Pembrolizumab/Cyclophosphamide Combo Yield Efficacy, Safety in Ovarian Cancer

Preliminary results from the PESCO study (NCT03029403), a phase 1b/2 trial evaluating BioVaxys' cancer vaccine, maveropepimut-S (MVP-S), show that in combination with pembrolizumab (Keytruda) and cyclophosphamide for patients with recurrent epithelial ovarian cancer (EOC), the treatment regimen yield efficacious results.^1,2

The combination therapy demonstrated promising clinical activity, particularly in platinum-sensitive patients, and induced a durable, survivin-specific immune response.

The study's primary efficacy end points showed an overall response rate (ORR) of 24% and a disease control rate (DCR) of 82%. The benefit was most pronounced in the platinum-sensitive patient cohort, which achieved an ORR of 40% and a DCR of 90%.

Notably, in the difficult-to-treat platinum-resistant cohort, the treatment exceeded the efficacy of standard single-agent chemotherapy, achieving a 16% ORR compared with a typical rate of approximately 11.8%. In this cohort, the DCR was 54%.

Immunological analysis revealed that MVP-S induced survivin-specific immune responses in 62% of tested patients, which correlated with disease control in 93% of those cases. The durability of this response is a key finding, with the longest detected immune response lasting 195 weeks and 1 patient remaining in complete response (CR) for 3 years. These results underscore the potential of the MVP-S vaccine, powered by the DPX antigen delivery platform, to address the significant unmet need in ovarian cancer by creating a potent and sustained anti-tumor immune response.

Trial Design and Patient Population

The PESCO study is an investigator-initiated, open-label, nonrandomized phase 1b/2 trial designed to assess a novel combination therapy for recurrent EOC.

A total of 47 patients with recurrent epithelial ovarian cancer were enrolled. The dose-escalation phase had a total of 16 patients, and phase 2 had a total of 31 patients. Patient exclusion criteria included, but were not limited to, having received prior immunotherapy including checkpoint inhibitors. All patients were followed for 2 years post treatment vaccination.

Immunological Activity

A significant finding from the study is the ability of MVP-S to generate a specific, robust, and persistent immune response against the survivin antigen. MVP-S induced survivin-specific immune responses in 62% of the patients tested. These immune responses were directly correlated with disease control in 93% of the responding patients. The study documented remarkable long-term responses. The longest detected immune response in a patient lasted for 195 weeks. One patient from cohort A (platinum-sensitive) remained in a CR for 3 years following the first cycle of therapy.

"The combination of MVP-S, pembrolizumab and low dose cyclophosphamide in [EOC] demonstrated promising and sustained clinical activity with good tolerability,” said Kenneth Kovan, president and chief operating officer of Biovaxys, in a news release.¹ “Other studies suggest that anti–PD1 enhances the robust antigen-specific, cytotoxic immune response already induced by MVP-S. These findings reinforce survivin as a viable target for immunotherapy in ovarian cancer, together with checkpoint inhibitors such as anti PD-1."

REFERENCES

1.BioVaxys reports positive clinical study results from phase 1b/2 PESCO trial of MVP-S with pembrolizumab (Keytruda ™) and low-dose cyclophosphamide for patients with recurrent epithelial ovarian cancer (EOC). News release. Biovaxys. January 20, 2026. January 22, 2026. https://tinyurl.com/bdewrxzj

2.Phase 2 study of pembrolizumab, DPX-survivac vaccine and cyclophosphamide in advanced ovarian, primary peritoneal or fallopian tube cancer. ClinicalTrials.gov. Updated September 19, 2025. Accessed January 22, 2026. https://clinicaltrials.gov/study/NCT03029403