Instil Bio Inc. (TIL) delivered a gut punch to investors Tuesday, announcing it's pulling the plug on its lead cancer drug without much explanation for why.
Axion Bio, a wholly-owned subsidiary of Instil, decided to discontinue clinical development of AXN-2510, a PD-L1xVEGF bispecific antibody the company was developing to treat multiple solid tumors. Think of it as the flagship product that was supposed to carry the company forward.
Making matters worse, Axion and ImmuneOnco Biopharmaceuticals agreed to terminate their license and collaboration agreement covering both AXN-2510 and another drug candidate, AXN-27M. All rights previously licensed to Axion, including global development and commercial rights outside Greater China, have now reverted back to ImmuneOnco. Axion retains only a limited license to wind down its existing clinical activities.
The Backstory Makes This Even Stranger
Here's where this gets interesting. Back in August 2024, Instil Bio in-licensed the ex-China development and commercial rights to ImmuneOnco's IMM2510 (which became AXN-2510) along with an anti-CTLA-4 antibody called IMM27M. Under that agreement, ImmuneOnco was set to receive an upfront payment and potential near-term payments totaling up to $50 million, plus potentially additional development, regulatory, and commercial milestones exceeding $2 billion. Add in single-digit to low double-digit percentage royalties on global ex-China sales, and you're looking at a potentially massive deal.
The confusing part? The drug was actually showing some promise. In July 2025, ImmuneOnco shared preliminary safety and efficacy data from a Phase 2 study of IMM2510/AXN-2510 combined with chemotherapy for front-line patients with advanced non-small cell lung cancer conducted in China. The interim data showed partial responses in 80% of squamous NSCLC front-line patients and 46% of non-squamous NSCLC front-line patients. Those aren't bad numbers for an early-stage cancer drug.
Just a few months ago in October 2025, Axion Bio even dosed the first patient in its U.S. Phase 1 trial of the drug as monotherapy in patients with relapsed or refractory solid tumors. Now that trial is presumably getting shut down.
Radio Silence On The Why
What makes this announcement particularly frustrating for investors is that the company offered no details about the rationale behind this decision. Was there a safety issue that didn't show up in the China data? Financial pressures? Strategic pivot? Your guess is as good as anyone's.
The market's reaction suggests investors aren't waiting around for answers. Instil Bio shares were down 52.48% at $5.84 at the time of publication Tuesday, hitting a new 52-week low. When you abandon your lead asset without explanation, that's the kind of response you get.
