Brewed up in Seattle: Tekmira and Halo-Bio Seek to Capitalize on Multi-Targeting Potential of RNAi Therapeutics with Multi-Valent RNAi Triggers

It must have been over either coffee, the fuel of scientific discovery and frequent source of business development inspiration, or beer, a beverage that you may enjoy but not mix with business, that Seattlelites Mark Murray (CEO of Tekmira) and Todd Hauser (CEO/inventor of Halo-Bio) initially came up with the idea of joining forces to revolutionize one of the attractions of RNAi Therapeutics: Multi-Targeting, especially for the treatment of complex diseases, cancer and viral infections (see also previous blog entry on Merck’s hypercholesterolemia efforts; link to press release, here).

The technology to which Tekmira acquired a worldwide exclusive license is referred to by Halo-Bio as multi-valent RNAs (mv-RNAs). It is a molecule that in its basic manifestation consists of three separate double-stranded regions, forming a structure similar to a Mercedes star. The RNAi machinery is thought to use each strand as a guide for the targeting of the same or, more interestingly, separate and independent genes.

Data from this technology is yet to emerge, although I would imagine that Tekmira has carefully evaluated mv-RNAs and various other RNAi trigger options before signing this deal given its increasing hints that it is looking at non-Alnylam RNAi triggers. It has become apparent that RNA interference is a robust naturally occurring process that it can harness various RNA molecules as substrates for efficient gene silencing. Of course, not all of them are created equal. Also worth noting in this context is that efficient RNAi largely depends on the 5’ end of the guide strand so that the 3’ end can function to satisfy complementarity requirements such as those for the formation of mv-RNAs.

Besides potency, additional practical and scientific questions remain to be answered. For example, the use of 3 RNA strands to generate one RNAi trigger may increase cost and quality. On the other hand, for those that follow the Tuschl II patent prosecutions in more detail or have seen the somewhat boring, yet useful study by Roche on the purity of annealed siRNAs, it should have occurred to a number of folks in the industry that strand annealing may not be the only way to generate double-stranded RNAs. Furthermore, even when using three strands (one and two may also be possible), the actual complexity may actually decrease compared to using 3 traditional RNAi triggers with 6 individual strands for targeting the same number of genes. Another question would be whether and which mv-RNAs are loaded directly into the RNAi RISC complex, or whether they require prior processing by other nucleases.

mv-RNAs may also have particular utility in lipo- and polyplex settings, or facilitate formulation of SNALP liposomes, because of their increased negative charge.

Of course, this deal also has to be seen in the context of the Tekmira-Alnylam feud. First of all, it is worth noting that Tekmira stated that mv-RNAs are an attractive alternative for multi-targeting RNAi Therapeutics. It still has the more traditional RNAi trigger options from Alnylam which, not least due to their simplicity, appear preferable over mv-RNAs for single-targeting applications.

The transaction also increases Tekmira's business development freedom from Alnylam. Due to the structural differentiation of mv-RNAs from traditional RNAi triggers, it is possible that certain of Alnylam's exclusive rights to Tekmira technology do not apply. In addition, mv-RNAs may also be sub-licensed independent of Tekmira's delivery technology.

Alnylam faces RNAi trigger uphill battle- even 3’ overhangs not safe

The worth of Alnylam’s RNAi trigger IP has deterioriated raplidly over the last two years and Tekmira may not require Alnylam IP even when using Tuschl siRNAs.

While Alnylam once had a decent shot at coming out as gate-keeping with Kreutzer-Limmer and Tuschl-I, failing in those patent prosecutions yet clinging on to ageing technology has meant that it failed to participate in RNAi trigger innovation, even if not gate-keeping. Anybody still remember Commodore or Atari or holds shares in Nokia and Research in Motion?

[correction 8/26/2011: I have re-read my entry and would like to clarify that Tuschl siRNAs are not 'out-dated' technology; it is more the underlying IP strategy that is failing].

