iTeos Therapeutics
Big-pharma partnerships aren't insurance. GSK, Merck and Roche have all walked away from TIGIT programs. If your thesis is 'partner data will validate us,' the partner's decision terminates you.
iTeos Therapeutics was a Biotech / Oncology startup founded in 2011 in Belgium. It raised $600M+ (public) before collapsing in 2025 — 14 years of runway burned. IdeaProof's AI Failure Score: 66/100, driven by gsk terminated tigit partnership after negative phase 2 lung cancer data. The shutdown affected employees, investors, and the broader Biotech / Oncology ecosystem. This case study breaks down the timeline, root causes, competitors that won, and replicable lessons for founders validating similar ideas today.
Why did iTeos Therapeutics fail?
iTeos Therapeutics failed in 2025 after 14 years of operation, losing $600M+ (public) in raised capital. The root cause was gsk terminated tigit partnership after negative phase 2 lung cancer data. Key lesson: Big-pharma partnerships aren't insurance. GSK, Merck and Roche have all walked away from TIGIT programs. If your thesis is 'partner data will validate us,' the partner's decision terminates you.
2011 → 2025
$600M+ (public)
Biotech / Oncology
Belgium
IdeaProof AI Failure Score
What Happened: The Timeline
2011
iTeos Therapeutics founded in Belgium. Positioned in biotech / oncology.
2011-2013
Raises $600M+ (public) from Public shareholders (Nasdaq: ITOS); MPM Capital, Novo Holdings previously.
2024
Warning signs emerge: gsk tigit termination.
2025
Shutdown announced. Root cause: gsk terminated tigit partnership after negative phase 2 lung cancer data.
Root Causes
iTeos Therapeutics was a Belgian oncology biotech IPO'd on Nasdaq in 2020 with a lead anti-TIGIT antibody, belrestotug, partnered with GSK in a $2B+ collaboration. In May 2025 GSK announced it was ending the TIGIT program after negative Phase 2 data. Two weeks later iTeos announced it would wind down operations, sell assets and return as much of its $600M+ cash pile to investors as possible. The failure follows Roche and Merck exits from TIGIT — an entire immuno-oncology mechanism has now been widely questioned. iTeos is a case study in how a single mechanism-of-action can take out multiple companies simultaneously.
Key Lessons Learned
Frequently Asked Questions
Sources & Confidence
Every data point is tagged with its source type and our confidence in it. How we grade sources.
Could This Failure Have Been Prevented?
IdeaProof's AI validates market demand, competitive positioning, and business model viability in minutes — catching the exact issues that sank iTeos Therapeutics.