SNALP Delivery Keeps On Giving: Tekmira Receives OK for Ebola Clinical Studies

On Monday, Tekmira announced that it has received the Green Light from the FDA to go ahead with clinical studies of its SNALP-enabled biodefense candidate for the treatment of Ebola infection. Tekmira is developing TKM-EBOLA under a $140M contract from the US Department of Defense following spectacular results in non-human primates reported last year in The Lancet. Depending on whether you want to count in the stalled TKM-ApoB program or not, this marks the 5^th or 6^th SNALP-enabled candidate in clinical development, illustrating the strength of this systemic RNAi trigger delivery platform: TKM-ApoB, ALN-VSP02, TKM-PLK1, ALN-TTR01, ALN-PCS02, and TKM-EBOLA.

In other words, 6 of the last 7 systemic RNAi INDs or IND equivalents were for SNALP-enabled product candidates (period: 2008-2011). This plus the unparalleled, strong pre-clinical track record of this platform demonstrating efficient knockdown in the liver, solid tumors, and viral infections not only in rodents, but also a number of non-human primate models supports the notion that Tekmira’s SNALP is the industry’s most advanced and valuable RNAi delivery platform. There are thankfully other promising RNAi delivery technologies lining up behind SNALP, but this is not Lake Wobegon where everybody can be above average

Next Steps for TKM-EBOLA

Since TKM-EBOLA, as a treatment for a disease in which controlled human studies are ethically or practically impossible, is being developed under the Animal Rule, this phase I study will not only have to demonstrate adequate safety, but more importantly yield pharmacokinetic and potentially biomarker data that replicates what is seen in the successful treatment of the pre-clinical animal models of the infection. At the same time, it may be worth trying to test the limits of how long treatment can be delayed after symptom onset in the animal models as a common criticism of these studies is that in the real world it may take some time before Ebola victims are identified and treated. In The Lancet studies, rhesus monkeys received first treatments already 30 minutes after exposure to the virus which may model a needle stick scenario in an Ebola research laboratory, but not exposure of the civilian population e.g. in a subway system. Similarly, achieving similar pre-clinical efficacies with 1mg/kg as with the tested 2mg/kg dose in The Lancet studies may bring it more in line with the clinical SNALP safety experience so far. On the manufacturing front, it would be helpful if Tekmira succeeded in providing SNALP in lyophilized form which would increase its utility in the field.

On the other hand, the fact that the rhesus model seems to closely replicate, if not represent a particularly severe form of the human disease, and the absence of a (experimental) therapy for Ebola that has shown comparable promise, should position TKM-EBOLA well for stockpiling despite any lingering real-world concerns. From an Army point-of-view, as long as it has been shown to be safe and well tolerated in humans, having the most promising treatment as a stand-by for a virus as deadly as Ebola is better than nothing at all, a consideration that may result in stockpiling even before, or in the absence of FDA licensure.

In that regard, TKM-EBOLA will be mainly competing with AVI Biopharma’s morpholino antisense candidate AVI-6002 which is being developed under an essentially identical contract with the DoD. A Nature Medicine paper published last year reported that this candidate was successful in rescuing ~60% of infected rhesus macaques, although this represents a roughly 3-fold increase in risk of dying compared to the highly comparable SNALP studies in The Lancet. Nevertheless, AVI Biopharma still enjoys a slight time advantage as it has already begun phase I safety studies earlier this year. A late-October 2011 update by AVI stated that treatment in the first 5 of 6 dose-escalating cohorts was well tolerated and that the Data Safety Monitoring Board recommended further escalation to the last 9mg/kg cohort. Nevertheless, once years behind the AVI program, Tekmira has done well catching up with the competition.

Importance beyond TKM-EBOLA

Besides representing an invaluable strategic asset for Tekmira (it is earning the company significant hard cash now and revenues from stockpiling may come well ahead of the customary 5-10 years it usually takes a normal drug to navigate the FDA approval maze), the approval of the IND further demonstrates that SNALP is indeed the productive delivery platform that also I have long had hopes for it to be, with applications not only for knockdown in the liver and solid cancers, but also phagocytic cells (an important target cell population for the Ebola indication). It is also a stamp of approval by various regulatory agencies around the world that SNALP (including reliable manufacturing) is fit for clinical development. An IND for ALN-TTR02 and phase I results for ALN-PCS02 are next.

