Abstract 50P
Background
Improving disease free and overall survival in advanced high grade serous ovarian carcinoma (HGSC) after primary treatment remains challenging. This phase 1 trial (NCT04739527) evaluated vididencel, a cell-based cancer vaccine, to prime or boost immune responses and prevent disease recurrence after primary treatment. Vididencel is highly immunogenic and expresses tumor associated antigens (TAA), such as WT1 and PRAME, which are also frequently upregulated in HGSC.
Methods
Patients with advanced HGSC (n=17) after primary treatment, were given vididencel four times biweekly, followed by 2 booster injections. Peripheral blood mononuclear cells (PBMC) were obtained at week 0, 4, 10, 14, 18 and 22. At week 22 patients were assessed for their disease status, both clinically and by CA125 levels in peripheral blood. IFNγ ELISpot was performed on PBMC for WT1, PRAME, MAGEA3/4 and NY-ESO1. Vaccine induced T-cell response (VIR) were calculated as ≥2-fold increase of the mock-corrected baseline response.
Results
As of April 2024, all 17 planned patients have completed treatment phase up to week 22 or end of treatment. One patient prematurely discontinued study treatment due to disease progression. Ten patients had stable disease and 7 patients had imaging confirmed recurrence at week 22 or end of treatment. The safety profile aligns with prior reports in AML patients, indicating the vaccine only gives mild adverse reactions, predominantly at the site of injection. VIR to any of the antigens tested were observed in 9/12 (75%) analyzed patients, with 3 patients not reaching a VIR due to high baseline responses. Notably, most immune responses were observed to WT1 (5/9 patients) and NY-ESO (4/9 patients). In 3 out of 9 patients responses to more than one antigen were observed.
Conclusions
The use of vididencel in this phase 1 trial for HGSC patients is feasible, well-tolerated, and results in a T-cell response against TAA in the majority of patients. The observed immune responses to a wide range of antigens provides a potential basis for an effective anti-tumor response. Long-term follow-up is ongoing to evaluate clinical benefit of this active immunotherapy approach.
Clinical trial identification
This study was approved by the central committee on research involving human subjects (CCMO) Ethics Board; approval number NL74250.000.20.
Legal entity responsible for the study
The authors.
Funding
Mendus AB.
Disclosure
H. Van Zeeburg, J. Rovers: Non-Financial Interests, Institutional, Full or part-time Employment: Mendus. M. De Bruyn: Financial Interests, Personal, Stocks/Shares: Sairopa; Financial Interests, Institutional, Funding: Genmab, Mendus. H. Nijman: Financial Interests, Personal, Stocks/Shares: Sairopa, ViciniVax; Financial Interests, Institutional, Funding: Genmab, Mendus. All other authors have declared no conflicts of interest.