The phase II Neo-Pembro trial: neoadjuvant pembrolizumab in stage IV high-grade serous ovarian cancer

While immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment, their efficacy in high-grade serous ovarian cancer (HGSOC) remains limited. Nevertheless, some patients achieve lasting responses, emphasizing the need to understand how the tumor microenvironment and molecular characteristics influence ICI response. We hypothesized higher efficacy of ICI when used in the neoadjuvant setting and preceded by induction chemotherapy. The phase 2 Neo-Pembro study (NCT03126812) included 33 untreated patients with stage IV HGSOC who were planned for 6 cycles of carboplatin-paclitaxel and interval cytoreductive surgery. Pembrolizumab (pembro) was added from cycle two and continued for one year. The primary objective was to assess intratumoral immune activation, through multiplexed immunofluorescence and immune-related gene expression. Our data provide evidence of immune activation, characterized by an increase in CD3+, CD8+, CD8+/FOXP3+ ratio, and TNF-α and interferon-γ signaling, and was most evident in major pathologic responders, which were 9/33 patients (27%, 95%CI 14-46) at time of surgery. Pathologic response was strongly associated with overall survival. At a median follow-up of 52.8 months, 8/9 major responders were alive, including 6 patients without recurrence, and 4 of 24 minor responders were alive, including one patient without recurrence. PD-L1 expression and homologous recombination deficiency were predictive of major response and may serve as potential biomarkers, warranting further exploration. In a post-hoc comparison, major responders treated with pembro had significantly better overall survival than major responders in a historic cohort treated without pembro. Our data indicate that immune activation was stronger in the subset of major pathologic responders and these patients may derive long-term survival benefits from the addition of neoadjuvant pembro.

Type: Exome Sequencing
Archiver: European Genome-Phenome Archive (EGA)

2 Datasets

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Dataset ID	Description	Technology	Samples
EGAD50000001150	Whole exome sequencing of DNA samples from tumor samples of patients in the Neo-Pembro trial. For each patient, up to four samples were sequenced; one tumor biopsy at baseline, one tumor biopsy after induction chemotherapy, a tumor sample from resection material at cytoreductive surgery, and a reference normal DNA sample isolated from whole blood. DNA was obtained from fresh-frozen samples where possible, or formalin-fixed paraffin-embedded when no fresh-frozen sample was available.	Illumina NovaSeq 6000	103
EGAD50000001151	Whole transcriptome sequencing of RNA samples from tumor samples of patients in the Neo-Pembro trial. For each patient, up to three samples were sequenced; one tumor biopsy at baseline, one tumor biopsy after induction chemotherapy, and a tumor sample from resection material at cytoreductive surgery. RNA was obtained from fresh-frozen samples where possible, or formalin-fixed paraffin-embedded when no fresh-frozen sample was available.	Illumina NovaSeq 6000	71