Sean Parker Gala Lead
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What do you get when an entrepreneur contributes $250 million towards cancer immunotherapy research? Game-changing momentum in the field—along with one epic Hollywood party featuring the world’s most famous faces.

That’s precisely what happened in L.A. Wednesday night, when Napster founder Sean Parker and his wife, Alexandra, welcomed beauties like Katy Perry, Allison Williams, and Emilia Clarke into their Holmby Hills home for a dress-to-the-nines gala in celebration of the newly minted Parker Institute for Cancer Immunotherapy organization, developed to bolster research of the approach to treating the disease.

“We believe that the creation of a new funding and research model can overcome many of the obstacles that currently prevent research breakthroughs,” Parker said in a statement. “Working closely with our scientists and more than 30 industry partners, the Parker Institute is positioned to broadly disseminate discoveries and, most important, more rapidly deliver treatments to patients.”

The stars in attendance—others included Katie Couric, Sean Penn, James Corden, Tom Hanks, Connie Britton, Goldie Hawn, Jaime King, Michelle Monaghan, Aaron Paul, and Ryan Seacrest, among many more—seemed to channel their support for the institute into unforgettable red carpet looks.

Perry donned a strapless leather dress and accessorized with dangly jewels while Williams celebrated the spirit of spring in a two-tone Giambattista Valli frock that would have been perfectly suited for a midsummer night’s garden party. Games of Thrones star Clarke dazzled in a body-hugging white Dolce & Gabbana dress with green graphic details (her pointed-toe white pumps killed it, too).

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Meanwhile, Orlando Bloom, who’s reportedly dating Perry, dropped jaws in a dapper black-tie getup

Over at the stage—and between yummy bites provided by celebrated chef Wolfgang PuckLady Gaga appeared before the crowd in a Yanina Couture deep-V frock with chiffon ballerina detailing. Naturally, she nailed her acoustic, piano-driven version of “Bad Romance,” among other hits, which she performed with longtime friend, singer, and trumpet-wielding musician Brian Newman.

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Credit: Kevin Mazur/Getty Images

That wasn’t all: Father-to-be John Legend also showed off his A+ piano skills and took to the stage for another jaw-dropping performance. Mark Ronson kept the crowd grooving from the DJ booth and even the Red Hot Chili Peppers performed.

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And among the hunkiest of them all: 41-year-old Bradley Cooper, who was all smiles as he posed with Parker (above, left). What a night!