Toripalimab

Binding of the PD-1 ligands, PD-L1 and PD-L2, to the PD-1 receptor found on T cells, inhibits T cell proliferation and cytokine production. Upregulation of PD-1 ligands occurs in some tumors and signaling through this pathway can contribute to inhibition of active T-cell immune surveillance of tumors. Toripalimab-tpzi is a humanized IgG4 monoclonal antibody that binds to the PD-1 receptor and blocks its interaction with PD-L1 and PD-L2, releasing PD-1 pathway-mediated inhibition of the immune response, including the anti-tumor immune response. In syngeneic mouse tumor models, blocking PD-1 activity resulted in decreased tumor growth.

The toripalimab-tpzi exposure-response relationships and time course of pharmacodynamic response are not fully characterized.

Toripalimab-tpzi pharmacokinetic parameters are presented as geometric mean (coefficient of variation [CV]%) unless otherwise noted. Toripalimab-tpzi concentrations increased in non-linearly over the dose range of 0.3 to 10 mg/kg every two weeks (0.1 to 3.3 times the approved recommended 3 mg/kg dosage in a 64 kg patient). Steady state was reached by Week 7. The mean accumulation ratio was approximately 1.4 for maximum concentration (C_max) and 1.9 for area under the serum concentration curve (AUC) following multiple doses at the approved recommended dosages of 240 mg Q3W in combination with cisplatin and gemcitabine and 3 mg/kg Q2W as monotherapy.

Distribution

The mean volume of distribution at steady state (V_ss) of toripalimab-tpzi was 3.7 L (27%).

Elimination

The mean clearance (CL) was 14.9 mL/h (31%) after the first dose and 9.5 mL/h (36%) at steady state. The mean terminal half-life (t_1/2) (± standard deviation) was 10 ± 1.5 days after the first dose and 18 ± 9.4 days at steady state.

Metabolism

Toripalimab-tpzi is expected to be metabolized into small peptides by catabolic pathways.

Specific Populations

No clinically significant differences in the pharmacokinetics were observed based on age (21 to 85 years), body weight (32 to 164 kg), sex, race (White and Asian), concomitant chemotherapy, mild renal impairment (creatinine clearance [CLcr] 60 to 89 mL/min), mild hepatic impairment (total bilirubin >1 to 1.5 times ULN with any AST or total bilirubin ≤ ULN with AST > ULN), tumor burden and primary cancer.

The effect of moderate (total bilirubin >1.5 to 3 times ULN and any AST) or severe (total bilirubin >3 times ULN and any AST) hepatic impairment or of moderate (CLcr 30 to 59 mL/min) or severe (CLcr 15 to 29 mL/min) renal impairment on the pharmacokinetics of toripalimab-tpzi has not been studied.