Final survival follow-up and translational associations using interval indirect immunization with oregovomab (O) and poly ICLC in patients (pts) with recurrent platinum-resistant ovarian cancer (PROC).

Robert W. Holloway AdventHealth Cancer Institute, Orlando, FL info_outline Robert W. Holloway, Sarah Madhu Temkin, Sarah W. Gordon, Sunil Gupta, Christopher F. Nicodemus, Madi Madiyalakan, William P. McGuire

Authors Robert W. Holloway AdventHealth Cancer Institute, Orlando, FL info_outline Robert W. Holloway, Sarah Madhu Temkin, Sarah W. Gordon, Sunil Gupta, Christopher F. Nicodemus, Madi Madiyalakan, William P. McGuire Organizations AdventHealth Cancer Institute, Orlando, FL, Virginia Commonwealth University, Massey Cancer Center, Richmond, VA, OncoQuest Pharma USA, Inc., Wilmington, DE, AIT Strategies, Franconia, NH Abstract Disclosures Research Funding Pharmaceutical/Biotech Company OncoQuest Pharma USA, Inc., DE Background: Indirect immunization with tumor specific antibody is an approach to triggering therapeutic immunity to cancer through activated immune cells. O is a monoclonal IgG1 specific to CA125 (MUC16). O is currently in phase III evaluation of front-line chemoimmunotherapy (CIT), having shown benefit relative to chemotherapy alone in a randomized phase II study (Brewer, Gyn Onc 2020). H is a TLR3 agonist used as a stimulatory immune adjuvant. The dosing phase of the protocol established safety and compatibility of this combination. The primary safety and response outcomes were reported at IGCS-2019. Immune parameters and long-term outcome associations are the focus of this final update. Methods: Pts with heavily treated RECIST evaluable platinum resistant ovarian cancer (median of 5 prior Rx) received 4 IV infusions with 2 mg O followed by 2mg H IM 30 min & 48 hrs post O at wks 0, 3, 6, 9. At wk 12 imaging was performed and elective salvage Rx allowed. A fifth O+H was optional at wk 16. Study endpoints included immune associations after O+H, after second-line chemotherapy, and survival outcomes. Results: 17 pts were enrolled at 2 centers; 15 patients were dosed and 13 completed the specified minimum 3 infusions. The treatment was well tolerated with local reactions and mild flu like symptoms (13/15 pts) as the only reported adverse events. There was no treatment related serious adverse events. Median survival was 15.0 m [95% CI:10.8m-NE] and 4 patients remained alive at data lock (median 26.5 m). H stimulated an early humoral antibody response to O at wk 6 in 7 of 9 pts (78%). Interval administration of second-line Rx (bevacizumab, paclitaxel, carboplatin, &/or doxorubicin) and O were associated with further antibody spikes. Baseline neutrophil monocyte to lymphocyte ratio (NMLR), a measure of myeloid-derived immune suppression was inversely associated with survival. PROC patients with baseline NMLR ≤4x (n = 8) had median OS 19.6m [15.0 m -NE] vs median OS 10.8m [3.6m-NE] HR 2.44 [0.73-8.15], ( p = 0.13) for pts with NMLR > 4.0 (n = 7). Conclusions: H is a viable immune adjuvant for combination with O suitable for further study in immune resistant settings. Immune responsiveness was similar to that observed in a prior study of same day schedule of carboplatin-paclitaxel front-line immunotherapy (Braly, JIT 2009; Battaglia, Cll, 2020). Patterns of immune response to O in the setting of recurrent ovarian cancer are influenced by concomitant anti-neoplastic therapy. Clinical outcomes appear sensitive to myeloid burden (NMLR > 4) which may be more prevalent in patients with treatment resistant disease than in chemotherapy naïve patients, as previously observed in front-line CIT trials. A phase III study to further evaluate these associations in the front-line setting is currently underway NCT04498117. Clinical trial information: NCT03162562