The price of one of the most commonly prescribed treatments for Parkinson’s disease has surged more than 200 percent over the past decade. That’s making the drug, Teva Pharmaceutical’s Azilect, unaffordable for some patients afflicted with the progressive and incurable disease.

According to market researcher Truven Health Analytics, the wholesale price of Azilect was $634.70 as of July 1 for 30 tablets, up from $204.60 in June of 2006, a month after the U.S. Food and Drug Administration approved the drug, also known as Rasagaline, to treat Parkinson’s disease.

More recently, Israel-based Teva (TEVA) in July hiked the prices it charges pharmacies and other middlemen for Azilect by 9.9 percent. However, consumers can pay much higher prices for the drug at the retail level, particularly if they’re footing the bill without insurance.

Drug companies often raise prices on medications before their patents expire and generic versions of the drug become available, according to Mike Thompson, head of the National Business Coalition on Health. Teva plans to release a generic version of Azilect next year.

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“[Employers] are very, very concerned at the pace at which drug prices are going up, and they increasingly want to have more control on how that’s managed in their benefit plans,” he said.

According to the Express Scripts Price Index, the average price for the most commonly used brand-name prescriptions have surged 164 percent since 2008. During that period, prices for Azilect jumped by 177 percent.

“The decision to increase pricing is determined by a number of factors as we constantly evaluate the marketplace and needs of our patients,” Teva spokeswoman Doris Saltkill said by email. “The company continues to research neurodegenerative diseases and other new compounds for treatment.”

She added that Teva tries to help Parkinson’s patients through a Parkinson’s support service that “brings together personalized support, education and financial resources that can help patients throughout their treatment with Azilect.”

Most health insurance and Medicare plans cover the cost of Azilect, and Teva offers coupons for people with private insurance that reduce their out-of-pocket expenses to $5 per prescription refill. It declined to comment further on its pricing for Azilect.

The increase in Azilect prices haven’t witnessed the headline-grabbing cost surge for Mylan’s (MYL) EpiPen (480 percent since 2009) or $84,000 per treatment regime for Gilead’s (GILD) hepatitis C treatment Sovaldi. Valeant (VRX ) has also come under fire for triple-digit price increases in its diabetes drug Glumetza, acid reflux treatment Zegerid and Wilson’s disease treatment Cuprimine. The last drug costs a whopping $26,189 for a one-month supply.

Still, the cost of Azilect is worrisome to many Parkinson’s patients.

“I have insurance that pays for it now. But I know from past experiences and through friends, a lot of insurance companies don’t pay for it due to its high price,” said Michael Sweet, a Parkinson’s sufferer who also administers a Facebook group for people with the disease. “I was fortunate to have my [Parkinson’s disease] specialist get involved and got it authorized.”

One Parkinson’s patient contacted by CBS MoneyWatch decided not to fill her Azilect prescription, which would have cost her $690 a month.

“Yes, I have insurance. But since it’s a tier-one drug, they won’t cover it until I meet my deductible, and then they would cover only 50 percent. And I have one of their best insurance plans,” she wrote in a message to CBS MoneyWatch on Facebook.

Facebook user Lisa Mueller said her insurer also refused to pay for Azilect and instead wanted her to use the generic Levodopa, the most common Parkinson’s treatment, which she said wasn’t the right choice for her.

“The problem is Levodopa isn’t a first-line treatment because it causes more side effects the longer it’s used,” she wrote to CBS MoneyWatch. “Without insurance, [Azilect] was near $900 per month. I qualified for a discount due to being a single mom with four kids. However, next year my income may be too high to qualify. I don’t know how I will afford it then.”

Teva, the largest manufacturer of generic drugs, had high hopes for Azilect. It had tried to convince the FDA to agree that the drug could slow the progression of Parkinson’s, something scientists have been trying for to do for decades.

However, an FDA advisory committee unanimously rejected that claim, saying there wasn’t sufficient evidence to prove it could slow Parkinson’s, which would have been a home run for Azilect. Like all Parkinson’s medications, the drug treats symptoms of the disease and is often paired with other medications such as Levodopa.

Sales of Azilect, though, continued to be brisk despite that setback. According to IMS Health, health care professionals write more than 400,000 prescriptions for it annually. Sales rose nearly 60 percent between 2012 and 2015, when they topped $322 million, according to IMS Health. As of June 2016, Teva’s Azilect sales were $176 million.