Moderna shares fell by as much as 25% on Thursday after partial data from its closely watched cancer vaccine partnership with Merck was leaked, despite later-released results appearing positive for patients and broadly stronger than Wall Street expectations.
The personalised vaccine, intismeran autogene, is being tested alongside Merck’s Keytruda in melanoma patients. The combination reduced the risk of recurrence or death by 42% compared with Keytruda alone.
It also cut the risk of the cancer spreading to distant parts of the body or death by 38%. After two years, about 82% of patients given the vaccine and Keytruda were alive without their melanoma returning, compared with 70% of those who received Keytruda alone.
Dr Hussein Tawbi, a trial investigator and melanoma specialist at the University of Texas MD Anderson Cancer Center, described the findings as “a huge development for our patients”. He said the additional benefit came with much milder toxicity, including side effects such as pain at the injection site, than some other cancer treatments.
The full phase three trial results were due to be presented at the European Society for Medical Oncology conference this weekend. A separate analysis found that, after the six-month vaccine regimen, the risk of recurrence or death was reduced by 58%.
However, the companies said it was still too early to establish whether the treatment helps patients live longer overall.
Moderna cancer vaccine data draws cautious investor response
Merck Research Laboratories president Dr Dean Li said the results showed a clear additional benefit when the vaccine was added to Keytruda.
“Whenever you put a therapy on top of something that works really well, like Keytruda, sometimes it’s harder to show additional benefit. We have no problems of showing additional benefit here,” he said in an interview before the results were released.
Several analysts said the market reaction appeared to reflect exceptionally high expectations for the treatment rather than a failure of the vaccine. BMO Capital Markets analyst Evan Seigerman said the reduction in recurrence and death was “clinically meaningful”.
UBS analysts described the results as “overall a strong data set”, adding that they increased confidence in forthcoming studies involving kidney and bladder cancers. Moderna shares had risen by more than 530% this year by Thursday afternoon, before the decline.
Merck shares, meanwhile, fell by about 1%. The larger drugmaker’s stock had climbed by nearly 41% this year.
The vaccine is designed around mutations unique to each patient’s tumour, rather than taking a one-size-fits-all approach. It aims to train the immune system to recognise and attack those cancer markers, while Keytruda helps strengthen the body’s response.
Moderna and Merck are studying the treatment in other cancers, including non-small cell lung cancer, bladder cancer and renal cell carcinoma. Dr Li cautioned that further evidence would be needed before its effectiveness across different tumour types could be established.
“I can dream of creating a log cabin, but we got some wood chops, and we’ve just knocked down one tree,” he said. “Knocking one tree does not give you a cabin or a village.”
The personalised manufacturing process can currently take six weeks. Merck chief executive Robert Davis has said the company believes that timeline could eventually be shortened, potentially allowing the vaccine to reach more patients more quickly.
