AACR | Osemitamab (TST001) achieves a research breakthrough in the field of pancreatic cancer treatment

In one refractory pancreatic cancer patient, the target lesion shrank by 86% after six weeks of TST001 treatment and achieved complete remission (CR) after 270 days of treatment.

Princeton, New Jersey, USA, and Suzhou, China, April 8, 2026 — Transcenta Holding (06628.HK), an international biopharmaceutical company with integrated capabilities in biologic drug discovery, development, process development, and manufacturing, will present significant findings at the 2026 AACR Annual Meeting (Abstract No. 2645): its lead asset, osemitamab (TST001), demonstrates clear early activity in pancreatic cancer treatment, with one late-stage patient achieving complete remission (CR), along with antitumor efficacy data from preclinical pancreatic cancer tumor models.

Notably, osemitamab (TST001) has previously received orphan drug designation from the US Food and Drug Administration (FDA) for the treatment of pancreatic cancer patients. At the 2022 International Gastric Cancer Congress (IGCC), related clinical data were disclosed: a pancreatic cancer patient with low Claudin18.2 expression treated with osemitamab (TST001) monotherapy showed sustained partial remission despite disease progression after multiple rounds of chemotherapy. This brings new hope to the treatment of pancreatic cancer, one of the most challenging tumor types, and highlights the breakthrough strength of Chinese innovative drugs in global prospective clinical research.

Pancreatic cancer is known as the 'king of cancers' — with a mortality-to-incidence ratio of approximately 0.94, and the five-year survival rate improving from only 4% two decades ago to 12%. It represents a classic example of a high unmet medical need tumor type. The systematic exploration of the preclinical and early clinical activity of osemitamab (TST001) marks a significant achievement by Chinese teams in exploring combination therapies for challenging tumor types. It aligns with the core developmental direction of Chinese innovative drugs at the AACR conference — focusing on high unmet medical needs, strengthening combination therapy exploration, and advancing biomarker-driven clinical development.

Osemitamab (TST001) is a high-affinity, specific Claudin18.2-targeting humanized monoclonal antibody enhanced with ADCC functionality, capable of effectively killing cancer cells by specifically targeting Claudin18.2 and activating immune cell-mediated ADCC mechanisms. With high affinity and stronger ADCC function, TST001 can cover approximately 55% of gastric cancer patients. Currently, its combination therapy with the PD-1 antibody nivolumab plus chemotherapy has entered a global Phase III clinical trial. Early data show that this combination therapy not only improves overall response rates but also significantly extends progression-free survival. Additionally, the FDA has granted osemitamab (TST001) orphan drug designation for the treatment of gastric and gastroesophageal junction cancers. This CLDN18.2-targeting antibody mediates tumor cell killing through ADCC and CDC mechanisms and originates from Transcenta’s IMTB immune tolerance-breaking platform. It is also one of the core products in the company’s portfolio of 16 differentiated innovative antibody pipelines.

Preclinical study data show that osemitamab (TST001) exhibited strong ADCC activity in two CLDN18.2-positive pancreatic cancer cell lines: in the KRAS wild-type BxPC-3-CLDN18.2 model, tumor growth inhibition (TGI) rates at doses of 3mg/kg and 10mg/kg reached 61% and 98%, respectively, with tumors completely disappearing from day 33 onwards in 7/10 mice in the 10mg/kg group; in the KRAS-mutant MIA PaCa-2-CLDN18.2 model, monotherapy TGI at 10mg/kg was 49%, increasing to 67% when combined with gemcitabine, providing solid data support for clinical combination therapy.

Clinical data come from the Phase I clinical trial (NCT04495296) conducted by Transcenta, a multicenter, open-label, dose escalation and expansion study. The core objective is to evaluate the safety, tolerability, pharmacokinetic characteristics, and preliminary anti-tumor activity of osemitamab (TST001) in patients with CLDN18.2-positive advanced solid tumors, with pancreatic cancer being one of the key tumor types explored. Osemitamab (TST001), as a CLDN18.2-targeting antibody granted orphan drug designation by the FDA, has demonstrated robust anti-tumor potential across various solid tumors. One enrolled pancreatic cancer patient had refractory disease after failure of standard chemotherapy regimens, including gemcitabine and S-1, along with liver metastasis, presenting two major treatment challenges – low tumor CLDN18.2 expression and carrying a KRAS G12R mutation (mutations which often lead to pancreatic cancer resistance to targeted therapies, posing a significant clinical challenge).

This patient received single-agent intravenous infusion of osemitamab (TST001) at 10mg/kg every three weeks, showing clear progress and significant efficacy: at week six of treatment, imaging evaluation showed an 86% reduction in target lesions compared to baseline, with rapid and substantial control of tumor burden and gradual relief of clinical symptoms. Continued treatment for 270 days (approximately nine months) resulted in complete disappearance of target lesions on imaging, meeting criteria for clinical complete response (CR), with no intolerable adverse reactions observed during treatment, demonstrating good safety. Details of this case were disclosed in a research abstract presented at the 2026 AACR conference (abstract number 2645), representing a significant breakthrough for osemitamab (TST001) in refractory pancreatic cancer. It broke the treatment deadlock for patients with low CLDN18.2 expression and KRAS mutations and validated the effectiveness of osemitamab (TST001)'s mechanism of action in mediating tumor cell killing through enhanced ADCC activity, aligning with the current industry trend of exploring precision targeted therapies in pancreatic cancer.

In addition, the study also explored a synergistic treatment strategy combining osemitamab (TST001) with TST003. TST003 is a humanized antibody targeting Gremlin-1 independently developed by Transcenta, with its clinical trial application approved by the National Medical Products Administration. In the BxPC-3-CLDN18.2/Gremlin1 co-expression model, the TGI of osemitamab (TST001) at 3mg/kg combined with TST003 at 30mg/kg was 60%, superior to either agent alone, laying the foundation for the advancement of subsequent combination therapies.

Osemitamab (TST001), a high-affinity humanized antibody independently developed by Transcenta, demonstrates potent ADCC activity in vitro against tumor cells expressing Claudin18.2, with clear anti-tumor activity shown in preclinical models of pancreatic cancer. Its effects are further enhanced when combined with gemcitabine or TST003. Additionally, the complete response observed in one treated pancreatic cancer patient provides strong support for the further clinical development of this drug in CLDN18.2-positive pancreatic cancer.

Pancreatic cancer, one of the most lethal malignant tumors, is difficult to diagnose early and has limited treatment options, resulting in a very low five-year survival rate. This breakthrough progress of osemitamab (TST001) not only fills the gap in treating CLDN18.2-positive pancreatic cancer but also reflects Transcenta's forward-looking layout in challenging tumor types.

About Transcenta

Transcenta is a clinical-stage biopharmaceutical company with comprehensive capabilities in biologic drug discovery, research and development, process development, and production.

Headquartered in Suzhou, Transcenta has successfully established a global business presence: it operates drug discovery, clinical, and translational research centers in Suzhou, a process and product development center and manufacturing facility in Hangzhou, and clinical development centers in China, the United States, and Europe. Transcenta is developing a diversified pipeline of dozens of novel biologics covering oncology and non-oncology indications, including orthopedics, autoimmune diseases, and kidney diseases.

For more information about Transcenta, please visit the company's website: www.transcenta.com or LinkedIn page: Transcenta. If you are interested in exploring capital cooperation opportunities with us, please feel free to reach out via ir@transcenta.com to discuss collaboration possibilities.

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