Small Molecules and Gene Therapy Muscle Out Oligonucleotide Therapeutics

Over the last two days, breathtaking data were reported for the treatment of two severe, inherited muscle-wasting diseases affecting children.  The investigative agents were a small molecule splicing modulator and a gene therapy both of which appear to achieve superior results compared to approved Oligonucleotide Therapeutics agents. 

The developments highlight the risk that while gain-of-function changes (here by splice modulation) may have proved to be low-hanging fruits for Oligonucleotide Therapeutics, they, unlike gene knockdown approaches, face increased challenges from other technology platforms.

Small molecule splicing modulation for Spinal Muscular Atrophy (SMA)

In 2011, Roche started collaborating with PTC Therapeutics on small molecule splice modulators for the treatment of SMA.  The idea is to screen small molecules for their ability to bring about changes in RNA processing that would hopefully be gene-specific enough so as not to cause widespread off-targeting.

I had always considered this to be a monumental, if not insurmountable task.  This is because a given splicing event brings together a set of proteins that each in turn also function at other genes.  So surely a small molecule that may bias splicing from SMN1 to SMN2, as does antisense oligonucleotide SPINRAZA from Ionis and Biogen through highly specific base pairing, would also affect a range of other genes.

If that were not enough of a challenge, a small molecule carries the extra baggage of being more widely available across tissue types such that off-targeting is a risk to not just the CNS as with SPINRAZA, but many other cell types where there may be no benefit from SMN upregulation.

Accordingly, the first compound in the PTC-Roche collaboration to enter clinical development, RG7800, had to be discarded last year due to retinal tox concerns.  Another small molecule competitor, branaplam from Novartis, had similarly been put on hold due to tox concerns although this compound has resumed development late last year.

It was therefore amazing to see updated results from the FIREFISH study of the follow-on compound RG7916 in type I SMA infants.  They show that 90% of children had an improvement in the CHOP-INTEND measure of physical functioning after 6 months on the drug.  The results are particularly impressive considering that treatment had been initiated relatively late compared to the new standard of care with SPINRAZA and the soon-to-be-approved gene therapy by Novartis (àAvexis).   

Not only that, there had been no treatment discontinuations due to safety issues with RG7916.

Given that SPINRAZA has to be given intrathecally while RG7916 can be given orally, and given that both the gene therapy and the orally available RG7916 appear to be somewhat more efficacious than the oligonucleotide, the focus of Biogen and Ionis should now be on testing combinations of SPINRAZA with both modalities.  Ideally, there is added efficacy from using the agents together either because due to higher achievable SMN protein levels and/or due to complementary biodistribution (note: the value of SMN increases outside motor neurons is debated).  If not, the SPINRAZA franchise may have a limited shelf-life.

Fake-it-‘til-you-make-it Sarepta with gene therapy breakthrough

The other piece of great news for families dealing with neuromuscular disease came yesterday at the Sarepta Therapeutics R&D Day. 

To wit, Sarepta had used dubious data and a lot of political lobbying to get the controversial exon skipper eteplirsen approved under accelerated approval.  While delaying the confirmatory study that is supposed to be part-and-parcel of an accelerated approval, Sarepta has been raking in billions in sales and added market capitalization.  This has allowed the company to build a veritable DMD powerhouse with a number of candidates that look much more promising than ordinary PMO-based eteplirsen.  They include peptide-conjugated PMOs and especially gene therapies.

If you are involved in drug development, better get used to the dubious morals of the industry.  If things go well, you behave like the paragon of virtue, if things don’t go so well you fake it until you get another chance at succeeding.  I digress…

Before the initial gene therapy data were to be presented by Jerry Mendell from Children’s Nationwide of SMA fame, I had dreaded the thought of having a hyped-up R&D Day being about divining the meaning of a biopsy slide or two on the barely-above-background expression of the microdystrophin transgene.

However, what was presented was anything but borderline.  Unlike with eteplirsen where we were dealing with debatable 1%-type absolute expression levels, there was robust microdystrophin expression: ~75% of cells expressed the transgene (by IF) with roughly 30% absolute expression of microdystrophin relative dystrophin from a normal person (by Western blot).

Not only this, the microdystrophin was functional at the molecular level as judged by restoring dystrophin-related protein complexes serving to protect the muscle from damage by acting as shock absorbers.  Accordingly, CK levels in the blood, a marker of muscle damage and elevated in children with DMD, were robustly (9x) and uniformly lowered in all 4 boys between the ages of 4 and 7.  Add to this the obligatory before-and-after videos and there is little doubt already at this relatively early stage already (~1-3 months after gene transfer) that AAVrh74.MHCK7.microdystrophin is a powerful agent applicable to essentially all types of DMD.