Comment on Roche Partnership with PTC

Roche disclosed today that it has signed a collaboration with PTC Therapeutics for the treatment of Spinal Muscular Atrophy, including a $30M upfront fee for pre-clinical assets. This follows a similar deal by AstraZeneca and PTC in oncology earlier this year. PTC develops a platform for the modulation of post-transcriptional processes using orally available small molecules.

What is disappointing to me is that these are examples of Big Pharma companies with an interest in RNA Therapeutics (note that AstraZeneca has a relationship with Silence Therapeutics for which a go/no-go is imminent), but which feel more comfortable risking their money on a technology based on phenotypic tissue culture screens with considerable uncertainty as to clinical relevance and the safety risks inherent in modulating very general gene regulatory mechanisms, instead of using the much more straight-forward oligonucleotide approaches. The reason? Oral bioavailability and coziness with small molecule chemistry. The fate of these collaborations will be an important test case of whether putting patient convenience and other marketing considerations ahead of what is the scientifically best approach will bring Big Pharma the desired outcome. Of note, only a few months ago, Genzyme handed back PTC a candidate for the treatment of Duchenne Muscular Dystrophy and Cystic Fibrosis after spending more than $100M on it.

My view: Technical success trumps patient convenience when it comes to diseases as severe as SMA, DMD, or cancer.

Interested in the Chinese market for RNAi Therapeutics, but language barriers exist? Get expert help from somebody that understands RNAi.

SNALP Works!

The long wait is finally over: Systemic RNAi delivery has been proven in Man. No 'ifs' or 'buts'. Alnylam just announced that Tekmira’s SNALP-enabled ALN-TTR01 reduced target transthyretin (TTR) protein levels in ATTR patients in a dose-dependent manner- without causing an elevation of liver enzymes or serious adverse event (SAE).

Following preliminary evidence in Tekmira’s TKM-ApoB study, this is the long-awaited moment where there is no doubt that successful systemic RNAi delivery has been achieved. With already about half a dozen SNALP-based programs in or very close to the clinic, this result de-risks a major segment of the RNAi Therapeutics pipeline and should stimulate further investments in SNALP-enabled RNAi Therapeutics development as well as provide a boost of confidence to the entire sector.

Today's presentation at the FAP meeting in Kumamoto can be found here. For a more detailed background on ALN-TTR01 for ATTR, please read yesterday’s blog entry.

In the phase I study (single-dose, dose-escalating), 5 patients received 1mg/kg, the highest planned dose. At this dose, there was a mean reduction of 41% in serum TTR levels from baseline. Despite the small patient numbers and natural TTR variability, this was stat significant at p=0.02 relative to placebo. While this level of knockdown may not seem dramatic and may or may not be useful for eventually achieving a therapeutic effect in ATTR patients, it is important to keep in mind that the other liver-targeted SNALP programs employ formulations that should be at least 10x more potent than the one used in TTR01 and probably also slightly better tolerated. As such, this was a stringent test for the safety and tolerability of SNALP technology and bodes well for the commercial potential of particularly the liver-targeted SNALP pipeline following TTR01, including TTR02 for which an IND is expected by year end.

The time course of TTR protein suppression in one patient provided a picture-book example of bona fide RNAi knockdown in Man. Consistent with the now extensive experience with SNALP in pre-clinical animal models, including non-human primates, this patient exhibited a rapid onset of knockdown (63% reduction at 48 hours) which became a peak knockdown of 81% a week after drug administration with 50% suppression still being observable 4 weeks after this single dose. There is no doubt that this was an RNAi-mediated response.

Preclinical repeat dosing studies have shown that in order to maintain the same level of gene suppression, one can reduce the amount of drug given at subsequent doses. This also means that perhaps giving patients two or three loading doses of 1mg/kg within a week or so may allow one to achieve the 70-80% knockdown with ALN-TTR01 not just in select patients.

Importantly, the safety profile seems to exceed even my own expectations. Unless Alnylam will reveal major immune stimulations in the upcoming conference call (at 8.30am Eastern Time; note added in proof 11/23: none were revealed), the only mild-to-moderate adverse reactions seemed to be infusion reactions that were experienced by 3 out of the 23 TTR01-treated subjects and which was well controlled by simply slowing the infusion rate. As the same was seen in the SNALP-enabled ALN-VSP02 study, it seems that this risk factor is indeed well manageable. What is more, even at the high dose of 1mg/kg, there were no signs of liver toxicity as evidenced by increases in liver function tests. As SNALP-RNAi for ATTR will be a chronic treatment, this should be the major safety focus in the future.

