TRexBio Initiates Phase 1b Study of TRB-061 in Moderate-to-Severe Atopic Dermatitis with First Patient Dosed
TRex Bio, Inc. (“TRexBio”), a clinical-stage biotechnology company focused on discovering and developing immunoregulatory therapies rooted in tissue regulatory T cell (Treg) biology, has announced a significant milestone in the advancement of its lead therapeutic candidate, TRB-061. The company revealed that the first patient has been successfully dosed in the Phase 1b portion of its ongoing clinical trial evaluating TRB-061, a novel tumor necrosis factor receptor 2 (TNFR2) agonist being developed for the treatment of moderate-to-severe Atopic Dermatitis. This development marks a meaningful step forward in TRexBio’s broader mission to pioneer innovative approaches to immune modulation by restoring balance within inflamed tissues.
The initiation of dosing in the Phase 1b segment builds upon earlier clinical progress and represents a critical transition toward generating proof-of-concept data in patients. Unlike conventional therapies that primarily suppress immune responses, TRB-061 is designed to recalibrate the immune system by selectively enhancing the function of regulatory T cells. This approach aims to address the underlying immune dysregulation that drives chronic inflammatory conditions such as atopic dermatitis, rather than simply mitigating symptoms.
Johnston Erwin, Chief Executive Officer of TRexBio, emphasized the importance of this milestone in the company’s clinical journey. He noted that while currently available therapies for atopic dermatitis—including biologics and small molecule inhibitors—have significantly improved patient outcomes in recent years, there remains a substantial unmet need. Many patients continue to experience incomplete responses, loss of efficacy over time, or adverse effects that limit long-term use. According to Erwin, TRB-061 has the potential to offer a differentiated treatment paradigm, one that leverages a novel mechanism of action to deliver more durable and targeted disease control.
TRB-061 is the company’s lead wholly owned program and is specifically engineered to selectively activate TNFR2, a receptor known to play a pivotal role in the expansion and activation of regulatory T cells. Tregs are essential for maintaining immune tolerance and preventing excessive inflammatory responses. In diseases like atopic dermatitis, the balance between pro-inflammatory and regulatory immune signals is disrupted, leading to persistent skin inflammation, barrier dysfunction, and chronic symptoms such as itching, redness, and lesions.
By selectively agonizing TNFR2, TRB-061 aims to expand and activate tissue-resident Tregs without stimulating other immune cell populations that may exacerbate inflammation. This targeted approach is particularly important, as broad immune activation or suppression can lead to unintended consequences, including increased susceptibility to infections or systemic side effects. In contrast, TRB-061 is designed to promote localized immune regulation within affected tissues, thereby enhancing both anti-inflammatory responses and tissue repair mechanisms.
Ariella Kelman, M.D., Chief Medical Officer of TRexBio, highlighted the scientific rationale underpinning the program. She explained that atopic dermatitis is not merely a superficial skin condition but a complex immunological disorder in which Treg dysfunction plays a central role. By restoring the activity of these regulatory cells, TRB-061 has the potential to directly address the root cause of inflammation. Moreover, the therapy may contribute to improved skin barrier integrity, which is often compromised in patients with moderate-to-severe disease.
The Phase 1b portion of the clinical trial is designed as a randomized, double-blind, placebo-controlled study—considered the gold standard for early-stage clinical evaluation. This segment will involve approximately 50 participants diagnosed with moderate-to-severe atopic dermatitis. TRB-061 will be administered subcutaneously, allowing researchers to assess its safety and tolerability as primary endpoints. These parameters are critical in determining whether the therapy can progress to later-stage trials.
In addition to safety, the study will evaluate several secondary endpoints, including pharmacokinetics (PK) and immunogenicity. PK assessments will provide insights into how the drug is absorbed, distributed, metabolized, and eliminated in the body, while immunogenicity analyses will determine whether the therapy elicits unwanted immune responses. Together, these data will help establish an initial profile of TRB-061’s behavior in human subjects.
Importantly, the trial also includes a range of exploratory endpoints aimed at understanding the biological activity of TRB-061. These include pharmacodynamic (PD) measures such as the expansion of regulatory T cells in both blood and skin tissue, as well as clinical assessments of disease severity and progression. By integrating these endpoints, the study seeks to establish a direct link between the drug’s mechanism of action and its potential therapeutic effects.
The anticipated timeline for the study indicates that initial data could be available in the first half of 2027. These results will be crucial in determining whether TRB-061 can deliver on its promise of a differentiated and potentially transformative treatment option for patients with atopic dermatitis. Positive findings could pave the way for larger Phase 2 and Phase 3 trials, ultimately bringing the therapy closer to regulatory approval and clinical use.
The broader implications of TRexBio’s approach extend beyond atopic dermatitis. The company’s platform, which centers on tissue-specific Treg biology, has the potential to be applied across a range of autoimmune and inflammatory diseases. By focusing on restoring immune balance rather than broadly suppressing immune activity, TRexBio aims to redefine how such conditions are treated.
Atopic dermatitis itself remains a significant global health challenge, affecting millions of individuals worldwide. The disease is associated with considerable physical discomfort, psychological stress, and reduced quality of life. Despite advances in treatment, many patients continue to struggle with persistent symptoms and limited therapeutic options. Innovations like TRB-061 could represent a new frontier in addressing these challenges by targeting the underlying mechanisms of disease.
In summary, the dosing of the first patient in the Phase 1b trial of TRB-061 marks an important milestone for TRexBio and the field of immunoregulatory therapeutics. By advancing a novel TNFR2 agonist designed to enhance regulatory T cell function, the company is exploring a promising new strategy for treating atopic dermatitis and potentially other inflammatory conditions. As the clinical program progresses, the data generated will provide valuable insights into the feasibility and effectiveness of this innovative approach, with the potential to significantly impact patient care in the years ahead.
About TRB-061
TRB-061 is a novel, selective TNFR2 agonist designed to restore immune balance by activating and expanding effector Tregs in tissue. TNFR2 is a crucial regulator of immune homeostasis, supporting tissue repair and counteracting inflammation. Defects in TNFR2 signaling are linked to multiple autoimmune and inflammatory diseases. Selective agonism of TNFR2 by TRB-061 may represent a new therapeutic pillar for long-term inflammatory disease control. TRB-061 is currently in a Phase 1 clinical trial for moderate-to-severe atopic dermatitis.
About Atopic Dermatitis
Atopic dermatitis (“AD”) is a chronic inflammatory skin disease characterized by rash, itching, and skin barrier dysfunction. AD affects up to 20% of children and 10% of adults, affecting approximately 204 million people worldwide. In moderate-to-severe cases, AD is associated with systemic immune activation, extensive body surface area involvement, and substantial quality-of-life impairment. While approved biologics have improved outcomes for some patients, more than half discontinue current therapies within two years due to ineffectiveness and long-term side effects.
About TRexBio
TRexBio is a clinical-stage biotechnology company developing novel therapeutics designed to modulate tissue regulatory T cell biology and restore immune balance in autoimmune and inflammatory diseases. The company’s Deep Biology Platform maps human tissue Treg behavior to disease processes to identify and characterize novel targets for therapeutic intervention in autoimmune and inflammatory diseases. This platform has yielded multiple development candidates for potential first-in-class and best-in-class medicines across TRexBio’s own pipeline, as well as with top pharma partners. TRexBio is led by an experienced management team and headquartered in South San Francisco, California. For more information, visit www.trex.bio.
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