On the safety side, there were considerable, but transient and manageable increases in liver enzymes.  This was to be expected, however, considering the very high doses of AAVRh74 needed to achieve widespread transgene expression in muscles throughout the body and treating physicians know to look for it.

If the safety holds up and expression continues to be long-lived, AAVrh74.MHCK7.microdystrophin could render many exon-specific oligonucleotide splice modulators obsolete. The duration of action is the most concerning issue to me at this point given the attendant cell turnover and attendant risk of losing episomal gene therapies in patients with muscle damage.    

There is No Doubt: Splice Modulator Drug for Spinal Muscular Atrophy Works

The fairy-tale story of the splice modulation for spinal muscular atrophy (SMA) continues.  This morning, Isis Pharmaceuticals provided an update on the phase II study of ISIS-SMNRx in type I SMA infants.  The data built on already highly promising data as of last September, showing that a doubling (~9 to ~18 months) of the median ‘event-free survival’ compared to the Natural History has now been reached with numbers still increasing as more than half the infants remain event-free.

Only one out of 12 infants still on study suffered an event (permanent ventilation) over the last 9 months.  This one in 108 month event rate compares to 6 events in ~200 months in the prior phase of the study, suggesting that if babies can be diagnosed and treated early enough so that they are covered during a critical period of development (e.g. maturation of the neuromuscular synapse) chances are that they will enjoy a very significant treatment benefit from ISIS-SMNRx.

This is thus consistent with the biomarker data showing that ISIS-SMNRx increases the missing functional full-length SMN protein by 2-3 times essentially turning a type I SMA infant (usually 2 copies of SMN2) with an 80% chance of dying or going on permanent ventilation by 18 months into a much milder form of the disease where patients have 4 or more copies of SMN2 and have an almost normal life expectancy (note: those with 3 copies, usually type II SMA, live into teens/early adulthood). 

While as a parent, I would almost do anything for my child to get access to the drug and I do understand there to be calls for immediate (à once diagnosed, the window of treatment opportunity may be quite narrow) regulatory action, the first consequence of today’s data should be getting SMA on mandatory genetic panels for newborn screening.  Only then will there be maximal benefit once the ongoing blinded phase III study reads out in late 2016/early 2017.

Antisense Technology Is Feasable for Neurodegenerative Drug Development

Last week at World Muscle, ISIS Pharmaceuticals provided an update on their phase II study results for ISIS-SMNRx for the infant- and child-onset forms of spinal muscular atrophy (SMA).  Importantly, biomarker and biodistribution results were reported that clearly showed that ISIS-SMNRx is doing exactly at what it was designed to do, namely meaningfully increase target gene expression in the central nervous system (CNS).

The data not only greatly de-risk ISIS-SMNRx, but open up phosphorothioate-based antisense technology for a whole range of other, largely severe CNS-based diseases of high unmet need, including Huntington's disease, the spinal cerebellar ataxias, Alzheimer's, Parkinston's- you name it!

Biodistribution

Specifically, the data showed that despite only a focal, intrathecal infusion of the antisense drug into the lower spine, it readily distributed throughout the CNS up to the brain and at concentrations (10-30ug per gram tissue) that are strongly predicted to support both steric blocking and RNaseH antisense mechanism of actions in the CNS for 2' MOE chemistry.  Further chemistry improvements such as cET are opening the therapeutic window even more so.  What is more, these concentrations were maintained for months, thus further supporting the apparent therapeutic benefits seen in these open-label studies.

Note that the effective concentration for antisense mechanisms will differ according to target tissues; e.g. in the liver, largely due to competition from phagocytic Kupffer cells, the effective concentrations are 100ug/g and above with 2' MOE chemistry.

With the generous support of SMA families, the company was also able to look for the drug and the SMN protein in tissue sections from 3 deceased infants.  These investigations showed that the phosphorothioate oligo had been taken up pretty much in every neuronal and non-neuronal cell types. 

Such broad-based uptake may be quite important according to the opening keynote address of ISIS collaborator Don Cleveland last night at the annual OTS meeting in San Diego, given that expressions of disease-causing genes in various cell types, not just the neurons, seem to contribute to most neurodegenerative diseases.


