In addition to delivery platform research and development, Tekmira is advancing its own RNAi therapeutic candidates, including:
Tekmira has obtained worldwide licenses to Alnylam's core technology and intellectual property for the discovery, development and commercialization of RNAi products directed to eight RNAi gene targets—including three exclusive and five non-exclusive licenses. Five of the targets, ApoB, PLK1, Ebola, WEE1 and CSN5, have already been selected on a non-exclusive basis, and ALDH2 was recently selected as an exclusive target.
Tekmira's lead oncology product candidate, TKM-PLK1, has been shown in pre-clinical animal studies to selectively kill cancer cells, while sparing normal cells in adjacent healthy tissue. TKM-PLK1 targets PLK1 (polo-like kinase 1), a protein involved in tumor cell proliferation and a validated oncology target. Inhibition of PLK1 expression prevents the tumor cell from completing cell division, resulting in cell cycle arrest and death of the cancer cell.
Tekmira's pre-clinical studies have demonstrated that a single, systemic intravenous administration of TKM-PLK1 blocked PLK1 expression in liver tumors causing extensive tumor cell death. After repeat dosing, this result translated into significant inhibition of tumor growth and prolonged survival without evidence of the toxicities often associated with oncology drugs. The TKM-PLK1 anti-tumor efficacy results were confirmed to be the result of silencing PLK1 via RNA interference. Furthermore, certain LNP formulations provided potent anti-tumor efficacy in pre-clinical models of tumors outside the liver.
In December 2010, Tekmira initiated patient treatment in a Phase I human clinical trial of TKM-PLK1. The Phase I clinical trial, conducted at three medical centers in the United States, is an open label, multi-dose, dose escalation study designed to evaluate the safety, tolerability and pharmacokinetics of TKM-PLK1 as well as determining the maximum tolerated dose. The trial is enrolling up to 52 patients with advanced solid tumors. Secondary objectives of the trial are to measure tumor response and the pharmacodynamic effects of TKM-PLK1 in patients providing biopsies.
On April 9, 2013, Tekmira released results from its Phase I clinical trial with TKM-PLK1, an RNAi therapeutic for the treatment of solid tumors, The data were presented at the annual meeting of the American Association for Cancer Research (AACR) in an oral presentation entitled "A phase I dose escalation study of TKM-080301, a RNAi therapeutic directed against PLK1, in patients with advanced solid tumors." In this Phase I study, TKM-PLK1 was generally well-tolerated and showed encouraging signs of drug activity with RNAi activity confirmed in tumor biopsy. TKM-PLK1 was administered to 24 patients at doses ranging from 0.15 mg/kg to 0.90 mg/kg; with a total of 152 doses administered and a mean number of 6.2 doses per patient (range of 1-31 doses). The most common grade 1-2 adverse events were rigors (33%) and fever (25%). No dose-dependent changes in liver function tests were observed. Dose-limiting toxicities included: one grade 3 transient thrombocytopenia in one patient (at 0.9 mg/kg) and one grade 3 hypoxia/dyspnea in another patient (at 0.9 mg/kg). Based on these data, the maximum tolerated dose is estimated to be 0.75 mg/kg. A 10-patient expansion cohort is currently enrolling patients at 0.75 mg/kg, with data expected later this year.
Patients had a mean of 5.1 prior treatment regimens (range of 1-14). Forty-four percent (4 out of 9) patients evaluable for response, treated at a dose equal to or greater than 0.6 mg/kg, showed clinical benefit. In particular, one patient with progressive, metastatic appendiceal carcinoid (neuroendocrine) cancer had a durable partial tumor response based on RECIST criteria, continuing for more than 10 months. Three other patients achieved stable disease, including one patient with metastatic appendiceal carcinoid (neuroendocrine) cancer, another patient with metastatic colorectal cancer, and a third patient with metastatic adrenocortical carcinoma.