Whatever Alnylam decides to do with ALN-TTR01 (I expect it to remain on the shelf as a viable alternative pending TTR02 results), today represents a milestone in the history of RNAi Therapeutics and I do believe that we have seen the bottom in RNAi Therapeutics. Credit belongs to Alnylam for pushing ahead with the SNALP clinical studies. Alnylam has a truly gifted, and in many ways inspirational drug development team, but it is probably also this talent that has made them blind to what they are actually entitled to. My sympathies are therefore with Tekmira today as it has developed (and owns) the delivery technology that is turning out to be quite literally the savior of RNAi Therapeutics: SNALP. Clinical results eventually follow strong science.

Do you believe that your writing style or English language skills put you at a disadvantage in publishing your research? OxTERMS can help you.

Phase I Study of ALN-TTR01 in Transthyretin Amyloidosis- A Preview

(For a discussion of the phase I results, see here).

Alnylam is about to reveal results from its phase I study with ALN-TTR01 for the treatment of transthyretin amyloidosis (ATTR) at the Nov20-22 FAP meeting in Kunamoto, Japan. This blog provides a brief overview of the rational for RNAi Therapeutics in this disease and the importance of this particular study for the field of RNAi Therapeutics.

ATTR is an autosomal dominant amyloidotic disease due to point mutations (>100 possible) in the TTR gene. These mutations cause protein misfolding and aggregation into fibrils that, depending on which tissues they accumulate in, can cause various organ dysfunctions, most notably polyneuropathy (FAP), cardiomyopathy (FAC), and gastrointestinal/nutritional defects. For those that develop the disease, death is common 5-15 years following the emergence of disease symptoms (usually between 30 and 50 years of age). Although there is genotype-disease phenotype overlap, the most common mutation, Val30Met, strongly predisposes to FAP, while the Val122 is associated with FAC. About 10,000 patients suffer from FAP and 40,000 from FAC. As a rare genetic disease, it occurs in clusters, with FAP cases for example concentrated in Portugal, Sweden, and Japan.

Until recently, the only accepted treatment has been liver transplantation for FAP where removing the source of the mutant TTR in blood serum can reverse the polyneuropathy. Pfizer just got European approval for FAP with its small molecule TTR conformational stabilizer Vyndaqel based on slowing the rate of peripheral neuropathic impairment.

There exists, however, great need for additional therapies as Vyndaqel actually missed the primary endpoint in its pivotal study (the FDA did not accept the NDA for review earlier this year), and because liver transplantation is ineffective for FAC. The latter seems to be due to wildtype TTR still being able to deposit into pre-existing plaques, for example in heart tissue, at a rate that is higher than the turnover of the amyloidotic plaque. In fact, the amyloidotic potential of wildtype TTR is illustrated by the fact that it frequently causes spontaneous amyloidosis in elderly people (senile ATTR).

RNAi Therapeutics Approach to ATTR

The contribution of both wildtype and mutant to disease pathology, the dynamic turnover of plaques, and the fact that TTR knockout mice have the same life expectancy and fertility as their wildtype littermates and are otherwise essentially asymptomatic, makes RNAi Therapeutics a highly attractive treatment approach for this disease. TTR is involved in the transport of vitamin A and thyroxine in the blood, but it appears that in the absence of TTR these carrier functions are compensated for by other carrier proteins in the serum. What is more, essentially all the life-limiting pathologies are caused by TTR that is expressed in the liver, and with Tekmira’s SNALP delivery technology, RNAi can address the relevant gene expression.

TTR01 vs TTR02

One source of confusion that I expect to affect the financial markets tomorrow stems from Alnylam developing two candidates for ATTR, ALN-TTR01 and ALN-TTR02, the difference between the two candidates being in the SNALP lipid composition. TTR01 is the subject of the present trial and is based on an early DLinDMA lipid-containing formulation. It was shown to be effective in knocking down TTR in non-human primates with an ED50 of around 0.3-0.4mg/kg. As the highest dose in the phase I study was 1mg/kg it is reasonable to expect there to be evidence for TTR knockdown in the ALN-TTR01 trial. I should warn, however, that because of the small patient number in each dose cohort and the natural intra- and inter-patient variability of TTR levels in the serum, the pharmacodynamic outcome measure in this trial, the pooled numbers may not give us a straightforward 'stat-significant' answer.

