The Ballad of TIGIT
This detailed analysis chronicles the dramatic, multi-billion dollar failure of TIGIT immunotherapy drugs, once heralded as the next breakthrough in cancer treatment. Despite initial promising signals and massive pharmaceutical investment, these drugs consistently failed to deliver clinical benefit, often with worse patient outcomes. The story resonates on HN as a stark reminder of the immense challenges and unpredictable nature of drug discovery, even with robust scientific theory and early positive data.
The Lowdown
The article recounts the spectacular downfall of TIGIT (T-cell immunoreceptor with Ig and ITIM domains) drugs, a class of cancer immunotherapies that consumed billions of dollars and years of research only to yield widespread disappointment. Likened to the previously 'cursed' amyloid-beta drugs for Alzheimer's, TIGIT drugs were initially seen as a natural successor to the highly successful Keytruda, targeting another 'immune brake' to unleash the body's anti-cancer response. However, despite enormous industry enthusiasm and investment, the clinical trials for TIGIT inhibitors universally failed, leaving a trail of abandoned programs and an important, expensive lesson for drug discovery.
- TIGIT drugs emerged in the wake of Keytruda's success, with the theory that blocking this protein, an 'immune brake,' could offer an even more potent anti-cancer effect.
- Roche's tiragolumab, the first anti-TIGIT drug, showed promising Phase 2 results in 2020, leading to a 'breakthrough designation' and triggering a massive investment frenzy across major pharmaceutical companies like Merck, Novartis, Gilead, and GSK.
- Roche launched 'SKYSCRAPER,' an unprecedented program with twelve concurrent Phase 2 and 3 trials, representing billions in investment and covering diverse cancer types.
- Beginning in 2022, Roche's trials started failing, missing progression-free survival (PFS) endpoints and in one alarming instance, showing patients on tiragolumab died faster than the control group.
- Merck's parallel vibostolimab program mirrored Roche's failures, with trials halted due to severe adverse events or futility, leading to its discontinuation by 2025.
- Even the 'Fc-silent' hypothesis, suggesting a different antibody structure (like Arcus/Gilead's domvanalimab) might succeed where others failed, was tested and definitively debunked in late 2025.
- Other smaller bets by Novartis, BeiGene, and GSK's partner iTeos also collapsed, with iTeos ultimately winding down its operations.
- A 2026 BMJ Oncology analysis dubbed the phenomenon 'herding,' estimating nearly 49,000 patients and over $3 billion were enrolled in anti-TIGIT trials, all for drugs that consistently failed.
The widespread failure of TIGIT drugs leaves the scientific community grappling with the question of 'what went wrong?' While the exact reasons remain elusive, the saga underscores that even with strong theoretical foundations, clean biological hypotheses, and early clinical signals, drug discovery remains profoundly unpredictable. TIGIT has become a cautionary tale, demonstrating that not every 'brake' in the immune system is attached to a functional wheel that can be easily manipulated for therapeutic benefit.