FDA Fast Tracks First-in-Class TNFR2 Antibody as Chemotherapy-Free Strategy for Platinum-Resistant Ovarian Cancer

The FDA has granted Fast Track designation to BI-1808, a first-in-class investigational antibody targeting tumor necrosis factor receptor 2 (TNFR2), in combination with pembrolizumab (Keytruda; Merck) for the treatment of ovarian cancer. The designation follows preliminary phase 2a findings demonstrating antitumor activity with the chemotherapy-free combination in patients with heavily pretreated, advanced platinum-resistant ovarian cancer.¹

Although these early findings require confirmation in larger studies, the approach could provide insight into whether targeting immunosuppressive regulatory T cells (Tregs) can enhance checkpoint inhibition in ovarian tumors, a setting in which immune checkpoint inhibitor monotherapy has historically demonstrated limited activity.¹˒²

Targeting an Immunosuppressive Tumor Microenvironment

BI-1808 is a ligand-blocking monoclonal antibody directed against TNFR2, a receptor that is highly expressed on immunosuppressive Tregs within the tumor microenvironment. TNFR2 signaling contributes to Treg expansion and survival, potentially helping tumors suppress antitumor immune responses.¹

According to BioInvent, BI-1808 is designed to deplete immunosuppressive Tregs while activating myeloid cells and CD8-positive T cells, potentially altering the tumor microenvironment in a way that increases sensitivity to PD-1 blockade.¹ This represents a different immunotherapeutic strategy from simply intensifying checkpoint inhibition: BI-1808 attempts to remove an additional mechanism of immune suppression while pembrolizumab blocks PD-1 signaling.

The strategy is particularly relevant in ovarian cancer, which has frequently been characterized as an immunologically “cold” tumor. A 2026 review of immune checkpoint inhibition in ovarian cancer noted that single-agent checkpoint inhibitors have generally produced objective response rates of approximately 8% to 15% in recurrent disease, prompting increasing interest in combinations capable of reshaping the tumor immune environment.²

Early Responses With BI-1808 Plus Pembrolizumab

BI-1808 is being evaluated in an ongoing first-in-human phase 1/2a, open-label trial (NCT04752826) involving patients with advanced malignancies whose disease progressed following standard treatment. The study is assessing BI-1808 both as monotherapy and in combination with pembrolizumab, with outcomes including safety, tolerability, objective response rate (ORR), duration of response, and progression-free survival (PFS).³

Interim phase 2a results presented at the 2026 American Society of Clinical Oncology Annual Meeting showed a 24% confirmed ORR and 56% disease control rate with BI-1808 plus pembrolizumab among heavily pretreated patients with advanced platinum-resistant ovarian cancer.¹ Responses were observed across high-grade serous and clear cell ovarian cancer, and several remained ongoing beyond 10 months. Preliminary median PFS was reported at 10.3 months.¹

These findings should be interpreted cautiously because they originate from an early-phase, nonrandomized study with a limited patient population. Cross-trial comparisons also cannot determine whether the regimen is superior to existing therapies.

Nevertheless, the activity supports further evaluation of whether TNFR2 inhibition can augment PD-1 blockade in ovarian cancer.

Evolving Role of Immunotherapy in Platinum-Resistant Disease

The treatment landscape for platinum-resistant ovarian cancer has already begun incorporating immunotherapy in selected patients. In February 2026, the FDA approved pembrolizumab in combination with paclitaxel, with or without bevacizumab, for adults with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal carcinoma whose tumors express PD-L1 with a combined positive score of at least 1 and who have received 1 or 2 prior systemic treatment regimens.⁴

That approval was supported by the randomized phase 3 KEYNOTE-B96 trial. Among patients with PD-L1–positive tumors, pembrolizumab-based treatment improved PFS compared with chemotherapy-based control treatment, and the trial also demonstrated an overall survival benefit in the broader study population.⁴˒⁵

BI-1808 therefore represents a substantially earlier and distinct investigational approach. Rather than pairing pembrolizumab with cytotoxic chemotherapy, the regimen is examining whether dual immune modulation through TNFR2 and PD-1 targeting could generate clinically meaningful activity without chemotherapy.¹

For pharmacists and oncology clinicians, the distinction will be important if development advances. Future studies will need to determine which patients are most likely to benefit, whether activity differs across ovarian cancer histologies or biomarker-defined populations, and how safety and durability compare with established regimens.

Expansion of the BI-1808 phase 2a program is ongoing, with enrollment focusing on high-grade serous and clear cell ovarian cancer. BioInvent expects an additional clinical data readout during the second half of 2026.¹

References

1. BioInvent International AB. BioInvent receives FDA Fast Track designation for BI-1808 for the treatment of ovarian cancer. Published August 7, 2026. Accessed August 11th, 2026. https://www.bioinvent.com/en/press/bioinvent-receives-fda-fast-track-designation-bi-1808-treatment-ovarian-cancer-2472829

2. Wu T, Zhang P, Xi R, et al. Beyond the “cold” barrier: redefining the clinical paradigm of immune checkpoint inhibitor therapy in ovarian cancer. Crit Rev Oncol Hematol. Published June 26, 2026. Accessed Augusr 11th, 2026. https://doi.org/10.1016/j.critrevonc.2026.105459

3. ClinicalTrials.gov. BI-1808 as a single agent and with pembrolizumab (KEYTRUDA) in treatment of advanced malignancies (Keynote-D20). NCT04752826. https://clinicaltrials.gov/study/NCT04752826

4. US Food and Drug Administration. FDA approves pembrolizumab with paclitaxel for platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal carcinoma. Published February 10, 2026. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-pembrolizumab-paclitaxel-platinum-resistant-epithelial-ovarian-fallopian-tube-or

5. Colombo N, Zsiros E, Parma G, et al. Pembrolizumab plus weekly paclitaxel in platinum-resistant recurrent ovarian cancer (ENGOT-ov65/KEYNOTE-B96): a multicentre, randomised, double-blind, phase 3 study. Lancet. 2026;407(10538):1525-1537. doi:10.1016/S0140-6736(26)00602-1