Toripalimab with nab-paclitaxel/gemcitabine as first-line treatment for advanced pancreatic adenocarcinoma: Updated results of a single-arm, open-label, phase Ib/II clinical study.

Abstract

e16213 Background: Currently nab-paclitaxel/gemcitabine (AG) is the standard first-line treatment for advanced pancreatic ductal adenocarcinoma (aPDAC), which is still needed to improve. The phase Ib/II study aiming to evaluate safety and efficacy of AG plus toripalimab, an anti-PD-1 monoclonal antibody, showed well tolerability and encouraging efficacy in aPDAC patients (preliminary data presented at 2020 ASCO). Here, we updated new results of this study. Methods: This was a single-arm, open-label, phase Ib/II clinical trial of AG with toripalimab as first-line treatment for aPDAC. Patients received toripalimab (240mg, Q3W), combined with AG (nab-paclitaxel 125 mg/m2, d1, d8 plus gemcitabine 1000 mg/m2, d1, d8) until the disease progresses/unacceptable toxicity or receiving toripalimab maintenance treatment. The primary objectives were safety and OS; the secondary objectives were ORR, DCR and PFS. Predictive biomarkers including MMR protein and PD-L1 expression, the tumor mutation burden (TMB) based on next-generation sequencing, genomic alteration signatures and the number of TILs were evaluated. Results: At data cutoff (Feb 3, 2021), 20 chemotherapy naïve aPDAC patients (female: 65.0%, median age: 55.5 years) with ECOG PS ≤ 2 were enrolled. Of the 17 evaluable patients, the ORR was 35.3%, the DCR was 82.4%, including 5 patients with PR and 1 patient with CR, respectively. 12 patients were alive and the study treatments for 9 patients were still ongoing. Median PFS was 5.0 months (95% CI：4.216-5.784), the 6-month PFS rate was 60%; median OS was 14.0 months (95% CI：9.445-18.555), the 1-year OS rate was 80%. 2 cases of pseudoprogression were observed. The most frequent treatment related adverse events were ALT elevation (35.0%), leukocytopenia (30.0%) metabolic disorder (25.0%) and hypothyroidism (25.0%). 4 patients (20.0%) experienced grade 3/4 TRAE (including myocardial enzyme elevation, neutropenia, vomiting and nausea). In the biomarker analysis, all patients were MMR-proficient status; 14 patients were evaluated for PD-L1 expression compared with PD-L1 negative cases (n = 5), PD-L1 positive cases (n = 9) did not show higher RR or longer PFS, responses were observed in both groups. 10 patients were investigated for NGS, 2 patients with TMB > 10 Muts/Mb, the most frequently mutated genes were KRAS (90%), TP53 (90%) and ARID1A (20%). Conclusions: The updated results of this phase Ib/II study provided preliminary evidence that toripalimab in combination with AG has a manageable safety profile consistent with known safety profile for each agent alone and demonstrates signals of clinical activity. The correlation between biomarkers with clinical efficacy are under investigation. The results supported ongoing combined treatment in aPDAC patients. Clinical trial information: ChiCTR2000032293.