Even as Max Planck, UMass, MIT, and Alnylam have just agreed to re-coordinate their Tuschl patent prosecution in the US, it is clear that the double-patenting issue was not the only issue preventing a strong Tuschl II from issuing. For example, by arguing that 3’ overhangs were implicit in T-I, yet T-I cannot claim this since it failed to recognize it, or by claiming 3' overhangs being obvious over other research on the discovery of Dicer in RNAi, the USPTO may have it both ways: deny a therapeutically useful T-I, yet reject T-II over obviousness involving T-I.

The T-II patents that have issued in the US are not that strong as they involve methods of synthesizing two RNA strands and annealing them to form double-stranded RNAs with 3’ overhangs. It is somewhat surprising that such a annealing method would have been granted a patent, and there are signs that the patent offices are starting to realize this.

Coffee or Beer? Have your say in whether you think the Tekmira-Halo deal is a hare-brained idea or stroke of genius by participating in the survey on the upper right hand corner of the blog.

Merck Seeks to Optimize Value of ApoB as Target for Hypercholesterolemia with Combinatorial RNAi Therapeutics

A series of recent papers (e.g. Ason et al. 1; Tadin-Strapps et al.; Ason et al. 2) shows that Merck wishes to use RNAi Therapeutics for the treatment of hypercholesterolemia, a precursor of cardiovascular disease. Despite the success that widely prescribed drugs such as statins have had in lowering bad cholesterol, there are still many patients in need of additional treatment options, patients that either have very high cholesterol levels to start off with or those that do not respond to or tolerate these drugs. As a result, interest in the pharmaceutical industry remains high in developing new approaches to treat these underserved patient populations.

The Pros and Cons of ApoB as a Target

ApoB has emerged as a very attractive, hitherto undruggable target in this endeavor, and indeed ISIS in partnership with Sanofi-Aventis are currently knocking on regulators’ doors to get their ApoB-targeting RNaseH-antisense drug mipomersen (commercial name: Kynamro) approved for familial hypercholesterolemia. Meanwhile, Tekmira and apparently Merck are in the early stages of developing ApoB-based RNAi Therapeutics for hypercholesterolemia.

What makes ApoB such an attractive target is that it is the critical protein component of bad LDL cholesterol (LDLc) and knocking it down therefore very potently reduces LDLc levels in the blood. Not only that, it seems that through the wonders of sophisticated feedback control mechanisms of lipid metabolism, essentially all other atherogenic lipids are reduced, too, following ApoB knockdown (e.g. Tadin-Strapps). There remain, however, two concerns with ApoB as a target.

The first one relates to the observation that in most rodent models, not only all the atherogenic lipids are reduced, but also the ‘good’ HDL-cholesterol which is responsible for reverse cholesterol transport from the plaques (where they are dangerous) back to the liver for excretion in bile (which is where they belong to). Research by Merck, of course using LNP technology, shows that when ApoB is knocked down by ~95%, both HDLc and LDLc where reduced by more than 2/3 (Tadin-Strapps et al. 2011; 79-90% non-HDLc lowering and 67-78% HDLc lowering in Ason et al). This was highly unlikely due to an off-target effect as various ApoB-targeting siRNAs exhibited this phenotype while non-targeting LNP formulations did not.

Nevertheless, it is unclear whether these rodent and similar non-human primate findings translate into humans, and what ApoB knockdown levels would need to be achieved to start seeing an effect on HDL. Mipomersen e.g. reduces LDLc by about a third and does not seem to affect HDLc in humans. The Merck scientists also speculate that the HDLc reduction simply reflects that in the absence of LDLc, ApoE redistributes to HDLc leading to their more rapid uptake in the liver. Therefore, despite the mantra that it is all about the HDL:LDL ratio, HDLc reductions via this route would actually be positive.

