A randomized, non-comparative, phase II study of maintenance OSE2101 vaccine alone or in combination with nivolumab (nivo) or FOLFIRI after induction with FOLFIRINOX in patients (Pts) with advanced pancreatic ductal adenocarcinoma (aPDAC): First interim results of the TEDOPAM GERCOR D17-01 PRODIGE 63 STUDY.

4148 Background: OSE2101 is a multiple neoepitope vaccine restricted to HLA-A2 positive Pts. This study aimed to assess the efficacy and safety of OSE2101 ± anti-PD1 nivo as maintenance therapy in Pts with aPDAC after FOLFIRINOX induction chemotherapy. Methods: TEDOPaM-PRODIGE 63 was initially a 3-arm, open-label, randomized, non-comparative phase II study. Pts with aPDAC, HLA-A2 positive (blood) and no progression after 8 cycles of (modified) FOLFIRINOX were randomized 1:1:1 to receive FOLFIRI (standard Arm A), OSE2101 (subcutaneous injection on D1 Q3W x 6 doses then Q8W until M12 then Q12W up to M24, experimental Arm B) or OSE2101 + nivo (360 mg IV on D1 Q3W x 6 then 480 mg Q4W up to M24, experimental Arm C). FOLFIRI was reintroduced at disease progression in Arms B and C. Primary endpoint was overall survival (OS) rate at 12 months (M12) (Fleming two-stage design, H0: 25%; H1: 50%, one-sided alpha: 2.5%, power: 90%). 156 Pts were planned. Results: Following the occurrence of 2 tumor flares in Arm C, an Independent Data Monitoring Committee (IDMC) recommended to continue FOLFIRI as backbone in experimental Arm B and stop Arm C. Interim analysis results refer to 29 randomized Pts: 9/10/10 in Arm A/B/C, respectively. Median age was 63 years, 52% were men, 55% had ECOG PS 0, and 83% were metastatic. Best response to induction FOLFIRINOX was partial response in 48% and stable disease in 52%. With a median follow-up of 23 months, M12-OS rate was 44%, 40%, and 30% in Arm A, B and C. Other efficacy results are summarized in Table below. No OSE2101-related toxicity of grade ≥ 3 (G≥3) were observed in Arm B; 1 G3 cytokine-release syndrome (OSE2101-related) and 2 tumor flares (nivo-related) leading to death were observed in Arm C. Conclusions: Maintenance OSE2101 monotherapy showed a favorable safety profile and encouraging time to strategy failure warranting further evaluation. OSE2101 + nivo was associated with poorer outcomes leading to close Arm C. Following IDMC recommendation, the study is ongoing with the new design (maintenance FOLFIRI vs. FOLFIRI + OSE2101). Clinical trial information: NCT03806309. [Table: see text]