NEW YORK (TheStreet) -- Shares of Ariad Pharmaceuticals (ARIA) were falling on heavy trading volume mid-Thursday afternoon after Senator Bernie Sanders (I-VT) and Representative Elijah Cummings (D-MD) sent a letter to the company asking for more information on the pricing of its Iclusig leukemia drug.

They noted that Cambridge, MA-based Ariad has increased the cost of the drug multiple times over the last four years, to $199,000 per year in 2016 from $115,000 per year in late 2012.

The price hikes are "staggering," Sanders and Cummings wrote.

The letter cited TheStreet's Adam Feuerstein, who noted that Ariad raised Iclusig's price four times this year since current CEO Paris Panayiotopoulos took the helm in January.

"In the interest of taxpayers, we are interested in learning more about the impact that the escalating price and restrictions on product availability have had," they added.

Sanders and Cummings requested that Ariad provide documents from 2012 onward detailing the company's revenue and profits from Iclusig, the factors that contributed to the price increases and total expenses related to the development and sale of the drug, among other information.

They asked Ariad to send the requested documents by November 4.

More than 16.27 million shares of Ariad have traded hands so far today vs. the 30-day average volume of 7.26 million shares.

Separately, TheStreet Ratings objectively rated this stock according to its "risk-adjusted" total return prospect over a 12-month investment horizon. Not based on the news in any given day, the rating may differ from Jim Cramer's view or that of this articles's author.

TheStreet Ratings rated this stock as a "sell" with a ratings score of D+.

Among the areas we feel are negative, one of the most important has been weak operating cash flow.

You can view the full analysis from the report here: ARIA