FDA Committee Rejects Pfizer’s Bid to Expand Talzenna Use

Unanimous Vote Against Label Expansion

In a decisive move, the U.S. Food and Drug Administration’s (FDA) Oncologic Drugs Advisory Committee has unanimously voted against Pfizer’s proposal to broaden the use of its PARP inhibitor, Talzenna. The pharmaceutical giant sought to include Talzenna, in combination with Xtandi, for first-line treatment in patients with metastatic castration-resistant prostate cancer (mCRPC) regardless of homologous recombination repair (HRR) mutation status.

The FDA’s Oncologic Drugs Advisory Committee unanimously declined to endorse a label expansion for Pfizer’s PARP inhibitor Talzenna, which the pharma is proposing as a combination regimen with its drug Xtandi for first-line treatment of patients with metastatic castration-resistant prostate cancer carrying a certain biomarker profile.

All eight committee members voted against the proposal, citing a lack of sufficient evidence to support efficacy in patients without HRR mutations. Committee member Dr. Neil Vasan of Columbia University Medical Center emphasized,"Precision oncology demands precision trials... The study was not powered to test the efficacy in the patients without HRR mutations,"underscoring the inadequacy of the data provided.

Concerns Over Data Integrity and Applicability

Pfizer based its application on results from the Phase III TALAPRO-2 trial, announced in October 2024. The trial showed that the combination of Talzenna and Xtandi improved overall survival (OS) compared to Xtandi alone, across all patients regardless of biomarker status. Roger Dansey, Pfizer’s then-chief oncology officer, highlighted that Talzenna is the"first and only PARP inhibitor" to demonstrate a significant survival benefit, when used with an androgen receptor blocker, in mCRPC patients, "regardless of mutation status."

However, the FDA's internal reviewers expressed skepticism in their briefing document, stating,"While the statistically significant OS improvement in the all-comers population provided the impetus for this application, interpretation of the OS result and its applicability to current U.S. standard of care are unclear."They further warned that"consideration of the all-comers OS result may be misleading when interpreting efficacy in the non-HRRm population."

Background on Talzenna's Approval Journey

Talzenna was initially approved by the FDA in October 2018 for treating HER2-negative, germline BRCA-mutated breast cancer. It received its first prostate cancer-related label expansion in June 2023, allowing its use in combination with Xtandi for patients with mCRPC who carry HRR mutations.

Highlights

• The FDA's advisory panel voted 8–0 against expanding Talzenna’s label for non-HRR mutated prostate cancer patients.
• Experts criticized Pfizer’s data, citing lack of trial power to assess efficacy in the targeted subgroup.
• The proposed label expansion was based on the Phase III TALAPRO-2 trial showing OS improvement across all patient groups.
• FDA reviewers cautioned that the results may not be applicable to U.S. standards of care and could mislead efficacy interpretations.
• Talzenna remains approved for use in HRR-mutated mCRPC when combined with Xtandi, as well as for a subset of breast cancer patients.