Netupitant and palonosetron trigger NK(1) receptor internalization in NG108-15 cells

Current therapy for chemotherapy-induced nausea and vomiting includes the use of both 5-HT(3) and NK(1) receptor antagonists. Acute emesis has largely been alleviated with the use of 5-HT(3) receptor antagonists, while an improvement in preventing delayed emesis has been achieved with NK(1) receptor antagonists. Delayed emesis, however, remains a problem with a significant portion of cancer patients receiving highly emetogenic chemotherapy. Like other drugs in its class, palonosetron, a 5-HT(3) receptor antagonist, has shown efficacy against acute emesis. However, palonosetron has also shown consistent improvement in the suppression of delayed emesis. Since both 5-HT(3) and NK(1) receptor antagonists are often simultaneously administered to patients, the question remains if palonosetron’s effect on delayed emesis would remain distinct when co-administered with an NK(1) receptor antagonist. Recent mechanistic studies using NG108-15 cells have shown that palonosetron and netupitant, an NK(1) receptor antagonist currently in phase 3 clinical trials, exhibited synergistic effects when inhibiting the substance P response. The present studies showed that both netupitant and palonosetron-induced NK(1) receptor internalization in NG108-15 cells and that when used together receptor internalization was additive. Palonosetron-induced NK(1) receptor internalization was dependent on the presence of the 5-HT(3) receptor. Results provide a possible explanation for palonosetron’s enhancement of the inhibition of the SP response and suggest that the effect of palonosetron and NK(1) receptor antagonists on prevention of delayed emesis could be additive.