Personalized cancer vaccines are now real

Researchers have spent decades trying to develop personalized cancer vaccines, and last week, the first one succeeded. It’s called intismeran autogene (mouthful), was developed by Moderna and Merck, and involves sequencing melanoma patients’ cancer mutations, creating a custom mRNA to target them, and delivering the vaccine to stop the cancer recurring. The news came as the drug passed its interim goal in a phase three trial, where it was given to people with high-risk resected melanoma.

It led to Moderna’s stock jumping 177%, which was apparently the largest one-day gain by any S&P 500 stock this century. I found the size of the surge surprising because you could have already been fairly confident that the drug would succeed since at least June: as I wrote in an earlier post, the company presented data from their phase 2b trial at an oncology conference almost three months ago, which showed a 49% reduction in the risk of recurrence or death (p = 0.0075). But, according to financial analysts, the huge market reaction was probably down to a short squeeze and the belief that mRNA could be a more widely useful platform to develop other cancer vaccines too.

That makes sense, but it’s worth knowing that melanoma is a much easier disease to develop cancer vaccines for than others. It carries a very high number of mutations, so you have thousands of possible ‘neoantigens’ to select from and can choose those that look strong on many measures, but this isn’t the case for many cancers. Many cancers have far fewer mutations to select from, and it’s currently hard to predict whether their mutations will be displayed or measure which ones actually are displayed.

But very few people thought this attempt would work either, until recently. According to a very interesting new STAT article detailing how this cancer vaccine came about, Moderna’s own executives didn’t expect it would work until 2023; it first entered clinical trials in 2017. In case you’re interested in more about personalized cancer vaccines, I’ll once again recommend this great podcast episode, How to design a cancer vaccine, hosted by Owl Posting and featuring Alex Rubinsteyn and Benjamin Vincent, two scientists whose work focuses on cancer immunology and vaccines.