Argenx Acquires Forte Biosciences for $2.2B, Adding Anti-CD122 Antibody FB102 to Immunology Pipeline

Argenx (Nasdaq: ARGX) agreed to acquire Forte Biosciences (Nasdaq: FBRX) for $77 per share in cash, a deal valued at approximately $2.2 billion that adds the first-in-class anti-CD122 antibody FB102 to argenx’s immunology pipeline. The transaction was announced July 27, 2026.

The $77 per share price represents a premium of approximately 86% to Forte Biosciences’ volume-weighted average price since the company reported positive Phase 1b data in vitiligo on July 9. Forte Biosciences closed at $54.78 on July 25, the last trading day before the deal was announced, meaning the offer is a 40.5% premium to the prior close. The deal is funded entirely from argenx cash on hand and is expected to close in Q3 2026, subject to customary closing conditions including a majority tender of Forte shares and Hart-Scott-Rodino antitrust clearance.

The prize: FB102

The target asset is FB102, a first-in-class anti-CD122 antibody that targets pathogenic T-cell and NK-cell activity through the interleukin-2/IL-15 receptor beta pathway. Forte Biosciences reported positive Phase 1b data in vitiligo earlier in July, with a 29.6% mean FVASI improvement from baseline at week 24 (p=0.020), and statistically significant improvements observed as early as day 64. Positive Phase 1b data in celiac disease was shared in 2025, with Phase 2 data expected in the second half of 2026.

argenx CEO Karen Massey called FB102 a “pipeline-in-a-product” opportunity, noting its potential to address vitiligo, celiac disease, alopecia areata, and additional autoimmune diseases. The asset complements argenx’s existing portfolio built around Vyvgart (efgartigimod), which generated $4.2 billion in global net sales in 2025, up 90% year-over-year.

Why argenx is paying up

The acquisition reflects argenx’s “Vision 2030” strategy to treat 50,000 patients across 10 indications with five late-stage molecules by the end of the decade. FB102 adds a mechanism distinct from argenx’s FcRn franchise: rather than modulating IgG antibody levels through FcRn blockade, FB102 targets the T-cell and NK-cell arm of the immune system through CD122 biology.

argenx had previously made a strategic investment in Forte Biosciences, so the acquisition deepens an existing relationship. Arjen Lemmen, argenx’s VP of corporate development and strategy, noted the deal is not necessarily at the “standard level of validation” the company requires every time, but said argenx’s role as a biotech innovator is to “take calculated risks” on novel target biology.

What to watch

FB102 enters argenx’s pipeline at the Phase 1b/Phase 2 stage. The next catalyst is the Phase 2 celiac disease data expected in the second half of 2026. argenx will also need to advance FB102 into Phase 2 trials in vitiligo and potentially alopecia areata. The deal is expected to close in Q3 2026.

argenx closed at $888.82 on July 27, down 3.2% from its $918.22 close on July 25, giving it a market capitalization of roughly $51 billion. The decline reflects some investor concern about the premium paid for a Phase 1b asset. Forte Biosciences closed at $76.50, just $0.50 below the $77 offer price, signaling that the market expects the tender offer to close without a competing bid.

BioSpace coverage | BusinessWire press release | Fierce Biotech

For context on argenx’s immunology franchise and the FcRn competitive market, see our JNJ nipocalimab JASMINE SLE analysis.

What It Means for the Trade

The 3.2% dip in ARGX on announcement day is the market voicing a legitimate complaint: $2.2 billion in cash — roughly 4% of a $51 billion market cap — for a Phase 1b asset is aggressive by any standard convention. Argenx’s own corporate development VP admitted the deal is not at the “standard level of validation” the company usually requires, framing it instead as calculated risk on novel target biology. Both readings are true. What the market is underweighting is the alternative: argenx has $4.2 billion of Vyvgart revenue growing 90% year over year and a stated Vision 2030 objective of five late-stage molecules across 10 indications. With that cash generation and a strategy that explicitly requires pipeline depth, the question is not whether argenx deploys capital — it is whether CD122 biology is the right place to deploy it. The Forte Phase 1b vitiligo data (29.6% mean FVASI improvement at week 24, p=0.020, with separation from baseline as early as day 64) is a credible early answer.

For traders, the near-term event is the Phase 2 celiac data in H2 2026 — and note the sequencing: the deal was announced in July, meaning argenx knew the celiac Phase 2 readout was coming within months of close. A buyer with this much visibility into imminent data is underwriting a specific near-term catalyst, not just target biology. A positive celiac readout validates the “pipeline-in-a-product” thesis across two autoimmune settings within the first year of ownership; a miss makes the $2.2 billion look like the peak of the Phase 1b enthusiasm curve.

Mechanism and Strategy Context

The strategic logic is mechanism diversification, and it is sound. Vyvgart works by stripping IgG autoantibodies via FcRn blockade — a humoral mechanism. FB102 blocks CD122, the shared IL-2/IL-15 receptor beta subunit, which suppresses pathogenic T-cell and NK-cell activity — a cellular mechanism. That matters commercially because the diseases FB102 targets (vitiligo, celiac, alopecia areata) are T-cell-mediated conditions where FcRn blockade has little to offer: argenx is buying access to indications its existing franchise cannot touch. The vitiligo market is being validated by competitors right now, and celiac disease has no approved therapy at all — a Phase 2 asset with positive Phase 1b data in a zero-treatment market is exactly the kind of option argenx’s balance sheet is built to buy.

The Forte position itself — closing at $76.50 against the $77 offer — tells you the arb market expects the tender to close without a competing bid, which is the rational read on a 40.5% premium over the prior close and roughly 86% over the post-Phase 1b VWAP. There is no merger-spread trade here; there is only the question of whether argenx paid a fair price for a real asset.

Risks and What Could Go Wrong

1. The celiac Phase 2 in H2 2026 is the first test of the acquired asset under argenx ownership — a miss directly impairs $2.2 billion of deployed capital and the “calculated risk” framing with it.
2. Vitiligo competition: the anti-T-cell vitiligo space is not empty, and FB102 must show its CD122 mechanism can keep pace with rival mechanisms on repigmentation depth and durability.
3. CD122 blockade carries inherent immunosuppression risk — IL-2 and IL-15 signaling also supports regulatory T-cell function and immune surveillance; a safety finding in larger trials would complicate the chronic-dosing profile these indications require.
4. Premium discipline: Vision 2030 implies more deals. If argenx normalizes paying Phase 1b premiums at $2 billion a ticket, the discipline that made its Vyvgart economics great starts eroding.

Position read: the 3.2% dip was noise, not a verdict. ARGX remains a franchise story with a freshly acquired catalyst — the celiac readout this half is where the acquisition thesis either earns its premium or starts to haunt the deal math.