Teaching the immune system what to fight - and what to spare

Two health announcements landed 48 hours apart last week, and hardly anyone connected them.

On Monday, the Emirates Drug Establishment approved a once-daily pill for non-segmental vitiligo, the condition that causes patches of skin to lose their colour. No regulator anywhere had licensed an oral treatment for these patients. The UAE went first.

On Wednesday, drug manufacturers Merck and Moderna said their experimental cancer vaccine had worked in a large late-stage trial in melanoma (a type of skin cancer). That is also a first. Nothing of its kind had ever cleared that hurdle.

What connects both stories is the immune system, which in one case attacks the wrong thing and in the other fails to attack the right one.

Vitiligo happens when the body destroys its own pigment-producing cells. Doctors have known this for years, but treatment has remained mostly surface-level, using creams, light therapy, or merely cosmetics. The pill approved in the UAE on Monday goes after the signaling that drives the attack. For a condition that affects roughly one person in a hundred and has no cure, that is not a small thing.

Mirror image

Cancer is the mirror image. Tumour cells are your own cells gone wrong, which is exactly why your immune system so often lets them pass. They carry the right identification.

So Merck and Moderna tried handing it a photograph.

Here is how it works. Surgeons remove the tumour. It is sequenced to identify the genetic errors that make those cells different from every other healthy cell in the body. Those errors are a fingerprint, unique to one tumour in one person. The vaccine carries that fingerprint back into the patient as a set of instructions: find these cells and remove them.

In a trial of more than 1,100 patients whose skin cancer had been removed but was likely to return, the vaccine plus an existing cancer drug delayed recurrence and cut the chance of the cancer spreading. No new safety problems turned up.

Read that again and notice what is strange about it. Every medicine you have ever swallowed was designed for a category of person or disease. This one is built for a person. The batch size is one.

Running logic backward

Some caution is warranted, because the coverage this week has been giddy. The companies put out a summary, not the full results. We do not know yet how long patients stayed cancer-free, and whether they live longer is still being measured. This is also one cancer. Trials are running in lung, bladder, and kidney cancers, but they are not yet finished.

The more interesting question is what happens when you run the logic backward.

If you can teach the immune system to spot something it has been ignoring, can you teach it to ignore something it has been attacking? Researchers are trying. The working name is inverse vaccines, and the goal is tolerance to one specific target rather than a general dampening of the whole system. Early versions have calmed a multiple-sclerosis-like disease in animals. Work is underway on celiac disease, type 1 diabetes, and rheumatoid arthritis, often at the same companies.

That would be a real improvement on what we have. Today’s autoimmune drugs, including the one approved on Monday, turn the immune system’s volume down. It works, and for many patients it works well. But a quieter immune system is also a less watchful one, and patients pay for that.

There will be more research into what exactly causes a specific autoimmune disease in the human body. Once these triggers are fully understood, a remedy for it can be developed.

None of this will reach patients next month. But something has shifted, and both announcements show it. Medicine has spent a century getting better at identifying a patient’s disease. It is now starting to ask what the patient’s own immune system can be trained to do about it.

Frederik Cyrus Roeder is a health economist and writer based in Dubai