The back-heavy deal includes a $5 million upfront payment for two novel T cell engagers, though the companies have yet to disclose priority indications.
Third Arc Bio is enlisting the help of Suzhou-based Adagene to develop two novel T cell engagers against what the California-based biotech describes as “unique” cancer antigens, joining the growing group of companies looking eastward for innovative assets.
The back-heavy deal, announced Thursday, will involve a $5 million upfront payment from Third Arc, plus up to $840 million in developmental and commercial milestones. Adagene, meanwhile, will be entitled to royalties on net sales. The licensing agreement will give Third Arc worldwide rights to the two cancer candidates, while Adagene will retain a no-cost option to lead development and commercialization of these assets in the Greater China region, Singapore and South Korea.
The companies did not disclose what specific cancers they plan on targeting.
At the heart of Tuesday’s agreement is Adagene’s SAFEbody technology, which according to its website is a “precision antibody masking platform” that allows an antibody to bind to its target only after being activated in certain tissues. Selectively activating a drug’s action in the tumor microenvironment could lead to better safety and prolonged clinical activity, Adagene explained.
Leveraging Adagene’s SAFEbody technology, Third Arc aims to develop T cell engagers targeting the CD3 and CD28 markers, both of which are found on T cells and can be activated to stimulate the immune system’s anti-cancer activity.
SAFEbody will open up “highly innovative molecules with a superior therapeutic index,” Third Arc CEO Peter Lebowitz said in a statement.
Third Arc launched in July last year, starting its drug development journey with $165 million in an oversubscribed series A round. The biotech’s cancer engine is its ARCStim technology, which co-stimulates the CD3 and CD28 proteins to facilitate a strong anti-cancer immune response, while also minimizing side effects.
Third ARc’s lead cancer candidate is ARC101, currently in Phase I development for ovarian and endometrial cancers. The molecule targets CD3 and CLDN6, the latter of which is a marker common in these two target indications. According to Third Arc’s pipeline page, ARC101 can be combined with another of its candidates, ARC151, which binds to CD28. The biotech dosed its first patient in a Phase I study of ARC101 in March.
With the Adagene partnership, Third Arc adds to the already-hefty sum of money that biopharma has paid to the Asian giant this year. According to an August analysis by IQVIA, the first half of 2025 saw as much as $48.5 billion in Chinese contracts, surpassing the $44.8 billion total payments made in the entirety of 2024.
Among the notable China deals this year are Kite’s $1.5 billion cell therapy partnership with Pregene and Pfizer’s $6 billion PD-1/VEGF play with 3SBio.
