Drugmaker Moderna's stock more than doubled on Wednesday morning after the company announced a successful experimental mRNA vaccine to treat melanoma, the deadly skin cancer from which more than 8,500 people in the U.S. are expected to die this year.

Moderna and Merck, its drug development partner, said the novel treatment prevented melanoma from returning or spreading in a study of high-risk melanoma patients.

Shares of Moderna surged $91.52, or 145%, to $154.48 in morning trading after touching an intraday high of $163. Merck's shares rose $14.35, or 10.6%, to $149.52.

The study, which focused on people who had undergone surgery to remove a melanoma, tested the drug's efficacy at reducing the risk of the cancer's return.

The study tested the companies' personalized cancer vaccine intismeran in combination with Merck's Keytruda, its cancer immunotherapy drug. Together, the drugs kept the cancer from returning for longer and prevented it from spreading to other organs.

The drugmakers plan to present the unpublished data to regulators at an upcoming international medical meeting.

"Landmark moment"
"Today's results represent a landmark moment for adjuvant melanoma treatment," Professor Georgina Long, the study's principal investigator and the chair of University of Sydney's Melanoma Medical Oncology and Translational Research, said in a statement Wednesday.

Long said the study is the first of its kind to show that treatment can "reduce the risk of recurrence or death in patients" with melanoma.

The advancement "has the potential to establish a new treatment paradigm in the adjuvant melanoma setting, helping patients remain cancer-free for longer," she added.

More than 234,680 cases of melanoma will be diagnosed in the U.S. in 2026, according to the Skin Cancer Foundation. Among the deadliest forms of skin cancer, melanoma starts in melanocytes, the cells that give the skin its color. Melanoma is characterized by the uncontrollable growth of these cells, according to the Mayo Clinic.

"By intervening earlier in the course of disease, when many cancers are considered most treatable, the goal of adjuvant therapy given after surgery is to increase the possibility of cure for more patients," Dr. Dean Y. Li, president of Merck Research Laboratories, said in a statement.

The findings amount to a "pivotal moment for the field of cancer research," added Moderna CEO Stéphane Bancel. "For many years, the idea of creating an mRNA treatment designed specifically for an individual patient's cancer was aspirational. We are now helping turn that vision into a reality."

Moderna shares are still far from their pandemic-era peak in late 2021 and 2022, when its stock soared on global demand for its COVID-19 vaccine.

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