• Plonmarlimab, China's first high-affinity GM-CSF antibody approved for clinical studies for MAS, now designated as a breakthrough therapy to facilitate clinical development in China and globally
• Plonmarlimab showed encouraging efficacy and safety in Phase 2 study, with all evaluable patients achieving clinical response within 8 weeks and significantly reducing steroid use
• The Company will expedite pivotal study for plonmarlimab to bring new treatment option for MAS, a disease with high mortality rates

HANGZHOU, China – September 20, 2024 – TJ Biopharma (“TJ Bio” or “Company”), a fully integrated biotech company in China that develops, manufactures, and partners on innovative biologics for autoimmune diseases and oncology, today announced that the Center for Drug Evaluation (CDE) of China's National Medical Products Administration (NMPA) has granted Breakthrough Therapy Designation to plonmarlimab (also known as TJM2), the Company's proprietary high-affinity GM-CSF antibody, for the treatment of rheumatic immune disease-related hemophagocytic lymphohistiocytosis, also known as Macrophage Activation Syndrome (MAS).

MAS is a life-threatening autoimmune disease characterized by persistent high fever, hepatosplenomegaly, central nervous system dysfunction, and hemorrhagic symptoms¹. Without prompt treatment, MAS can rapidly progress to multiple organ failure and death². Currently, there are no approved innovative therapies for MAS treatment in China or globally³. Existing steroid-based treatments offer limited efficacy and come with significant side effects, underscoring the substantial unmet medical need in this field.

The Breakthrough Therapy Designation was granted based on promising results from the Phase 2 study (CTR20230579), an open-label, single-arm, multi-center clinical trial evaluating the safety, tolerability, and efficacy of plonmarlimab in MAS patients. Among 12 efficacy-evaluable MAS patients who had an inadequate response to 3-day high-dose steroid pulse therapy, the results were compelling:

• Efficacy: All patients achieved clinical response after 8 weeks of plonmarlimab treatment, with a high complete response rate
• Steroid reduction: All patients reduced their steroid use by at least 50%
• Safety: The treatment was well-tolerated, with most adverse events being Grade 1 and no dose-limiting toxicities observed

“Receiving Breakthrough Therapy Designation for plonmarlimab is a pivotal moment for TJ Bio and our global autoimmune pipeline. This milestone underscores the potential of plonmarlimab, not just for MAS, but across a broader spectrum of autoimmune diseases,” said Dr. Jingwu Zang, Founder and Chairman of TJ Bio. “The compelling results from our Phase 2 study have shown the potential impact of this therapy on patients’ lives. With this designation, we’re now on an accelerated path to advance our pivotal study, bringing us closer to providing a much-needed therapy for MAS patients. This recognition from the CDE reinforces our commitment to addressing high unmet medical needs and potentially reshaping the autoimmune treatment landscape."

According to China’s Drug Registration Regulation implemented on July 1, 2020, Breakthrough Therapy Designation is one of the accelerated drug registration procedures. Biologics receiving this designation benefit from increased communication opportunities during clinical trials and faster regulatory feedback. This streamlined process aims to improve R&D success rates, shorten development timelines, and ultimately provide patients with faster access to potentially life-changing treatments.

1. Experimental and therapeutic medicine 22: 904, 2021

2. Nature Reviews Rheumatology. Mar 2021 ;17 :146-157

3. Chinese Guidelines for Diagnosis and Treatment of Hemophagocytic Syndrome. 2022

About Plonmarlimab

Plonmarlimab is an internally discovered neutralizing antibody against human GM-CSF, an important cytokine that plays a critical role in chronic inflammation and destruction in autoimmune diseases such as RA. GM-CSF can polarize macrophages into the pro-inflammatory M1 phenotype and is known to induce an inflammatory cascade involving other pro-inflammatory cytokines such as tumor-necrosis factor (TNF), interleukin-1 (IL-1), IL-6, IL-12, and IL-23. It is evident that GM-CSF plays a crucial role in the pathogenesis and disease progression of multiple autoimmune conditions. Plonmarlimab specifically binds to human GM-CSF with high affinity and can block GM-CSF from binding to its receptor, thereby preventing downstream signaling and target cell activation. As a result, it can effectively inhibit inflammatory responses mediated by macrophages, neutrophils, and dendritic cells, leading to reduced tissue inflammation and damage.

About TJ Biopharma

TJ Biopharma is a fully integrated biotech company pioneering innovative biologics in autoimmune diseases and immuno-oncology. Committed to bringing life-changing immunotherapies from lab to patients worldwide, TJ Biopharma features a differentiated pipeline of advanced clinical assets, state-of-the-art GMP manufacturing capabilities, and a diverse, sustainable revenue model that drives value throughout the innovation pathway in China and globally. For more information, please visit: TJBio.com.