Withaferin-A (WA) is the principle component of Withania somnifera (Ashwagandha). It has several biological activities including anti-cancer, anti-diabetic, neuroprotective, hepatoprotective and immune-modulatory properties. The acute and sub-acute toxicity of oral WA was investigated in mice. In the acute toxicity study, up to 2000 mg/kg of WA was well tolerated without any signs of toxicity or death. In the sub-acute toxicity study, mice were orally administered 10, 70 and 500 mg/kg of WA respectively, daily for 28 days. Upon physiological, serum chemistry, hematology and histopathogical examination, no features suggestive of drug-induced toxicity were observed at any dose levels, thereby confirming the No-Observed Adverse Effect Level (NOAEL) to be at least 500 mg/kg. Furthermore, the oral bioavailability of WA was evaluated using single intravenous and oral doses of 10 mg/kg and 70 mg/kg respectively using sparse sampling strategy. Bioanalysis was carried out using a validated LC-MS/MS method. The AUC of WA was found to be 3996.9 ± 557.6 ng/mL*h and 141.7 ± 16.8 ng/mL*h for the intravenous and oral routes of administration respectively. The oral bioavailability was determined to be 1.8%. To conclude, WA was found to be extremely safe even at high doses, with a low oral bioavailability.

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 C_max and AUC_0-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.