RAPT Therapeutics, Inc. (RAPT)

RAPT Therapeutics, Inc. was a clinical-stage immunology-focused biopharmaceutical company headquartered in South San Francisco, California. The company was founded in 2015 and operated for several years as FLX Bio before changing its name to RAPT Therapeutics. It aimed to develop oral small-molecule medicines for oncology and inflammatory diseases by modulating the immune system.

RAPT's early lead program was FLX475, an oral CCR4 antagonist designed to block the recruitment of regulatory T cells into tumors, with the aim of enhancing anti-tumor immune responses. The company also developed RPT193, later known as zelnecirnon, an oral CCR4 antagonist studied for inflammatory conditions including atopic dermatitis and asthma. Over time, its inflammation programs became its main focus, and it later shifted attention toward an oral anti-IgE approach for food allergy and other allergic disease. Allergic and immune-mediated conditions were an area of growing interest for drug developers, and RAPT's strategy was to use oral small molecules where established treatments were mainly injectable biologics. The company reported clinical data from its programs at scientific conferences and in company announcements.

RAPT completed its initial public offering in October 2019, listing its common stock on Nasdaq under the ticker RAPT. As a clinical-stage company with no approved products, it financed operations through equity offerings and partnerships. Clinical setbacks, including a clinical hold on one program in 2024, affected its share price, and the company restructured its pipeline and workforce.

In January 2026, GSK announced an agreement to acquire RAPT for $58.00 per share in cash. The acquisition was structured as a two-step transaction in which a GSK subsidiary, Redrose Acquisition Co., would commence a tender offer for all outstanding RAPT shares, followed by a merger. The tender offer structure allowed the transaction to close within roughly six weeks of its launch, and the board of RAPT recommended that stockholders tender their shares, as set out in a Schedule 14D-9 filed with the SEC.

The tender offer was launched on February 2, 2026, and expired on March 2, 2026. About 93.36 percent of outstanding shares were tendered, satisfying the minimum condition. The merger took effect on March 3, 2026 under Section 251(h) of Delaware law, which allows a merger without a stockholder vote following a successful tender offer. RAPT survived as a direct wholly owned subsidiary of GlaxoSmithKline LLC.

RAPT asked Nasdaq to halt trading and delist its shares before the market opened on March 3, 2026, and to file a Form 25 to remove the listing and deregister the stock. The company also said it intended to file a Form 15 to terminate its SEC registration and suspend reporting obligations. GSK plc, the parent company, guaranteed the buyer's obligations and continues to be listed on the New York Stock Exchange.