Palonosetron-3-ene Hydrochloride is a synthetic intermediate used in the pharmaceutical manufacturing process for producing Palonosetron hydrochloride, a selective serotonin 5-HT3 receptor antagonist. This compound serves as a key building block in the synthesis of the active pharmaceutical ingredient (API) employed to prevent acute and delayed nausea and vomiting associated with emetogenic cancer chemotherapy. It is not intended for direct therapeutic use but contributes to the production of medications that offer prolonged antiemetic protection due to high receptor affinity and extended half-life. Also relevant in formulations for postoperative nausea prevention.