The second, probably more pressing concern is that ApoB inhibition leads to a failure to export lipids from and their accumulation in the liver, a condition known as hepatosteatosis or ‘fatty liver’. This has not only been observed in pre-clinical studies of ApoB knockdown, but was also observed in the mipomersen clinical studies (Visser et al. 2010). ISIS Pharmaceuticals, the discoverers behind mipomersen, argue that this accumulation is likely to be temporary only as compensatory genetic circuits get switched on to reverse the phenotype, a mechanism that is supported by Merck's own gene expression analysis. Moreover, it has yet to be shown that ApoB-related fatty liver predisposes to the development of liver fibrosis and ultimately liver failure or cancer which is really why we care about fatty liver in the first place.

Enhancing the Therapeutic Profile of ApoB-targeting Drugs

Giving up on ApoB in hypercholesterolemia because of the fatty liver concerns would mean forfeiting the potential of one of the most if not the most potent target in the hypercholesterolemia space. I therefore fully agree with the strategy by Merck to exploit the combinatorial potential of RNAi Therapeutics to optimize the profile of an ApoB-targeting RNAi Therapeutic, a strategy that I would fully expect of Tekmira to be evaluating as well.

The combinatorial potential of RNAi Therapeutics is one of the major attractions of this technology. Because of the almost identical pharmacological behaviors of siRNAs, it is relatively simple to employ multiple instead of just a single siRNA payload in an RNAi Therapeutic. This is particularly useful for complex diseases such as metabolic syndromes and diseases that involve resistance/escape such as cancer and viral infections. ALN-VSP02 is a dual-targeting example in oncology that is already in the clinic, and Tekmira’s Ebola RNAi Therapeutic candidate slated to enter the clinic in early 2012 will also involve at least two different RNAi triggers.

You can thus imagine that knocking down a gene along ApoB that leads to increased lipid excretion via the bile, increased fat oxidation in the liver, or redu­ced hepatic fat synthesis or reduced uptake of dietary fats in the liver, would greatly enhance the therapeutic profile of an ApoB-based drug by countering the development of fatty liver. It is the latter approach that Ason and colleagues from Merck took in their recent paper by targeting fatty acid transport protein 5 (Fatp5) alongside ApoB as Fatp5 had been described, also through the elegant application of ddRNAi, to reverse diet-induced hepatosteatosis.­

To study the effect of Fatp5 co-knockdown on ApoB-induced fatty liver, the researchers formulated both siRNAs into LNPs and infused them into mice. Both genes were knocked down efficiently (89-95%) and as you can imagine, at these ApoB knockdown levels, the fatty liver phenotype was quite robust. Predicted Fatp5-dependent phenotypes, such as an almost 1000-fold increase in the ratio of unconjugated to conjugated bile acids in the bile, were also observed (Fatp5 plays a role in bile acid conjugation) confirming the functional knockdown of both ApoB and Fatp5.

Unfortunately, despite the potent knockdown of Fatp5, the ApoB-dependent fatty liver phenotype was not reversed in the mice which were fed a ‘Western low-fat diet’. It therefore appears that Fatp5 intervention is only useful for diet-induced fatty liver, and that approaches specific to fat excretion or fatty acid oxidation in the liver will be more promising. Nevertheless, the scientists seem to be on the right track, and with SNALP siRNA delivery, it should be relatively easy to characterize other candidate genes. Indeed, due to competition, the Mercks, Tekmiras, and Alnylams may not necessarily want to disclose their magic siRNA cocktail.

So as we are on the eve of seeing mipomersen being approved as the first ApoB-targeting compound for the treatment of hypercholesterolemia, a second generation of ApoB-targeting RNAi Therapeutics are being readied that not only aim at incremental improvements in potency and dosing frequency, but completely rehaul the therapeutic profile of ApoB-based therapeutics.

Tekmira and Arrowhead Advance Cancer RNAi Therapeutics

This week, important developments for two of the most advanced cancer RNAi Therapeutic candidates were announced. Arrowhead reported that it has now completed enrolment of the phase I CALAA-01 study and is initiating a dose-optimizing phase Ib study, while Tekmira disclosed that it has received the green light from the FDA to go ahead with an additional phase I study of TKM-PLK1, this time using Hepatic Arterial Infusion to complement an ongoing effort involving intravenous administration. This study will be conducted in collaboration with the National Cancer Institute (NCI).

