ESMO Congress 2026

Olaparib is an oral PARP inhibitor whose antitumor activity comes not only from catalytic inhibition but also from trapping PARP1/PARP2 on damaged DNA, forming complexes more cytotoxic than unrepaired single-strand breaks ^[6]; this synthetic lethal strategy gained clinical validation in a phase 1 trial enrolling BRCA1/2 mutation carriers ^[1]. A series of phase 3 trials then anchored the benefit in BRCA and homologous recombination repair–deficient populations: in germline BRCA-mutated, HER2-negative metastatic breast cancer, the olaparib monotherapy group reached a median PFS of 7.0 months, significantly longer than physician's-choice single-agent chemotherapy ^[2]; as maintenance after first-line platinum in germline BRCA-mutated metastatic pancreatic cancer, median PFS was 7.4 vs 3.8 months, HR 0.53 ^[5]; the indication map also extended to maintenance after platinum response in newly diagnosed BRCA1/2-mutated advanced ovarian cancer (391 patients randomized) ^[3], and to metastatic castration-resistant prostate cancer with HRR gene alterations ^[4].

Two pieces of on-site news at ESMO26 involve olaparib. One is the DUO-E OS signal: the post advises reading the olaparib effect mainly within the pMMR group, since dMMR tumors derive most of their benefit from durvalumab alone; specific OS figures were not disclosed in the post. The other is the phase 2 DOVACC trial: in BRCA wild-type recurrent ovarian cancer, adding the UV1 cancer vaccine to olaparib +/- durvalumab did not significantly improve PFS.

Together these two items place olaparib in a position of being re-examined outside BRCA/HRD deficiency. Prior maintenance benefit evidence concentrated in BRCA1/2-mutated populations ^[3], whereas DOVACC directly enrolled BRCA wild-type recurrent ovarian cancer to test whether vaccine plus PARP inhibition +/- immunotherapy could extend the benefit — the answer was negative; the DUO-E discussion suggests that, given the dMMR benefit is mainly attributed to durvalumab, the pMMR group is the key population in which olaparib's contribution can be read out, requiring a stratified reading by MMR status of each component's role in the combination.

The limitations are equally clear: the post provided no specific DUO-E OS data, DOVACC is phase 2 with a negative primary PFS endpoint, and sample sizes, follow-up and statistical details of both trials were absent from the posts; conclusions await confirmation by formal data.