Tiumbio's Dual TGF-β/VEGF Inhibitor Tosposertib Shows 70.6% Response Rate in Head and Neck Cancer Trial
Key Insights
Tiumbio (search)'s first-in-class dual inhibitor Tosposertib (search) (TU2218) demonstrated a 70.6% overall response rate when combined with pembrolizumab in patients with recurrent/metastatic head and neck squamous cell carcinoma.
The Phase II interim data presented at SITC 2025 showed responses across different PD-L1 (search) expression levels, with 72.7% response rate in first-line patients and 66.7% in second-line or later patients.
The oral dual TGF-β (search)/VEGF (search) inhibitor was well-tolerated with no major bleeding or cardiovascular toxicities typically associated with VEGF or TGF-β inhibition observed in the 27-patient study.
Tiumbio (search) Co., Ltd. presented promising interim Phase II clinical data for its first-in-class dual inhibitor Tosposertib (search) (TU2218) at the Society for Immunotherapy of Cancer (SITC) 2025 annual meeting, demonstrating a 70.6% overall response rate when combined with pembrolizumab in patients with recurrent/metastatic head and neck squamous cell carcinoma (HNSCC).
The South Korean clinical-stage biopharmaceutical company shared data from 27 enrolled patients as of July 31, 2025, with 17 patients comprising the efficacy-evaluable population who had received prior treatments including surgery, chemotherapy, or radiotherapy.
Strong Efficacy Across Treatment Lines
The interim results showed robust antitumor activity across different treatment settings. In first-line patients (N=11), the overall response rate reached 72.7% (8/11), including 6 confirmed partial responses and 2 unconfirmed partial responses. Second-line and beyond patients (N=6) achieved a 66.7% (4/6) response rate, with 3 confirmed and 1 unconfirmed partial responses, all assessed by Response Evaluation Criteria in Solid Tumors (RECIST) v1.1.
Notably, responses were observed across different PD-L1 (search) expression levels, with 66.7% (8/12) response rate in patients with Combined Positive Score (CPS) 1-19 and 80% (4/5) in those with CPS ≥20. At the data cutoff, 17 of the 27 enrolled patients remained on treatment, with a median follow-up of 2.6 months.
Novel Dual Mechanism of Action
Tosposertib (search) (TU2218) is a highly potent, oral dual inhibitor designed to block signaling pathways of transforming growth factor-beta (TGF-β (search)) and vascular endothelial growth factor (VEGF (search)), two critical mediators of tumor growth and metastasis. The drug specifically targets TGF-β type I receptor (TGF-βRI (search)/ALK5 (search)) and VEGFR2 (search), developed to enhance the therapeutic efficacy of immune-oncology agents such as pembrolizumab.
"The data presented at SITC mark an important milestone, demonstrating that the strong antitumor activity continues to be sustained with accumulating clinical data and ongoing follow-up," stated Hun-Taek Kim, Ph.D., CEO of Tiumbio (search). "The combination of Tosposertib (search) (TU2218) and Keytruda has shown meaningful potential and value as an immuno-oncology therapy capable of overcoming the limitations of existing immunotherapies or immunotherapy/chemotherapy combinations in recurrent or metastatic head and neck cancer."
Favorable Safety Profile
The combination therapy demonstrated a manageable safety profile across the 27-patient cohort. Treatment-emergent adverse events (TEAEs) were reported in 26 patients, with most being Grade 1 or 2 in severity and no Grade 5 events observed. Grade ≥3 TEAEs occurred in 11 patients (40.7%), with the most common adverse events including rash and mucositis.
Importantly, no cases of major bleeding or cardiovascular toxicities—safety concerns typically associated with VEGF (search) or TGF-β (search) inhibition—were observed. The study found no significant overlapping toxicities with pembrolizumab, suggesting the combination's tolerability.
Development Strategy and Future Plans
Tiumbio (search) plans to actively advance patient enrollment for the Tosposertib (search) combination therapy and expand global clinical trial sites to accelerate studies required for regulatory approval. The company aims to provide patients with recurrent or metastatic head and neck cancer earlier access to treatment and, in collaboration with global partners, continue pursuing combination trials and broader indication expansion.
The clinical-stage biopharmaceutical company, listed on KOSDAQ (321550), is dedicated to developing novel therapies for rare and intractable diseases, with Tosposertib (search) representing a potentially significant advancement in immuno-oncology treatment approaches for head and neck cancer patients.