Wachtell, Lipton, Rosen & Katz corporate partner Allison Preiss, after close to two decades at the firm, has moved to Simpson, Thacher & Bartlett. Simpson confirmed the lateral hire on Tuesday.A spokesperson for Wachtell said the firm wishes her well in her future endeavors. Preiss is at least the fourth partner to leave Wachtell in a lateral move since the beginning of 2025. Others include Viktor Sapezhnikov (DLA Piper), Zach Podolsky (Latham & Watkins) and John Sobolewski (also to Latham). The firm also lost partner David Shapiro to the Commerce Department in March 2025. Preiss advises public and private companies in mergers, acquisitions, divestitures, leveraged buyouts, complex restructuring deals, cross-border transactions, securities offerings and joint ventures. She also advises boards of directors and board committees with respect to proxy contests, takeover defense strategies and other corporate governance matters. “Clients are navigating unprecedented complexity—transformative market forces, heightened activist pressure and evolving regulatory considerations, all of which require sharp, creative and pragmatic counsel,” Alden Millard, Chair of Simpson Thacher’s Executive Committee, said in a statement. “Alison is a star. She’s dynamic, exceptionally commercial and known for delivering solutions that advance business objectives." Eric Swedenburg, global head of Simpson's M&A practice, said in a statement that her addition "reflects our continued investment in our preeminent transactional team focused on strategic M&A, corporate governance and activism defense." "In addition to Alison, we’ve made several other impactful moves in this space, both through lateral hires and internal elevations, across our global platform.” Some of her transactional highlights include representing Pfizer Inc. in its $5.2 billion acquisition of Anacor Pharmaceuticals and in its $160 billion terminated transaction with Allergan plc. She also represented Alexion in its $8.4 billion acquisition of Synageva BioPharma Corp. Preiss began her late career as a summer associate at Calfee, Halter & Griswold in 2004 before summering at Wachtell in May 2005. She joined the firm the following year and became a partner in 2016.