On December 9, 2025 Fennec Pharmaceuticals Inc. (NASDAQ:FENC; TSX: FRX), a specialty pharmaceutical company, reported the planned initiation of an investigator-sponsored study (IST) by City of Hope, a U.S. cancer research and treatment organization, to evaluate PEDMARK (sodium thiosulfate injection) for the prevention of cisplatin-induced ototoxicity (CIO) in adult men with stage II-III metastatic testicular germ cell tumors.

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"Cisplatin has transformed outcomes for patients with germ cell tumors, turning what was once a highly fatal disease into one of oncology’s true success stories. However, as many as four out of five survivors are left with permanent hearing loss that impacts their quality of life long after treatment ends.i Through this investigator-initiated study, City of Hope aims to better understand how protecting hearing can become an integral part of comprehensive cancer care," said Alexander Chehrazi-Raffle, M.D., City of Hope assistant professor, Department of Medical Oncology & Therapeutics Research, and principal investigator of the study.

PEDMARK is currently approved for pediatric patients one month of age and older with localized, non-metastatic solid tumors, and is also recognized by the National Comprehensive Cancer Network with a 2A recommendation for use in adolescent and young adult patients.

"Initiation of this study by City of Hope reflects the growing clinical interest in addressing the burden of hearing loss among patients receiving cisplatin-based chemotherapy, an indispensable treatment with high survival rates but significant long-term quality-of-life consequences," said Pierre S. Sayad, PhD, M.S., chief medical officer of Fennec Pharmaceuticals. "With cancer rates rising, especially among younger populations, the future of oncological care needs to focus on both survival and survivorship. Fennec is proud to see independent investigators driving important research that not only has the potential to change the standard of care for their patients today but also expand the evidence base for PEDMARK into metastatic disease, where cisplatin is widely used but hearing protection options remain limited."

Study Details:

City of Hope: Duarte, California:

Principal Investigator: Alexander Chehrazi-Raffle, M.D.

Title:

Testing the Addition of PEDMARK to Cisplatin Chemotherapy for Reducing Drug-Induced Ear Damage in Men With Stage II-III Metastatic Testicular Germ Cell Tumors.

Overview:

Phase I study (NCT07218913) to evaluate whether adding PEDMARK to standard of care cisplatin-based chemotherapy reduces drug-induced ear damage (ototoxicity) in men with stage II-III testicular germ cell tumors that have spread from where they first started (primary site) to other places in the body (metastatic).

Multiple other investigator-initiated studies have already been submitted to Fennec and are currently under review, with several others in advanced contracting or evaluation stages. These collaborations are expected to further strengthen Fennec’s clinical and commercial foundation. Additional details will be shared as these programs progress.

About Cisplatin-Induced Ototoxicity

Cisplatin and other platinum-based chemotherapies are widely used to treat solid tumors and have been vital in improving survival rates. Unfortunately, these life-saving treatments often result in permanent, irreversible hearing loss, also known as ototoxicity.ii

Hearing loss from cisplatin treatment is not rare. Studies show that between 60-90% of patients treated with cisplatin may develop hearing loss, depending upon the dose and duration of chemotherapyiii. Many of those treated with cisplatin will require lifelong hearing aids or cochlear implants, which can be helpful for some, but do not reverse the hearing loss and can be costly over time.iv Treatment-induced hearing loss can reduce quality of survivorship as it impacts many aspects of life, such as speech and language skills, academic performance, social-emotional development, career potential and the ability to live independently.v,vi While audiologic monitoring is recommended to help manage ototoxicity, it is currently underutilized in certain cancer patient populations.

PEDMARK (sodium thiosulfate injection)

PEDMARK is the first and only U.S. Food and Drug Administration (FDA) approved therapy indicated to reduce the risk of ototoxicity associated with cisplatin treatment in pediatric patients 1 month of age and older with localized, non-metastatic, solid tumors. It is a unique formulation of sodium thiosulfate in single-dose, ready-to-use vials for intravenous use in pediatric patients. PEDMARK is also the first and only therapeutic agent with proven efficacy and safety data with an established dosing regimen, across two open-label, randomized Phase 3 clinical studies, the Children’s Oncology Group (COG) Protocol ACCL0431 and SIOPEL 6.

