Shares of Tempus AI (NASDAQ: TEM) surged as much as 21% on Wednesday, August 19, 2026, rocketing from a previous close of $49.36 to an intraday high of $61.40 on volume of more than 13.5 million shares — over four times the stock’s typical turnover.
The rally was sparked by a landmark clinical trial announcement from Merck & Co. and Moderna, not by news from Tempus itself. The pharmaceutical partners revealed Phase 3 results from their INTerpath-001 trial evaluating intismeran autogene, a custom mRNA-based individualized cancer vaccine paired with Keytruda, showing a statistically significant improvement in recurrence-free survival among melanoma patients. It marks the first successful Phase 3 readout ever for a personalized mRNA cancer therapy.
The connection to Tempus: Moderna’s vaccine platform depends on genomic sequencing technology from Personalis Inc., a company Tempus agreed last month to acquire for roughly $1.5 billion.
When that deal was first announced, investors balked at the price tag and dilution, sending TEM shares lower. Wednesday’s trial results flipped that narrative, as traders recognized Tempus is set to inherit critical infrastructure behind one of oncology’s biggest breakthroughs in years.
Tempus CEO Eric Lefkofsky celebrated the news publicly, congratulating Merck and Moderna while highlighting the company’s role through its Personalis partnership.
The move was amplified by unusually heavy call-option buying and a technical setup: TEM had slid to multi-week lows heading into Wednesday, leaving it primed for a sharp rebound once sentiment turned positive.
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