8 to 0 Rejection FDA Halts Pfizer’s Prostate Cancer Combo Despite 9 Month Survival Boost

In a resounding 8-0 vote, the FDA’s Oncologic Drugs Advisory Committee (ODAC) rejected Pfizer’s combination of Talzenna and Xtandi for treating mCRPC patients without HRR mutations (non-HRRm). This decision deals a blow to one of Pfizer’s high-profile oncology strategies, despite notable improvements in survival outcomes reported in the TALAPRO-2 Phase III trial.

According to final data, the combination extended radiographic progression-free survival (rPFS) to 33.1 months compared to 19.5 months in the control group. Overall survival (OS) improved by nearly 9 months, reducing the risk of death by over 20%. Among HRRm-positive patients, rPFS nearly doubled, and OS was prolonged by 14 months. However, the core issue lay with non-HRRm patients, where regulators questioned whether the observed OS improvement was statistically credible or the result of confounding variables.

ODAC members raised concern that over a quarter of patients lacked confirmed HRR mutation status at randomization, and many of them were later found to be HRRm-positive. This undermined the reliability of the subgroup analysis. The FDA emphasized that biomarker-driven approvals must be rooted in prospective stratification, not retrospective data that might skew conclusions.

While Pfizer argued the mechanistic rationale was strong—citing synergy between PARP inhibition and androgen receptor blockade—and manageable safety signals, including anemia and absence of MDS/AML, the advisory panel stood firm. Regulators warned this could set a dangerous precedent by encouraging biomarker-independent use of PARP inhibitors, a direction unsupported by past trials with olaparib and rucaparib in similar settings.