Because of the rapid developments in improving the efficacy and tolerability of SNALP technology, it is therefore almost assured that Alnylam will drop TTR01 and prioritize TTR02 which takes advantage of these developments and for which the filing of an IND is imminent.

Consequently, the importance of tomorrow’s results for the RNAi Therapeutics field lies in providing proof-of-concept for RNAi knockdown following systemic delivery at OKish tolerability. That’s it. It also sets up the results from the phase I studies with ALN-PCS02, the PCSK9-targeting hypercholesterolemia candidate, which are expected to be reported by the end of this year. As PCS02 uses one of the more recent SNALP formulations, this will be the SNALP candidate that has to shine both in terms of knockdown efficacy and safety/tolerability.

ATTR Economics

If you had any doubts as to the commercial potential of ATTR, it is worth noting that Vyndaqel, Pfizer's just-approved TTR drug, is expected to be priced at more than 100,000 Euros per patient year and that most (known) FAP patients are in healthcare systems that will still bear such costs. Pfizer last year paid $200M in upfront considerations for FoldRx, the original developer of Vyndaqel, with another $200M in contingent milestones. Although FoldRx has a mission of developing other protein folding-based drugs, this price tag was essentially for a drug with results from a pivotal trial that failed to meet the primary endpoint and for which approval was far from certain. Considering Alnylam’s cash position, this one registrational drug candidate valued FoldRx higher than all of Alnylam- although you might justify that with the mounting existential risks stemming from Alnylam's alleged theft and misuse of Tekmira's SNALP technology.

Given these economics, it is not surprising that other companies have similarly recognized the commercial potential of ATTR. Importantly, ISIS Pharmaceuticals will also present progress with its antisense candidate for ATTR (ISIS-TTRRx) at the meeting. This candidate entered clinical development in May and is financed by GSK which retains an option for its exclusive license.

Do you believe that your writing style or English language skills put you at a disadvantage in publishing your research? OxTERMS can help you.

Genable Finds EUR5M for ddRNAi-Gene Replacement Approach

5 million Euros these days is serious money in RNAi Therapeutics. Last week, Irish biotechnology company Genable Technologies announced that it succeeded in raising such funds for its pre-clinical DNA-directed RNAi Therapeutics-Gene Replacement combo for the treatment of rhodopsin-linked autosomal dominant retinitis pigmentosa (RHO-adRP), an inherited retinal degenerative condition leading to blindness.

To see it flow into DNA-directed RNAi Therapeutics at that makes it particularly noteworthy. It illustrates that ddRNAi is somewhat uncoupled from the current depression in the synthetic RNAi Therapeutics arena due to some technical differences which make it in many ways more similar to traditional gene therapy. Gene therapy, of course, is experiencing a revival, fueled by more and more clinical validation. Incidentally, it which follows a similar boom-bust cycle as RNAi Therapeutics is going through now.

One of the great benefits of ddRNAi Therapeutics is that it can be combined with other DNA-directed modalities, especially the co-expression of protein-encoding genes from the same DNA template. As such, it is particularly amenable to treat autosomal dominant-negative diseases in which the affected gene is important for cellular function thereby precluding approaches that eliminate both the mutated and the healthy copies of a gene. Accordingly, one could use a single DNA molecule from which to direct the suppression of endogenous versions of the affected gene (wildtype and mutant forms) and then replace gene function by providing a version of the gene that is immune to the RNAi.

In Genable’s case, AAV vector capacity limitations meant that a mix of two AAV vectors had to be co-administered by subretinal injection, one carrying the ‘immunized’ rhodopsin gene, the other the shRNA against the endogeneous rhodopsin copies. This apparently did not affect much treatment efficacy. Indeed, it was argued that the co-administration approach would actually increase dosing flexibility by being able to adjust the amount of each component independently. On the other hand, it is possible that the use of vectors with larger capacities, such as the lentiviral system that Oxford Biomedica and Sanofi-Aventis are busy exploring for ocular gene therapy, may have its advantages here. Importantly, it was shown that therapeutic efficacy in the retinitis pigmentosa animal models strictly depended on the presence of both gene replacement and gene knockdown components.

