What is the row between Wes Streeting and pharmaceutical companies about?

Two sides have failed to come to agreement over financial terms for provision of drugs to the NHS

• Wes Streeting criticises ‘shortsighted’ drug firms for rejecting pricing offer

Wes Streeting, the health secretary, has accused pharmaceutical companies of being “shortsighted” and undermining their relationships with the government after the two sides failed to come to an agreement last week, but what is the row all about?