Fennec reports Phase 2 PEDMARK data from Japan met primary endpoint at SIOP 2026

Fennec Pharmaceuticals Inc. announced on September 17, 2026 the oral presentation of detailed results from the investigator-initiated Phase 2 STS-J01 trial of PEDMARK® (sodium thiosulfate injection) in Japan, presented during the 58th Annual International Society of Pediatric Oncology (SIOP) Annual Meeting in San Antonio, TX.¹

The trial enrolled 33 patients at 11 institutions in Japan, split between 27 patients in a primary cohort and six in exploratory cohorts.¹ Among the 25 patients in the primary efficacy population, ASHA-defined hearing loss occurred in 24.0% (6/25), compared with a prespecified historical benchmark of 56.4% (P=0.001).¹ The company said 19 of 25 patients, or 76.0%, had no ASHA-defined hearing loss, and by Brock criteria 84.0% of patients scored Grade 0, with no Grade 3 or Grade 4 hearing loss reported.¹

On tumor response, 23 of 24 evaluable patients, or 95.8%, showed objective responses, which the company said offers reassurance about giving PEDMARK six hours after cisplatin.¹ Pharmacokinetic work in the study added mechanistic detail on the interaction between PEDMARK and cisplatin-derived platinum, supporting the six-hour dosing approach in pediatric and AYA patients.¹

On safety, the company said the profile matched PEDMARK's known tolerability and cisplatin's expected toxicities, with no serious adverse event tied to PEDMARK and no Grade 4 PEDMARK-related toxicity.¹

Fennec said it is pursuing registration of PEDMARK in Japan and is exploring partnering or licensing options there.¹ PEDMARK is already FDA-approved for reducing ototoxicity risk from cisplatin in pediatric patients 1 month and older with localized, non-metastatic solid tumors, and carries an NCCN 2A endorsement for AYA use.¹