CALAA-01: Optimizing dosing schedule

CALAA-01 is a targeted cyclodextrin-based nanoparticle formulation (RONDEL) of unmodified siRNA against RRM2, a gene involved in DNA synthesis (more background on CALAA-01 here). Enrolment in the phase I clinical trial commenced 3 years ago. Interim data were presented last year in a Nature paper and the ASCO annual meeting. At that time, about 15 patients with various forms of advanced solid cancers had been treated. Encouraging qualitative biopsy results showed that at least some of the RNAi Therapeutic reached its physical target and was able to mediate RNAi target cleavage there.

Until then, no dose-limiting toxicities had been seen. The ASCO presentation, however, revealed that there were fairly widespread, albeit low-grade (g1-2) immune stimulations (‘flu-like symptoms’). The reason why immune stimulation with this candidate was fairly common is likely related to the fact that unmodified siRNAs were used. Judging from Arrowhead’s quarterly conference call this week, it seems as if the immune stimulation warranted a discontinuation of further dose escalation. The company stated, and I certainly agree, that it should use modified siRNAs in the future to mitigate this side effect.

Interestingly, what the company apparently found in the study is that in some patients the immune stimulation subsided following repeat-administration of the drug, as if they became desensitized to the immunostimulatory potential. It is therefore the goal of the newly announced phase Ib study to find dosing regimes that take advantage of this preliminary finding to achieve higher doses, e.g. by first giving a lower dose in order to desensitize before continuing with the predicted higher, hopefully efficacious dose. If this hypothesis can be confirmed, it would not only be positive for CALAA-01, but a valuable insight for the entire field of RNAi Therapeutics.

Having said that, in light of the clinical findings so far and reservations about the chosen gene target, I do not find CALAA-01 to be a compelling candidate. While I can agree with the phase Ib study, it is more because it will allow the company to gather further information about the RONDEL delivery system without much further delay as it continues its efforts to partner and monetize the delivery technology.

Situations like these highlight the risk of RNAi Therapeutics platform companies like Arrowhead/Calando and Benitec that refuse to have in-house R&D. In this case, in-house R&D could have already readied a modified RRM2 siRNA formulation, or even a formulation targeting a more exciting cancer gene target, without too much additional effort. Instead, more needs to be invested in a candidate that is difficult to partner already and may never make it into phase II, leaving Arrowhead to hope that their argument that the CALAA-01 studies are a way of de-risking the RONDEL delivery platform will convince potential partners and investors.

In my opinion, virtual drug development may be possible for one-in-a-kind therapeutic candidates, but is not compatible with building a platform.

Tekmira and NCI to Begin Hepatic Arterial Infusion (HAI) Study of PLK-1

The clinical development of TKM-PLK1 began earlier this year with a phase I dose escalation study using intravenous administration. Similar to ALN-VSP02, TKM-PLK1 is a SNALP-based formulation, but should be more widely applicable because its pharmacology was tailored so that it can also reach tumor tissues outside the liver. What makes TKM-PLK1 particularly exciting is that its gene target is probably the most potent one in the cancer field, having emerged many times as a top hit in genome- and kinome-wide RNAi screens for rapidly killing cancer cells without affecting normal cells.

The new phase I study of TKM-PLK1 that was announced this week will not only allow the company to more quickly gather important pharmacologic information on the drug, but should also be a viable alternative route of administering TKM-PLK1 for treating primary liver cancer and cancers with liver involvement by using Hepatic Artery Infusion to expose tumors to very high concentrations of the drug which would otherwise not be possible by simple intravenous administration.

Black box less black

One challenge in the development of novel cancer therapeutics is that it can take a long time before their true potential becomes clear. Biomarkers are therefore highly sought after, with RECIST tumor response criteria being a popular way of determining anti-tumor efficacy. Unfortunately, merely measuring immediate tumor responses is not always predictive of therapeutic success as sometimes you see such responses, but without concomitant increases in life expectancies (e.g. Avastin in advanced breast cancer, and many chemotherapeutic settings), and sometimes you don’t see them, yet you do get increases in life expectancies, an issue particularly relevant for targeted therapeutics (e.g. Provenge in prostate cancer).

