Early Phase 3 trials like JAVELIN adding immunotherapy to chemoradiation failed to improve outcomes. However, subgroup analyses consistently showed a potential benefit in PD-L1 high-expressing patients, a crucial lesson that informed the design of subsequent, more successful studies.

Unlike most trials that avoid patients who failed other therapies, Corvus intentionally included them, considering it a 'stacking deck against yourself'. This high-risk bet, based on their drug's unique mechanism, paid off by showing efficacy in a tough-to-treat population and demonstrating a lack of cross-resistance.

The Durvalumab monotherapy arm showed a promising disease-free survival signal (HR 0.74), but due to reduced recruitment from COVID-19, the trial was underpowered for statistical significance. This shows how external factors can compromise a trial's ability to deliver a definitive clinical answer, leaving a potentially effective therapy in limbo.

A fundamental conflict exists between optimal clinical practice and rigid trial design criteria. As seen with Replimune's RP1, injecting all tumors—the logical therapeutic approach—can leave no untreated lesions to measure systemic effect by RESIST criteria, leading the FDA to statistically disqualify a majority of responders.

In an ongoing confirmatory trial, investigators rarely re-challenge PD-1 refractory patients with another PD-1 inhibitor alone. This real-world clinical consensus, viewing the practice as futile, provides strong practical evidence that the nivolumab in the combination isn't the sole driver of efficacy, supporting RP1's significant contribution.

Developers often test novel agents in late-line settings because the control arm is weaker, increasing the statistical chance of success. However, this strategy may doom effective immunotherapies by testing them in biologically hostile, resistant tumors, masking their true potential.

Current bladder cancer trials often fail to differentiate between patients with primary resistance (never responded) versus acquired resistance (responded, then progressed). Adopting this distinction, common in lung cancer research, could help identify patient subgroups more likely to benefit from immunotherapy re-challenge and refine trial eligibility criteria.

In solid tumor immunotherapy, significant efficacy gains almost always correlate with increased toxicity. This study's claim of nearly doubled progression-free survival with identical toxicity rates is biologically implausible and was a primary reason for skepticism, even before analyzing the trial's methodology.

A significant criticism of the pivotal KEYNOTE-564 trial is that only half the patients in the control arm received standard-of-care immunotherapy upon relapse. This lack of subsequent optimal treatment complicates the interpretation of the overall survival benefit, raising questions about its true magnitude.