The FDA just published a list of drugmakers the agency says are using "gaming" tactics to keep generic competition off the market.

The list of 52 drugs are made by some of the biggest pharmaceutical companies including Novartis, Pfizer, Mylan, and Valeant.

" FDA is committed – among other things – to addressing and improving transparency about this and other gaming tactics that delay the generic competition Congress intended," the agency said on Thursday

The FDA is calling out drugmakers it says are getting in the way of generic competition.

The Food and Drug Administration published a list on Thursday of 52 drugs it deemed are facing delays to getting generic versions because of "gaming" happening on the part of brand drugmakers.

Having generic alternatives to branded drugs is key to lowering drug prices. However, the companies that make the branded versions of the drugs stand to lose a lot of money once generic competition comes into the market.

As part of the process of getting a generic alternative approved, drugmakers need to purchase samples of the branded drug. Often, the companies that make the branded version make it difficult for that to happen which slows down the process of getting that generic version on the market.

"FDA is committed – among other things – to addressing and improving transparency about this and other gaming tactics that delay the generic competition Congress intended," the agency said on Thursday.

Last week, President Donald Trump laid out his plan to lower prescription drug prices. After the speech, FDA Commissioner Scott Gottlieb said that one of the steps the agency would be taking as part of that plan would be to address some of the "gaming" taking place around prescription drugs.

The list, which the FDA said will be updated semi-annually, names 39 major pharmaceutical and biotech companies who the agency says make it hard for generic competitors to get samples of their drugs. Those include:

Novartis

Mylan

AstraZeneca

Teva Pharmaceuticals

Boehringer Ingelheim

Biomarin Pharmaceuticals

GlaxoSmithKline

Gilead Sciences

Insys Therapeutics

Celgene

Pfizer

Valeant

Celgene was down 1% Thursday after the list came out, while generic drugmakers Mylan and Teva — which also made the list from a branded-drug perspective — were up 3% and 1%, respectively.