A Phase Ib Study of Indirect Immunization with Oregovomab and Toll-like-Receptor-3 Stimulation with Hiltonol® in Patients with Recurrent Platinum-Resistant Ovarian Cancer

<i>Objectives</i>: This phase Ib study assessed the safety and compatibility of indirect oregovomab immunization and Toll-like-receptor-3 (TLR3) stimulation with immune adjuvant Hiltonol^® (poly-ICLC) and induced clinically relevant CA125-specific anti-tumor immunity in heavily pretreated patients with progressive platinum-resistant ovarian cancer (PROC). <i>Methods</i>: Patients with elevated serum CA125 level >50 U/mL received four intravenous infusions with 2 mg oregovomab followed by 2 mg Hiltonol^® intramuscular 30 min and 48 h post-oregovomab at weeks 0, 3, 6, and 9. At week 12, imaging was performed, and salvage chemotherapy was allowed post-progression per the investigator's discretion. The Fifth/final oregovomab with Hiltonol^® infusion was given at week 16. <i>Results</i>: Fifteen enrolled patients were analyzed for safety and efficacy. Thirteen (87%) patients completed at least three Hiltonol^® infusions with oregovomab, specifically, two cycles (<i>n</i> = 2), three cycles (<i>n</i> = 2), four cycles (<i>n</i> = 3), and five cycles (<i>n</i> = 8). Adverse events included mild fatigue, flu-like symptoms, chills, axillary pain, and injection site discomfort in 13 (87%) patients. Serious adverse events were reported in seven (47%) patients, including Grade 3 hypertension (<i>n</i> = 2), thrombocytopenia (<i>n</i> = 1), and Grade 3 events attributed to underlying disease (<i>n</i> = 4). Ten (67%) patients had disease progression, three (20%) had stable disease, and two were unevaluable. Early humoral response by week 6 was observed in seven of nine (77%) patients, median progression-free survival was 2.7 months (95% confidence interval [CI]: 2.2, 3.3), and median overall survival was 15.0 months (95% CI: 8.2-23.9). <i>Conclusions</i>: The safety and compatibility of combining oregovomab with Hiltonol^® have been demonstrated in this study. The potential to enhance activity of chemotherapy using oregovomab indirect immunization and Hiltonol^® stimulation is proposed.