Rare Disease Report

Oral Suspension of Orfadin Approved to Treat HT-1 in Canada

NOVEMBER 27, 2017
Mathew Shanley
The original United States approval of Orfadin (nitisinone) for the treatment of hereditary tyrosinemia type 1 (HT-1) was more than 15 years ago. In September, a dosage reduction of the drug was approved by the U.S. Food and Drug Administration (FDA).

This morning, Sobi announced that it has received approval from Health Canada for an oral suspension, or liquid formulation, of Orfadin. With the news, the therapy becomes the first medicine approved in multiple countries for use in combination with dietary restriction of tyrosine and phenylalanine for the treatment of HT-1.

The oral suspension provides an additional option for receiving the therapy for infants, small children, and patients with difficulty swallowing capsules.

In the rare genetic disease HT-1, a deficiency of the fumarylacetoacetate hydrolase (FAH) enzyme leads to difficulty in breaking down tyrosine and an accumulation of toxic metabolic products in several of the body’s tissues. The condition is characterized by progressive liver, renal and neurological complications and the potential for organ failure if left untreated.

“The introduction of new nitisinone dosing options, such as Orfadin oral suspension, is the result of Sobi listening to feedback from patients and caregivers and continuing to innovate to meet their needs,” said Bob McLay, Vice President and General Manager of Sobi Canada Inc. In October, Rare Disease Report sat down with Rami Levin, President of Sobi in North America to discuss the challenges that may come with working in pharmaceuticals on behalf of the rare disease community.

Orfadin has been designed to block the breaktown of tyrosine and reduce the amount of toxic tyrosine byproducts in the body. The oral suspension of the drug is now available in Canada, in addition to the 20mg capsules, and the original 2mg, 5mg, and 10mg capsules.

“Oral suspension Orfadin is good news for parents of infants with HT-1 who typically cannot swallow a capsule, and we are grateful to Sobi for bringing this formulation to Canada. Indeed, Canadians with HT-1 have benefitted from Sobi’s commitment in providing Orfadin capsules for many years through the Special Access Program when there was no other drug available and recently in securing regulatory approval through Health Canada,” said Durhane Wong-Rieger, President of the Canadian Organization for Rare Disorders in a press release.

In the open-label study in 291 patients with HT-1 that served as the basis for the original Canadian approval of Orfadin, patients younger than 2 months of age who were treated with Orfadin in combination with a special diet experienced 2-, 4-, and 6- year survival probabilities of 93%, compared to 2- and 4- year probabilities of 38% and 29%, retrospectively, for historical controls treated with dietary restrictions alone.

Sobi suggests that protein supplements be taken in addition to Orfadin, as foods high in protein like meat, fish and eggs should be avoided whenever possible. Little- and no-protein foods like breads, fruits and vegetables are highly recommended. The dietary regimen of an HT-1 patient is life-long, and requires commitment. The company notes that registered dieticians should be sought out as needed.

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