Palonosetron, sold under the brand name Aloxi, is a medication used for the prevention and treatment of chemotherapy-induced nausea and vomiting (CINV).

In less than 1% of patients, other gastrointestinal disorders occur, as well as sleeplessness, first- and second-degree atrioventricular block, muscle pain and shortness of breath.

There are case reports about serotonin syndrome when the drug is combined with serotonergic substances, such as selective serotonin reuptake inhibitors (SSRIs) and serotonin–norepinephrine reuptake inhibitors (SNRIs), two common types of antidepressants.

40% of the substance are eliminated in the unchanged form, and a further 45–50% are metabolized by the liver enzyme CYP2D6 and to a lesser extent by CYP3A4 and CYP1A2.

The two main metabolites, the N-oxide and a hydroxy derivative, have less than 1% of palonosetron's antagonistic effect and are thus practically inactive.

Over the next 10 years, Helsinn filed four patent applications that claimed priority to the January 2003 date.

While developing the drug, Helsinn entered into a confidential licensing agreement with a company called MGI to sell palonosetron in the United States.

The District Court held that the AIA's “on sale” provision did not apply, because the public disclosure of the agreements did not disclose the 0.25 mg dose.