Moderna shares fell as much as 25% on Thursday after partial data on its closely watched cancer vaccine, developed with Merck, leaked ahead of the planned full release.
The drop came even though the complete results, published later that day, looked positive both for patients and against Wall Street's expectations. The personalised vaccine, known as intismeran autogene, was tested alongside Merck's immunotherapy Keytruda. In certain melanoma patients, the combination cut the risk of recurrence or death by 42% compared with Keytruda alone, and the risk of the cancer spreading to distant parts of the body, or death, by 38%. About 82% of patients who received the vaccine with Keytruda were alive without their melanoma returning two years on, compared with 70% of those given only the immunotherapy.
Hussein Tawbi, a melanoma expert and trial investigator at the University of Texas MD Anderson Cancer Center, called the results a major development for patients, and said the added benefit came with much milder side effects, such as injection-site pain, than other cancer treatments.
The phase 3 trial results, reported by CNBC, were due to be presented at the European Society for Medical Oncology conference this weekend. Dean Li, president of Merck Research Laboratories, said ahead of the release that adding a therapy on top of something that already works well, like Keytruda, can make extra benefit hard to show, but that they had no trouble doing so here.
The benefit looked larger still after the six-month vaccine regimen, with a separate analysis pointing to a 58% reduction in the risk of recurrence or death. The companies say it is too early to tell whether the treatment helps patients live longer overall.
Several analysts pointed to high expectations ahead of the release. BMO Capital Markets analyst Evan Seigerman called the relative reduction clinically meaningful and said the share reaction likely reflected inflated hopes rather than any genuine problem with the therapy. UBS analysts also described it as a strong data set, giving more confidence in upcoming studies of the vaccine in kidney and bladder cancers.
The vaccine targets the specific mutations in each patient's tumour, training the immune system to recognise and attack those markers, with Keytruda helping the body go after the cancer more effectively. Merck and Moderna are studying it across other tumours, including non-small cell lung cancer, bladder cancer and renal cell carcinoma, though Li acknowledged there is more to prove across tumour types. He likened progress to building a log cabin, saying they had knocked down one tree, which does not yet make a cabin or a village.
For Moderna, the shot could add a key commercial product beyond its Covid-19, flu and respiratory syncytial virus vaccines. Its shares have risen more than 530% so far this year as of Thursday afternoon. Merck, a far larger company, saw its stock slip about 1% on the day, and is up nearly 41% this year. Because the vaccine is personalised, manufacturing can take six weeks, though Merck chief executive Robert Davis said last week that the company believes it can shorten that in future to reach more patients more quickly.