Access to tumor biopsies is therefore very valuable in determining at an early stage whether your drug functions as expected on a molecular level and what tissue concentrations you need to achieve to trigger these responses. It is therefore an attraction of the new study that it will allow for biopsy collection. Through this, Tekmira should further learn more about which tumors types may be most suitable (e.g. primary/metastatic, genotype, pH).

Aside from the scientific value of the study, this study has the added benefit in that it could help validate Tekmira's platform technology for cancer in a controlled and timely manner, at a time when Alnylam evaluates Tekmira’s technology mainly for knocking down genes in ‘normal’ liver. Clinical data from both these approaches are expected in coming months and should serve as catalysts.

A treatment in its own right

Liver tumors almost exclusively derive their blood supply from the arterial circulation, whereas 75% of the blood flow in normal liver comes from the portal vein. Because of SNALP pharmacokinetics, this means that directly infusing TKM-PLK1 should have the benefit of increasing the drug exposure of liver tumors while at the same time greatly reducing potentially dose limiting exposures of the normal liver(***see correction and clarification below), the predicted dose-limiting organ for SNALP technology. This therefore should make it possible to achieve higher maximally tolerated doses, an important goal in most cancer drug developments.

It is for this reason that Hepatic Artery Infusion (HAI) has become an accepted and frequently used drug delivery modality in the treatment of unresectable liver tumors. Therefore, should the results suggest therapeutic efficacy in this setting, it could well pave the way towards studying HAI of TKM-PLK1 directly in phase III studies.

****Correction and clarification: I have received justified criticism of my statement that HAI would ‘greatly reduce potentially dose limiting exposures of the normal liver’.

The criticism was based on the notion that the normal liver in patients with liver tumors would still go on and be supplied by blood from the hepatic artery in addition to the blood supplied by the portal vein. Consequently, a good chunk of what you provide by HAI would also end up in the normal liver parenchyma. On the other hand, the critique was based on the assumption that the liver tumors would not compete for blood from the hepatic artery. My take on that is that this is probably a good assumption especially for smaller tumors, but in cases where liver tumors make up the bulk of the total liver mass, at least based on high-school physics (pressure and diameter of a tube determining the flow of liquids), there should be at least some quantitative shunting of hepatic arterial blood away from the normal liver.

Moreover, the criticism raised another factor determining whether direct HAI of SNALP will enhance SNALP uptake by cancer cells relative to intravenous infusion, namely whether the SNALP particles get taken up efficiently during the first pass of SNALP through the liver tumor. SNALP uptake is determined by various factors such as time, ionization behavior, active targeting, LDL-receptor status, so that’s probably a more complicated discussion.

Overall, the point is well taken, and while SNALP administration by HAI should have a positive effect on the ratio of drug concentration in Tumor relative to Normal Liver and therefore should increase the therapeutic index, I will have to partially retract my statement in that this is mainly due to optimized exposure of liver tumors during first pass and may vary significantly from tumor to tumor, and that another reason for choosing the hepatic artery vs portal vein may be just the relative surgical ease of accessing these structures.

Data from Nucleonics HepB DNA-directed RNAi Therapeutics Study Published

Following major IP battles with Benitec and tensions high within the company, DNA-directed RNAi Therapeutics company Nucleonics became the first major RNAi Therapeutics company to go out of business in 2008. During the liquidation process, Alnylam surprised observers by scooping up Nucleonics’ IP assets. Adding to the confusion, Nucleonics had just initiated dosing in a phase I study of NucB1000, a candidate for the treatment of Hepatitis B Viral infection. The fate of this trial has been a mystery.

Now, after three years, scientists and clinicians involved in the study broke their silence and reported data from the study in the journal Antiviral Therapy (Gish et al., 2011). The results from the prematurely terminated study that had enrolled only three patients in the first dose cohort were largely in line with (at least my) expectations. More surprising, however, were some disclosures related to Alnylam’s apparent interest in NucB1000 and DNA-directed RNAi Therapeutics.

