Moderna Tumbles 20% After Cancer Vaccine Breakthrough Sends Shares Skyrocketing

Moderna shares plummeted 20% on Thursday after delivering one of the biotech sector's most extraordinary single-day moves earlier in the week. On Wednesday, the stock skyrocketed 177% following Phase 3 results for its experimental cancer vaccine, intismeran autogene (mRNA-4157), which sent partner Merck shares rallying 12.5%. The mRNA-based shot, combined with Merck's immunotherapy Keytruda, met key goals in a trial of patients with higher-risk or advanced melanoma whose detectable cancer had been removed.

Investors are taking profits and reconsidering the potential impact of this cancer vaccine on Moderna's business. Despite the 20% drop, the stock is still up an impressive 117.31% over the past week and 369.03% year-to-date. The company has said nine Phase 2 and Phase 3 studies are underway across melanoma, NSCLC, bladder cancer, and renal cell carcinoma.

An approved adjuvant melanoma combination would extend Merck's Keytruda franchise into earlier lines of therapy, potentially creating a new oncology franchise for Moderna. The upside is enormous, but investors are paying for a great deal of clinical and commercial success before approval has arrived.