Although the concern with causing harm by knocking down the wild-type allele is often only a theoretical one, as is for example the case with Huntington’s Disease (HD), and depends on the degree of knockdown, other applications for which this approach holds promise are sickle cell anemia, alpha-1 antitrypsin, pachyonychia congenita (PC), amonst many others.

The PC project by TransDerm and collaborators is a good example in the RNAi Therapeutics space for the challenges faced by the alternative approach to treating such autosomal dominant diseases, namely by specifically directing the drug candidate towards the mutated gene/gene product so as to leave the wild-type copy untouched. The problem here is that because the potential mutations can be broadly distributed over a gene, restricting a therapeutic to targeting only one such genetic lesion (or associated gene polymorphisms) can dramatically reduce the number of patients eligible for such a targeted therapeutic. This also explains why the first clinical trial by TransDerm was a placebo-controlled, split-body dose-escalation trial in a single patient (!) as there may not be more than a handful of known patients in the world with the applicable mutation.

The 5 million Euros will be used to bring Genable’s lead candidate, GT038, into clinical development. RHO-adRP seems like a good ddRNAi application as even the correction of only a fraction, e.g. 1/3 to 1/2 of the affected photoreceptors, may be enough to support vision. It is good to finally see a number of ddRNAi Therapeutics candidates based on sound pre-clinical data move into the clinic.

(For another promising late preclinical candidate, see Calimmune's HIV approach)

Arrowhead Research Lifts Veil on Recent Progress in DPC Delivery

Four years after Mirus scientists published their seminal paper in polymer-mediated siRNA delivery, and 3 years after the acquisition of the Dynamic Polyconjugate (DPC) technology by Roche, Arrowhead Research, the new owner of the technology, finally lifted the veil on recent progress in bringing DPC technology to the clinic.

The White Paper reveals, for the first time, that DPCs have been successfully delivered to the livers of non-human primates, and moreover that they may also have use for applications outside the liver, one of the theorized attractions of DPCs based on their small size. Reading between the lines, however, it is also possible to identify some of the factors that have delayed clinical translation, and despite the progress and substantial investments by Roche, it remains an open question when the first DPC-based RNAi Therapeutic will enter clinical development.

Short circulation times were one of the deficiencies of 1^st generation DPCs. In order to reach tissues besides the liver, it is critical to achieve circulation times that are long enough so that the drug gets a chance to find and accumulate in its target tissues. Although DPCs on paper seemed to incorporate the features necessary for achieving such long circulation times, it came somewhat as a surprise when a DPC imaging paper last year showed DPC circulation times to be quite poor (Mudd et al., 2010). Although the particles were still able to accumulate in the liver, the data also raised questions whether the causes of the unexpected pharmacokinetics could have other consequences besides impacting biodistribution, for example in terms of safety.

It turns out that the short circulation times were the result of the premature exposure of the chemical groups that were supposed to shield the membranolytic functionalities of the DPCs outside their target cells. This would also explain why there seem to have been toxicity issues not just due to the poor biodegradability of the polymers, but also because such premature exposure renders DPCs as troublesome as many of the positively charged first-generation polymer approaches.

The White Paper indicates that the instability (and biodegradability) issue has been remedied to some degree such that the longer-circulating DPCs now show first promise for delivery outside the liver. But DPCs may also be competitive for delivery to the liver considering the following performance in non-human primates (excerpt from the White Paper):

‘Latest generation DPCs are remarkably efficacious in rats and non-human primates with ED80 values of ~0.1 mg/kg siRNA after a single dose. Increasing the dose two-fold in non-human primates results in >99% knockdown with a duration of effect of nearly 7 weeks. This is a 10-fold increase in efficacy compared to first generation DPCs containing PBAVE polymer. Latest generation DPCs are also better tolerated and have therapeutic indices of >10 in non-human primates as calculated from ED80 and NOAEL values.’

A 99% knockdown with 0.2mg/kg for 7 weeks- I’m impressed! It will be important to publish these data so that it is possible to see which model system was used, whether the 99% knockdown was seen for pretty much the 7 weeks, what the tox/tolerability profile was, the route of administration, and finally an explanation why a simple 2-fold increase in dosage had such a dramatic effect on knockdown efficacy.