Click here to read the news release, view the slides presented at AACR, or listen to Tekmira's webcast that provides more details on the Phase I TKM-PLK1 clinical trial.
TKM-PLK1 Phase II Clinical Trial
Tekmira expects to initiate a Phase II clinical trial in patients with previously treated gastrointestinal carcinoid (neuroendocrine) cancer in the second half of 2013. Details of the trial design will be disclosed later this year. Tekmira is also evaluating additional indications for Phase II development and will provide guidance later this year. Tekmira also expects to present data from the expansion cohort of the TKM-PLK1 Phase I clinical trial this year.
For many years, the Zaire species of Ebola virus (ZEBOV) has been associated with periodic outbreaks of hemorrhagic fever in human populations with mortality rates reaching 90%. Currently, there are no approved treatments for Ebola or other hemorrhagic fever viruses.
In May 2010, Tekmira announced the publication of a series of studies demonstrating the ability of an RNAi therapeutic utilizing our LNP technology to protect non-human primates from Ebola virus, a highly contagious and lethal human infectious disease. We conducted the studies in collaboration with infectious disease researchers from Boston University and the United States Army Medical Research Institute for Infectious Diseases (USAMRIID) and were funded in part by the U.S. Government’s Transformational Medical Technologies (TMT) program. These preclinical studies were published in the medical journal The Lancet and demonstrated that when siRNA targeting the Ebola virus and delivered by Tekmira’s LNP technology were used to treat previously infected non-human primates, the result was 100 percent protection from an otherwise lethal dose of Zaire Ebola virus (Geisbert et al., The Lancet, Vol 375, May 29, 2010).
In July 2010, Tekmira signed a contract with the United States Government to advance an RNAi therapeutic utilizing our LNP technology to treat Ebola virus infection. In the initial phase of the contract, which is expected to last approximately three years and is funded under the TMT program, we are eligible to receive up to US$34.7 million. This initial funding is for the development of TKM-Ebola, including completion of pre-clinical development, filing an IND application with the FDA and completing a Phase I human safety clinical trial. The United States Government has the option of extending the contract beyond the initial funding period to support the advancement of TKM-Ebola through to the completion of clinical development and FDA approval. Based on the budget for the extended contract this would provide the Company with a total of up to US$140.0 million in funding for the entire program.
In November 2011, Tekmira announced that an Investigational New Drug (IND) application for TKM-Ebola was approved by the United States Food and Drug Administration (FDA). In February 2012, we initiated the TKM-Ebola Phase I clinical trial, which is a placebo-controlled, single-blind, single-ascending dose study with additional multiple-ascending dose cohorts in healthy human volunteers. The objective of the Phase I trial is to assess the safety and tolerability of TKM-Ebola and evaluate the pharmacokinetics and systemic exposure following both a single-ascending dose and multiple-ascending doses of TKM-Ebola.
TKM-Ebola will be developed under specific FDA regulatory guidelines called the “Animal Rule.” The Animal Rule provides that under certain circumstances, where it is unethical or not feasible to conduct human efficacy studies, the FDA may grant marketing approval based on adequate and wellcontrolled animal studies when the results of those studies establish that the drug is reasonably likely to produce clinical benefit in humans. Demonstration of the product’s safety in humans is still required.
ADDITIONAL PRODUCT CANDIDATES
In June 2011, Tekmira announced that we have secured non-exclusive licenses from Alnylam targeting two validated oncology targets: WEE1 and CSN5. Our collaborators at the National Cancer Institute (NCI) identified the novel cancer genes WEE1 and CSN5 from human tumor samples, and together we have generated encouraging pre-clinical data by leveraging our expertise in siRNA design and delivery. Gene expression data from human tumor samples indicate that both CSN5 and WEE1 are up-regulated in a number of human cancers and have been identified as potential molecular targets in breast, liver, lung, ovarian and skin cancer, amongst other tumor types. We are conducting pre-clinical work to further evaluate these targets before initiating formal toxicology studies.