HSK21542 for Postoperative Analgesia in Gynecological Surgery: A Pooled Post-Hoc Analysis of Two Phase III Randomized Controlled Trials

BACKGROUND: Effective postoperative pain management in gynecological surgery is challenging because of complex visceral–somatic pain interactions and the adverse effects of conventional analgesics. HSK21542, a novel peripherally restricted kappa-opioid receptor (KOR) agonist that selectively targets visceral pain pathways enriched with KORs, may provide adequate analgesia without systemic adverse events. METHODS: We conducted a pooled post-hoc analysis of data from two phase III, multicenter, triple-blinded, randomized controlled trials (Study 301, HSK21542 vs placebo; Study 303, HSK21542 vs tramadol vs placebo). Eligible patients undergoing elective gynecological surgery were included. The primary outcome was the summed pain-intensity difference over 12 and 24 hours (SPID 12h and SPID 24h ). Secondary outcomes were pain-relief quality (proportion of patients relieved from severe pain with a pain numerical rating score ≤ 3 between 0 and 24 hours) and rescue-analgesic requirements (number of doses and time to first rescue analgesic). Adverse events were also assessed. RESULTS: A total of 370 patients were analyzed: 150 received HSK21542, 139 received a placebo, and 81 received tramadol. After inverse probability of treatment weighting (IPTW) adjustment, baseline characteristics were well-balanced across treatment groups (all standardized mean differences [SMD] <0.1; see Table 1 for 95% CIs). HSK21542 produced greater reductions in pain intensity over 12 and 24 hours than placebo (least-squares mean differences –8.1 and –16.3 for SPID 12h and SPID 24 h , respectively. Both P < .001) and no statistically significant difference was observed between HSK21542 and tramadol ( P > .05). Significantly more patients in the HSK21542 group were relieved from severe pain at 0 to 12 hours (92.7% vs 82.7%, P < .001) and required fewer rescue doses at 0 to 12 hours (0.00 [IQR 0.00–1.00] vs 1.00 [IQR 0.00–2.00], P < .001) and 0 to 24 hours (0.00 [IQR 0.00–1.00] vs 1.00 [IQR 0.00–2.00], P < .001) than those in the placebo group, whereas no significant differences with tramadol both in 0 to 12 and 0 to 24 hours. HSK21542 was also associated with significantly lower incidences of nausea (24.7% vs 66.7%) and vomiting (21.3% vs 60.5%) than tramadol. Only one case of dizziness occurred in the tramadol group. CONCLUSIONS: HSK21542 could provide adequate postoperative analgesia with few adverse events in patients undergoing gynecological surgery.