On August 19, 2026, Mountain Time (MT), the World Conference on Lung Cancer (WCLC) 2026 has officially released the abstracts selected for this year’s congress, including results from the dose-expansion cohort of an ongoing Phase 1 clinical study evaluating HLX43, an innovative PD-L1 antibody-drug conjugate (ADC) developed by Henlius, in patients with previously treated advanced thymic squamous cell carcinoma (TSCC). The study is led by Professor Jie Wang of Cancer Hospital, Chinese Academy of Medical Sciences. The full data will be presented during the Poster Tour session at WCLC on September 14, 2026, from 1:45 p.m. to 1:53 p.m. Seoul Time.
HLX43 is a novel PD-L1-targeting ADC, composed of a fully humanized anti-PD-L1 IgG1 antibody, a novel tripeptide linker and topoisomerase inhibitor payload. The drug to antibody ratio (DAR) is around 8. Its mechanism of action integrates targeted cytotoxic delivery and immune checkpoint activation through PD-L1/PD-1 blockade. Upon binding to PD-L1-expressing tumour cells, HLX43's cytotoxic payload can be delivered into tumour cells via dual mechanisms—First, the ADC undergoes receptor-mediated endocytosis, releasing the cytotoxic payload intracellularly via linker cleavage, and the payload further diffuses into neighbouring tumour cells via bystander effect, thereby blocking DNA replication and triggering tumour cell apoptosis. Meanwhile, the anti-PD-L1 antibody of HLX43 activates immune modulation and blocks immune checkpoints, driving synergistic antitumour efficacy. Early clinical data from its first-in-human study, along with multiple proof-of-concept results across solid tumours, have been presented at several international scientific conferences, including ASCO, WCLC etc., showing a favourable efficacy and safety profile across several solid tumour types, including non-small cell lung cancer (NSCLC), TSCC, gynecologic malignancies, and esophageal squamous cell carcinoma (ESCC). Beyond monotherapy, the Company is actively exploring combination strategies of HLX43 with anti-EGFR mAb pimurutamab or anti-PD-1 mAb serplulimab, aiming to further expand its clinical potential.
Thymic squamous cell carcinoma (TSCC) is a rare, aggressive malignancy with poor prognosis. Patients with advanced TSCC often have limited therapeutic options after failing standard treatment. According to the updated abstract, HLX43 continues to demonstrate promising efficacy and manageable safety in patients with advanced or metastatic TSCC who experienced disease progression after first-line platinum-based chemotherapy, thereby addressing the unmet clinical need for effective treatments for advanced TSCC. The abstract data are as follows:
Patients with advanced or metastatic TSCC who experienced disease progression after first-line platinum-based chemotherapy were administered HLX43 at 2.0 mg/kg, 2.5 mg/kg, or 3.0 mg/kg every three weeks. The primary endpoint of the TSCC cohort was objective response rate (ORR). Secondary endpoints included progression-free survival (PFS), duration of response (DOR), overall survival (OS), safety, immunogenicity, pharmacokinetics, and biomarkers.
By the data cutoff date of March 1, 2026, 34 patients were enrolled and treated with HLX43 at doses of 2.0 mg/kg (n=11), 2.5 mg/kg (n=12), and 3.0mg/kg (n=11). The median number of prior anti-tumor therapies was 3.0 (range, 1-7). A total of 73.5% of the patients had received prior immunotherapy.
Among the 33 response-evaluable patients, blinded independent central review (BICR) per RECIST v1.1 demonstrated an ORR of 39.4% and a disease control rate (DCR) of 84.8%. The ORRs were 58.3%, and 45.5% in the 2.5 and 3.0 mg/kg groups, respectively. At the time of analysis, median PFS, OS, and DOR had not yet been reached. The 6-month PFS rates were 88.9% and 85.7% in the 2.5 and 3.0 mg/kg groups, respectively.
Treatment-related adverse events (TRAEs) of grade ≥3 were reported in 20 (58.8%) patients. The most commonly reported grade ≥3 TRAEs were decreased lymphocyte count (32.4%), decreased white blood cell count (23.5%), and decreased neutrophil count (20.6%). TRAEs leading to treatment discontinuation occurred in two (5.9%) patients, one each in the 2.0 and 3.0 mg/kg dose groups. Treatment-related serious adverse events occurred in four (11.8%) patients, including three in the 2.0 mg/kg dose group and one in the 3.0 mg/kg dose group. No treatment-related deaths were reported.
Notably, HLX43 is the first PD-L1-targeting ADC globally to enter clinical development for thymic carcinoma. International multicenter clinical studies are currently underway in China, the United States, Japan and other countries. In October 2025, HLX43 received Orphan Drug Designation from the U.S. FDA, highlighting its potential to address a significant unmet need in this rare and highly aggressive malignancy. Previously, Phase 1 data of HLX43 in advanced solid tumors, led by Professor Jie Wang of the Cancer Hospital, Chinese Academy of Medical Sciences, were first reported at the 2025 ASCO Annual Meeting. The full data from the dose-expansion cohort of the phase 1 clinical study in TSCC will be presented during the Poster Tour session at the upcoming WCLC conference on September 14, 2026.