$2.2 Billion Bet on a New Immunology Target: argenx to Acquire Forte and Add Anti-CD122 Antibody FB102

The immunology market has seen another major acquisition centered on early clinical signals. Belgian-Dutch biotechnology company argenx has agreed to acquire Forte Biosciences for approximately $2.2 billion in cash, adding the anti-CD122 monoclonal antibody FB102 to its pipeline in an effort to extend its existing antibody development portfolio into autoimmune diseases driven by T cells and natural killer cells.

Under the definitive agreement announced by the two companies, argenx will launch a cash tender offer of $77 per share, funded entirely with cash on hand and not subject to any financing condition. The transaction is expected to close in the third quarter of 2026, but remains subject to the tender of at least a majority of outstanding shares and the expiration or early termination of the antitrust waiting period under the U.S. Hart-Scott-Rodino Act.

FB102 targets CD122, the beta subunit shared by the interleukin-2 and interleukin-15 receptors. This signaling pathway is involved in the proliferation and activation of certain T cells and natural killer cells; by blocking CD122, Forte aims to reduce the activity of immune cells associated with disease. For argenx, this mechanism could add a cellular-immunity dimension that is less represented in its existing immunology antibody portfolio.

The primary basis for the acquisition is the positive results Forte reported from late-stage Phase 1 trials in vitiligo and celiac disease. The company described these data as clinical proof of concept and identified other autoimmune diseases, including alopecia areata, as potential development directions. argenx was already a strategic investor in Forte; its move from investment to a full acquisition indicates a willingness to secure the asset and control its subsequent development while the evidence of efficacy is still early.

However, the $2.2 billion valuation also magnifies the clinical risk. FB102 has not been approved for marketing, and late-stage Phase 1 studies typically have limited sample sizes and are still primarily used to assess safety, dosing, and preliminary activity; whether the effects can be replicated across different diseases also cannot be inferred directly from a single early-stage trial. The currently available positive data were mainly released by the developer and are not yet sufficient for definitive comparisons of benefit with established therapies.

The next key milestone will be the Phase 2 celiac disease data expected in the second half of 2026. If a larger study can confirm treatment efficacy, durability, and acceptable safety, FB102 will have a better chance of evolving from an early-stage asset acquired at a high price into a platform that can be developed across indications; if the results are inconsistent, argenx will have to bear the cost of acting before clinical validation was mature.