(SeaPRwire) –
By: Oliver Hawthorne
T-cell engagers have a problem nobody in oncology likes to say out loud. They work. That is precisely the issue. Drag a T cell against a solid tumor hard enough and the immune system responds systemically, flooding the patient with cytokines and punishing healthy tissue that merely whispers the target antigen. HER2 is the classic offender. It sits on tumor cells, yes, but also on cardiac and epithelial tissue, which is why bispecific T-cell engagers against HER2 have stalled in the clinic for years while antibody-drug conjugates like Enhertu swept the market instead. The entire industry has been circling one question. Can you make a T-cell engager blind everywhere except inside the tumor? Adagene now has regulatory permission to find out in humans. China’s NMPA cleared the IND for ADG138 on September 22, 2026, and the first-in-human Phase 1 study in advanced solid tumors is slated to begin in China in the fourth quarter of 2026. That clearance is not the story. The architecture underneath it is.
Strip the press release down to its data and the design logic becomes clear. ADG138 is a HER2×CD3 bispecific built on Adagene’s SAFEbody precision masking technology, but with a twist most masked programs skip. Both binding arms are masked, not just one. Masking peptides are covalently linked to the HER2 arm and the CD3 arm alike, so in circulation the molecule barely touches either target. Preclinical figures presented at AACR in 2022 put the numbers at roughly a 220-fold reduction in HER2 binding and greater than 1,000-fold reduction in CD3 binding in the inactivated state, with proteases in the tumor microenvironment cutting the masks off to restore full killing activity. The payoff claimed is a therapeutic window widened enough that ADG138 was tolerated at doses over 300-fold higher than an unmasked T-cell engager, with markedly reduced cytokine release, a longer apparent half-life, and higher systemic exposure than the parental molecule. Efficacy data mattered too. Regression showed up in HER2-high and HER2-low tumor models, including a model refractory or resistant to Enhertu, and the molecule paired well with anti-CTLA-4, anti-PD-1, or anti-CD137 antibodies. Peter Luo, Adagene’s Chairman and President of R&D, framed the NMPA’s rapid approval as validation of that preclinical package. The Phase 1 is open-label, dose-finding, aimed at safety, preliminary efficacy, and a recommended Phase 2 dose.
Now the commercial reading. Adagene is not really selling ADG138. It is selling proof that SAFEbody generalizes. The lead asset, muzastotug, is a masked anti-CTLA-4 in Phase 1b/2 and Phase 2 combinations for microsatellite stable metastatic colorectal cancer, carrying FDA Fast Track designation. If masking rescues CTLA-4 and then rescues a double-masked T-cell engager in solid tumors, the platform claim extends across Fc-empowered antibodies, ADCs, and multispecifics, which is where the partnering economics live. The risks are equally concrete. Protease activity varies wildly across human tumors, so a mask that sheds cleanly in a mouse model may shed unevenly in patients. Enhertu resistance data in animals does not guarantee post-ADC activity in the clinic. And a Q4 2026 start in China puts human data years behind the pitch. Watch the dose-escalation cohorts. If ADG138 climbs past the exposure levels that killed unmasked HER2 engagers without grade-three cytokine release, every big oncology player with a shelved TCE program will come knocking. If it cannot, masking remains an elegant solution still hunting for its first undeniable human win.
Author bio: Oliver Hawthorne is a Principal Correspondent permanently stationed at an international technology review, covering biotechnology platforms, translational oncology, and the gap between preclinical promise and clinical reality.