For the first time ever today, the FDA approved the use of a copy of a costly biotech medicine, The Wall Street Journal reports. The "quasi-generic" drug could be the first step towards shrinking the US's $375 billion in yearly drug spending.

The generic drug, called Zarxio, is made by Novartis. It's a copycat version of Neupogen, an injectable treatment made by Amgen used to help prevent infections in patients undergoing chemotherapy. Unlike most pharmaceuticals, biotech drugs are created in living cells, which makes regenerating them a challenge. A daily dose of Neupogen can cost anywhere from $315 to $500, and many patients need to take multiple doses per week, WSJ reports.

Biotech drugs are some of the most expensive in the world

The copycat drugs are called "biosimilars," because they aren't exact replicas of brand-name biotech drugs. In some states, doctors cannot switch a patient who is already taking a name-brand biotech to a biosimilar version of it, according to the Associated Press.

The FDA released regulatory guidelines for biosimilars in 2012. Because the proteins used in biotech drugs are larger and more complex than those used in small molecule pills, the FDA may need to expand regulations as the drugs enter the market. Biotech drugs are produced by genetically modified organisms, and even slight changes in how they are grown can affect the properties of the proteins produced.

The US health system puts an estimated $82 billion towards biotech drug spending annually. A cheaper version of a biotech drug could help curb the costs of medical treatments, but these drugs are still some of the most expensive in the world. There's no promise Zarxio will be significantly cheaper than its counterpart. US sales of Neupogen alone reached $839 million last year, according to AP. Novartis won't disclose the cost of Zarxio until it's commercially available, but it told WSJ the drug would be "competitively priced."

Generic biotech drugs have been available in Europe since 2006, and AP reports the copies are usually 20 to 30 percent cheaper than their counterparts. Generic versions of typical drugs often sell for 90 percent less than brand-name drugs.

"I don’t think it’s going to be an overnight sensation." Gary Lyman, an oncologist at the Fred Hutchinson Cancer Research Center told WSJ. "I think oncologists are going to have to gain from experience that [biosimilars] are safe, they’re efficacious, and patient convenience and quality of life is maintained."

The copy could be commercially available in a matter of weeks

Amgen has asked a federal judge in California to block the sale of Zarxio, claiming the product doesn't meet regulatory standards. A court hearing is set for March 13th, AP reports. Novartis plans to make the drug available after the ruling or by April 10th, whichever comes first.