Here's a classic biotech story: a big pharma company partners with a smaller biotech on a promising drug, and then decides it likes the asset so much it wants to own the whole thing. That's what's happening with Gilead Sciences (GILD) and Arcellx Inc. (ACLX).

On Monday, Gilead announced it's buying Arcellx outright. The deal values Arcellx at $115 per share in cash, plus a contingent value right of $5 per share, which adds up to an implied equity value of $7.8 billion. Gilead already owns about 11.5% of Arcellx's stock, so this is about acquiring the remaining 88.5% to get full control.

So, what's Gilead buying? The crown jewel is a drug called anitocabtagene autoleucel (anito-cel for short, because nobody wants to say the full name). It's a CAR T-cell therapy designed to treat multiple myeloma, a type of blood cancer. This isn't some early-stage science experiment; the therapy's Biologics License Application (BLA) has already been accepted by the FDA, with a target decision date of December 23, 2026. The application is for using anito-cel as a fourth-line treatment for patients whose cancer has relapsed or is resistant to other therapies.

"This agreement reflects our conviction in the potential of anito-cel and our intention to move with speed so we can make the most of that potential for patients with multiple myeloma," said Daniel O'Day, Chairman and CEO of Gilead Sciences. In other words: we believe in this drug, and owning it completely lets us develop and sell it faster.

The data backing this up comes from a Phase 1 study and a pivotal Phase 2 trial called iMMagine-1. Arcellx shared updated results from that Phase 2 study in December 2025, showing what the company described as deep, durable responses and a manageable safety profile.

From a business perspective, the move makes sense for Gilead. By owning Arcellx, it eliminates the profit-sharing and royalty structures that were part of their previous collaboration. The company expects the deal to be accretive to its earnings per share starting in 2028, assuming the FDA gives anito-cel the green light.

Now, let's talk about the stock reaction, because it's a doozy. Arcellx shares were up a staggering 78.58% at $114.49 in premarket trading on Monday, hitting a new 52-week high. Gilead's shares, meanwhile, were down slightly, about 0.83% at $150.15.

For those who like to look at the charts, Gilead's stock is currently trading 2.5% below its 20-day simple moving average and 3.8% below its 100-day average, which suggests a bearish short-term trend. Its Relative Strength Index (RSI) is sitting right at 50, which is neutral—not overbought, not oversold. The MACD indicator, however, is below its signal line, pointing to some bearish pressure. In short: mixed technical signals.

Key resistance for Gilead's stock is seen at $157.50, with support around $145.00.

What are the analysts saying? The consensus rating on Gilead is a Buy, with an average price target of $139.65. Recent moves include Barclays initiating coverage with an Equal-Weight rating and a $155 target, RBC Capital maintaining a Sector Perform rating but raising its target to $118, and Truist Securities keeping a Buy rating and lifting its target to $152.

At its core, this is a $7.8 billion bet by Gilead that it can bring a promising cancer therapy to market faster and more profitably by owning the whole company behind it. The market's initial verdict on Arcellx's stock suggests investors think it's a good deal for the biotech's shareholders. Now we wait to see if the drug lives up to the hype.