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Merck and Moderna's cancer vaccine works. Making it affordable is the next test

Merck and Moderna build a custom mRNA vaccine for each melanoma patient from tumor mutations. The strategy stumbles in cancers lacking enough targets

Pavlo Gonchar / SOPA Images / LightRocket via Getty Images

When Merck $MRK and Moderna $MRNA reported in August that their melanoma treatment had succeeded in a large late-stage human trial, they cleared a bar that had teased researchers for years. It's the first cancer vaccine made to order that keeps cancer from coming back. Each of the 1,137 patients in their trial got a different drug — a vaccine built from the mutations found inside their own tumor — and the combination kept patients cancer-free longer than standard treatment.

"An important thing we've learned through cancer genomics is that every patient's genetic profile of their cancer is different, even if two patients have the same type of cancer," Jane Healy, who leads early clinical development in oncology at Merck, told Drug Discovery Trends. "A patient with melanoma is different from another patient with melanoma, even though they are diagnosed with the same disease."

The production pipeline begins in the operating room and the pathology lab. After a surgeon removes the patient's tumor, technicians take a piece of its tissue, draw a sample of the patient's blood, and run next-generation sequencing on both. Comparing the two lets scientists subtract out the person's normal, inherited DNA and isolate only the changes the cancer itself created. The mutations produce proteins the body has never seen and might learn to attack.

Those mutations number in the thousands, and most of them will never provoke an immune response, so a piece of software has to sort them. Moderna's prediction software scores each mutation by how likely that patient's own immune system is to recognize it, then narrows the candidates down to the 34 with the best odds........

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