On September 20, 2022, the FDA approved sodium thiosulfate (Pedmark; Fennec Pharmaceuticals), an inorganic sodium salt, for risk reduction of hearing loss (ototoxicity) associated with cisplatin treatment in children aged ≥1 month to 18 years with nonmetastatic solid tumors. Sodium thiosulfate received an orphan drug designation for this indication.
The safety and efficacy of sodium thiosulfate when used after cisplatin infusions for ≥6 hours have not been determined; if hearing loss had already occurred, this drug may not reduce its risk after long cisplatin infusions.
This approval was based on the results of 2 phase 3 clinical trials: the multicenter, open-label, randomized controlled SIOPEL 6 and the Clinical Oncology Group (COG) ACCL0431. The SIOPEL 6 study included 114 pediatric patients with standard-risk hepatoblastoma who had received perioperative cisplatin-based chemotherapy. The main end point was the percentage of patients with Brock grade ≥1 hearing loss. The incidence of hearing loss was lower in the sodium thiosulfate plus cisplatin arm than in the cisplatin monotherapy arm (39% vs 68%, respectively; relative risk [RR], 0.58; 95% confidence interval [CI], 0.40-0.83).
The COG ACCL0431 study included 125 pediatric patients with solid tumors who received cumulative cisplatin doses of ≥200 mg/m2, with individual cisplatin doses infused over ≤6 hours. The incidence of hearing loss was lower in the sodium thiosulfate plus cisplatin arm than in the cisplatin monotherapy arm (44% vs 58%, respectively; RR, 0.75; 95% CI, 0.48-1.18).
The most common (≥25% with a between-arms difference of >5% vs cisplatin monotherapy) adverse reactions in both trials were vomiting, nausea, decreased hemoglobin, hypernatremia, and hypokalemia.