Targeted Drug Delivery - Current State
After more than 100 years, the concept of targeted drug delivery isn’t merely a dream, it has become reality. Nowadays, clinically approved application of targeted drug therapy has become an integral part of cancer therapy. Targeted drug delivery relies on the release of therapeutic agents in a controlled manner to a certain site of the body, such as cancer cells. This can reduce systemic side effects due to lower overall concentration of the drugs in the whole body. Increasing the drug concentration only in the affected tissue, results in the improvement of the efficacy of the treatment2.
Drug targeting requires the drug to fulfill certain criteria such as physicochemical stability in vivo, predictable concentration on the target site and specific binding to the target6,7. Controlled drug delivery can increase patient compliance and the patients’ quality of life and survival outcome8.
Until now, clinically approved agents used in targeted drug delivery are either humanized monoclonal antibodies also known as drug conjugated antibodies (ADCs) or small molecules, which activate immune cells to kill the targeted cells or activate apoptotic pathways through receptor binding9–11. Humanized monoclonal antibodies target specific antigens found on cancer tissue and thus, deliver conjugated cytotoxic agents to cancer cells. However, ADCs and small molecules such as peptides are subjected to renal clearance and enzymatic degradation in the human body thus, hampering their efficacy and requiring continuous administration12 To address those issues, some drugs must be conjugated to a vector or additional compounds in order to prevent degradation and to enhance solubility13,14,15.
Figure 1. Antibody drug conjugates.
An antibody facilitates the targeting of disease-associated antigens. When linked to a cytotoxic agent antibody drug conjugates enable to specifically target affected cell.
Figure 2. Nanoparticles in targeted drug delivery.
Polymer-based nanoparticles offer the advantage of carrying multiple functionalities increasing their flexibility for various applications.
6-mercaptopurine is the active compound that kills all proliferating cells, and thus dampens the immune system in the complete body causing the severe symptoms as mentioned before. Even worse, being a modifiying DNA agent it is regarded as a carcinogen.
Using this established probiotic as a carrier, makes it unlikely that the carrier causes side effects, such as inflammation. The potential use of targeted drug delivery in other medical fields than cancer therapy is promising. A method to deliver drugs in other chronic diseases has yet to be developed.
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