Axion Bio abandons its flagship therapeutic candidate as Instil Bio rethinks its strategy

Clinical suspension of AXN-2510 causes a 52% drop in TIL’s stock price

Shares of Instil Bio, Inc. (NASDAQ: TIL) experienced a sharp decline on Tuesday following the announcement that Axion Bio Inc., its operating subsidiary, would suspend the clinical development of AXN-2510, its leading pharmaceutical candidate. The asset, a bispecific antibody targeting PD-L1 and VEGF simultaneously, was being evaluated in multiple solid tumor oncological indications.

The clinical program and its performance

Recent trials showed promising results. In July 2025, ImmuneOnco revealed interim data from a Phase 2 study conducted in China, where AXN-2510 was being tested in combination with chemotherapy for patients with newly diagnosed non-small cell lung cancer (NSCLC). The data indicated partial response rates of 80% in the squamous variant and 46% in the non-squamous in the first-line treatment. Additionally, Axion Bio had initiated a Phase 1 trial in the United States at the end of 2025, administering the antibody as monotherapy in patients with recurrent or refractory tumors.

Despite these favorable preliminary results, the company decided to halt the research without publicly revealing the technical or commercial reasons behind the decision.

Changes in collaboration agreements

Axion Bio and ImmuneOnco have agreed to mutually terminate their license and collaboration agreements for AXN-2510 and the related candidate AXN-27M. As a result of this termination, all worldwide development and commercialization rights, except in Greater China, will revert to ImmuneOnco. Axion will retain only a restricted license to complete its ongoing clinical activities.

Context of the initial agreement

In August 2024, Instil Bio acquired rights outside China for IMM2510 (called AXN-2510 in the collaboration) and the CTLA-4 inhibitor IMM27M. The compensation structure included an upfront payment, contingent payments of up to $50 million in the short term, and milestone rights exceeding $2 billion, plus royalties on global sales ranging from single digits to low double digits.

Market impact

At the close of Tuesday’s session, TIL was trading at $5.84, representing a 52.48% decline and marking the 52-week low. The magnitude of the drop reflects the strategic importance that investors attributed to AXN-2510 within Instil Bio’s portfolio.