Fennec Announces Presentation of Positive Interim Sodium Thiosulfate Phase III Safety Data at the 2015 ASCO Annual Meeting

RESEARCH TRIANGLE PARK, NORTH CAROLINA–(Marketwired – May 31, 2015) – Fennec Pharmaceuticals, Inc. (TSX:FRX) (OTCQB:FENCF), announced the presentation of positive interim results from a poster presented today entitled, “Anti-tumor efficacy in SIOPEL6: A multi-centre open label randomised phase III trial of the efficacy of sodium thiosulphate (STS) in reducing ototoxicity in patients receiving cisplatin (Cis) monotherapy for standard risk hepatoblastoma (SR-HB).” The data was presented at the American Society of Clinical Oncology (ASCO) 2015 Annual Meeting in Chicago. The poster is available today on the websitehttp://fennecpharma.com/investors/presentations-events/.

“I am excited to be sharing very encouraging safety data on the impact of STS in children with standard risk heptoblastoma at ASCO”, said Dr. Penelope Brock, MD, PhD, FRCPCH, International Chair of SIOPEL. “STS is very well tolerated. We are especially encouraged to see the safety after six courses of Cisplatin with the addition of STS.”

“Our company’s mission is to serve an unmet medical need for patients treated with cisplatin chemotherapy by improving the quality of life through the reduction of hearing loss,” said Rosty Raykov, Chief Executive Officer. “We are very pleased with the interim safety results presented at ASCO especially the conclusion, that, to date, STS as a chemoprotectant appears to have no adverse effect on the efficacy of cisplatin. We look forward to the data from the audiological results from the trial.”

SIOPEL 6 is a multi-centre open label randomized phase 3 study evaluating the efficacy of STS in reducing ototoxicity in patients receiving Cis monotherapy for SR-HB. The study is closed to recruitment and all protocol pre-specified IDMC safety reviews are now complete.

From the beginning of 2007 to the end 2014, 45 sites from 11 countries enrolled 109 evaluable patients. Newly diagnosed patients with SR-HB were treated with weekly cycles of Cis every two weeks including 4 chemotherapy courses before primary tumor resection and 2 courses after surgery. Patients were randomized to Cis alone or Cis and STS. Cis of 80 mg/m2 was administered i.v. over 6 hrs. STS was administered i.v. exactly 6 hrs after stop of Cis over 15 minutes at 20 g/m2. Tumor response was assessed after 2 and 4 cycles pre-operative with serum AFP and liver imaging. In case of progression after 2 cycles, STS was stopped and doxorubicin 60 mg/m2 continuous infusion over 48 hrs added. The primary endpoint is centrally reviewed absolute hearing threshold, at the age of ≥ 3.5 yrs, by pure tone audiometry. The trial has 80% power to detect a reduction in hearing loss defined as Brock grade ≥ 1 from 60% of patients with Cis to 35% with Cis+STS.

The efficacy results indicate that it is safe to treat SR-HB with six cycles of Cis monotherapy with the addition of the chemoprotectant STS. Efficacy results at the end treatment for the 109 evaluable patients (52 Cis, 57 Cis+STS) were complete response/partial response/progressive disease for Cis: 85%/6%/4% and for CIS+STS: 91%/7%/0%.

Status at end of treatment (6 cycles):

Efficacy Cisplatin          Cisplatin + STS
(n=52) (n=57)
Complete response 44 (84.6%) 52 (91.2%)
Stable disease 3 (5.8%) 4 (7.0%)
Progressive disease 2 (3.9%) 0
Died (1) 1 (1.9%) 0
Not available 2 (3.9%) 1 (1.8%)

(1) Died from surgical complications.