Biomarker

In terms of drug action, the SMN protein was found to be re-expressed in the corresponding cells as intended for the splice-modulating approach of ISIS-SMNRx.  This was shown by immunofluorescent analysis.  Moreover, quantitative PCR showed that the expression of the intended full-length SMN2 mRNA was increased by 2 to 3-fold, consistent with the 2 to 3-fold increases in SMN2 proteins found from cerebrospinal fluid (CSF) samples in the child-onset studies.

No dose-limiting safety issues were seen and the intrathecal infusions which are predicted to be needed on a ~6 month-basis for many of the anticipated CNS-related antisense applications could be performed without having to resort to general anesthesia.

For SMA, genetically speaking all this essentially turns a type I infant-onset SMA baby into a less severe type II/III child, and a type II/III SMA child into a normal one, with the caveat that this benefit obviously only accrues from the time the drug is given which, unfortunately, may be too late for many type I SMA babies.  I was e.g. somewhat disappointed that no apparent correlation was seen between onset of antisense administration and therapeutic outcomes in the infant study, although clearly the numbers may well have been too small (n=20). I am very hopeful, however, that those infants making it out to say 18 months and beyond with ISIS-SMNRx may see very good outcomes indeed.

Despite the caution, all this was accompanied by apparent therapeutic benefits in terms of survival and muscle strength.  While highly intriguing, due to the open-label nature of the studies and the small patient numbers, it is not my intention to delve more into that aspect of the data and instead focus today on the truly mind-blowing pharmacodynamic data.  These should provide hope for many patients and families with neurodegenerative diseases. If not, we might as well give up on rational drug development.

 

Black Box Therapeutics Finds Small Molecule Cure for Spinal Muscular Atrophy

After curing Cystic Fibrosis and Duchenne Muscular Dystrophy with nonsense drug ataluren, PTC Therapeutics is moving on to relieving the sufferings of many more children afflicted with severe genetic diseases.  This time it is spinal muscular atrophy (SMA).  In a publication that recently appeared in SCIENCE, PTC Therapeutics has stumbled upon another orally bioavailable small molecule that is claimed to modulate an RNA processing event for therapeutic purposes.

The reason why I’m interested in the PTC story is that their small molecule approach to RNA modulation is counter-intuitive as it instinctively calls for a nucleic acid-based solution.  On the other hand, an oral alternative to what are usually more invasive routes of administration could have certain advantages such as patient convenience and access.

Naryshkin paper

The paper by Naryshkin and colleagues is on the discovery of RG7800, a compound partnered with the new LNA antisense owner Roche.  It is an illustration of the general strategy taken by PTC Therapeutics of finding RNA sequence-specific small molecule modulators of genes of interest. 

In this example, the company began the panning process by hooking up RNA elements from the SMN2 gene that are involved in the splicing of an exon of interest with a luciferase reporter gene so as to enable large-scale small molecule library screening.  If left untouched, this reporter construct will produce very little light emission due to luciferase expression.  On the other hand, if the small molecule is successful in biasing splicing towards the inclusion of exon 7, the intended outcome of this particular SMA treatment approach, then light is produced.

As one might expect there are numerous ‘hits’ that come out of such primary screens.  In this case, 2000 small molecules from the library increased luciferase expression.  Since such expression changes can be due to a myriad of causes, selected candidates were put through a number of tests such as whether the increase was dependent on the SMN2 sequence elements (reporter constructs without the SMN2 sequences would take care of this), whether the selected small molecules change the expression or splicing of other RNAs (à off-targets; e.g. by RNA seq) etc.

RG7800 apparently survived all these tests and was found to increase the desired SMN2 splice form by about 70% in a number of cell models (including patient-derived cells) and in a mouse model.  It also has entered clinical development.

Comparison with ISIS drug

Since RG7800 is in direct competition with antisense drug candidate ISIS-SMNRx by ISIS and Biogen as both aim to increase SMN2 exon inclusion, a brief comparison is warranted.

While RG7800 has the obvious advantage of being orally bioavailable versus the need for intrathecal administration of ISIS-SMNRx, in terms of molecular outcome, exon inclusion in spinal motor neurons, it appears to be lacking: a ~70% increase compared to ~100-150% increases in the good SMN2 isoform achieved by ISIS-SMNRx in two clinical trials in SMA infants and children, and even more than that in rodent studies before (Passini et al. 2011).    However, RG7800 achieves SMN2 splice modulation not just in the motorneurons of the CNS, but in many other places, in and outside the CNS. 