NucB1000 Background

The active ingredient of NucB1000 is a plasmid DNA that encodes for 4 shRNAi triggers targeting various regions of hepatitis B virus. The ability to easily accommodate a number of RNAi trigger sequences in one clinical candidate is one of the advantages of ddRNAi Therapeutics and particularly useful for antiviral applications as it should minimize viral escape. Using ddRNAi as opposed to a synthetic siRNA for HepB infection is also reasonable given the chronic nature of the disease.

This, however, is about it in terms of the positive attributes of NucB1000. The reason why I never thought this candidate had even a remote chance of clinical success is the fact that it uses a cationic lipid formulation to deliver the DNA to affected hepatocytes. Unlike the efficient liposomal delivery of small, synthetic siRNAs to the cytoplasm of hepatocytes, the field of gene therapy is still far away from using non-viral means to efficiently deliver large plasmid DNA- about 100-200x the molecular weight of siRNAs- to the nuclei of hepatocytes where the DNA can serve as the template for shRNAi trigger transcription. It is not just the size that complicates the cellular uptake and release of the nucleic acid, but the requirement for getting the DNA from the cytoplasm to the nucleus is the major rate-limiting step differentiating it from synthetic siRNA delivery.

The authors addressed this deficiency by stating that even if uptake efficiency was limited per given plasmid infusion, the long-lived expression from the plasmids means that it may be possible to achieve ddRNAi activity in sufficient numbers of hepatocytes simultaneously by multiple administrations. While I can follow the logic, in the absence of convincing pre-clinical data of this concept, it remains just that, a concept.

Of equal concern is that cationic lipid-formulated large plasmid DNA carries a high risk of triggering innate immune stimulations following intravenous administration. This has already been a challenge for lipid-formulated small siRNAi triggers, but it is less of a fundamental challenge there because of the limited sequence information in a given siRNA. This means that any inherent innate immune stimulatory potential can be relatively easily controlled by chemistry. The much larger plasmid DNA, which typically is of bacterial origin, does not allow for such control.

I should mention that in light of these concerns the authors state that no apparent immune stimulations were observed in the mouse and dog studies at much higher dosages than were anticipated for the trial.

Nevertheless, it is surprising to me that the FDA allowed this trial to go ahead based on pre-clinical co-transfection efficacy results that appeared to me to be glorified in vitro, and not in vivo models of HepB infections. It may be for this reason that the study authors made the point that they saw antiviral efficacy in a model that did not involve co-transfection:

‘Preliminary data showed that 1% of mouse hepatocytes were transfected. Subsequent experiments in which spike recovery was performed demonstrated that nearly 10% of cells were transfected; actual rates varied between 6% and 9% (Nucleonics, Inc. and Alnylam, unpublished data). A number of explanations for the discrepancy between this rate and the 20% knockdown of HBsAg have been postulated.’

‘A 20% knockdown of HBsAg’ to me does not sound like a robust pre-clinical efficacy result in support of clinical studies. I doubt that the FDA would have let the IND application pass solely based on this animal efficacy model.

I know, a non-viral ddRNAi approach sounds great on paper, and would you believe it, not just the VC investors and Nucleonics management were fooled, but also a company like J&J was about to contribute a fair amount to a planned $25M round C capital raise.

NucB1000 phase I results

Altogether only 3 of the planned 15 patients received NucB1000 in the phase I study. This was the first dose cohort which involved 5mg of plasmid DNA, ~0.06mg/kg. As expected, immune stimulation was observed in all 3 patients: a transient fever, accompanied by cytokine elevations, which quickly resolved following antipyretic treatment. This was described by the authors as a mild event and not a reason why patients would have dropped out of the trial- definitely not ‘life-threatening’.

Needless to say, given the nature of NucB1000 and the size of the trial, no signs of antiviral efficacy was seen.