Status at last follow up after 6 cycles (May 2015):

Efficacy Cisplatin Cisplatin + STS
(n=52) (n=57)
Complete Response 48 (92.3%) 52 (91.2%)
Non CR 1 (1.9%) 3 (5.3%)
Died 3 (5.8%) 1 (1.8%)
Not available 0 1 (1.8%)

Further, the results presented showed that treatment was well tolerated and acute toxicity similar between arms. The table below presents the toxicities of the two arms:

Grade 3 and 4 Acute Cisplatin Cisplatin + STS
Toxicities (n=52) (n=57)
Allergy 3 1 (1.9%) 0
Febrile neutropenia 3 4 (7.7%) 5 (8.8%)
Infection 3 5 (9.6%) 6 (10.5%)
Hypomagnesemia 3 1 (1.9%) 1 (1.8%)
Hypermatremia 3 0 1 (1.8%)
Vomiting 3 1 (1.9%) 3 (5.3%)
Nausea 3 3 (5.8%) 2 (3.5%)
Left ventricular systolic disfunct. 3,4 0 0
Other toxicities 3 14 (26.9%) 20 (35.1%)
Other toxicities 4 3 (5.8%) 5 (8.8%)

Other G 3/4 toxicities encompass: hematological, liver and other biochemistry parameters.

About Sodium Thiosulfate (STS)

Cisplatin and other platinum compounds are essential chemotherapeutic components for many pediatric malignancies. Unfortunately platinum-based therapies cause ototoxicity in many patients, and are particularly harmful to the survivors of pediatric cancer.

In the U.S., it is estimated that over 2,000 children are diagnosed with local cancers that may receive platinum based chemotherapy and globally over 5,000. The incidence of hearing loss in these children depends upon the dose and duration of chemotherapy, and many of these children require lifelong hearing aids. There is currently no established preventive agent for this hearing loss and only expensive, technically difficult and sub-optimal cochlear (inner ear) implants have been shown to provide some benefit. Infants and young children at critical stages of development lack speech language development and literacy, and older children and adolescents lack social- emotional development and educational achievement.

STS has been studied by cooperative groups in two Phase 3 clinical studies of survival and reduction of ototoxicity, The Clinical Oncology Group Protocol ACCL0431 and SIOPEL 6. Both studies are closed to recruitment. The COG ACCL0431 protocol enrolled one of five childhood cancers typically treated with intensive cisplatin therapy for localized and disseminated disease, including newly diagnosed hepatoblastoma, germ cell tumor, osteosarcoma, neuroblastoma, and medulloblastoma. SIOPEL 6 enrolled only hepatoblastoma patients with localized tumors.

About Fennec Pharmaceuticals

Fennec Pharmaceuticals, Inc., is a specialty pharmaceutical company focused on the development of Sodium Thiosulfate (STS) for the prevention of platinum-induced ototoxicity in pediatric patients. STS has received Orphan Drug Designation in the US in this setting. For more information, please visit www.fennecpharma.com.

Forward looking statements

Except for historical information described in this press release, all other statements are forward- looking. Forward-looking statements are subject to certain risks and uncertainties inherent in the Company’s business that could cause actual results to vary, including such risks that regulatory and guideline developments may change, scientific data may not be sufficient to meet regulatory standards or receipt of required regulatory clearances or approvals, clinical results may not be replicated in actual patient settings, protection offered by the Company’s patents and patent applications may be challenged, invalidated or circumvented by its competitors, the available market for the Company’s products will not be as large as expected, the Company’s products will not be able to penetrate one or more targeted markets, revenues will not be sufficient to fund further development and clinical studies, the Company may not meet its future capital requirements in different countries and municipalities, and other risks detailed from time to time in the Company’s filings with the Securities and Exchange Commission including its Annual Report on Form 10-K for the year ended December 31, 2014. Fennec Pharmaceuticals, Inc. disclaims any obligation to update these forward-looking statements except as required by law.

For a more detailed discussion of related risk factors, please refer to our public filings available at www.sec.gov and www.sedar.com.

CONTACT INFORMATION

Fennec Pharmaceuticals Inc.

Rosty Raykov

Chief Executive Officer

(919) 636-5144