AstraZeneca Shows Continued Commitment Towards RNAi Therapeutics through Partnership with Silence Therapeutics

One week after announcing the grant of a US patent covering RNAi triggers with enhanced guide strand loading, Silence Therapeutics today announced the one-year extension of its R&D collaboration with AstraZeneca for the ‘identification and optimization’ of five siRNAs targeting genes involved in cancer and respiratory disease. This relationship dates back to 2007 when AstraZeneca paid Silence a 7.5M pounds Sterling technology access fee plus the usual potential for future fees and milestones. After similarly extending and expanding relationships earlier this year with AstraZeneca and Dainippon Sumitomo in RNAi delivery, Silence Therapeutics has met important partnership goals earning it time to now prove to the investor and pharma worlds that its merger with Intradigm also brought with it technological synergies.

The way I read the AstraZeneca extensions is that Silence Therapeutics was certainly able to convince AstraZeneca that it is a RNAi Therapeutics company with scientific credibility, but that AstraZeneca still needed extra time before it could fully commit to Silence Therapeutics. It is interesting to speculate that AstraZeneca was a major force behind the Silence Therapeutics-Intradigm merger, as Intradigm had filed for a number of patents covering siRNA sequences against cancer-related as well as inflammatory targets also useful for respiratory diseases. Some of these have actually started to issue and may come in handy for this siRNA-specific collaboration [update: the company informed me that the Intradigm RNAi triggers would not be part of this collaboration, and re-confirmed that the RNAi trigger and delivery collaborations are separate. Sounds to me like they are holding back, possibly hoping to monetize some of these assets on even better terms to another potential licensee or as part of a larger collaboration with AZ eventually].

As to the targets, I could imagine that, based on the unmet need and AstraZeneca’s interests, RSV infection, asthma, COPD, and solid cancers esp. primary liver cancer are among them. Of note, mdRNA announced earlier this year an early collaborative effort with AstraZeneca China for studying that company's liposomal delivery technology for liver cancer, and today’s press release mentioned that AstraZeneca's Chinese R&D branch was part of the Silence collaboration, too. Since Silence Therapeutics appears to be keen to emphasize that the siRNA and delivery collaborations are separate- scientifically not necessarily the most sensible approach, but a deficiency that may open up the prospect of a more lucrative arrangement in the future- it is certainly an interesting thought if Silence’s siRNAs were to be formulated in mdRNA’s liposomes. Of course, it is more likely that mdRNA and Silence compete with each other for AstraZeneca China’s favor in liver cancer, but still...

As I said, it would eventually make a lot of sense to consolidate the two efforts, siRNA and delivery, into one larger collaboration. Based on Silence’s own data, I am fairly encouraged that its lipoplex-siRNA formulations could be generally useful for knocking down genes in the vascular endothelia, which not only would be of obvious relevance for cancer, but also lung disease which often involves vascular escape and infiltration of the lung by inflammatory cells. An alternative approach to siRNA delivery to the lung is, of course, by inhalation, desirable e.g. for RSV infection involving lung epithelial cells, although Silence hasn’t reported much progress in that regard. It remains to be seen what Intradigm's technology can add to that.

Ultimately, I consider today’s extension a major de-risking event for the near-term health of Silence Therapeutics. While much remains to be done, the stock at 5.5 pence and a market cap of little over $20M is simply too cheap, if not an insult to RNAi Therapeutics in general. It is especially encouraging that AstraZeneca shows continued interest in RNAi Therapeutics, a company that I honestly had at the bottom fifth of Big Pharma companies willing to embrace cutting-edge platform technologies to once again efficiently develop drugs that make a difference. Unless their goal is to buy back all their shares and eventually liquidate operations or become consumer healthcare companies selling diapers and skin lotions, realistically, it is their only way forward.

Silence Therapeutics in RNAi Therapeutics Deal with AstraZeneca

Silence Therapeutics, formerly known as SR Pharma/Atugen, disclosed today the signing of a significant collaboration agreement with AstraZeneca. In addition to initial upfront investments of £7.5M (~$15M), Silence stands to receive up to £200M in future developmental milestone payments plus royalties on any resulting drug sales. For this, AstraZeneca may target up to 5 genes for therapeutic purposes using Silence Therapeutics’ AtuRNAi platform with a focus on respiratory diseases.

The AtuRNAi platform is at the heart of Silence Therapeutics. AtusiRNAs are blunt-ended, double-strand oligos with a particular 2’O-methylation pattern that induce post-transcriptional gene silencing. Silence believes that its AtuRNAi platform sufficiently differentiates it from competing RNAi platforms, most notably Tuschl siRNAs, to be considered proprietary. Indeed, the European Patent Office has been a good ally of the company by granting them a core patent relating to this technology earlier this year and restricting the scope of the competing Kreutzer-Limmer patents before that. This has allowed Silence to attract a number of reputable collaborators even before today’s deal with AstraZeneca.

It will be interesting, however, to see whether the value of the AtuRNAi patents are as significant as is claimed, since the seminal Tuschl II patent series demonstrates the use not only of 3’ overhang siRNAs, but also those without such overhangs. It should be noted that while retaining RNAi activity, blunt-ended siRNAs have been shown to be less potent than 3’ overhang siRNAs. Moreover, Tuschl II, to which Alnylam Pharmaceuticals holds exclusive rights, covers siRNA modifications in general and 2’O-methylations in particular. Only last week, Alnylam has strengthened this position by securing exclusive rights to ISIS’ fundamental nucleic acid modification patents for the use in RNAi Therapeutics.

Indeed, at least one licensee appears to have started to doubt the strength of the AtuRNAi IP position. After it had licensed two AtuRNAi agents from Silence that have entered phase I clinical studies this year, Quark subsequently decided to be covered through Alnylam’s InterfeRx siRNA licensing program as well.

However, unless Alnylam feels threatened in its ability to negotiate high-value collaborations due to secondary RNAi IPs such as the AtuRNAi platform, I do not expect them to resort to legal measures at this point. Today’s deal should be seen as yet another validation for the RNAi Therapeutics platform and the considerable funding stream flowing in should strengthen the whole field. Silence has certainly proven its business savvy, now is the time for them to show that they can also execute on their own cancer focussed clinical programs.