The Destiny Breast 11 trial compared a new drug to a chemotherapy regimen (ACTHP) that many US oncologists no longer use. This choice of a less common control arm makes it difficult for them to directly compare the new treatment's efficacy against their own current standard (TCHP), complicating adoption.

The Sac o six nineteen trial showed compelling results adding BCG to a chemo-immunotherapy backbone. However, the standard of care has already shifted to a newer combination (enfortumab vedotin and pembrolizumab), making it difficult to translate the study's findings into current practice and complicating the design of future trials.

The current pace of innovation in CLL treatment means new options become available faster than long-term clinical trials can conclude. This creates a critical need for more efficient trial designs and validated intermediate endpoints that can provide reliable answers sooner.

Pivotal trials for PARP inhibitor and ARPI combinations (e.g., PROPEL, MAGNITUDE) enrolled patients who were largely ARPI-naive. However, in modern practice, most patients receive an ARPI earlier in their treatment. This creates significant uncertainty about the benefit of these combinations for the majority of today's patients.

Clinicians identify outdated control arms—like single-agent chemotherapy without newer targeted agents—as a major deterrent for patient trial participation. Patients are unwilling to be randomized to a therapy that doesn't reflect the current, more effective standard of care. This pressure is forcing sponsors and the FDA to design trials with more realistic comparator arms.

The FIGHT-302 trial for FGFR2-rearranged cholangiocarcinoma closed early, like similar trials, because the standard of care evolved faster than patients could be recruited. This highlights a fundamental challenge in studying rare molecular subtypes, requiring alternative trial designs where thousands of patients must be screened to find a few eligible participants.

The ELEGANT trial uses a "switch strategy," introducing elicestrin only after 2-5 years of standard therapy. This design pragmatically adapts to the evolving clinical landscape where CDK4/6 inhibitors are now standard initial treatment, ensuring the trial's relevance by testing the drug in a post-CDK4/6 inhibitor setting.

While the Lidera trial showed a benefit for the oral SERD giredestrant in the adjuvant setting, experts advise caution before changing practice. The trial's control arm (standard endocrine therapy) does not reflect the current standard of care for high-risk patients, which now includes CDK4/6 inhibitors, making a direct comparison difficult.

As effective treatments like EV Pembro become the standard of care in oncology, it is no longer ethically feasible to conduct randomized trials for new "me-too" drugs against the outdated platinum chemotherapy standard in many markets. This severely limits development pathways for fast-follower drugs.