Henlius (02696) has announced that its wholly-owned subsidiary, Henlius USA Inc., has received a letter from the U.S. Food and Drug Administration (FDA) granting orphan drug designation to HLX43 injection (targeting PD-L1 antibody conjugate) for the treatment of thymic epithelial tumors (TETs). HLX43 is a conjugate drug developed by the company, combining a novel DNA topoisomerase I inhibitor with a self-developed PD-L1 targeted antibody. It is designed for the treatment of advanced/metastatic solid tumors. In September 2025, updated Phase I clinical data for HLX43, particularly related to lung cancer populations, was presented at the 2025 World Lung Cancer Conference (WCLC). The results indicate that HLX43 exhibits a sustained high response rate in advanced solid tumors, especially in non-small cell lung cancer (NSCLC) patients who have previously failed checkpoint inhibitors and chemotherapy, while maintaining good safety across all dosage levels. The objective response rate (ORR) assessed by researchers was 37.0%, with a disease control rate (DCR) of 87.0%. Additionally, at the 2025 American Society of Clinical Oncology (ASCO) annual meeting, related Phase I clinical data indicated encouraging preliminary efficacy in thymic squamous cell carcinoma (TSCC) patients. To date, no PD-L1 targeted antibody conjugates have been approved worldwide. The orphan drug designation from the FDA will support the subsequent research, registration, and commercialization of HLX43 for thymic epithelial tumors (TETs) in the U.S., providing policy incentives such as (1) tax credits for clinical trial costs; (2) exemption from new drug application fees; and (3) seven years of market exclusivity post-approval. Before HLX43 receives FDA approval for thymic epithelial tumors (TETs), if another drug for the same indication is approved first, HLX43 will need to demonstrate superior clinical efficacy to retain the orphan drug market exclusivity policy support.