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Tacere Evaluates New Drug Opportunities As Development of HCV Drug Continues

Having found licensees for its lead expressed RNAi drug, the preclinical hepatitis C therapy TT-033, Tacere Therapeutics continues to seek its next pipeline candidate.
According to Tacere CEO and co-founder Sara Hall, the company is in “evaluation mode” and has been in discussions with a number of undisclosed parties, both from academia and industry, about potentially in-licensing new programs.
“We had some really good meetings at [the Biotechnology Industry Organization’s international meeting in San Diego last month] and we’ve done some pretty extensive due diligence on a couple things,” she said.
Still, the search is early-stage, and Hall declined to comment in detail on the indications or therapeutic areas Tacere is considering.
“Some [possibilities] we are still looking at [and] some we’ve passed on,” Tacere Chairman, President, and CFO Mike Catelani, added. “We’re not in a position at this point to talk about anything we’re looking at, but there are some interesting things out there.”
But Hall noted that hints as to the fields Tacere is exploring can be found in two recent additions to the company’s staff.
“We’ve recently hired two more scientists,” she said. While both have experience with RNAi, “one has more of a [neurology] background and one has an immunology background.” Catelani noted that Tacere now has six full-time employees.
Despite Hall’s reticence, she did note that Tacere expects to find its next pipeline program outside of its own labs and that it will likely remain focused on expressed RNAi.
“We don’t really want to start over again like we did with TT-033 because that’s a long, hard road,” Hall said. “We’d like to pick up something that’s at the translational research stage.”
TT-033 was originally developed by Avocel, a company Hall co-founded and which was acquired by Australian expressed RNAi firm Benitec in 2004 (see RNAi News, 5/21/2004). Following a sweeping corporate reorganization, Benitec licensed the drug’s worldwide rights to Tacere in late 2006 (see RNAi News, 10/12/2006).
At the same time, Tacere is keeping its attention on expressed RNAi after a brief flirtation with small-molecule drugs. Specifically, when it acquired TT-033 from Benitec, Hall told RNAi News that Tacere would also be developing small molecules for HCV in order to leverage the company’s expertise with the virus.

“We don’t really want to start over again like we did with TT-033 because that’s a long, hard road. We’d like to pick up something that’s at the translational research stage.”

“We recognized that our core competence isn’t just RNAi, but hepatitis C — we spent so much time working on that as a clinical indication that we knew a lot about it as a disease target,” she said at the time. As such, “we really didn’t need to be limited as far as therapeutic modality.”
But after Tacere out-licensed TT-033’s global rights, excluding Asia, to Pfizer early this year, Hall changed course, saying that the company would instead remain a pure-play RNAi shop, a decision she said was validated by the big pharma’s willingness to jump into the expressed RNAi pool (see RNAi News, 1/10/2008).
Currently, Pfizer and Tacere are working together on investigational new drug application-enabling studies for TT-033, with a toxicology and biodistribution study in cynomolgus monkeys slated to begin in the next couple of months, according to Hall. She declined to provide a timeline for when an IND might be filed.
As for the possibility of Tacere’s extending into traditional RNAi using synthetic siRNAs, Hall said this week that such a move is unlikely, but not impossible.  
“We’re not ruling it out, but as we’ve said all along, we’re biologists, not chemists,” she explained. “If we did go the route of synthetic oligos, it would probably be [through] a collaboration. It’s just not where our expertise lies.
“We’ll stick with what we know for now,” she added.
Ready to RAC
As it makes progress towards the clinic with TT-033, Tacere is also facing its first meeting with the National Institutes of Health’s Recombinant DNA Advisory Committee.
The RAC was formed in 1974 to address concerns over the safety of using recombinant DNA techniques to manipulate genetic material. Among the RAC’s duties is to provide the NIH with “advice concerning various advances in recombinant DNA technology, as well as ethical and safety considerations associated with novel or possibly risky forms of recombinant DNA research,” according to the NIH. 
Because TT-033 uses plasmid DNA to express its RNAi payload, the drug is eligible to be reviewed by the committee.
“The general dogma is that it is not really required [to go before the RAC] but they don’t advise that you skip them — and we wouldn’t,” Hall said. “When we do go, it will be jointly as Tacere and Pfizer, and it will be with a package ready for submission to the FDA. We’ll be very thorough and well-prepared.”
Preparation will likely be key when the time comes for Tacere and Pfizer to face the RAC, given the committee’s reaction in late 2006 to another expressed RNAi drug, Nucleonics’ hepatitis B drug NucB 1000.
At that time, the RAC expressed a number of concerns about NucB 1000, including the drug’s potential to overwhelm a patient’s natural RNAi processes (see RNAi News, 12/21/2006). Despite the committee’s concerns, Nucleonics went forward with a phase I trial of the drug, although that study was prematurely halted after the company shut down amid financing problems and allegations of scientific misconduct (see RNAi News, 7/3/2008).
Noting that the RAC meets quarterly, Hall said that Tacere has a good idea of when it will go before the committee, but she declined to disclose it.

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