DNAJB1-PRKACA peptide vaccine (NCT04248569)

Most liver cancer is the end of a long story. Decades of hepatitis, or alcohol, or fatty liver, scarring the organ until something breaks.

Fibrolamellar carcinoma is not that story. It turns up in teenagers and young adults with healthy livers and no risk factors at all. In this trial the median age was twenty-four, and the youngest patient twelve. It is rare: recent work estimates about six hundred new cases a year in the United States. Surgery can cure it, if the whole tumor can be removed. If it cannot, there is no standard drug treatment, and half of those patients live about a year.

But this cancer has an unusual feature. Its cause is known, and it is a single event.

In twenty fourteen, researchers sequenced these tumors and found that a stretch of chromosome nineteen, about four hundred thousand letters long, had gone missing. The deletion pulled two neighboring genes together and fused them into one. One makes a chaperone, a protein that helps other proteins fold. The other makes the working half of an enzyme called protein kinase A. Joined, they make a hybrid that still works as an enzyme, and that hybrid drives the cancer. It was in all fifteen tumors they examined, and in none of the normal liver beside them.

So block the hybrid enzyme. That was the obvious move, and it failed. Protein kinase A is essential everywhere in the body, and the drugs were too toxic to use. The field called the target undruggable.

Which leaves a different approach. Do not attack the protein. Point at it.

Where the two genes join, the protein has a seam, a short run of amino acids that exists in no healthy cell in the body. To the immune system, that seam looks foreign. So the vaccine in this trial is simply that seam. A peptide twenty-four amino acids long, made in a lab, injected under the skin alongside something that tells the immune system to pay attention.

Two things make this seam remarkable. The tumor cannot drop it, because it is the engine. And because the break always falls in the same place, the seam is identical from patient to patient. One vaccine fits everyone with this disease.

The vaccine raises T cells. A tumor can still switch them off, so it is given with two antibodies, nivolumab and ipilimumab, that release the brakes on T cells.

The first results came out in twenty twenty-five. Sixteen patients enrolled and twelve finished the vaccine course. Nine of the twelve developed T cells that recognized the seam, where only one had them at the start. Nine had their disease held in check, and three tumors shrank by at least a third. Every patient who responded also developed those T cells, which is the link the trial was built to test. A thirteen-year-old was still responding after two years. Side effects were mostly sore injection sites, headache and fatigue, though about a third of patients had a more serious reaction to the antibodies.

And when the cancer did escape, the tumor had not hidden the seam. The T cells had worn out, which is a different and more tractable problem.

The trial continues at Johns Hopkins, led by Mark Yarchoan, and now includes other cancers that carry the same fusion.

Everything in this film comes from the published record, and it is not medical advice.