To this day, it is not clear to me why exactly the trial was terminated. Did Nucleonics and their investors attempt a Hail Mary with the first dose cohort before cutting their loss on an increasingly improbable investment, or did they suddenly get cold feet as allegations of scientific misconduct relating to the pre-clinical data were raised? Given that money and lawsuits were involved, I favor the former with the latter serving as justification.

Curious publication

Overall, the Gish et al. paper is a most unusual one. The introduction already states:

'The proprietary nature of these data imposes limitations; however, the authors felt the results merited presentation and discussion as they involve a first-in-human study with potentially important clinical implications.'

I agree that the data was valuable, if not somewhat predictable, and am glad the authors had the courage to publish them. At the same time, the publication can also be read as a justification for why the trial went ahead.

It is also a curious publication because it suggests that Alnylam did not just acquire the Nucleonics IP estate to bolster its synthetic RNAi IP, as Barry Greene stated at the time, but that it was quite a bit more interested in DNA-directed RNAi Therapeutics in general, and NucB1000 in particular than one would have thought. While it cannot be determined conclusively how much NucB1000-related work was actually performed on Alnylam’s dime, the following passages suggest that it was not insignificant:

‘Exhaustive cell culture studies have demonstrated specific down-regulation of all HBV RNAs, including pregenomic RNA as compared with mismatch controls (Nucleonics, Inc.; Alnylam Pharmaceuticals; CS and CP, unpublished data; Recombinant DNA Advisory Committee).’

‘Additionally, significant inhibition of HBV antigen expression and viral replication is also observed, and is consistent with mRNA knockdown (Nucleonics Inc. and Alnylam Pharmaceuticals; CS and CP, unpublished data).’

'When administered intravenously, the nanoparticle been shown in preclinical models to transfect hepatocytes and delivers the eiRNA plasmid to hepatocytes and to the cells of some other tissues, such as the skin (Nucleonics, Inc. and Alnylam Pharmaceuticals, unpublished data).’

Etc, etc, I think you get the idea. But before Benitec supporters get excited about this, I would caution that Alnylam’s situation 3 years ago was much different from what it is today. With a dwindling cash reserve and after Tuschl, Tekmira, and Bass, Alnylam’s appetite for confrontation and lawsuits should have cooled considerably.

This story is yet another example of how concern about appearances (virus = scary) and short-term profit thinking (questionable model systems and lack of scientific rigor) in RNAi Therapeutics caused precious capital to flow into undeserving projects and lawsuits.

Alnylam Says Adverse Event in Tekmira ApoB Trial Was ‘Life-Threatening’

One apparent tactic employed by Alnylam in the ongoing litigation with Tekmira is not to win on arguments, but by coming out with 'revelations' aimed at unsettling Tekmira investors and potential collaborators. A weakened share price and financial position would supposedly make Tekmira more amenable to a light settlement or lowball takeover offer. Much of this has been discussed on this blog before, but today I would like to bring to the attention of the readers here one particularly grave and damaging remark that Alnylam made in their Response to the Amended Complaint, namely that the one case of immunostimulation in the phase I ApoB study that caused Tekmira to stop the trial was ‘life-threatening’:

From the Response:

‘Further, Alnylam invited Tekmira to join a joint development committee that Alnylam had formed with one of its pharmaceutical partners with the goal of assisting Tekmira and the whole field in advancing LNP technology. Moreover, it is through clinical trials conducted, mainly by Alnylam, that critical elements of Tekmira’s siRNA delivery technology have been validated in the clinic, and Alnylam has provided critical advice and counsel to Tekmira related to their pre-clinical and clinical development activities for their own products. For example, Alnylam’s chief medical officer provided critical and urgent counsel to clinicians attending to a patient in a Tekmira clinical trial that experienced a serious, life-threatening adverse reaction to Tekmira’s drug [emphasis mine].'

Not only does Alnylam make it sound like they are holding little Tekmira’s hands, have the new Chief Medical Officer rush to inept Tekmira's help, and more or less run the trials for them, this statement essentially accuses Tekmira of lying to investors and in front of regulators about the adverse event. These are very serious allegations, some of which by the way were part of the rumor mill even before Alnylam made these statements now in public (!).