Additionally, PEDMARK is recommended for the adolescent and young adult (AYA) population by the National Comprehensive Cancer Network, or NCCN, with a 2A endorsement.

Approximately 500,000 patients in the U.S. are diagnosed annually with cancers that could be treated with a platinum-based chemotherapy.vii,viii The incidence of ototoxicity depends upon the dose and duration of chemotherapy, and many of those treated will require lifelong hearing aids. Until the FDA approval of PEDMARK, there were no preventative agents for this hearing loss. Patients with hearing loss resulting from cancer treatment have a statistically significant worse quality of life compared with peers who have no hearing loss.ixx

PEDMARK has been studied by co-operative groups in two Phase 3 clinical studies of survival and reduction of ototoxicity, COG ACCL0431 and SIOPEL 6. Both studies have been completed. The COG ACCL0431 protocol enrolled childhood cancers typically treated with intensive cisplatin therapy for localized and disseminated disease, including newly diagnosed hepatoblastoma, germ cell tumor, osteosarcoma, neuroblastoma, medulloblastoma, and other solid tumors. SIOPEL 6 enrolled only hepatoblastoma patients with localized tumors.

Indications and Usage

PEDMARK (sodium thiosulfate injection) is indicated to reduce the risk of ototoxicity associated with cisplatin in pediatric patients 1 month of age and older with localized, non-metastatic solid tumors.

Limitations of Use

The safety and efficacy of PEDMARK have not been established when administered following cisplatin infusions longer than 6 hours. PEDMARK may not reduce the risk of ototoxicity when administered following longer cisplatin infusions, because irreversible ototoxicity may have already occurred.

Important Safety Information

PEDMARK is contraindicated in patients with history of a severe hypersensitivity to sodium thiosulfate or any of its components.

Hypersensitivity reactions occurred in 8% to 13% of patients in clinical trials. Monitor patients for hypersensitivity reactions. Immediately discontinue PEDMARK and institute appropriate care if a hypersensitivity reaction occurs. Administer antihistamines or glucocorticoids (if appropriate) before each subsequent administration of PEDMARK. PEDMARK may contain sodium sulfite; patients with sulfite sensitivity may have hypersensitivity reactions, including anaphylactic symptoms and life-threatening or severe asthma episodes. Sulfite sensitivity is seen more frequently in people with asthma.

PEDMARK is not indicated for use in pediatric patients less than 1 month of age due to the increased risk of hypernatremia or in pediatric patients with metastatic cancers.

Hypernatremia occurred in 12% to 26% of patients in clinical trials, including a single Grade 3 case. Hypokalemia occurred in 15% to 27% of patients in clinical trials, with Grade 3 or 4 occurring in 9% to 27% of patients. Monitor serum sodium and potassium levels at baseline and as clinically indicated. Withhold PEDMARK in patients with baseline serum sodium greater than 145 mmol/L.

Monitor for signs and symptoms of hypernatremia and hypokalemia more closely if the glomerular filtration rate (GFR) falls below 60 mL/min/1.73m2.

Administer antiemetics prior to each PEDMARK administration. Provide additional antiemetics and supportive care as appropriate.

The most common adverse reactions (≥25% with difference between arms of >5% compared to cisplatin alone) in SIOPEL 6 were vomiting, nausea, decreased hemoglobin, and hypernatremia. The most common adverse reaction (≥25% with difference between arms of >5% compared to cisplatin alone) in COG ACCL0431 was hypokalemia.

Please see full Prescribing Information for PEDMARK at: www.PEDMARK.com.

(Press release, Fennec Pharmaceuticals, DEC 9, 2025, View Source [SID1234661313])