China-based commercial-stage biopharmaceutical company Antengene Corporation Limited (HKG:6996) announced on Tuesday that its in-house discovered antibody-drug conjugate ATG-022 has received Breakthrough Therapy designation from the Centre for Drug Evaluation of the National Medical Products Administration in China.

The designation applies to the treatment of CLDN18.2-positive, HER-2 negative unresectable or metastatic gastric or gastroesophageal junction adenocarcinoma in patients previously treated with at least two lines of therapy.

This milestone follows the US Food and Drug Administration's earlier Orphan Drug Designation for ATG-022 in gastric and pancreatic cancers, reflecting its global development potential.

Clinical results from the ongoing CLINCH Phase I/II study have reportedly shown strong efficacy across patient groups. In moderate-to-high CLDN18.2 expressors, ATG-022 achieved an Objective Response Rate of 40% and a Disease Control Rate of up to 90%, with median progression-free survival nearing seven months. Importantly, anti-tumour activity was also observed in patients with low or ultra-low CLDN18.2 expression, broadening its potential applicability.

To date, three patients across all expression levels have achieved complete responses.

Antengene has advanced to Phase II dose-expansion trials in Mainland China and Australia, both as monotherapy and in combination with pembrolizumab and chemotherapy. This Phase II study includes a basket trial cohort covering multiple tumour types, which remains open for enrolment.