Argenx to Buy Forte Biosciences for $2.2 Billion, Adding a First-in-Class Antibody

Argenx is acquiring Forte Biosciences in a $2.2 billion all-cash deal, adding a first-in-class antibody to its growing autoimmune-disease pipeline.

Announced July 27, Argenx will pay $77 per share — roughly a 41% premium to Forte’s prior close. The Dallas-based biotech’s lead asset is FB102, a first-in-class anti-CD122 monoclonal antibody that dials down the activity of T cells and natural-killer cells.

Why CD122 is an interesting target

CD122 is a shared component of the receptors for two immune signalling molecules, interleukin-2 and interleukin-15. Blocking it interrupts both pathways at once.

Those two cytokines do overlapping but distinct work. IL-2 drives expansion and activity of T cells; IL-15 is essential for natural-killer cells and for maintaining certain long-lived T-cell populations, including the tissue-resident memory cells that persist in organs and skin.

Tissue-resident memory T cells are increasingly implicated in autoimmune conditions that recur in the same location — a patch of skin, a segment of gut — because they remain in place indefinitely and reactivate. Conventional immunosuppression, which acts largely on circulating cells, reaches them poorly.

Targeting a receptor those cells depend on is a mechanistically distinct proposition from broadly suppressing immune activity.

The two lead indications

FB102 has produced encouraging Phase 1b results in vitiligo and celiac disease — two conditions with high unmet need.

The pairing looks eclectic and is coherent on this mechanism. Both involve tissue-resident T cells attacking a specific target in a specific location: melanocytes in skin in vitiligo, the intestinal lining in celiac disease.

Celiac disease is the more striking choice commercially. It has no pharmacological treatment at all — management is lifelong strict gluten avoidance, which is burdensome, socially limiting and frequently imperfect, with inadvertent exposure causing symptoms and ongoing intestinal damage.

A drug allowing tolerance of incidental exposure would address a population that currently has nothing.

The pipeline-in-a-product claim

Argenx frames the drug as a pipeline-in-a-product with potentially broad autoimmune applications, validating CD122 as a target.

The phrase describes an asset expected to work across many indications rather than one. It is what justifies a price of this size for an early-stage drug: the valuation cannot rest on one indication, so it rests on the mechanism generalising.

Whether it does is the risk. Immune mechanisms that look broadly applicable frequently prove effective in a narrower set of conditions than the biology suggested.

Why it fits Argenx

Argenx built its reputation on Vyvgart, an antibody therapy for the neuromuscular disorder myasthenia gravis and a rare nerve condition, with steadily rising sales.

Vyvgart works by accelerating clearance of antibodies from circulation, which treats diseases caused by self-reactive antibodies. FB102 addresses cell-mediated autoimmunity instead.

The two are complementary rather than overlapping. Autoimmune diseases divide roughly along that line, and a company with mechanisms for both can pursue conditions the other cannot — while reusing the same commercial infrastructure aimed at immunologists and specialist centres.

Why it matters

At $2.2 billion for a drug still in early clinical testing, the deal is a bet on breadth rather than proven revenue — the kind of high-conviction wager that defines immunology dealmaking now.

The safety question a CD122 blocker must answer

Suppressing IL-2 and IL-15 signalling simultaneously is a substantial intervention, and the risks follow directly from what those pathways do normally.

Natural-killer cells depend on IL-15 for their development and survival. They provide early defence against virally infected cells and contribute to controlling tumours, and depleting them meaningfully would be expected to raise susceptibility to both.

IL-2 signalling also sustains regulatory T cells, which suppress autoimmune responses. Blocking the pathway that maintains them is, in principle, counterproductive in autoimmune disease — and drugs exploiting the opposite approach, low-dose IL-2 to expand regulatory T cells, have been pursued as autoimmune therapies.

That the same receptor is being blocked in one strategy and stimulated in another is not a contradiction so much as a matter of which cell populations are more sensitive at which exposures. Regulatory T cells express a higher-affinity form of the IL-2 receptor than effector cells, which is what makes selective effects possible at all.

Establishing that window in humans — enough suppression of pathogenic cells, not enough to disable defence or deplete regulatory populations — is what the clinical programme has to demonstrate, and it is the risk embedded in the price.

The 41% premium reflects a competitive assumption as much as a valuation: paying substantially above market is how an acquirer discourages a rival bid for an asset with a novel target. The acquisition is expected to close in the third quarter of 2026, subject to regulatory approval. Business news, not investment advice.