Tumor Microenvironment-Targeting BI-1808 Multiplied Pembrolizumab’s Effect in Ovarian Cancer
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A Chemotherapy-Free Immunotherapy Signal in Recurrent Ovarian Cancer
Study design
This study is the ovarian cancer cohort of a phase 1/2a program assessing BI-1808 as a single agent or in combination with pembrolizumab in advanced, previously treated solid tumors. In the poster data, patients with recurrent ovarian cancer had received at least one prior platinum-containing treatment.
| Treatment arm | Patient group | Treatment | Main message |
|---|---|---|---|
| BI-1808 monotherapy | 17 patients with recurrent ovarian cancer | BI-1808 1000 mg every 3 weeks | Limited activity alone; 1 CR and 41% DCR. |
| BI-1808 + pembrolizumab | 25 response-evaluable patients | BI-1808 1000 mg + pembrolizumab 200 mg every 3 weeks | A signal of 24% ORR and 10,3 months of mPFS with a chemotherapy-free combination. |
TNFR2 is considered an immune target with a prominent role in suppressive regulatory T cells in the tumor microenvironment. BI-1808 aims to reduce this suppressive environment and enhance the effect of PD-1 inhibitors such as pembrolizumab.
Main efficacy data
| Outcome | BI-1808 monotherapy | BI-1808 + pembrolizumab | Clinical interpretation |
|---|---|---|---|
| Response | 1 complete response | 1 complete response + 5 partial responses | The combination increases measurable tumor shrinkage. |
| DCR | %41 | %56 | Disease control is more pronounced with the combination. |
| mPFS | 3,6 months | 10,3 months | The early PFS signal favors the combination. |
| Subtypes | Limited response | Responses in high-grade serous and clear-cell subtypes | The signal in clear-cell ovarian cancer is also striking. |
Biological significance
The poster presents translational data showing that BI-1808 reduces regulatory T cells and can reprogram myeloid cells toward a more proinflammatory state. In combination with pembrolizumab, CD8+ T-cell activation, increases in IFN-gamma / CXCL9, and elevations in tertiary lymphoid structure-associated chemokines such as CCL19 / CXCL13 were reported.
It refers to immune cells forming more organized clusters within the tumor. In some cancers, these structures may be associated with a more effective and lasting antitumor immune response.
Safety
The combination generally appears manageable. Immune-related adverse events were reported as manageable in 74 patients with solid tumors receiving BI-1808 + pembrolizumab. The treatment-related discontinuation rate in the combination arm was below 5% . In the monotherapy arm, no grade 3 or higher events or treatment discontinuations for safety reasons were reported.
Points requiring attention
These are early-phase data with a small patient number. Although the ORR and mPFS signals are striking, they do not change the standard of care. The possibility of pseudoprogression or delayed response is an important note in the poster, but not every instance of early growth should be interpreted as pseudoprogression.
Drozdogan Academic Commentary
The BI-1808 + pembrolizumab data show that we should consider the failure of immunotherapy in recurrent ovarian cancer not only through the PD-1/PD-L1 axis, but also through Treg and myeloid suppression in the tumor microenvironment.
A 24% ORR, 56% disease control, and early mPFS signal of 10,3 months with a chemotherapy-free regimen are important early-phase indications that targeting TNFR2 may meaningfully strengthen PD-1 blockade.
The true value of this approach will become clearer with larger patient numbers, ctDNA-supported response monitoring, correct interpretation of late responses, and outcomes from triple combinations incorporating chemotherapy.
Conclusion
The phase 2a data on BI-1808 + pembrolizumab presented at ASCO 2026 show that meaningful clinical activity signals can be achieved with a chemotherapy-free immune combination in heavily pretreated recurrent ovarian cancer. In 25 response-evaluable patients, 24% ORR, 56% DCR, and a median PFS of 10,3 months in the early analysis were reported.
This approach is not standard treatment today, but it strongly reminds us that improving the success of immunotherapy in ovarian cancer requires targeting immune barriers in the tumor microenvironment alongside PD-1/PD-L1 blockade.
- ASCO 2026 Abstract 2605. BI-1808 + pembrolizumab: Responses to a chemotherapy-free regimen in advanced ovarian cancer.
- BioInvent. BI-1808 and pembrolizumab in advanced ovarian cancer at ASCO 2026.
- ClinicalTrials.gov. NCT04752826.
- Matulonis UA et al. KEYNOTE-100: pembrolizumab in advanced recurrent ovarian cancer. Annals of Oncology. 2019.
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