A Defining Month for Tekmira

As if Ebola has not showered Tekmira with enough attention, Tekmira will be front and center in the RNA Therapeutics industry in October.  It will be clinical results from two other drug candidates utilizing Tekmira’s RNAi delivery technology (TKM-PLK1 and ALN-TTR02) and pre-clinical data for TKM-HBV that will define Tekmira's trajectory as a 'normal' biotech company.  'Normal' as I have little idea how Ebola will change all this.

Accordingly, depending on the dataflow, Tekmira could finally be transformed into an established biotech company.  If there are serious disappointments, Tekmira risks being delegated to being 'the Ebola company'.

Event 1 (October 10-11): Do GI-NET patients respond to TKM-PLK1?

The first upcoming data event is the phase IIa update for TKM-PLK1 in gastrointestinal neuroendocrine tumor (GI-NET) and adrenocortical carcinoma (ACC) patients.  This one can be considered a bonus event for Tekmira as barely anybody has been paying attention to the potential of this first-generation SNALP-based product candidate.

 

Results from a  multi-dose escalating phase I study suggested a dose-dependent benefit with patients receiving 0.6mg/kg or more having an increased likelihood of showing ‘clinical benefit’ (stable disease or partial response) than those receiving less of the drug.  In particular, almost all (5/6) GI-NET and ACC patients in that trial with otherwise enrolled across a wide range of cancer types exhibited at least stable disease, with a partial response by RECIST and a 19.3% reduction in tumor size.

One aspect that I found particularly encouraging in these results was that TKM-PLK1 which involves a long-circulating form of SNALP achieved ‘several fold’ increased target tumor concentrations compared to an earlier, short-circulating SNALP product (ALN-VSP02 from Alnylam).   Unfortunately, the precise differences were not disclosed.

The factor that makes me most optimistic about a positive update (--> multiple tumor responses) at the upcoming 7^th Annual NET Conference in Nashville is that there is evidence that SNALP LNP delivery should work particularly well in the GI-NET and ACC settings.  Not only did GI-NET and ACC patients seem to perform well in the phase I study, there have historically been apparent biological effects of other nanoparticulate cancer RNAi Therapeutics in neuroendocrine tumor patients, including cases of extended stable disease with Atu027 by Silence Therapeutics.  

Moreover, the adrenal cortex, and possibly other endocrine structures, seems to be a preferred target organ (next to liver) for SNALP LNP delivery.

What makes me less excited about this program is that TKM-PLK1 is based on fairly old SNALP LNP delivery technology, and wouldn’t it be nice to see the potent PLK1 RNAi trigger being utilized in the latest delivery formulation.

Event 2 (October 13): Does ALN-TTR02 show a therapeutic benefit in TTR amyloidosis?

At the upcoming American Neurological Association’s 2014 Annual Meeting, Alnylam will present first data from its high-profile ALN-TTR02 product candidate that will look not just at target gene knockdown (expected to be in the 80% range), but also whether this translates into an apparent therapeutic benefit.

ALN-TTR02 is an RNAi Therapeutic for the treatment of the FAP form of TTR amyloidosis and uses Tekmira’s delivery technology.  As a result, Tekmira stands to financially benefit from it in the form of development milestone payments and royalties (in the low to mid single-digit percent of revenues) which may reach ~$50-100M annually for this $500M market cap company if analyst projections as to the FAP market prove correct.

The data to be presented comes from the open-label extension (OLE) of the relatively short phase II study.  In this OLE study, Alnylam will look every 6 months how patients are doing according to the mNIS+7 functional score which will then be compared to data gathered from a Natural History study of the disease. 

It is expected that 20 patients that had been rolled over from the phase II study will now have reached the first 6 month time-point.  The phase II study was too short (2 doses spaced apart 3-4 weeks) to reasonably expect an obvious therapeutic benefit from the knockdown of the disease-causing transthyretin gene.

It is important to remember that a failure to see a therapeutic improvement after 6 months with ALN-TTR02 does not necessarily reflect badly on SNALP LNP delivery technology as long as the knockdown remains in the 80% range and is well tolerated.  In that scenario, target risk and an insufficient period of knockdown may be responsible instead and this is where each RNAi Therapeutic has its unique development risk.

My prognosis is that first divergences from the Natural History will be seen if the preclinical experiences and those from other amyloidotic diseases such as AA amyoloidosis are any guide (~50% knockdown and beyond should lead to a benefit).  From a Tekmira technology point-of-view, I will pay close attention as to the safety and tolerability of longer-term dosing, which so far looks quite good.

  

                Event 3 (October 15): Coming out for TKM-HBV

Possibly the dataset with the most impact on Tekmira is the revelation of the company’s RNAi candidate for HBV infection.  Based on data revealed earlier this year by Alnylam which showed a SNALP LNP-based RNAi compound to have multi-log viral knockdown and 2 log HBsAg knockdown in the challenging chimpanzee model with moderate amounts of drug, TKM-HBV is set to become most-potent and therefore hopefully best-in-class among the knockdown approaches by Arrowhead Research (ARC520, first-mover), ISIS/GSK, and Alnylam.

To facilitate cross-comparisons, Tekmira may wish to directly compare its candidate with Arrowhead’s ARC520 for which the structural identity is known.

One aspect that I will be paying particular attention to is whether the data support dosing without transient immune suppression.  This is because I am concerned that such a regimen, especially if it involved steroid use, would not be acceptable in the HBV setting. As you may remember, the company attempted to get away without immune suppression with TKM-EBOLA in a trial in healthy volunteers, but at moderate-to-high dose levels immune stimulations were seen prompting the FDA to put that program on Clinical Hold for the volunteer population. 

Having said that, TKM-Ebola is now being used in much more fragile patients actually infected with Ebola, and anecdotally even the most stringent dosing regimens such as 7x daily appear to be tolerated here, presumably without pre-medication.

As per the last quarterly conference call, Tekmira management seemed confident that TKM-HBV would not require pre-medication.  Since such immune stimulation is thought to be highly sequence-dependent, I do not fully understand their confidence, but maybe a little bit of immune stimulation is not that bad in the Ebola setting after all.

An IND for TKM-HBV is planned by the end of the year with first dosing starting in early 2015.

Buckle up for an exciting month with Tekmira, and if all that weren’t enough, it unfortunately looks like we are still in the early innings with Ebola as being ahead of the curve is a concept foreign to the governing authorities.

Disclosure: long Tekmira.