Oct 12 (Reuters) - Merck & Co Inc (MRK.N) opted to jointly develop and potentially sell a personalized mRNA vaccine with Moderna Inc (MRNA.O) for a $250 million upfront payment on Wednesday, sending the vaccine maker's shares up over 8%. Moderna's experimental vaccine is being tested in combination with Merck's blockbuster cancer immunotherapy, Keytruda, in a mid-stage trial to treat patients with melanoma. Data on the vaccine, mRNA-4157, is expected in the fourth quarter of this year. In 2016, Merck and Moderna entered a strategic partnership to develop a personalized vaccine for treatment of various types of cancer. Merck in 2020 sold its equity investment in Moderna, benefiting from a surge in the vaccine-maker's stock price that year. https://www.reuters.com/business/healthcare-pharmaceuticals/merck-opts-jointly-develop-cancer-vaccine-with-moderna-2022-10-12/