Tiumbio to Present First Clinical Data for Dual TGF-β/VEGF Inhibitor Tosposertib (TU2218) at SITC 2025, "Robust Response Rate"

• 70.6% Partial Response and 82.4% Disease Control Rate Observed in Interim Phase II Data

SEONGNAM, South Korea, Nov. 10, 2025 /PRNewswire/ -- On Friday, 7 November (local time) at the Society for Immunotherapy of Cancer (SITC) 2025 annual meeting, Tiumbio Co., Ltd. (KOSDAQ: 321550), a clinical-stage biopharmaceutical company dedicated to developing novel therapies for rare and intractable diseases, today shared the interim Phase II clinical data for its "first-in-class" Tosposertib (TU2218), a dual inhibitor against TGFβ type I receptor (TGFβRI /ALK5) and VEGFR2. The study evaluated Tosposertib in combination with MSD's Keytruda (pembrolizumab) as a first-line therapy for patients with recurrent/metastatic(r/m) head and neck squamous cell carcinoma (HNSCC).

Tosposertib (TU2218) is a highly potent, oral dual inhibitor designed to block the signaling pathways of transforming growth factor-beta (TGF-β) and vascular endothelial growth factor (VEGF), two critical mediators of tumor growth and metastasis. This novel drug candidate was discovered and developed by Tiumbio to enhance the therapeutic efficacy of immune-oncology agents such as Keytruda.

Hun-Taek Kim, Ph.D., CEO of Tiumbio, stated "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." He added, "The combination of Tosposertib (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."

The company plans to actively advance patient enrollment for the Tosposertib combination therapy and expand its global clinical trial sites to accelerate the studies required for regulatory approval. Through these efforts, 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 to pursue combination trials and broader indication expansion.

Tosposertib (TU2218: TGF-β/VEGF dual inhibitor): Solid Tumors

Poster title: Phase 2 trial of TU2218, TGFβ-RI and VEGF-R2 dual inhibitor in combination with Pembrolizumab in patients with head and neck squamous cell carcinoma (HNSCC)

Observations in the poster presentation include:

• As of July 31, 2025 data cutoff date, 27 patients (pts) were enrolled
  • The efficacy-evaluable population consisted of 17 patients who had received prior treatments such as surgery, chemotherapy, or radiotherapy.
  • Response rates overall (N=17): 70.6%, including 9 confirmed partial responses (PRs) and 3 unconfirmed PRs by Response Evaluation Criteria in Solid Tumors (RECIST) v1.1. per investigator assessment, including
    • 1L : Response rates overall (N=11) : 72.7% (8/11), including 6 confirmed partial responses (PRs) and 2 unconfirmed PRs
    • 2L+ : Response rates overall (N=6) : 66.7% (4/6), including 3 confirmed partial response (PRs) and 1 unconfirmed PRs
    • Responses observed across PD-L1 levels (CPS 1-19: 66.7% [8/12]; CPS≥20: 80% [4/5])
  • At the time of data cutoff, 17 patients of the 27 enrolled, remained on treatment.
  • Median follow up of 2.6 months for the 27 patients
  • In 27 patients the combination was well tolerated and no significant overlapping toxicities with pembrolizumab were observed.
  • Treatment-emergent adverse events (TEAEs) were reported in 26 pts
    • Most were Grade (G) 1 or 2 in severity (no G5 were observed)
    • G≥3 TEAEs occurred in 11 patients (40.7%)
    • Most common adverse events included rash and mucositis.
    • No cases of major bleeding or cardiovascular toxicities-safety concerns typically associated with VEGF or TGF-β inhibition- were observed

About Tiumbio Co., Ltd.

Tiumbio is dedicated to the discovery and development of innovative therapies that alleviate the burden of serious and debilitating disease. Tiumbio's mission is to expand hope and improve the quality of life for people through science. For further information, visit our website at www.tiumbio.com/en and connect with us on LinkedIn.

Contacts:

Director Dae-hun Park, Management Office / [email protected]
Manager Hyun-kyoung Kim, Future Growth Team / [email protected]

SOURCE TiumBio