Merck/Moderna cancer vaccine cuts risk of melanoma death or recurrence by over 40%

By Julie Steenhuysen and Michael Erman

Oct 22 (Reuters) - Moderna MRNA.O and Merck MRK.N said on Thursday that the mRNA cancer vaccine they developed combined with a widely used immunotherapy cut the risk of death or recurrence of melanoma by 42% and disease spread by 38% in a large trial.

The data from the Phase 3 trial of more than 1,100 patients potentially paves the way for a new era of personalized treatment. Moderna and Merck announced in August that the treatment had succeeded but did not provide details from the trial.

It is the first to show that the combination of a vaccine based on mutations unique to each patient's tumor plus a drug that helps the immune system fight cancer can keep the disease at bay. The vaccine was tested along with Merck's blockbuster immunotherapy Keytruda, among the world's biggest-selling medicines.

Moderna shares, which have rocketed since the August trial announcement, nearly quadrupling through Wednesday's close, fell over 20% after the results leaked on an oncology website earlier on Thursday. Merck shares were down about 0.7%.

The results, based on patient data for the first two years after treatment, are scheduled to be presented on Saturday at the European Society for Medical Oncology meeting in Madrid.

Several Wall Street analysts said before the meeting that investors were looking for the combination to cut the risk of recurrence by 40% or more.

"This is highly statistically significant. It is not by chance," Dr. Hussein Tawbi, a melanoma expert and trial investigator at the University of Texas MD Anderson Cancer Center, said of the results.

The trial tested nine doses of the vaccine, known as intismeran, along with Keytruda, beginning 13 weeks after surgery to remove melanoma lesions. Their response was compared with patients treated with just Keytruda, a standard therapy for melanoma.

Among those who received the vaccine in addition to Keytruda, 82.2% were still cancer-free after two years, compared with 70% of patients who received Keytruda alone.