Celldex Therapeutics Inc. plunged by more than half after saying it will stop a final-stage study of its experimental brain cancer vaccine Rintega.
An independent board overseeing the trial determined that newly diagnosed patients getting Celldex’s drug weren’t showing a difference compared with those in a control group, the company said in a statement Monday. Celldex decided to end the study based on that recommendation. The trial, called ACT IV, enrolled 745 patients, Celldex said last month in a filing.
The shares dropped 51 percent to $4.03 at 10:37 a.m. in New York. The stock had already slumped 48 percent this year through Friday.
“We are genuinely shocked with this outcome and we are digging into this now,” Chief Executive Officer Anthony Marucci said on a call with analysts Monday. Rintega performed as well as it had in previous trials, but patients in the control group fared unusually well, living longer than the company expected, he said. The patients who got Celldex’s therapy had a median survival of 20.4 months compared with 21.1 months among those in the control group, the company said.
Celldex doesn’t expect to have more costs for work on Rintega, which had shown efficacy in a previous mid-stage trial. In November, the company reported that the vaccine had lengthened some patients’ lives in a 73-person study looking at those with recurrent disease. Celldex has seven company-led clinical trials across five product candidates ongoing and expects to report data from some of these studies over the next three to 18 months.