Monday, August 20, 2012

Eventful Months for Tekmira


Last week, Tekmira reported its quarterly results and provided a corporate update.  With interim phase I results for its lead clinical candidate TKM-PLK1, well received clinical results by its licensee Alnylam, the Stop-Work Order from the Department of Defense, milestone payments from Talon and Alnylam, and the prospect of a jury trial following a key decision by the judge in the litigation with Alnylam, these certainly must have been one of Tekmira’s busiest 4 months ever.


TKM-PLK1 Results

20 months after trial start, Tekmira finally reported first data from its lead clinical program, TKM-PLK1 for advanced solid cancers.  The most informative data from this early-stage trial, as expected, related to safety/tolerability and pharmacokinetics. 

Accordingly, it appears that the maximally tolerated dose using an aggressive once-weekly dosing regime is 0.75mg/kg after encountering dose-limiting toxicities in the form of a case of transient thrombocytopenia and hypoxia/dyspnea each at 0.9mg/kg.  These data are in line with the clinical safety/tolerability data from other DlinDMA-based SNALP formulations (ALN-VSP02, ALN-TTR01) where the maximally tolerated dose was slightly higher, but which were dosed in in less aggressive schedules.  Although there seems to be a trade-off between dosing frequency and safety/tolerability, I would agree that for cancer applications where gene knockdown is targeted in rapidly dividing cells, more frequent dosing vs higher, but less frequent dosing may be desirable.  This is because the duration of gene knockdown is known to be largely inversely correlated with cell division frequency.   

Looking back at the overall DLinDMA results (ALN-VSP02, ALN-TTR01, TKM-PLK1), given the fairly uniform maximally tolerated doses, it is possible that lipid-specific toxicity can be as dose-limiting as siRNA sequence-specific immune stimulations.  It will therefore be interesting to see whether there will be a general shift in the maximally tolerated dose with SNALP formulations comprising different lipids.

While, as in many of these small, dose escalation trials, there were encouraging signs of therapeutic efficacy, here in the form of one partial response by RECIST and one stable disease, what excited me most about the released data was that this particular SNALP formulation achieved ‘several fold’ higher drug exposure levels than previous formulations (aka ALN-VSP02).  High/long exposure levels, of course, are thought to be critical for efficient drug delivery via the EPR effect.  The advance can be attributed to Tekmira’s rational SNALP design approach involving the use of a long-chain lipid-anchored PEG such that the cloak of invisibility is shed only after longer circulation times.  This is unlike in ALN-VSP02 (short chain anchor SNALP formulation) which exhibited short circulation times suitable for RNAi trigger delivery into various hepatic cell types.  Similar to ALN-VSP02 this time, further important pharmacokinetic data showed that the PK profile did not change upon repeat administration.  It is therefore unlikely that neutralizing antibodies are generated to the PEG component.  In certain old preclinical studies this had been shown to be an obstacle to repeat administration.

I look forward to learning about the more detailed clinical results.  In particular, I’d like to see not only the blood PK data, but possibly also the drug accumulations in tumor biopsies which could be compared to the ALN-VSP02 biopsy data.  By this, one would be able to model how exactly the higher blood exposure levels translate into tumor delivery benefits.  


Ebola Stop-Work Order

Earlier this month, Tekmira and competitor Sarepta received Stop-Work Orders from the US Department of Defense relating to their Ebola biodefense programs.  Tekmira has greatly benefitted from the DoD contract- not so much in terms of making a direct profit from the contract, but in that it also provided funding for progressing its technology platform.  A significant number of employees would have to be laid off if the final decision on whether to continue with the program, expected by September 1, were negative.  Although the impact on Tekmira’s science would not be immediate, it would definitely impact the speed of Tekmira’s technology advances if no substitute funding was found soon (see litigation section).  What is particularly frustrating about this Order is that it comes in the middle of an ongoing phase I clinical trial (at least wait for the results before making a final decision) and because budgetary uncertainties, not scientific deficiencies apparently being the reason for it.  Ironically, therehave been two recent outbreaks of Ebola in Africa highlighting that Ebola is not just a bioterrorist, but also persistent public health threat.


Tekmira Partners Celebrate Successes, Company Collects Milestones

The recent past were particularly exciting for Tekmira’s technology licensees Alnylam and Talon Therapeutics.  As discussed on this blog before, the ALN-TTR02 knockdown results, critically enabled by Tekmira’s delivery technology, were very positively received by the biotech community, including investors.  These results also paved the way for the initiation of a phase II trial of ALN-TTR02 triggering a $1M milestone to Tekmira.  As important as the milestone is to Tekmira on the eve of the jury trial, once the company has fully recovered possession of its technology, the liver knockdown results should allow the company to turn many of those companies on the sidelines into willing customers once there is a resolution to the litigation.

A somewhat unexpected $1M milestone came from Talon Therapeutics, a small biotech company that had licensed early Tekmira small molecule liposomal drug candidates.  The milestone was triggered by the FDA approval of one of the licensed product candidates, Marqibo (liposomal vincristine), for the treatment of advanced Ph- ALL.  In addition, the company is entitled to receive sales milestones.   


All Set for a Jury Trial

Despite all the important events above, the most important news regarding the financial viability of the company came when the judge made the important decision to reject the delay and cost-intensifying tactic (here: Motion for Summary Judgment) by Alnylam paving the way for a jury trial at the end of October.  As the case will be tried on all counts and, according to Alnylam’s regulatory disclosure, could cost the company in excess of $1 billion, you would think that Alnylam has no choice but to settle the matter (or buy Tekmira).  The longer Alnylam waits, the more dearly it is likely to cost them.

In that light, the next 2-3 months should be even more exciting for Tekmira shareholders and hard-working employees.

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By Dirk Haussecker. All rights reserved.

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