BACKGROUND: Several programmed cell death ligand 1 (PD-L1)/programmed cell death 
protein 1 (PD-1) antibodies have been approved for cancer treatment worldwide. 
Their pharmacokinetic and pharmacodynamic characteristics have been reported 
mainly in western countries, but related data in Chinese patients are limited. 
This study was conducted to investigate the safety, efficacy, pharmacokinetics, 
and pharmacodynamics of an anti-PD-1 antibody, toripalimab, in Chinese patients.
METHODS: A single-center phase I study was conducted in Sun Yat-sen University 
Cancer Center. Eligible patients were adults with histologically confirmed, 
treatment-refractory, advanced, solitary malignant tumors. Toripalimab was 
intravenously infused every 2 weeks in dose-escalating cohorts at 0.3 mg/kg, 
1 mg/kg, 3 mg/kg, 10 mg/kg, and 240 mg. The study followed standard 3 + 3 
design.
RESULTS: Between 15th March 2016 and 27th September 2016, 25 patients were 
enrolled, of whom 3 (12.0%), 7 (28.0%), 6 (24.0%), 6 (24.0%), 3 (12.0%) received 
0.3 mg/kg, 1 mg/kg, 3 mg/kg, 10 mg/kg, and 240 mg toripalimab, respectively. 
After a median follow-up time of 5.0 months (range: 1.5-19.8 months), we 
observed that the commonest treatment-related adverse events (TRAEs) were 
fatigue (64.0%) and rash (24.0%). No grade 3 or higher TRAEs were observed. No 
dose-limiting toxicity, treatment-related serious adverse events (SAEs), or 
treatment-related death occurred. Objective response rate was 12.5%. The 
half-life of toripalimab was 150-222 h after a single dose infusion. Most 
patients, including those from the 0.3 mg/kg group, maintained complete PD-1 
receptor occupancy (> 80%) on activated T cells since receiving the first dose 
of toripalimab.
CONCLUSIONS: Toripalimab is a promising anti-PD-1 antibody, which was well 
tolerated and demonstrated anti-tumor activity in treatment-refractory advanced 
solitary malignant tumors. Further exploration in various tumors and combination 
therapies is warranted.