RESUMEN
PURPOSE: Nivolumab is approved at various doses, including 3 mg/kg, 240 mg and 480 mg flat doses at various dosing intervals. The concept of low-dose immunotherapy is gaining traction in recent years. However, there is a need to better understand the pharmacokinetics and clinical outcomes at lower doses. METHODS: Patients were either administered 40 mg flat dose or 3 mg/kg Q2W/Q3W, depending on affordability as per prevailing hospital practice. All patients were hospitalized on day 1 and pharmacokinetic samples were collected at 0, 0.5, 1.0, 6.0, 24.0, 72.0 h and day 14 following administration of the first dose of nivolumab. Plasma nivolumab levels were measured by ELISA. Patients were followed up for response and toxicity. RESULTS: Twenty five patients were included in the study. Fourteen received nivolumab at conventional dose (3 mg/kg), while 11 patients received low-dose (40 mg flat). The geometric means of dose normalized Cmax and AUC0-t were comparable between those who received conventional dose and low-dose of nivolumab (0.28 versus 0.23 µg/mL/mg and 0.0014 versus 0.0011 d/mL respectively). Nineteen patients were evaluable for response. ORR among patients who received conventional dose was 5/11 (45.5%) whereas it was 4/9 (44.4%) in the low-dose cohort. All 14 (100%) patients in conventional dosing group and 7/11 patients (63.64%) in low-dose group had treatment emergent adverse events. Grade ≥ 3 toxicities were observed in 4/14 patients in conventional dose group and none in low-dose group. CONCLUSION: Low-dose nivolumab leads to lower exposure in patients as compared with conventional dose, but low-dose was better tolerated, while response rates were comparable to conventional dose.