We’ve all seen commercials for new drugs: ______ is the next big thing to treat ______, ask your doctor today! In the span of 30 seconds, the character on-screen goes from chronic suffering to laughing on a sunset hike. What these commercials don’t show is the journey that had to occur to bring this new wonder treatment into existence. Drug discovery can change lives, but it’s not always a simple process.
Identifying Potential Treatments
There are two common paths to initiating a drug discovery – drug first and disease first. For most of human history, new drugs have been discovered by investigating chemicals from natural sources, like plants and fungi.
Many drugs that have changed the world have come from drug first discovery, such as the antibiotic penicillin.
While new compounds are still being discovered in rare plants today, modern drug discovery commonly starts with the disease doctors hope to treat. Scientists work to understand diseases at the molecular level and predict how different compounds might affect the body. They can then chemically engineer molecules in the lab that they hope will behave as predicted in the body.
Unveiling How a Molecule Behaves in Cells
No matter how a molecule was isolated, the next step in drug discovery is testing how cells respond to it ex vivo, or outside the body. Scientists can usually guess how a molecule will impact a particular biological process, but it can be difficult to foresee all the potential interactions a candidate drug might have in a cell or body. Thus, it is critical to test would be future drugs in a manner that lets researchers observe exactly how the molecule impacts different cell types.
In recent years, advances in cell technology have made this part of the process more accurate for more parts of the body. Scientists can now grow many different kinds of cells and tissues in the lab to gain a comprehensive understanding of how a drug is likely to impact different organs under different conditions. From liver cells to heart muscle cells that actually beat, many critical human organs can be replicated in the lab, offering researchers a more in-depth view of how a drug will alter a patient’s body.
Pharmaceutical biologists use results from ex vivo trials to rule out poor drug candidates and tweak promising compounds to make them more effective and safer. Out of thousands of molecules that scientists create, only a few hundred will move on to the next stage.
Understanding How a Drug Impacts the Body
The next stage of drug discovery is in vivo animal trials, meaning trials in a living organism. Just as it can sometimes be difficult to predict how a drug will impact a cell even when you know how it will impact some biological processes, unexpected results can emerge when a drug circulates through a complex living system. For example, a drug may be safe for heart cells and liver cells in a dish but cause unwanted symptoms in the brain or lungs of a mouse. Animal trials help scientists determine how safe a candidate drug is and if there are any unforeseen complications that may make it a bad option for use in humans. They also help determine what dosages will work well in humans and if the drug is effective for mouse versions of a disease.
Only a handful of drugs do well enough in animal trials to continue to clinical trials.
Moving into Patients
When a drug is deemed safe in human cells grown in the lab and animals, it is considered safe enough to try in humans. The next stage of drug discovery is clinical trials, testing done in human patients. These trials are often run double-blind – half the patients receive an inactive placebo and half receive the drug, neither the patients or doctors monitoring them know which is getting which. This works to prevent bias in assessing how well a drug treats a disease and parse out if the drug performs better than a placebo.
Human trials are critical for determining if a candidate drug is effective enough to go to market and if there are any side effects that may not have been possible to detect in animals. If a drug is effective and side effects are not dangerous (or at least less dangerous than the disease being treated), it will proceed through legal and regulatory review before being distributed to the public. For every 5,000-10,000 potential drug candidates that start this process, only one or two will make it to pharmacy shelves.
An Ongoing Cycle
Drug discovery often takes 15-20 years from initial molecule discovery to being prescribed by doctors. Very few molecules that scientists dream up will eventually make it into patient hands. It may seem like a daunting task with little hope for reward. However, even research on compounds that don’t make it help illuminate different aspects of health and biology that improve future drug discovery. Iterations of drug testing in ex vivo models help researchers understand precisely how molecules interact in a cell, thus empowering them to design better molecules that are safer and more effective than past versions.
Drug discovery takes time and effort, but the results can change the world. The next time you see a commercial for the next big medication, know that over a decade of research went into bringing that drug to your screen.