Shares fell 12.4 percent to C$12.81 at 9:33 a.m. in Toronto, paring this year's rally to 52 percent.
The Vancouver, British Colombia-based company said in a statement today that it has received verbal notice from the FDA that the TKM-Ebola Phase I healthy volunteer clinical study has been placed on clinical hold.
This notice applies only to this study, it said.
"We have completed the single ascending dose portion of this study in healthy volunteers without the use of steroid pre-medication," Chief Executive Officer Dr. Mark Murray said in the statement.
"The FDA has requested additional data related to the mechanism of cytokine release, observed at higher doses, which we believe is well understood, and a protocol modification designed to ensure the safety of healthy volunteer subjects, before we proceed with the multiple ascending dose portion of our TKM-Ebola Phase I trial."
"We will continue our dialogue with the FDA, provided for under our Fast Track status, in order to advance the development of this important therapeutic agent."
The TKM-Ebola Phase I clinical trial is a randomized, single-blind, placebo-controlled study and involves single ascending doses and multiple ascending doses of TKM-Ebola. The study is assessing the safety, tolerability and pharmacokinetics of administering TKM-Ebola to healthy adult volunteers without administering any steroid pre-medications. http://www.proactiveinvestors.com/companies/news/55171/tekmira-tumbles-after-fda-puts-ebola-drug-on-clinical-hold-55171.html