Why the hardest part of medicine is getting the drug there
A drug that never reaches its target is just a molecule. Here is what I’m testing to change that.
Dr. Younes MedkourOctober 2026 · 7 min read
Most people think the hard part of medicine is finding a drug that works. Often it isn't. Many drugs work well in a dish and fail in the body, because too little reaches the cells that need it, and too much reaches the cells that don't.
Chemotherapy is the classic example. Many chemotherapy drugs kill cancer cells, but they also damage healthy tissue, including the heart. The drug is not the problem. The delivery is.
A delivery system the body already uses
Our cells constantly release extracellular vesicles: tiny bubbles of membrane that carry proteins and RNA from one cell to another. They are how cells send messages. Because the body already makes them, they may be able to carry drugs past defenses that stop synthetic particles.
- 1. LoadPack a drug or other molecule into the vesicle.
- 2. MeasureCheck that the cargo reaches cells and works.
- 3. Check safetyMake sure the immune system tolerates it.
In my work, I develop vesicle carriers: EVX-1, for chemotherapy, and ProbioVesicle, probiotic yeast vesicles carrying anti-aging actives. With EVX-1, we test how well it kills aggressive breast cancer cells. In parallel, I test their immunogenicity, how human immune cells respond to them. If a carrier triggers the immune system, it can't be used in people, however well it delivers.
The drug is not the problem. The delivery is.
A carrier that works in a dish still has a long road ahead. It has to be made the same way every time, in large enough amounts, and it has to behave the same way in an animal as it does in a cell. Each of those steps filters out most candidates.
What I look for in a carrier
When I evaluate a delivery system, I ask four questions. Can it be loaded efficiently, without damaging the cargo? Does it reach the cells that need the drug, and fewer of the cells that don’t? Once inside, does the cargo still do its job? And does the immune system leave the carrier alone, the first time and the tenth time?
Most candidates fail at least one of these. Synthetic particles are often easy to make but get recognized and cleared. Natural vesicles are better tolerated, but harder to produce consistently. The work is in finding the version that passes all four, and proving it with data rather than hope.
That is the logic behind the two carriers I work on now: EVX-1, for chemotherapy, and ProbioVesicle, probiotic yeast vesicles carrying anti-aging actives. Different cargo, same four questions.
That is why I care as much about safety as about potency. A delivery system the body already recognizes could make old drugs safer and new ones possible. The question I keep coming back to is simple: can we send the right molecule to the right cell, and nowhere else?