On November 10, 2025 at the Society for Immunotherapy of Cancer (SITC) (Free SITC Whitepaper) 2025 annual meeting, Tiumbio Co., Ltd. (KOSDAQ: 321550), a clinical-stage biopharmaceutical company dedicated to developing novel therapies for rare and intractable diseases, reported 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).

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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 (Free SITC Whitepaper) 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

(Press release, TiumBio, NOV 10, 2025, View Source [SID1234659743])