These characterizations are in sharp contrast to the way Tekmira used to describe them: serious enough to be taken into consideration for future SNALP development, but not a show-stopper and certainly not life-threatening. Here is how:

Disclosure of adverse event in the phase I ApoB press release:

‘The primary endpoints of the ApoB SNALP Phase 1 clinical trial were measures of safety and tolerability. ApoB SNALP was well tolerated overall in this study with no evidence of liver toxicity, which was the anticipated dose-limiting toxicity observed in preclinical studies. Of the two subjects treated at the highest dose level, one subject experienced flu-like symptoms consistent with stimulation of the immune system caused by the ApoB siRNA payload. The other subject treated at the highest dose level experienced no side effects. Based on the potential for the immune stimulation to interfere with further dose escalation, Tekmira decided to conclude the trial [emphasis mine].’

If the adverse event had been ‘life-threatening’, then not disclosing this in the press release and subsequent investor discussions would obviously have been misleading.

The clinical details of the adverse event were then disclosed at the Drug Information Association '3rd Oligonucleotide-based Therapeutics Conference' held in Bethesda on March 23, 2010. An important function of these DIA meetings is to further the dialogue between industry and the US regulatory authorities and I assume that the FDA was in attendance and that Tekmira assumed the same when it reported the following:

‘Adverse Event in Suject 190:

- 53 Year old 103 kg male w/ hyperlipidemia

- Second in cohort to be treated with 0.6 mg/kg

- Tolerated infusion well

- ~2.5 hours felt ‘wobbly in legs’

- ~4 hours rigors, vomiting, fever, hypotension, hypoxia, HR 110 BPM

- Treated with Ibuprofin, O2, saline infusion

- Fever resolved in 3 hours

- ~5 hours BP reached nadir

- Patient continued to receive fluids

- IV methylprednisolone (120mg)

- BP, HR, O2 Sat improved

- Patient normal that night

- Returned to study unit the next morning

- Discharged the next day as per protocol

- Patient maintained perfect cogntion throughout episode

Event described as moderate in severity and related to study drug [emphasis mine].'

The account above is consistent with characterizing the event as ‘moderate’ and in no way suggests a ‘life-threatening’ event. While not exactly encouraging, such safety findings are common in clinical trials.

I’m confident that if this comes to trial, this damaging characterization of the ApoB trial will add another few millions to the damages awarded to Tekmira. I simply cannot believe that Tekmira’s management would risk getting in trouble with the SEC and FDA in such a way. There simply is no middle-ground. I know Tekmira shareholders are getting tired of hearing this, an attitude attesting to the success of Alnylam's tactics.

In related News: Alnylam guides down cash as ALN-VSP02 wraps up

Alnylam reported Q2 financial results after the close yesterday. Months after the departure of the former CFO and following the $150M shelf filing, the replacement had the pleasure of announcing that Alnylam is guiding down cash from ‘greater than $275M’ guided 3 and 6 months ago to now ‘greater than $250M’. No explanations were provided for the implied 50% increase in net burn. I hope that the new CFO has retained his ‘sense of humor’- apparently a job requirement at Alnylam [correction 5 August, 2011: in the conference call that followed the press release of the financial results the increase in expenditures were attributed largely to the 5x15TM efforts; not very illuminating really, but there was an explanation].

On the day of the financial results, Alnylam also disclosed that it has completed the phase I study in liver cancer with ALN-VSP02. There was no real new development in this study from the comprehensive data presented at this year’s ASCO (related blog here). What I noticed though is that this drug candidate has now been fully renamed ALN-VSP, dropping the '02' which may have been a painful reminder that Alnylam got all its clinically-relevant LNP delivery from Tekmira [hint: my strong impression based on the VSP conflicts that emerged 4 years ago with the remarks by David Bumcrot is that ‘01’ was a lipidoid formulation, and the ‘02’ formulation resulted from Alnylam giving up and seeking help from Protiva (now part of Tekmira, of course)].