Shares of Regado Biosciences Inc. (NASDAQ:RGDO) fell 60.2 percent Monday, closing at $1.13, after the company permanently terminated enrollment in a phase III trial of its lead program, the anticoagulant Revolixys Kit (REG1), following a string of serious allergic events found by its data and safety monitoring board (DSMB).

Regado is reviewing unblinded data from the trial, called REGULATE-PCI, a process it expects will take several months and may impact its second most advanced program, the anticoagulant REG2. David Mazzo, CEO of the Basking Ridge, N.J.-based company, told investors Monday the company is unable to provide additional details on Revolixys' future until its analysis of the data is complete, but the firm would share "definitive" insights as they become available.

Regado first alerted investors to trouble with the trial July 2, halting enrollment after the DSMB initiated an unplanned review of data from the first 3,234 patients enrolled, en route to enlisting a total of 13,200 patients undergoing percutaneous coronary intervention to help compare Revolixys Kit to Angiomax (bivalirudin, The Medicines Co.). An FDA clinical hold on the study followed July 9. (See BioWorld Today, July 7, 2014.)

Now that the DSMB has completed its review, Regado determined that the level of serious adverse allergic events observed in the Revolixys treatment arm were frequent and severe enough to quit enrollment altogether, Mazzo said.

Regado now will move ahead with cleaning and locking the total unblinded database, undertaking a complete review to try to determine the causes of the allergic reactions and to develop a plan for how to proceed, said Mazzo. The initial focus of the review will be on the study's primary efficacy endpoint, based on a composite of death, nonfatal myocardial infarction, nonfatal stroke and urgent target lesion revascularization through the third day after the procedure, and on safety, Mazzo said.

Revolixys Kit is a two-component system consisting of pegnivacogin, an anticoagulant targeting coagulation factor IXa, and its active control agent, anivamersen, both of which are administered by intravenous bolus injection. It was Regado's hope that it could beat out Angiomax. Following an April 2014 offering in which it netted about $57.5 million and an 2013 initial public offering, Regado was geared to fund a big pivotal trial, holding about $72.7 million in cash and equivalents at June 30. (See BioWorld Today, April 14, 2014.)

At least in the near term, Regado's costs will be significantly lower, mostly due to expenses associated with closing down clinical sites, analyzing the REGULATE-PCI trial data and preparing reports for health agencies, said the firm's chief financial and compliance officer, Don Elsey. But exact numbers about future burn weren't yet clear. "We'll probably give additional guidance on that as we get a little bit further down the path," Elsey said. "After that point it will just be what I'd consider your bare bones structure until such time as we decide what to do with Revolixys and the other preclinical candidates."

The company did not comment on its lead antiplatelet candidate, the preclinical program REG3, and declined a request for further comment.

Jefferies analyst Biren Amin downgraded Regado shares from "buy" to "hold" following the news. "The failure of Revolixys also means that RGDO's other pipeline programs face uncertainty," he wrote, reducing the firm's price target for Regado to $1.50 per share from $7.50. Given recent events, Biren said, Regado's plans to expand Revolixys' use into other cardiovascular indications seemed unlikely, also calling into question plans for REG2, an extended-release formulation of pegnivacogin, the anticoagulant in Revolixys.

"At this point it's impossible and premature for us to make any determinations about REG2," Regado's Mazzo said during the investor call. "We need to understand more about the causes behind the serious allergic adverse events associated with REG-1 before we'll be able to make those determinations."