Novartis just started selling the first biosimilar drug in the U.S. (AP Photo/Rafiq Maqbool, File)

The first in a long-awaited category of drugs that have been projected to save tens of billions of dollars over the next decade became available today. But its price tag highlights a question economists and industry watchers have been wrestling with for the past few months: how much will these new drugs actually bring down prices?

The new drug, Zarxio, is the first American "biosimilar" -- a copycat version of a complex biologic drug. Biologics have grown to a huge market -- eight of the top 20 drugs ranked by sales in 2011 were biologics, and their prices are growing more than twice as fast as regular drugs, according to one study. Many observers are counting on biosimilars to bring those prices down.

The popular notion is that copycat drugs enter the market and the price drops off a cliff. But for a variety of reasons, the prices of complex, large-molecule protein drugs biosimilars may do something more like slowly roll down a hill and eventually settle in a gully halfway down the mountain and not at the bottom of a ravine.

Zarxio is made by Novartis. It is similar to an Amgen biologic cancer drug called Neupogen that brought in $1.2 billion last year. The wholesale price for Zarxio is $438.98 for a 480 microgram syringe, a spokesman said. On paper, that looks like a significant drop from the wholesale price of Neupogen, which is $516.45 for a comparable syringe -- roughly a 15 percent discount.

"With the launch of Zarxio, we look forward to increasing patient, prescriber and payor access to filgrastim in the US by offering a high-quality, more affordable version of this important oncology medicine," Richard Francis, global head of Sandoz, a Novartis company, said in a statement.

But an arcane fact about how the drugs are initially priced suggest that the spending on the drug will be far closer -- around 3 percent. Zarxio's wholesale price should really be compared to the average sales price of Neupogen, which is how Medicare reimburses for the drug. For Neupogen, that price is a little less than $449.81. That means for at least the first six months -- the time it will take regulators to determine the average sales price of Zarxio -- the drug prices will actually be almost exactly the same. It's a difference of nearly 3 percent.

Until an average sales price is established, "we estimate that reimbursement for Neupogen and Zarxio will be comparable under the Affordable Care Act's biosimilar reimbursement formula," Adam Fein, president of Pembroke Consulting wrote in an e-mail. Once that price is established, he estimated that Zarxio would be 12 to 15 percent cheaper than the Amgen drug it's trying to unseat.

"This pricing strategy suggests that Sandoz does not want to trigger a biosimilar price war," Fein wrote. "It's consistent with my view that we'll likely see a moderate pace for adoption for infused biosimilars paid under the medical benefit."

Andrew Mulcahy, a health policy researcher at RAND Corporation, said that the initial price of Zarxio was within the ballpark of what people expected and is comparable to how the drug was priced when it began to challenge Neupogen in European markets. He says that although the initial discount is modest, prices should drop more in the long run. In a study funded by Sandoz earlier this year, he estimated a cost savings of somewhere around $44 billion over a decade from biosimilar drugs, assuming that prices drop by about 35 percent.

"The most important point is this is the starting point in the race; this is not where we’re going to land," Mulcahy said.

But there are a variety of unknowns in the nascent market. Economists are unsure how much competition there will actually be in the space, and if there are fewer companies making these drugs, prices won't drop as much.

Alex Brill, a research fellow at the American Enterprise Institute, has argued there may not be enough customers to support multiple companies making the large upfront investment in developing biosimilars. That may lead to a situation where only the biggest drugs have a healthy biosimilar market and significant price competition.

"The point is we’re going to have biosimilars for the blockbusters," Brill said. "And the footnote is the way the market evolving is more and more of the products, brand products on the market today are not blockbusters."

Irena Royzman, co-chair of the biotechnology practice at Patterson Belknap Webb & Tyler, has warned that at least in the initial period the pricing may seem paradoxical to people who were expecting the new drugs to significantly undercut the drugs they are competing against.

"I think it’s unclear how much savings we will see in the short term and in the long term," Royzman said. "I think the Obama administration may see what they didn’t intend, because I think they had hoped this would result in immediate and sizeable cost savings, and that is far from clear."