What happened

Shares of Moderna (MRNA 0.17%) were skyrocketing 24.3% higher as of 10:21 a.m. ET on Tuesday. The huge gain came after the company, along with its partner Merck (MRK 0.24%), announced positive results from a phase 2 clinical study evaluating experimental personalized messenger RNA (mRNA) cancer vaccine mRNA-4157/V940 in combination with immunotherapy Keytruda as an adjuvant treatment for stage III/IV melanoma. 

So what

You know clinical results have to be spectacular for a vaccine stock with a market cap of greater than $60 billion to jump more than 20%. And they were.

Moderna and Merck reported that the combination of mRNA-4157/V940 and Keytruda reduced the risk of recurrence of melanoma or death by a whopping 44% compared with Keytruda alone. The safety profile for the combo looked pretty good as well. Serious treatment-related adverse events occurred in 14.4% of patients receiving the personalized mRNA cancer vaccine plus Keytruda compared to 10% of patients receiving only Keytruda.

There was already a hint that Merck was optimistic about the combination therapy. In October, the big drugmaker exercised its option to develop and market mRNA-4157/V940 with Moderna. 

The good news could have even more far-reaching implications for Moderna. The study results were the first to show the potential for mRNA to be used as a cancer treatment in a randomized clinical trial. Moderna CEO Stéphane Bancel said that his company hopes to develop personalized cancer treatments for other types of cancer in addition to melanoma.

Now what

Moderna and Merck now plan to talk with regulatory authorities about the phase 2 results. They expect to kick off a phase 3 study in melanoma next year. The two companies also intend to publish the full data from the phase 2 study and share the results at a cancer-focused medical conference in the near future.