Cara tanks as the FDA clamps a hold on its painkiller trial

Cara CEO Derek Chalmers

The FDA put a clinical hold on Cara Therapeutics' ($CARA) Phase III painkiller study over a worrying spike in patients' sodium levels, sending the company's share price plunging.

The drug, CR845, is an intravenous opioid therapy meant to relieve pain in postoperative patients. In its ongoing Phase III trial, Cara noted that four patients getting the highest doses of CR845 developed hypernatremia, an elevation of blood sodium levels. The study's protocol mandated that Cara stop dosing if any patients crossed the hypernatremia threshold, the company said, and the FDA followed up with a clinical hold that won't lift until Cara completes a review of safety data.

Cara's shares fell as much as 42% on the news, as the safety scare dented investors' faith that CR845 can eventually win FDA approval.

The company pointed out that all four of the high-sodium patients returned to normalcy within 24 hours of dosing, adding that none presented symptoms of hypernatremia. And there have been no drug-related serious side effects observed in any of the 90 patients dosed so far, according to Cara, and no instances of hypernatremia in patients receiving smaller amounts of CR845.

"We are working closely with the FDA to review patient safety data and resolve this issue in a timely manner," Cara CEO Derek Chalmers said in a statement. "... We look forward to continuing the study, pending FDA review, as we work to bring this novel class of therapeutics to patients in need of additional pain treatment options."

The trial was designed to enroll 600 patients undergoing abdominal surgery, administering intravenous CR845 or placebo before and after procedures to determine whether the drug can make a significant difference in patient-reported pain over 24 hours.

Cara is also developing an oral formulation of CR845, reporting positive Phase II results in osteoarthritis pain last year and planning to begin late-stage development later in 2016.

The company pulled off a $55 million IPO in 2014 on the promise that CR845 could establish itself as an alternative to commonly used analgesics.

- read the statement