BREAKING: $MRNA is up 112% in premarket after the first ever positive Phase 3 results for a personalized cancer vaccine. Moderna and Merck ran the trial together. $MRK is also up 9% on the news. Doctors take a sample of the patient's tumour and read its DNA. Every tumour has its own set of mutations. They then build a custom mRNA shot for that one person, which teaches the immune system what to hunt for. The trial covered 1,137 melanoma patients. Those who got the shot alongside Keytruda saw the cancer come back less often than those who got Keytruda alone. No new safety problems were found. Keytruda is the current standard treatment and brought Merck $8 billion in a single quarter. This is the first time anything has improved on it. The shot does not replace Keytruda, it is added on top. Nine trials are running across other cancers including lung, bladder and kidney.