develop a successful delivery system that will provide new and improved means to treat many intractable diseases and disorders. In this review, we discuss a wide range of molecular platforms for drug delivery, and focus on those with more success in the clinic, given their potential for targeted therapies.