Sanders and Rep. Elijah Cummings of Maryland, who is the ranking member of the House Committee on Oversight and Government Reform and has made pharma price hikes one of his central issues, sent a letter to Ariad on Thursday requesting more information about its price hike for Iclusig, which is used to treat the rare blood cancer chronic myeloid leukemia.

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Iclusig’s list price (before discounts and rebates) has risen from about $115,000 to $199,000 between 2014 and 2016. Sanders and Cummings note that this is the result of at least four price hikes that have taken place in the last year alone.

Sanders and Cummings are demanding that Ariad provide information about the process behind its price hikes by Nov. 4.

Ariad is defending its pricing tactics by drawing attention to its R&D costs. “Iclusig is the first drug that we have brought to market after years of risk taking and research, and it serves a very small and seriously ill group of cancer patients,” the company said in a statement.

Drug companies have been under siege during the 2016 presidential election. Democratic nominee Hillary Clinton has also made the pharmaceutical industry and drug price hikes a central component of her campaign.