The White Paper is also a reminder that for RNAi delivery technologies to be viable, there needs to be efficient scale-up. Apparently, manufacturing was, and possibly still is, a major issue with DPCs. At least the initial formulations had to be purified so extensively such that the yield became unacceptable for clinical translation and commercialization. Besides general liposomal expertise, quality manufacturing, of course, is what has always differentiated RNAi delivery company Tekmira from its competition.

My sense is that DPCs still have the potential to become an important delivery alternative. However, it is also clear that the path of DPCs was a tough one and, in the absence of guidance from Arrowhead Research, I expect additional delays (2-3 years?) before we will see the first DPC-based RNAi Therapeutic candidate in the clinic. This view is possibly shared by Alnylam as $10M in upfront and an increase of about $10M in annual operating costs would have been a small price to pay for Alnylam if DPCs were as advanced as Alnylam’s current systemic delivery workhorse, Tekmira’s SNALPs.

Until then, Arrowhead Resesarch needs to hit the ground running on the business development front given the increase in expenses that come with the 40+ research team in Wisconsin. The $15M facility with Lincoln Park Capital at least provides Arrowhead with increased financial flexibility. Ironically, it is positive clinical data from the RNAi Therapeutics candidates that are based on Tekmira’s SNALPs, DPCs most direct competitor that would greatly aid in that goal by re-igniting interest in the RNAi Therapeutics platform.

RNAi Therapeutics Investors Hoping for a Merry Christmas

I’ve just come back from working at the Starbucks across my street which strongly reminded me that Christmas was just around the corner. Christmas this year in RNAi Therapeutics is synonymous with data releases by Alnylam from its transthyretin amyloidosis (ALN-TTR01; data presentation November 20-22 in Japan) and hypercholesterolemia (ALN-PCS02; release of top-line results by year-end) phase I clinical trials. These have the potential to demonstrate, for the first time, direct and physiologically meaningful target gene knockdown following systemic RNAi delivery, and thereby have the potential to turn around still negative RNAi Therapeutics sentiments and depressed valuations.

Some of the anticipation can already be felt in the form of appreciating share prices of Alnylam and Silence Therapeutics, together with Tekmira the companies most directly exposed to the current RNAi Therapeutics dataflow, and the financial analyst-investment community which have turned noticeably bullish on Alnylam. Only Tekmira, the inventor of SNALP technology that powers ALN-TTR01, ALN-PCS02 and 5 other candidates in or close to clinical development, has not participated in the rally by failing to find investors willing to defend its stock after taking on well-connected Alnylam.

In assessing the data, a primary focus will be on whether dose escalation was able to proceedeup to the highest planned doses (1.0mg/kg for ALN-TTR01 and 0.25mg/kg for ALN-PCS02) and whether, despite the small number of patients at the high dose levels, there are clear signs for target gene knockdown. 50% target gene knockdown in both cases would be reasonable goals, and probably also necessary ones to have the desired impact. In the case of ALN-PCS02 there should also be at least a 30% reduction in ‘bad’ LDL-cholesterol, the intended pharmacologic outcome of a PCSK9-targeting agent. In terms of safety, the absence of grade 3 adverse events or worse would be highly welcome, of course, as we would be the absence of consistent and clinically meaningful innate immune activations.

Santaris’ anti-miR122 HCV Drug Continues to Impress

MicroRNA Therapeutics seems to have found its poster child already with Santaris’ miR122 LNA antagonist for the treatment of HCV. In an oral presentation at The Liver Meeting which is just wrapping up in San Francisco, the company reported robust dose-dependent anti-HCV activity in a phase IIa study, with close to a 3-log mean reduction of HCV RNA from baseline and viral load below detection in 4 of 9 patients at the highest dose of miravirsen (7mg/kg). The corresponding abstract marking a milestone in microRNA Therapeutics by reporting first clinical activity of an microRNA Therapeutic was released in early October (click here for commentary). There is no doubt that this drug candidate works as expected/hoped for, and unless the future of HCV treatment is in all-oral combos, anti-miR122 with its uniquely differentiated mechanism of action looks like a valuable addition to the fast-moving field of HCV care.