Progress in drug development often hides inside failures. A therapy that fails in one clinical trial can provide critical scientific learnings. One company leveraged insights from a failed study to redesign a subsequent trial, which was successful and led to the drug's approval.

For antibody-drug conjugates (ADCs) to make a meaningful impact in prostate cancer, the clinical development bar is exceptionally high. Merely showing activity in late-line settings is insufficient; the true measure of success is demonstrating superiority over the established chemotherapy standard, docetaxel.

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.

Despite billions invested over 20 years in targeted and genome-based therapies, the real-world benefit to cancer patients has been minimal, helping only a small fraction of the population. This highlights a profound gap and the urgent need for new paradigms like functional precision oncology.

The failure of the PERSEVERA trial, which tested a similar drug in an unselected patient population, highlights the critical importance of SERENA-6's biomarker-driven approach. It proves that targeting only patients with the ESR1 mutation is necessary for efficacy, reinforcing the core value of precision oncology.

The failure of Mirati's 1133 agent, which was effective preclinically but failed in trials, shows that impressive lab results are not enough. A drug's clinical viability hinges on pharmacological properties like bioavailability, which can prevent an effective compound from reaching its target in patients.

The LEAP-010 trial showed a combination therapy improved tumor response and progression-free survival but failed to improve overall survival, the ultimate measure of benefit. This highlights the risk of relying on surrogate endpoints, which can be misleading, especially when a treatment adds significant toxicity.

Unlike late-stage treatments, therapies for newly diagnosed cancer patients cannot be highly toxic or delay standard care like surgery. This creates a challenging three-week window for a drug to show efficacy, a major constraint that eliminates most potential treatments.

The Avera trial's strong results for jiridestrant were overwhelmingly driven by patients with ESR1 mutations. Analysis revealed minimal benefit for patients without the mutation (wild-type), suggesting the mutation is a key predictive biomarker and the drug may not be for "all comers."