Background: PALO (0.50 mg), a distinctive second-generation 5-HT₃ receptor antagonist (RA), is a component of the oral fixed combination agent NEPA, the second component being the NK₁ RA netupitant. Oral NEPA is approved for acute and delayed CINV prophylaxis after moderately (MEC) and HEC. This study was conducted in support of the NEPA IV formulation (0.25 mg PALO + 235 mg fosnetupitant) administered as a 30-min IV inf, currently under FDA review. Methods: Chemotherapy-naive patients (pts) with solid tumors were randomized (1:1) to receive a single 0.25-mg PALO as a 30-min IV inf or a 30-sec IV bol, 30 min before reference HEC (cisplatin; dacarbazine), with oral dexamethasone (20 mg [D1]; 8 mg BID [D2–4]) (NCT02557035). Primary objective: noninferiority (NI; lower limit of the 99% CI to be >–15% [prespecified NI margin]) in complete response (CR; no emesis/no rescue) in the acute (0–24 h) phase. Secondary objective: safety. Results: 440 pts (median age 59.4 y [25–79]; cisplatin: 97.3%; dacarbazine: 2.7%) were randomized to IV inf (n=225) or IV bol (n=215). Baseline characteristics were similar. Acute CR rate was 82.7% (IV inf) and 86.5% (IV bol), with risk difference of –3.8% (99% CI: –12.2; 4.7) meeting the primary objective of NI. Treatment-emergent AE and study drug-related AE frequency was similar in both arms (Table). One PALO IV inf patient with pre-existing cardiac symptoms, experienced 1 serious AE that eventually lead to death and was considered possibly study drug-related by the investigator. No G≥3 infusion site reactions occurred. No patient in IV inf arm had infusion interruptions. Conclusions: PALO IV inf was noninferior to IV bol in acute CINV prevention after receiving non-AC HEC. Safety profiles were similar. No specific infusion toxicities were observed. The results show that PALO 0.25 mg IV inf is appropriate for the NEPA IV formulation. Clinical trial information: NCT02557035

PALO, palonosetron; SAE, serious AE.