Data From Moderna's Cancer Therapy Leaked

“Moderna shares plunged after details from a closely guarded mRNA-based cancer-vaccine study were shared on social media, raising concerns that the treatment might not be as effective as initially hoped.

 

The Cambridge, Mass., biotech's stock closed down 17.5% on the Nasdaq. The results, which appeared largely positive according to analysts, fell short of market expectations.

 

In August, Moderna's shares more than doubled after the company announced the vaccine had prevented melanoma from returning or spreading. The result was hailed as remarkable, though experts cautioned it was critical to see the details in the study, which had been scheduled to be released Saturday at the European Society for Medical Oncology conference.

 

A cancer-focused website OncologyCentral appeared to have published some of those results Thursday, according to screenshots on X. The medical society said an agreement to not publish the data in advance had been breached. Moderna, Merck and ESMO released the data Thursday.

 

"We fully recognize the seriousness of the situation and the potential consequences," a spokeswoman for the medical body said, adding the organization is investigating the situation and that "appropriate measures are being taken."

 

Merck closed down 1.8% on the New York Stock Exchange. Representatives for Merck and OncologyCentral didn't respond to requests to comment.

 

Moderna stock had been rising on investors' hopes for the data. Since doubling on the news the cancer vaccine worked, the stock rose 40% through Wednesday.

 

The vaccine reduced the risk of the cancer spreading by 38% in patients with high-risk melanoma when compared against a standard treatment. TD Cowen analyst Tyler Van Buren said that figure, while favorable, was short of expectations, in an investors's note before the full data was released.

 

Van Buren said worsening results between the mid- and late-stage trials could potentially mean the vaccine would have a lower likelihood of success in cases in which cancer has spread throughout the body or in "more difficult" tumors. Moderna and its partner Merck are studying this vaccine in several types of cancer.” [1]

 

1. Data From Moderna's Cancer Therapy Leaked. Martinez, Xavier; Lawrence, Lizzy.  Wall Street Journal, Eastern edition; New York, N.Y.. 23 Oct 2026: B1.