Argenx's $2.2B Forte Deal Puts CD122 in the Autoimmune Spotlight

Why FB102 is drawing industry attention, and what the acquisition means for CD122 target validation, antibody discovery, and preclinical drug development?

On July 27, 2026, Argenx announced an agreement to acquire Forte Biosciences for approximately $2.2 billion in cash. The transaction gives argenx control of FB102, a clinical-stage anti-CD122 monoclonal antibody with proof-of-concept data in vitiligo and celiac disease ^[1]. Phase 2 celiac disease data are expected in the second half of 2026.

The deal is notable not only for its size, but also for what it signals scientifically. CD122 has moved from an emerging immunology target to a clinically supported mechanism with potential across multiple autoimmune diseases.

What Is CD122, and Why Does It Matter?

CD122, also known as interleukin-2 receptor beta, IL-2Rβ, or IL2RB, is a shared signaling subunit of the IL-2 and IL-15 receptor systems. It is expressed primarily on natural killer cells, CD8+ T cells, and selected CD4+ T-cell subsets.

In the IL-15 pathway, IL-15 is commonly presented by IL-15Rα on one cell to the CD122/CD132 receptor complex on a neighboring immune cell. This process, known as trans-presentation, activates JAK1/JAK3-STAT3/STAT5, PI3K-AKT-mTOR, and MAPK signaling ^[2]. These pathways regulate immune-cell proliferation, survival, cytotoxicity, and memory formation.

Figure 1. IL-15 activates lymphocytes by engaging the IL-2Rβ/γc receptor complex through trans-presentation, soluble IL-15/IL-15Rα complexes, or cis-presentation ^[2].

This biology creates an important therapeutic opportunity. Persistent IL-15 and CD122 signaling can support pathogenic tissue-resident memory T cells, cytotoxic CD8+ T cells, and NK-cell activity in autoimmune and inflammatory diseases.

Blocking CD122 can suppress both IL-2- and IL-15-mediated activation in disease-driving immune populations. At the same time, precision-engineered antibodies may preserve regulatory T-cell activity mediated through the high-affinity IL-2 receptor, which includes CD25, CD122, and CD132.

From Mechanism to Therapeutic Indications

The strongest current interest in CD122 inhibition centers on diseases in which pathogenic memory T cells remain active within affected tissues.

In vitiligo, CD122-positive tissue-resident memory T cells can sustain IFN-γ-driven inflammation and recurrent melanocyte destruction. In celiac disease, IL-15 signaling supports intraepithelial lymphocyte activation, epithelial injury, and persistent intestinal inflammation, including in patients who continue to experience disease activity despite following a gluten-free diet ^[3].

The same mechanism may also be relevant to alopecia areata and other T-cell- and NK-cell-mediated autoimmune disorders.

Figure 2. IFNγ and type I IFNs activate distinct signaling pathways leading to the upregulation of IL-15 ^[3].

FB102 is designed to inhibit pathogenic IL-2 and IL-15 signaling through CD122 while retaining regulatory immune function. Forte reported positive Phase 1b findings in both vitiligo and celiac disease, which argenx identified as important drivers of its acquisition decision ^[4]. Argenx now sees the molecule as a potential “pipeline-in-a-product” opportunity across several autoimmune indications.

A Competitive but Still Open Market

The IL-15/CD122 therapeutic landscape remains relatively early, but industry activity is increasing. Development strategies generally fall into two distinct categories.

In autoimmune disease, companies are developing antagonistic antibodies against IL-15 or CD122 to reduce pathogenic immune-cell survival and activation. Clinical programs have included FB102, ANB033, TEV-53408, CALY-002/GIA632, and ordesekimab. Target indications include vitiligo, celiac disease, alopecia areata, atopic dermatitis, and other inflammatory conditions.

In oncology, the strategy is usually reversed. IL-15 agonists and engineered cytokine complexes are used to stimulate NK cells and cytotoxic T cells. N-803, an IL-15 superagonist, provided important clinical validation for activating this pathway in cancer, although systemic immune activation and therapeutic-window management remain major development considerations ^[5-6].

Figure 3. Tumor-derived IL-15 activates IL-2Rβ on tissue-resident cytotoxic ILC1s, promoting their expansion and antitumor activity in chRCC and PyMT breast cancer ^[5].

No pure anti-IL-15 or anti-CD122 monoclonal antibody has yet established a marketed category in autoimmune disease. This leaves room for differentiated programs that can demonstrate:

• Durable efficacy within affected tissues
• Selective modulation of pathogenic immune cells
• Preservation of regulatory immune function
• Convenient systemic or subcutaneous administration
• A clear safety advantage over broader immunosuppressive approaches

The Argenx-Forte transaction indicates that companies are increasingly willing to invest in targets supported by mechanistic clarity, early clinical validation, and expansion potential across multiple indications.

