The main cause, experts agree, is the underlying weakness of the generic drug industry, which are made mostly overseas because U.S. manufacturers are setting their sights instead on high-priced drugs with plump profit margins.

A more aggressive Federal Trade Commission is starting to target drug mergers and industry middlemen – pharmacy benefit managers, as part of Biden's push for lower drug prices.

Insulin and pharmacy benefit management company executives testified before the Senate Health, Education, Labor and Pensions Committee this week in Washington in preparation for a vote on PBM legislation.

Although Horizon says it now has 20 drugs under development, in its 15 years of existence it has yet to license a product it invented.

Eli Lilly's announcement that it is capping the cost of insulin at $35 a month also casts light on pharmacy benefit managers at a time when Congress has shifted its focus on them.

The FDA's accelerated approval is usually based on a "surrogate marker" of effectiveness.