During Mylan CEO Heather Bresch's 28-year stint there, the company has utterly transformed into a generics giant—and courted controversy along the way.

And now, Bresch says she's stepping aside to clear the way for an even bigger version of Mylan.

Mylan is joining forces with Pfizer's Upjohn business, the companies said Monday, and when the deal's done in mid-2020, Bresch will retire. Mylan's executive chairman Robert Coury will stay on in the same role, as will President Rajiv Malik, who's been named in a generics price-fixing suit brought by state attorneys general.

Bresch's tenure as CEO has spanned a series of controversies, from a résumé scandal at the beginning through price hikes, executive pay pushback, federal investigations and a congressional hearing. Through all of that, Mylan snapped up one generics company after another to expand geographically and diversify beyond garden-variety generic pills.

Mylan's stock price hasn't necessarily kept pace, though, and in recent quarters, market watchers and investors have pushed for change. Last year, the company said it would take on a "strategic review," but hadn't said much since then—until now.

Bresch is set to collect about $37.6 million with the change in leadership, per a Mylan proxy filing highlighted in a Monday note by Wells Fargo analyst David Maris. She's been among the highest-paid CEOs across pharma in years past, although the didn't make the top 20 in 2018.

Bresch's predecessor Robert Coury—who is now Mylan's executive chairman and is himself among the highest-paid in the industry—implemented a growth-by-M&A strategy that led to significant job cuts. When Bresch started as a data entry clerk at Mylan in 1992, the company employed 300 people and pulled in $100 million yearly.

Fast forward nearly three decades later and the company has more than 45,000 employees and more than $20 billion in annual revenue from 165 countries.

Bresch's time at Mylan featured confusion back in 2008 when the Pittsburgh Post-Gazette found that she hadn't earned enough credits for the MBA listed on her résumé. In the end, West Virginia University rescinded a degree it retroactively awarded—but turned out, Bresch didn't need it to keep her post.

More recently, Mylan disclosed that it is among a group of generics companies facing price-fixing allegations from dozens of states, and federal prosecutors are investigating the issue on their own. Mylan’s president, Rajiv Malik, is among the executives personally named in the lawsuit, although Mylan has stood by its president. 

But Mylan first became something of a household word back in 2016, when the EpiPen pricing controversy broke. News surfaced that the drugmaker had been hiking prices for years on its lifesaving epinephrine injector to the point where many parents had a hard time paying for their back-to-school packages. Lawmakers struck up investigations and consumers blasted the drugmaker’s motives.

Bresch, for her part, defended Mylan's pricing by pointing to the drug pricing and rebating system in the U.S. Along with the EpiPen fiasco, Mylan paid $465 million to the federal government to settle claims it underpaid Medicaid rebates. 

In a letter to employees, Bresch reflected on her 28 years of service at Mylan, saying ensuring patient access has always been a core mission. She's served as chief integration officer, COO and president, and numerous other roles. She said the journey "has been life-altering, and the many relationships I have forged will be life-long," she wrote.

Bresch also said she’s always worked to "break down barriers to access" for medicines.

Before the Upjohn announcement, Mylan's share price has been struggling lately—analysts believed some investor frustration was due to management.