The Translational Roadblock: Overcoming Species-Specific CD122 Barriers

Moving CD122-targeted candidates from early discovery to clinical validation presents a critical translational roadblock. Therapeutic antibodies directed against human CD122 (IL2RB) frequently exhibit poor binding affinity to murine receptors due to profound species-specific differences in the extracellular domains.

For biopharma developers, relying on conventional wild-type mouse models can completely compromise the evaluation of target engagement and pharmacological activity, leading to costly false-negative preclinical readouts. Cyagen effectively dismantles this barrier with advanced humanized CD122/IL2RB mouse models (Product ID: C001820). By expressing the human receptor under endogenous regulatory control, these precision models provide the essential foundation for rigorously assessing antibody binding, STAT5 signaling, immune-cell responses, and in vivo efficacy.

Figure 4. Gene editing strategy of B6-hIL2RB mice. The mouse Il2rb endogenous signal peptide and extracellular domain were replaced with the human IL2RB signal peptide and extracellular domain.

An End-to-End Discovery and Validation Engine for CD122 Assets

Translationally relevant animal models are only one half of a successful development strategy. Robust CD122 programs demand superior antibody candidates characterized by exceptional binding affinity and precise functional modulation of IL-2 and IL-15 signaling.

Cyagen accelerates this entire lifecycle through an integrated preclinical platform. Our HUGO-Ab™ platform supports fully human antibody discovery through HUGO-Mab™ for monoclonal antibodies, HUGO-Light™ for common light-chain multispecific antibodies, and HUGO-Nano™ for single-domain antibodies targeting challenging epitopes.

By uniting human immunoglobulin repertoires with in vivo affinity maturation, developers can generate high-affinity CD122 candidates with minimal humanization requirements. When coupled seamlessly with our humanized IL2RB mouse models, Cyagen delivers an unmatched infrastructure for integrated expression, binding assays, immune profiling, and definitive in vivo pharmacodynamic evaluation.

👉 Explore our HUGO-Ab™ fully human antibody discovery platform

What Comes Next for CD122 Drug Development?

The Argenx-Forte transaction dictates a clear industry mandate: mechanistic clarity combined with early clinical differentiation generates massive strategic value. As the therapeutic landscape expands across vitiligo, celiac disease, and oncology, securing candidates with absolute selectivity and validating them in human-relevant models is no longer optional—it is required for clinical survival.

Ready to advance a CD122 or IL-15 antibody program?

👉 Schedule a Strategy Session with Our Experts to Accelerate Your IL-15/CD122 Antibody Discovery Program

Reference

[1] Forte Biosciences, Inc. argenx to acquire Forte Biosciences, Inc., adding first-in-class anti-CD122 antibody, FB102, to its immunology pipeline [Internet]. Dallas (TX): Forte Biosciences, Inc.; 2026 Jul 27 [cited 2026 Jul 29]. Available from: https://www.fortebiorx.com/investor-relations/news/news-details/2026/argenx-to-Acquire-Forte-Biosciences-Inc--Adding-First-in-Class-Anti-CD122-Antibody-FB102-to-Its-Immunology-Pipeline/default.aspx

[2] Skariah N, James OJ, Swamy M. Signalling mechanisms driving homeostatic and inflammatory effects of interleukin-15 on tissue lymphocytes. Discov Immunol. 2024 Jan 30;3(1):kyae002. doi: 10.1093/discim/kyae002. PMID: 38405398; PMCID: PMC10883678.

[3] Lee H, Park SH, Shin EC. IL-15 in T-Cell Responses and Immunopathogenesis. Immune Netw. 2024 Feb 16;24(1):e11. doi: 10.4110/in.2024.24.e11. PMID: 38455459; PMCID: PMC10917573.

[4] Forte Biosciences, Inc. FB102 achieves statistically significant improvement in vitiligo at week 24 after completion of 12-week treatment period [Internet]. Dallas (TX): Forte Biosciences, Inc.; 2026 Jul 9 [cited 2026 Jul 29]. Available from: https://www.fortebiorx.com/investor-relations/news/news-details/2026/FB102-Achieves-Statistically-Significant-Improvement-in-Vitiligo-at-Week-24-After-Completion-of-12-Week-Treatment-Period/default.aspx

[5] Franz T, Negele J, Kahlfuss S. Cytotoxic innate lymphoid cells sense tumor-derived IL-15: a novel mechanism of cancer immunosurveillance. Signal Transduct Target Ther. 2022 Sep 17;7(1):326. doi: 10.1038/s41392-022-01173-x. PMID: 36115839; PMCID: PMC9482643.

[6] Li Z, Wrangle J, He K, Sprent J, Rubinstein MP. IL-15: from discovery to FDA approval. J Hematol Oncol. 2025 Feb 18;18(1):19. doi: 10.1186/s13045-025-01664-8. PMID: 39966991; PMCID: PMC11837486.