Gilead Sciences Inc. announced Monday that it has agreed to acquire clinical-stage biotechnology company Arcellx Inc. for $115 per share in cash plus one contingent value right worth $5 per share, reflecting an implied equity value of $7.8 billion.

Ropes & Gray LLP is advising Gilead, and Wilson Sonsini Goodrich & Rosati PC is representing Arcellx.

Under the agreement, a Gilead subsidiary will commence a tender offer for all outstanding Arcellx shares not already owned by Gilead, which already holds roughly 11.5% of Arcellx's stock, according to the announcement.

The cash offer represents a 68% premium to Arcellx's 30-day average share price as of Friday, Gilead said.

Arcellx stock was up more than 77% on Monday.

The deal builds on an existing collaboration between Gilead's Kite unit and Arcellx to co-develop and sell the latter's lead drug, anitocabtagene autoleucel, or anito-cel, a treatment for patients with the blood cancer multiple myeloma, the announcement said.

The therapy is being developed as a fourth-line treatment for patients with relapsed or refractory multiple myeloma.

"Beyond the potential launch this year, anito-cel could become a foundational treatment for multiple myeloma over time, including earlier lines of therapy," Daniel O'Day, chair and CEO of Gilead, said in the announcement.

He noted that the technology behind anito-cel could also support the company's broader work in in-vivo cell therapy, further strengthening Gilead's oncology and inflammation pipeline.

The U.S. Food and Drug Administration has accepted a biologics license application for anito-cel, with an action date under the Prescription Drug User Fee Act set for Dec. 23, the announcement said.

Rami Elghandour, chair and CEO of Arcellx, said the company had found a "world-class partner" in Gilead. He praised the potential of anito-cel to benefit patients and clinicians, while acknowledging the contributions of Arcellx's team and study participants.

The boards of both companies approved the deal, which is expected to close in the second quarter of 2026, subject to customary conditions including regulatory approvals and tender of a majority of outstanding Arcellx shares.

BofA Securities Inc. and Morgan Stanley & Co. LLC are acting as financial advisers to Gilead.

Centerview Partners LLC is acting as exclusive financial adviser to Arcellx.

A Kirkland & Ellis LLP team is advising Centerview, led by partners Laura Knoll and Graham Robinson.

The Ropes & Gray team is led by partner Emily Oldshue.

The Wilson Sonsini team is led by partners Rob Ishii, Dan Koeppen, and Ross Tanaka.