"Regression to the truth": lessons learned from negative IPF trials.

Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease with limited treatment options. Despite the approval of pirfenidone and nintedanib that slow disease progression, IPF remains a disease with poor survival. Promising therapeutic candidates were tested as potential treatments for IPF and while some drugs were successful in phase II clinical trials, their successful transition to positive phase III was unfortunately disappointing. This highlights the "regression to the truth" concept in drug development, whereby positive phase II trial results may simply be a statistical anomaly rather than the result of true efficacy. We examine three pivotal trials of novel IPF therapies, zinpentraxin alfa, ziritaxestat and pamrevlumab, that failed in late-stage clinical development. These failures underscore common pitfalls in IPF drug development, including inadequate phase II sample sizes, reliance on surrogate endpoints like forced vital capacity, and challenges integrating background antifibrotic therapies. Moving forward, innovative approaches like adaptive trial designs, Bayesian statistics and composite endpoints could improve trial robustness. Moreover, platform trials may accelerate drug development by testing multiple therapies simultaneously. Negative trials are not failures but opportunities for learning. By recognising and addressing these challenges, while also embracing novel trial methodologies, we can enhance drug development and improve IPF outcomes.