The outlook for Ariad Pharmaceuticals Inc. went from bad to worse Thursday after the troubled maker of cancer drugs bowed to regulatory pressure to stop marketing its leukemia treatment in the United States, casting a shadow over the company's future.
Ariad said the move came in response to a request by the Food and Drug Administration, which on Thursday issued a drug safety communication warning that the company's pill, called Iclusig, carried "the risk of life-threatening blood clots and severe narrowing of blood vessels."
It was the latest in a series of setbacks for Cambridge-based Ariad, sending its shares plummeting 44.4 percent, or $1.76, to $2.20 in trading on the Nasdaq exchange. The stock was trading above $18 a share in early October.
"This is a big disappointment," said biotechnology analyst Phil Nadeau, managing director at the investment bank Cowen & Co. in New York, who noted that the move took Wall Street by surprise.
"We're in uncharted territory," he said. "It's almost unheard of for an oncology company to suspend its marketing. It suggests the use of their drug may be limited to the most severely ill patients."
Ariad executives, in a conference call with stock analysts, took the unusual step of publicly taking issue with the FDA's approach. Although acknowledging that Iclusig may have to be restricted to a smaller set of patients, they said they suspended sales and distribution mostly so they could better work with regulators to design a revised drug label.
"We think there are other ways to achieve the objective of optimal utilization of Iclusig," Ariad's chief executive, Harvey Berger, told the analysts repeatedly throughout the call.
Ariad executives took pains to note that the temporary marketing suspension does not mean the leukemia drug — the first and only Ariad medicine approved for sale — has lost its FDA approval or been pulled from the US market. Iclusig continues to be sold in Europe, though Ariad has notified regulators there of the most recent clinical safety data.
There is no timetable for when Ariad can resume marketing Iclusig in the United States, said FDA spokeswoman Stephanie Yao.
"We are working with the company to further understand the risks of the drug and identify the potential patient populations where the benefits of the drug may outweigh the risks," Yao said. She also released a statement indicating that "at this time, the FDA can not identify a dose level or exposure duration that is safe for patients" taking the drug.
There are four other FDA-approved medicines on the market to treat blood cancers, including the market-leading Gleevec, sold by the Swiss pharmaceutical giant Novartis AG.
Ariad has long been considered one of the Boston area's most promising biotechnology companies. That view seemed to be validated last December, when the FDA gave Ariad the green light more than three months ahead of schedule to sell Iclusig in the United States to treat two rare blood cancers — chronic myeloid leukemia and Philadelphia chromosome positive lymphoblastic leukemia — for patients resistant to other drugs.
The company, which has 444 employees, including 312 in Cambridge, has continued to run clinical trials globally aimed at expanding the set of patients who could be eligible to take the therapy. But problems surfaced Oct. 9, when Ariad halted enrollment in its ongoing trials after new data showed that an increased number of patients suffered blood clots and heart problems in the study leading to Iclusig's approval.
On Oct. 18, the company abruptly ended a pivotal clinical trial aimed at winning approval of Iclusig to treat newly diagnosed leukemia patients.
Three days later, Ariad confirmed that it had put on hold plans to move into a new two-building headquarters-and-laboratory complex under construction in the Kendall Square neighborhood.
Ariad executives declined to be interviewed about the marketing suspension Thursday, a company spokesman said.
Management came under additional pressure this week when the Connecticut hedge fund Sarissa Capital Managment — led by Alexander Denner, a protege of activist investor Carl Ichan — disclosed it had purchased 6.2 percent of Ariad's outstanding shares and would be seeking representation on the Ariad board.
The company may still be able to build a viable if smaller-than-hoped-for business by focusing on a narrower population of patients who cannot tolerate other leukemia drugs, said Nadeau, the Cowen analyst. But, he said, Ariad is unlikely to reach profitability until 2019. "There's still a lot of uncertainty" about the company's future, Nadeau said.
Robert Weisman can be reached at firstname.lastname@example.org.