Recombinant Humanized Anti-Pd-1 Monoclonal Antibody (Js001) In Patients With Refractory/Metastatic Nasopharyngeal Carcinoma: Interim Results Of An Open-Label Phase Ii Clinical Study.

6017 Background: Metastatic nasopharyngeal cancer (NPC) patients progressed afterstandardtherapy have limited treatment options. Toripalimab, also known as JS001, a humanized IgG4 antibody specific for human PD-1, has been approved for 2nd line treatment of metastatic melanoma in China. Here we report the results from a phase IIstudy in metastatic NPC patients treated with toripalimab.(Clinical trial ID: NCT02915432). Methods: This multi-center, open-label, phase II registration study is designed to evaluate the safety and efficacy of toripalimab in metastaticNPC patients who have failed systemic treatment. Toripalimabis given at 3 mg/kg IV Q2W until disease progression or intolerable toxicity.Tumor PD-L1 expression, plasma EBV DNA level and other biomarkerswill be correlatedwith clinical response. Results: Enrollment of 190chemo-refractory metastatic NPCpatients was completed by Feb 2019 from 17 participating centers. The median age was 46 years, with 89.5% patients received at least 2 lines of prior systemic therapies. Treatment related adverse events (TRAE)occurred in 92% patients, which were mostly grade 1 or 2.Common TRAE includedanemia, hypothyroidism, AST increased, proteinuria, pyrexia, cough, constipation, ALT increased, hypoalbuminemia and pruritus.Grade 3 or higherTRAEoccurred in 25% patients.By the cut-off date of Jan 7 2019, among 135 evaluable patients, 3 complete responses, 31 partial responses and 40 stable diseaseswere observed for an objective response rate (ORR) of 25.2% and a disease control rate of 54.8%. PD-L1 expression results were obtained from 125 patients and 45.6% (57/125) were PD-L1+.PD-L1+ patientsachieved slightly higherORR than PD-L1- patients, 29.8% versus 22.1%. In addition, an average drop of 47-fold plasma EBV DNA copy number was observed in responding patients, which typically proceeded the radiographic identification of clinical benefit. Conclusions: Toripalimab has demonstrated a manageable safety profileand encouraging clinical activity in the largest check-point blockade study in NPC to date. A change in plasma EBV DNA copy number might serve as a predictive marker for favorable clinical response. Patients will be continuously monitored for additional safety and survival readouts. Clinical trial information: NCT02915432.