Olaparib–tremelimumab ovarian cancer study misses efficacy target and reports substantial toxicity
Published in Drugs development & discovery, Immunology, Journals, Personalized medicine.
October 8, 2026 — An accepted, peer-reviewed study released today by Nature Communications reports mixed findings from olaparib combined with the CTLA4-blocking antibody tremelimumab in recurrent ovarian cancer.
The multicentre, single-arm phase I/II trial enrolled 50 women with inherited BRCA1 or BRCA2 mutations (NCT02571725). It did not meet its prespecified efficacy endpoint. The reported response rate was 32.7% (95% confidence interval: 19.5–45.8%), with median progression-free survival of 3.0 months and overall survival of 24.3 months.
Safety is central to interpreting the results: 57% of the 49-person safety cohort experienced grade 3 or 4 non-haematological toxicity, and 34.7% discontinued tremelimumab. Six participants had progression-free survival beyond 12 months.
Exploratory, post-hoc analyses linked low VSTM5 or IFIT1B expression with benefit. These associations require validation before they can guide treatment selection. Without a randomized comparison, the study cannot establish superiority over olaparib alone. The findings provide research evidence rather than a new treatment approval; the journal notes that the early article version remains subject to editing.
Source: Adams et al., Nature Communications, published October 8, 2026. DOI: 10.1038/s41467-026-78395-y.