Something remarkable is happening with a new class of living drugs

The FDA was on a roll as far as drug approvals go in 2015.

Over the course of 12 months, the agency responsible for making sure the medicine we put into our bodies is safe and effective approved 45 drugs, the most since 1996, when 53 new drugs got approval.

And roughly a third of those approvals were for drugs to combat cancer, including four immunotherapies, part of an emerging class of cancer-fighting drugs.

The tally includes only completely new molecular entities, or drugs that haven't been approved in any other context (for a hypothetical example, if Botox gets approved to treat another kind of wrinkle, that wouldn't count as a new drug, because it's already approved to treat other conditions).

Expanding a newer way to fight cancer

Notably, this year saw the most cancer immunotherapy approvals, especially if including treatments such as Imlygic, a genetically modified herpes virus that's programmed to attack tumor cells (Imlygic wasn't included on the list of 45 drug approvals). These new approvals to the class of cancer immunotherapies seriously expand its potential to be an effective tool in the fight against cancer. Unlike chemotherapy, which involves administering powerful drugs that kill both cancerous and healthy cells (most healthy cells can repair themselves), immunotherapies harness the power of the immune system to help it identify and knock out just the cancerous cells.

Investors expect new cancer immunotherapies still to come to make billions of dollars in sales in the next couple of years.

Other key approvals

It was a big year in other aspects as well. About 30% of all approvals were for biologic-based medicines, which are produced by living cells. This kind of medicine includes cancer immunotherapies. As a result, they tend to be a lot more complex, and often much more effective (not to mention more expensive) than their chemical counterparts.

Six of the approvals were specifically for rare diseases, or diseases that affect fewer than 200,000 people in the US.

Some of the approvals last year were more contentious than others. Addyi, a drug to enhance female sexual desire, got approved over the summer after previously being rejected twice. This prompted skepticism about just how frequently the FDA approves new medications, as opposed to turning them down if their effectiveness is iffy.

Why the rise?

There are a few reasons why the number of approvals is seemingly on the rise, especially in the last two years (41 were approved in 2014, while just 27 got approved in 2013). The Associated Press suggests it could be because drug companies are getting better at picking out which drugs will make it to the finish line. Another factor could be that the drugs approved are more specialized, so they more effectively treat a smaller population of people as opposed to more overarching medications that have been approved in the past.

The drug approvals are coming in faster for some drugs too, thanks to fast-tracked approval processes for rare diseases and conditions seriously in need for new treatments.