In a jaw-dropping conclusion to a bitter feud between two of the state’s academic titans, USC agreed this week to pay the University of California $50 million and apologize for tactics used to poach a star Alzheimer’s researcher from the public university’s San Diego campus.

The agreement settled unprecedented litigation in which UC accused its private rival of repeatedly stealing away top scientists and their lucrative research grants with “predatory” practices and a “law-of-the-jungle mind-set.”

In its apology, USC said it regretted the way neurology professor Paul Aisen and his lab staff left UC San Diego in 2015, departures that were secretly coordinated with high-level administrators at the Los Angeles university.

“These actions did not align with the standards of ethics and integrity which USC expects of all its faculty, administrators and staff,” the apology stated.

The self-described “quarterback” of Aisen’s recruitment was the then-dean of USC’s Keck School of Medicine, Carmen Puliafito, subsequently revealed to have been using drugs and partying with criminals during the time he was courting the scientist.

The settlement comes as USC is attempting to emerge from a series of scandals that culminated with longtime president C.L. Max Nikias departing last year.

One of Nikias’ key strategies to rapidly raise USC’s reputation and academic rankings was wooing big-name professors and their funding from other institutions.

Scores of so-called “transformative faculty” were lured to USC during Nikias tenure, often with perks that cash-strapped public institutions struggled to match: Huge raises, million-dollar housing loans and brand new facilities.

In its apology, USC did not mention Nikias but presented the unethical behavior in the UCSD recruiting as part of a larger cultural problem that Nikias’ successor, Carol L. Folt, and university leaders are working to address.

“USC is committed to, and wants to be known for, ethics, integrity and the pursuit of academic excellence, and it has already implemented sweeping changes to this end,” the university said.

UCSD Chancellor Pradeep Khosla welcomed the settlement and said he was open to working with USC in the future.

“For California and the country, it’s good that two great research universities can work on the Alzheimer’s problem,” he said in an interview. “I look forward to a constructive collaboration in the future in solving other societal problems.”

It is not unusual for professors to move to other institutions, but it is often a collegial process in which the universities work together to transfer grants and research.

Over several years, UC became convinced that USC was crossing ethical norms by targeting academics based on grant funding and strategizing covertly with scientists and their lab employees about moving research money.

UC San Diego believed it was unethical for USC to hire away such a large group of researchers at one time, attempt to deny access to the trove of Alzheimer’s data its campus researchers had gathered over years and bypass the established process for transferring grants to new institutions. Since federal grants belong to the institution and not the individual researcher, UC San Diego officials believe Aisen should have notified them that he wanted to leave and they in turn would have asked the federal agencies about shifting the grants. That did not happen.

More broadly, UC leaders also wanted to demonstrate that they would fight to protect public research institutions from losing their competitive edge to more well-heeled private universities.

UC was, as it is now, grappling with budget problems that linger from the recession a decade ago. As it scrambles to make ends meet, a large concern has been retaining faculty in the face of attractive offers from deep-pocketed private universities.

UC faculty salaries were 8.4% below eight comparative public and private universities in 2016-17 — a gap that UC President Janet Napolitano has since reduced to 6.7%.

“We have a serious problem consistently competing with the well-heeled privates — not only for senior faculty but also for the best young faculty and junior faculty,” Robert May, UC Academic Senate chairman, said. “It’s one of our most serious concerns.”

In 2013, Puliafito lured two well-funded brain researchers from UCLA, outraging the state university, which complained to government regulators. USC agreed to pay UCLA more than $2 million in a confidential settlement.

Two years later, Puliafito and other university administrators were at it again — this time courting Aisen at UCSD. The research group he headed, the Alzheimer’s Disease Cooperative Study, was a point of pride and revenue for UCSD. Aisen was a field leader and the ADCS was in line for more than $340 million in research grants at the time USC approached him.

USC offered Aisen annual compensation of $500,000 — a salary bump of $110,000 — and a loan for a new home. Aisen was already displeased with what he saw as a lack of attention and commitment by UCSD leadership to his research. He and many of his key staffers decided to leave, setting off a battle with UCSD over the ADCS clinical trial data as well as funding.

At one point, Napolitano got personally involved, unsuccessfully lobbying one pharmaceutical company to leave its grants with UCSD.

The suit UC subsequently pursued in San Diego County Superior Court is believed to be the first time a university has sued another over faculty poaching.

In 2017, in the midst of the litigation, The Times revealed Puliafito’s drug history. The former dean had been expected to play a role in defending USC’s conduct and had given sworn testimony that his university was not motivated by grant money in trying to hire Aisen.

After his problems became public, a lawyer for USC said that although the former dean was only a “bit player” in the matter, he expected UC to try to make Puliafito’s personal travails an issue in the case.

The $50 million USC has agreed to pay by month’s end suggests the risk USC and its lawyers had calculated in airing the dispute before a jury. UC was seeking damages of $185 million as well as a punitive award that could be several times that.

Dr. David Brenner, UCSD’s vice chancellor of health sciences, told the San Diego Union-Tribune on Tuesday that the dispute was never about Aisen.

“We lose people all of the time,” Brenner said. “This was about how USC sabotaged our program.”

Aisen has continued to work in San Diego, but under an operation created by USC for him and known as the Alzheimer’s Therapeutic Research Institute.

He told the Union-Tribune that he’s glad the dispute is over, as he and his staff “have two major trials” of experimental Alzheimer’s therapies to conduct.

“I’m very happy to be moving forward,” Aisen said. “We have a lot of work to do.”

Gary Robbins and Bradley J. Fikes of the San Diego Union-Tribune contributed to this report.