NEW YORK (GenomeWeb) – Tekmira Pharmaceuticals this week said that it is currently amending the protocol of a Phase I trial of its RNAi-based Ebola infection therapy TKM-Ebola after US regulators halted the study amid safety concerns.
Tekmira, which has seen its stock fall more than 25 percent since the US Food and Drug Administration put a hold on the clinical trial early this month, said that it expects the matter will be resolved by the end of the year. Tekmira shares closed a little over $10 on Wednesday, and remain well off a 52-week high of $31.48.
TKM-Ebola combines Tekmira's proprietary lipid nanoparticle delivery technology with siRNAs against three targets in the Zaire strain of the Ebola virus. The drug is being developed under a contract from the US Department of Defense that could be worth up to $140 million and fund the drug's development through to commercialization.
Tekmira had moved a first-generation version of the drug into Phase I testing in 2012, but cut that study short so that it could reformulate the drug to take advantage of advances made with its lipid nanoparticles. By late 2013, the company had gotten the green light for a new Phase I trial, which would first test single ascending doses of the improved TKM-Ebola and then multiple ascending doses.
In May, Tekmira unveiled data from the single-dose portion of that study, which showed that TKM-Ebola was well tolerated at doses up to .3 mg/kg. However, adverse events were observed at all dose levels examined.
Notably, no study subjects received pre-medication to address immune responses associated with siRNAs — something that Tekmira has done in previous clinical studies of other drugs but does not intend to do with TKM-Ebola.
At the time, Tekmira President and CEO Mark Murray said that the Phase I data demonstrate that the company's latest lipid nanoparticle technology can enable dosing of siRNAs at efficacious levels without the need for pre-medication.
Tekmira had intended to start treating healthy individuals with multiple .3 mg/kg doses of TKM-Ebola. But those plans were put on hold early this month when the FDA ordered a hold on the study until the company could provide it with additional data related to the cytokine release observed in those receiving higher doses of the drug in the first part of the trial.
This week, Tekmira provided more detail on the situation, stating that the FDA is also requiring changes to the Phase I study's design to "ensure the safety of healthy volunteers" in the multiple ascending dose portion of the trial.
"The mechanism for cytokine release is understood, and we will be modifying our study protocol to further ensure subject safety," Murray said in a statement this week.
He added that Tekmira is aware of the Ebola infection outbreak currently ongoing in West Africa, but added that TKM-Ebola is currently unapproved anywhere in the world and that "the regulatory framework to support its use in Africa has not been established at this time."