Moderna Sheds Up to 25% and 18 Billion in Market Cap as Investors Pocket Gains From Historic Cancer Vaccine Surge

Moderna shares fell as much as 25% on Thursday, erasing roughly 18 billion dollars in market value after closing Wednesday up 176.9% on breakthrough Phase 3 cancer vaccine trial results. The stock, which had consolidated near 152 to 154 dollars in pre-market trading, dropped to around 142.70 in midday trade before extending losses to approximately 24% by afternoon, according to multiple market trackers. Moderna's market capitalization fell to 51.5 billion dollars from 69.6 billion at Wednesday's close.

The selloff was driven by profit-taking and analyst caution: while price targets were raised across the street, several remained below Wednesday's closing level, raising questions about how much of the clinical breakthrough had already been priced in. The underlying catalyst was the Phase 3 INTerpath-001 trial of intismeran autogene, Moderna's personalized mRNA-based cancer vaccine developed in combination with Merck's Keytruda, which met its primary endpoints in patients with completely resected stage IIB-IV melanoma, marking the first successful late-stage trial for an mRNA cancer vaccine. Moderna led all pre-market volume with roughly 14.2 million shares changing hands early Thursday.

BioNTech fell about 4% and Merck slipped in sympathy, while the XBI biotech index dropped around 4%. A Morgan Stanley analyst nonetheless maintained that Merck stock remains a buy. Barron's reported that Wednesday's surge burned short sellers and spilled over into the semiconductor sector.

A congressional disclosure revealed that President Trump had purchased up to 50,000 dollars of Moderna shares on March 2 and again on March 17, with only a partial sale in May, meaning he held a position through Wednesday's 177% gain. Despite Thursday's steep retreat, Moderna shares remained up approximately 351% year-to-date.