NEW YORK, Jan 2, 2026, 15:39 ET — Regular session
- Kymera shares were down about 6.9% at $72.42 in afternoon trading, after touching $72.18.
- A regulatory filing disclosed a year-end share sale by CEO Nello Mainolfi under a pre-arranged trading plan.
- Focus is shifting to 2026 execution milestones for KT-621, including a planned asthma trial start in the first quarter.
Kymera Therapeutics Inc (KYMR.O) shares fell nearly 7% on Friday afternoon after a regulatory filing disclosed a year-end sale by Chief Executive Nello Mainolfi. Kymera was down 6.9% at $72.42, after earlier touching $72.18.
The move matters because Kymera has become a high-sensitivity biotech name, with investor expectations tied closely to clinical progress for its experimental immunology drug KT-621. In that setup, insider selling can test sentiment, even when the transactions are scheduled in advance.
Friday’s drop stood out against a steadier tape. The SPDR S&P Biotech ETF (XBI) was down about 0.3%, while the S&P 500 ETF (SPY) was up about 0.2%.
A Form 4 filed with the U.S. Securities and Exchange Commission showed Mainolfi sold 30,000 shares on Dec. 31 for about $2.34 million, in two blocks at weighted-average prices of $77.95 and $78.52. He also exercised 30,000 stock options at $2.08 and held 663,077 shares after the transactions, the filing showed. 1
The filing said the trades were made under a Rule 10b5-1 plan — a pre-set trading instruction that allows insiders to sell stock on a schedule set ahead of time, rather than reacting to day-to-day news. Investors often view those plans as less informative about near-term fundamentals than discretionary sales.
Kymera drew investor attention in early December when it said its once-daily oral STAT6 “degrader” KT-621 showed deep target reduction and improvements on eczema endpoints in a Phase 1b study. The company said it expects data from its ongoing Phase 2b trial in atopic dermatitis by mid-2027 and plans to start a Phase 2b asthma study in the first quarter of 2026. 2
The company has also said the U.S. Food and Drug Administration granted Fast Track status to KT-621, a designation intended to speed development and review for serious conditions with unmet need. “Receiving Fast Track designation will allow us to explore ways to accelerate the development of KT-621,” Mainolfi said in a Dec. 11 statement. 3
KT-621 targets Type 2 inflammatory diseases, an area dominated by injectable Dupixent from Regeneron and Sanofi, and it sits inside the broader push into targeted protein degradation — drugs designed to remove disease-driving proteins rather than just block them. Nurix Therapeutics, which is working with Sanofi on its own STAT6 program, is among the companies investors watch in the same space. 4
Kymera also raised fresh capital in December, closing a $602 million public offering and selling 8.05 million shares at $86, the company said. Gross proceeds were about $692 million before fees, giving it additional firepower to fund trials while expanding its share count. 5
Friday’s pullback leaves the stock below the levels at which the CEO sold shares at the end of 2025, sharpening attention on whether supply from insiders and recent issuance continues into early 2026.
With no near-term Phase 2 efficacy data expected for years, day-to-day trading in KYMR can swing on smaller signals — including insider filings — as investors continually re-price the probability and timing of future clinical success.
Investors’ next checkpoints include confirmation that the asthma trial starts as planned in the first quarter, any updates on enrollment or safety in the ongoing atopic dermatitis study, and the company’s next quarterly update on cash burn and operating outlook.
