By Doug Macron
Mirna Therapeutics has pushed back to next year the anticipated filing date for its first investigational new drug application as it continues to work to close a Series B financing round, a company official told Gene Silencing News this week.
At the same time, Mirna has gained some traction in its efforts to form an industry partnership, having inked technology-evaluation deals with two pharmaceutical companies, Mirna President and CEO Paul Lammers said.
Last summer, Lammers told Gene Silencing News that Mirna was close to finalizing the roughly $25 million Series B, which, in combination with $10.3 million received from the Cancer Prevention and Research Institute of Texas, was expected to give the firm funds enough to last into 2014 (GSN 6/24/2010).
However, by October, the microRNA drug shop had not closed the financing round, and Lammers was predicting it would take until the end of 2010 to do so (GSN 10/21/2010). At that time, Mirna was also anticipating filing two INDs in 2011.
But this week, Lammers said that the financing round would not likely be completed until next year at the earliest, attributing the delay to concerns by investors over decisions by key pharmaceutical companies regarding their RNAi activities.
Chief among these, he said, was Roche's recent restructuring, which included the elimination of its in-house RNAi activities (GSN 11/18/2010).
Lammers stressed, however, that discussions with potential investors continue, and that "they are very committed to Mirna, our approach, and our targets. [The financing round] will just take a bit longer to complete."
In the end, he said that securing the financing will require the generation of additional proof-of-concept evidence around the company's miRNA mimics.
"Data talks, and [possible investors] would definitely like to see more data to make sure there is a consistent delivery by systemic administration and uptake by tumors [that would suggest] efficacy in the clinic," Lammers noted. "That's what … we're in the process of doing."
While he declined to provide specific guidance on when the Series B may close, Lammers said that he would "like to make it happen in the first half of next year," before the company begins phase I testing of its lead drug candidate.
"A big part of [the investment] is to provide funding for that [clinical work and] get our lead microRNA mimic past phase I," he said. As such, "we're working hard to close the financing this year."
Mirna's pipeline comprises eight candidates, and while several had been advancing in parallel, Lammers said that the firm has selected miR-Rx34, a mimic of miR-34 designed to treat prostate cancer and other solid tumors, as its lead molecule.
"We have generated the most data on [miR-34, a key miRNA] just downstream of p53," which is implicated in more than half of all solid tumors, he said. "Therefore, we think that miR-34 may be a fantastic tumor suppressor, and we have a ton of in vitro and in vivo data to support it. It makes a lot of sense for us to push [that program] forward."
Just this week, Mirna researchers and collaborators from the University of Texas MD Anderson Cancer Center reported in Nature Medicine that miR-34a, a member of the miR-34 family, could inhibit prostate cancer stem cells and metastasis by repressing the adhesion molecule CD44 (related story, this issue).
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An IND for miR-Rx34 is now expected to be filed in 2012, with a phase I study beginning later that year. But in addition to getting the financing needed to move the candidate into humans, Mirna must also select the appropriate delivery technology, Lammers noted.
Delivery remains the key hurdle for all firms working in the nucleic acid drugs space, "and we're no exception to that," he said. "We're working to make sure we pick the right delivery system for our microRNA mimics."
The company has an in-house neutral lipid emulsion delivery under development, but it is also considering licensing access to delivery technologies from other companies.
"There is a lot of movement forward in the delivery space with delivery companies," Lammers said. "We want to benefit from that and take what we think is the latest and greatest."
Meanwhile, Mirna continues to pursue industry alliances for miR-Rx34 and its other pipeline programs. According to Lammers, the firm has already signed two deals giving undisclosed pharmaceutical companies access to its miRNA mimics for evaluation in vivo.
"They want to make an initial assessment of the effectiveness of using the microRNA mimic approach in cancer models," he explained. "They're interested in using our mimics, which means our targets, because they feel that based on published work coupled with the data we have so far, they think we're sitting on some key tumor-suppressor microRNAs."
Such arrangements, it is hoped, could lead to formal collaborations or even an acquisition. But Lammers was cautious about the timing of any deals, stressing that these kinds of transactions "will only happen if you have some solid clinical data.
"Realistically, that's several years away," he added.
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