COPENHAGEN (Reuters) - Novo Nordisk will offer cheaper insulin to U.S. diabetics, the Danish drugmaker said on Friday, in response to criticism over the high price of the medication and after similar moves by rivals Sanofi and Eli Lilly.

FILE PHOTO: Employees stand in the insulin production plant of Danish multinational pharmaceutical company Novo Nordisk in Chartres, north-central France, April 21, 2016. REUTERS/Guillaume Souvant/Pool

President Donald Trump has made high prescription drug prices a top issue in the 2016 presidential campaign and said that drug companies were “getting away with murder”.

Novo will offer a generic version of its most heavily prescribed insulin drug Novolog, used by about a million U.S. patients, at a 50% discount compared to the current list price, the company said in a statement.

The list price for one vial will be $144.68.

Novo will also introduce a so-called $99 cash card program from Jan 2020, which patients can use to buy three vials or two packs of pens of Novo’s analog insulins for a flat cost of $99, which for most diabetics is an adequate supply for one month.

The cost of insulin for treating type 1 diabetes in the United States has nearly doubled over a five-year period, leading some patients to put their own health at risk by rationing the medication.

“While we will continue to do what we can to help address affordability challenges in the short-term, changes within the system are required to make sustainable and meaningful affordability a reality,” said Novo in a statement.

In April, France’s Sanofi said it would cut the cost of its insulin products to $99 per month for uninsured patients and others who pay cash in the United States.

Eli Lilly started selling a half-price version of its Humalog insulin in May. The list price for Lilly’s authorized generic insulin -- sold under the name Insulin Lispro -- is $137.35 per vial.

In April, a U.S. congressional committee called on executives from Novo, Sanofi and Eli Lilly to testify about the rising costs of the lifesaving drug.