Danish drugmaker Novo Nordisk said two patients in Japan who were being treated with its Victoza type 2 diabetes drug died from the discontinuation of their insulin treatment and not by Victoza.

Novo Nordisk’s chief science officer said on Friday the patients, who had type 1 diabetes and required insulin, died from a condition called ketoacidosis, in which sugar in the body is burnt into acid, which can induce a coma in patients who go off insulin suddenly.

“These unfortunate fatalities are not related to Victoza,” Novo Nordisk Chief Mads Krogsgaard Thomsen told Reuters. “Because insulin was inappropriately discontinued, they developed ketoacidosis and died from it,” he said.

“Both (patients) were insulin-dependent, both had been receiving insulin treatment for a long time, and for some reason the treating Japanese physicians completely discontinued insulin treatment and gave them a low dose of Victoza instead,” he said.

Victoza is not approved as a substitute for insulin. It and rival GLP-1 drugs stimulate cells to release natural insulin in the body when blood sugar levels are high and are used to treat patients that can control their blood sugar levels without insulin injections. Rivals include Eli Lilly’s Byetta.

“Victoza is for type 2 diabetes patients who are not dependent on insulin, and that is reflected in the label,” Thomsen said.

Novo began rolling out Victoza, which it hopes will become a blockbuster with sales of more than $1 billion, in Europe last year, in the all-important U.S. market in February, and recently in Japan and Canada.

Thomsen said that Novo Nordisk is working on getting approval for use of Victoza in combination with insulin.

“But that is a different story from patients who have been using insulin for a long time and then having insulin discontinued,” he said.

He said that Novo Nordisk reported the deaths to Japanese medical regulators as required.

Thomsen said he expected Japanese regulators would explain to physicians Victoza was not a substitute for insulin in insulin-dependent patients and was not approved for treatment of patients with type-1 diabetes. Type 1 diabetes is fatal unless treated with insulin.

“Our view is that the Japanese authorities will ... ensure that this does not happen again by making sure that it is not used in insulin-dependent patients,” he said.

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COPENHAGEN (Reuters)