The future of medical drugs will largely involve the manufacture of proteins that precisely interact with our biochemistry to achieve specific effects. They will either be existing proteins with a role in regulating metabolism, stem cell activity, immune cell response, and so on, or they will be entirely new nanomachinery intended to produce results that our biology cannot achieve on its own, such as the effective destruction of harmful waste products, for example. These designed proteins will be delivered the old-fashioned way, via injection, for a good many years yet. Ultimately, however, managing the manufacture and the timing and location of protein delivery will move into the body under the control of sophisticated tiny factory machines - mass-produced entities that will in fact bear a great deal of resemblance to cells.
What is a cell, after all, but a flexible protein factory that manages its output in response to the surrounding environment? Why reinvent the wheel when a perfectly functional version is right there to be reverse engineered? Or used as-is, for that matter: present day stem cell therapies are just like future treatments that will deliver tiny mobile drug factories into a patient's tissues. Today's crude cell therapies appear to work because the newly introduced cells are, for a short time at least, manufacturing proteins that change the behavior of local cells. This is a little bit of the future made possible by harnessing existing biological machinery. Researchers can even reach beyond the use of plain cells today, such as by altering stem cells to generate specific desired compounds:
[Researchers] used adult stem cells from human bone marrow and genetically engineered the cells to produce compounds called growth factors that can support damaged nerve cells. The researchers then implanted the cells directly into the muscles of rats that were genetically modified to have symptoms and nerve damage resembling ALS.
In people, the motor neurons that trigger contraction of leg muscles are up to three feet long. These nerve cells are often the first to suffer damage in ALS, but it's unclear where the deterioration begins. Many scientists have focused on the closer end of the neuron, at the spinal cord, but [others] observes that the distant end, where the nerve touches and activates the muscle, is often damaged early in the disease. "We know that the neuro-muscular junction is a site of early deterioration, and we suspected that it might be the villain in causing the nerve cell to die. It might not be an innocent victim of damage that starts elsewhere."
The injected stem cells survived for at least nine weeks, but did not become neurons. Instead, their contribution was to secrete one or both growth factors. "These motor nerve cells have extremely long connections, and replacing these cells is still challenging. But we aim to keep the neurons alive and healthy using the same growth factors that the body creates, and that's what we have shown here."
Cells and cell-like entities are steadily on their way to becoming the dominant tools of medicine. The more that researchers know about cells, the more useful they become in this role. Programmable protein factories in the form of cells or pseudo-cells will ultimately take over from the direct delivery of designed protein machinery in the same way that the creation of designed protein machinery will soon replace the old-fashioned and haphazard process of discovering and testing naturally occurring drugs. This is progress.