Head-to-head evidence
Exemestane vs Letrozole
Same mechanism, same race: design-graded trial evidence for both assets, with the grading rationale shown. Grades describe the quality of the evidence, never the merits of either security.
HR+/HER2- Metastatic Breast Cancer
Shared mechanism: Aromatase · full HR+/HER2- Metastatic Breast Cancer pipeline
Exemestane
Marketed by Pfizer
NCT00038467 · Phase 3 · completed
This was a randomized, double-blind, active-controlled trial with 4,724 participants (2,352 assigned to exemestane and 2,372 to tamoxifen). The hard clinical primary endpoint, 36-month disease-free survival, was statistically significantly better with exemestane (90% vs 86%; hazard ratio 0.69, p=0.00003).
Next expected readout: November 2026 · NCT04906395 (registry estimate)
Letrozole
Marketed by Novartis
NCT00004205 · Phase 3 · completed
The study randomly assigned 8,028 participants and used quadruple blinding with active tamoxifen-based comparator groups. Its primary endpoint was the hard clinical outcome of disease-free survival, but the registry provides no results showing whether the comparison was met or missed.
Next expected readout: November 2026 · NCT04906395 (registry estimate)
The full competitive landscape for each asset (every same-race competitor with aligned evidence, sortable) is on the asset pages: Exemestane's landscape · Letrozole's landscape