John Tseng-Chung Lee

John Tseng-Chung Lee, then-CEO, sold 10,000 shares of MKSI at $315.48 under 10b5-1 plan; stock up 18.2% in 30 days post-sale.

John Tseng-Chung Lee, who was CEO at the time of the transaction, sold 10,000 shares (10.0K shares) of MKSI at $315.48 on 2026-05-22 under a pre-arranged 10b5-1 trading plan adopted on 2026-02-20, reducing his holdings by 6.5% to 144,696 shares (144.7K shares). The stock has appreciated 18.2% over the 30 days following the sale and currently trades at $332.13, only 1.6% from its 52-week high of $326.84. His prior trades at MKSI on 2026-02-20 show post-transaction returns of -11.3%, -11.6%, -11.9%, and -12.5% over 30 days, establishing a pattern of short-term stock appreciation after his sales at this ticker. The scheduled nature of this trade under a 10b5-1 plan removes discretionary timing from the interpretation, though the subsequent price action and historical pattern at MKSI remain observable context for investors evaluating insider activity.

CEO Lee John Tseng-Chung sold 30,000 shares of MKSI for $7,703,242.05 at blended average price $256.77 (2026-02-20).

Lee John Tseng-Chung, President & CEO of MKS Inc, executed 4 separate sales totaling 30,000 shares for $7,703,242.05 on 2026-02-20, reducing his holdings by 16.2% from 184,696 to 154,696 shares. The sales occurred at an average price of $256.77, near the 52-week high of $262.94 and significantly above the current price of $253.71. The stock has appreciated 70.3% over 90 days and 16.9% over 30 days, yet carries a notably elevated P/E of 61.13 against flat annual revenue growth (-1.0%), suggesting the market is pricing in substantial future expectations. The magnitude of this reduction—nearly one-sixth of his prior holdings in a single transaction—and the timing near 52-week highs merit examination of company fundamentals and forward guidance to determine whether the sale reflects valuation concerns or merely portfolio rebalancing by the CEO.