SUZHOU, China, Nov. 11, 2022, Transcenta Holding Limited ("Transcenta") (HKEX: 06628), a clinical stage biopharmaceutical company with fully-integrated capabilities in discovery, research, development and manufacturing of antibody-based therapeutics, announces that it has presented two scientific posters at the 37th Society for Immunotherapy of Cancer's (SITC) Annual Meeting in Boston, MA, November 8-12, 2022.

• One related to TST001 (Osemitamab), a high affinity humanized anti-Claudin18.2 monoclonal antibody with enhanced ADCC, regarding the prevalence of Claudin18.2 and PD-L1 Expression in Chinese patients with gastric/gastroesophageal junction adenocarcinoma using Transcenta's proprietary Claudin18.2 specific IHC antibody and a commercial kit for PD-L1 detection.

• The other is a Trial in Progress (TiP) abstract on TST005, a bi-functional anti-PD-L1 and TGF-β trap fusion protein: a phase 1, first in human, open-label, dose escalation and dose expansion study in patients with locally advanced or metastatic solid tumors.

Details are as follows:

Abstract#105: Prevalence of Claudin18.2 and PD-L1 Expression in Chinese Gastric/Gastroesophageal Junction Adenocarcinoma

Claudin18.2, expressed at a significant level in multiple tumor types including gastric cancer, is a promising target for gastric cancer treatment. Immunotherapy targeting PD-1 combined with chemotherapy has been approved as the first line treatment of gastric/gastroesophageal junction (G/GEJ) adenocarcinoma. Understanding the expression profiles of Claudin18.2 and PD-L1 could offer guidance for the development of combination therapies that maximize the benefits of both agents. This study investigated the prevalence of Claudin18.2 expression from surgical resections of G/GEJ adenocarcinoma at diagnosis and its correlation with PD-L1 expression in a cohort of Chinese patients.

A total of 300 G/GEJ resected adenocarcinoma tissue samples were assessed using Transcenta's proprietary Claudin18.2 specific antibody 14G11 and commercial kit PD-L1 IHC 28-8 pharmDx. Claudin18.2 staining in ≥ 10% of the tumor cells at 1+ or above intensity was present in 216 (72%) tissue samples tested. For PD-L1 expression, 51 (17%) had PD-L1 CPS ≥ 5. About 19% (n=41/216) of the Claudin18.2 positive samples also showed PD-L1 CPS ≥ 5.

No correlation between the two markers expression was observed.

Abstract#771: A phase 1, first in human, open-label, dose escalation and dose expansion study of TST005 in patients with locally advanced or metastatic solid tumors

TST005 is a novel bi-functional fusion protein combining a high affinity PD-L1 monoclonal antibody (mAb) in a fragment crystallizable (Fc) silenced immunoglobulin G1 (IgG1) backbone and a differentiated transforming growth factor beta (TGF‑β) trap with improved stability.  This study investigated the safety, tolerability and preliminary anti-tumor activity of TST005 in solid tumors.

In a preclinical EMT6/hPD-L1 breast tumor model with high TGF-β expression, TST005 treatment showed better tumor inhibition compared to M7824 analog, a PD-L1/TGFβ bi-functional fusion protein.

This study is ongoing at 4 sites in the US and China. As of Aug 24, 2022, the first three dose cohorts have been completed and no DLT was observed.

The full text of posters is available on Transcenta's website: https://www.transcenta.com/

About TST001 (Osemitamab)

TST001 (Osemitamab) is a high affinity humanized anti-Claudin18.2 monoclonal antibody with enhanced antibody-dependent cellular cytotoxicity ("ADCC") and complement-dependent cytotoxicity ("CDC") activities and potent anti-tumor activities in tumor xenograft models. TST001 (Osemitamab) is the second most advanced Claudin18.2 targeting antibody being developed globally. TST001 (Osemitamab) is generated using Transcenta's Immune Tolerance Breaking Technology (IMTB) platform. TST001 (Osemitamab) kills Claudin18.2 expressing tumor cells by mechanisms of ADCC and CDC. Leveraging advanced bioprocessing technology, the fucose content of TST001 (Osemitamab) was significantly reduced during the production, which further enhanced NK cells mediated ADCC activity of TST001 (Osemitamab). Clinical trials for TST001 (Osemitamab) are ongoing in the U.S. and China (NCT04396821, NCT04495296/CTR20201281). TST001 (Osemitamab) was granted Orphan Drug Designation in the U.S. by FDA for the treatment of patients with gastric or gastroesophageal junction (G/GEJ) cancer.

About TST005

TST005 is the second bi-functional anti-PD-L1 and TGF-β trap fusion protein entering the global clinical stage. It simultaneously targets two immuno-suppressive pathways, transforming growth factor -β (TGF-β) and programmed cell death ligand-1 (PD-L1), that are commonly used by cancer cells to evade the immune system. TST005 consists of a high affinity PD-L1 antibody fused with an engineered TGF-β Receptor Type II protein in its C-terminal. TST005 lacks FcR binding activity and thus has reduced FcR mediated killing of PD-L1 expressing effector T cells. TST005's high PD-L1 binding activity and enhanced TGF-β trap stability enables the targeted delivery of TGF-β trap into PD-L1 expressing tumors, thereby minimizing off-target toxicities of systemic inhibition of TGF-β signaling. TST005 displayed potent activity in vitro in reversing TGF-β induced T-cell suppression. In multiple syngeneic tumor models, TST005 induced significant increase of CD8+ T-cell infiltration into PD-L1 expressing tumors and displayed dose-dependent tumor growth inhibition in tumor model not sensitive to PD-(L)1 treatment due to high level TGF-β. TST005 is well tolerated in non-human primates and displayed a linear PK profile. TST005 is a potentially differentiated bi-functional immunotherapy candidate with improved therapeutic window. TST005 is being investigated in a FIH trial in the US and China (NCT04958434/CTR20221397).

About Transcenta Holding Limited

Transcenta (HKEX: 06628) is a clinical stage biopharmaceutical company with fully integrated capabilities in antibody-based biotherapeutics discovery, research, development and manufacturing.

Transcenta has established global footprint, with Headquarters and Discovery, Clinical and Translational Research Center in Suzhou, Process and Product Development Center and Manufacturing Facility in Hangzhou, and Clinical Development Centers in Princeton, US and in Beijing, Shanghai and Guangzhou of China, and External Partnering Center in Boston and Los Angeles, US. Transcenta has also initiated the construction of the Group Headquarters and the second high-end biopharmaceutical facility with ICB as its core technology in Suzhou Industrial Park. Transcenta is developing ten therapeutic antibody molecules for oncology and selected non-oncology indications including bone and kidney disorders.

For more information, please visit www.transcenta.com and https://www.linkedin.com/company/transcenta.

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