There is ongoing debate as to whether such body-wide modulation is required, a question also prompted by a study by ISIS and collaborators on the systemic/subQ application of the antisense drug (Hua et al. 2011).  Parenthetically, this also means that if ISIS/Biogen wanted global SMN2 regulation, they have an option with subcutaneous administration in addition to intrathecal administration.  Interestingly, with the subcutaneous administration of ISIS-SMNRx, the mice lived much longer than when the oligo was given intrathecally (days/weeks versus months).  Indeed, consistent with those studies, the PTC small molecule also prolonged the lives of SMA mice considerably.  

I guess it will have to be the clinical trials which will be most informative as to whether this is an artefact of the mouse model or not.  If so, systemic drug exposure would add no benefit and only increase the risk of adverse events from off-targeting.

At the end of the day, what I find remarkable is that it is apparently possible to find small molecules that can modulate gene expression in a fairly sequence-selective manner.  While I don’t doubt that you can change splicing with small molecules, it is the apparent specificity of a simple molecule such as RG7800 that perplexes me.  

PTC Therapeutics did not disclose how many compounds they had to sift through to find RG7800.  If they really just picked one or a few after the initial screen that yielded ~2000 hits and then got lucky, I’d be quite skeptical.  Adding to my skepticism is that drug concentrations in the CNS were reported that greatly (>10x) exceeded those in the plasma (supplementary figure S7).  I’m no small molecule guy, but for an oligo guy who has been following drug development in general, that seems very unique. The blood-brain-barrier apparently does not exist for PTC.  

As a result, and also given the controversy around the discovery of ataluren (artefact or not) and the fact that PTC Therapeutics itself can only remotely speculate on the mechanism of action of RG7800, I acknowledge the publication as interesting, but am not ready to jump on board just yet.

ISIS Wasting No Time to Find Out Clinical Utility of Spinal Muscular Atrophy Drug

Yesterday at the 2014 Annual Academy of Neurology (AAN) meeting, ISIS Pharmaceuticals provided an update (presentation here, press release here) on their splice modulation antisense drug candidate ISIS-SMNRx for the treatment of spinal muscular atrophy (SMA).  The data were largely consistent with those presented about two months ago.  

Disease progression, including deaths in the infant trial, however, dashed hopes that this drug would be on its way to Accelerated Approval.  In light of the small number of subjects (15) in this trial, these events make it difficult to determine the impact of ISIS-SMNRx.  Similarly, the open-label nature of both the infant (type I SMA) and children (type II/III SMA) studies leaves open the possibility that apparent treatment benefits seen in motor-function outcomes could have been a placebo effect.

As a result of these concerns, the company has taken the bold step to run placebo-controlled, blinded pivotal phase III trials in infants and children to ascertain the tantalizing signs of efficacy seen thus far.  Most importantly, the drug more than doubled target therapeutic SMN protein levels (based on measuring surrogate levels in the cerebrospinal fluid) thereby genetically converting type I into type II/III SMA and similarly type II/III into near-healthy status.   In addition, the motor function increases seen were not only clinically relevant, but were also dose-related and hardly, if ever seen in the natural history of the disease.

Clearly, the apparent disease progression in the infant study would seem contrary to this conclusion.  Type I SMA babies have a mere life expectancy of 10 months, whereas type II/III children are faced with only somewhat shortened life expectancies.  The reason for this discrepancy is probably that in a treatment paradigm, SMN protein levels only catch up with type II/III SMA a few months after birth, whereas in normal development the SMN gene is already expressed in the womb.  The fact, however, that in the mouse model of the disease, ISIS-SMNRx restored mice to near-healthy status when given after birth, supports the notion that the drug should be efficacious when given post-delivery.

In the case of the infant study, drug administration commenced around months 4-5.   Considering that rapid functional decline and death occur soon after this in the natural history of the disease, the more optimal use of the drug would be when given starting right after birth.  However, until whole genome sequencing at birth becomes a routine screening tool for genetic disease (it should be routine already in my opinion), such optimal use has to wait for probably another 7-10 years.  Nevertheless, since ISIS-SMNRx seems safe and was shown to successfully address the disease at its root in babies and children- which also means that it could synergize with other future treatments- regulators should consider the full potential of this drug, present and future, when making a decision as to its approvability in 2016/2017.

One thing is clear, ISIS and partner BiogenIdec want to conduct the most rigorous trials possible to do ISIS-SMNRx justice when it could have taken the present data and pressed for accelerated approval in type I SMA largely based on the increases in SMN protein.  Knowing the real benefit of a drug can only benefit SMA patients and their families, and as we have found out in the case of Sarepta and DMD, the timelines ultimately do not have to be that different.     

Oligonucleotide Therapeutics for Spinal Muscular Atrophy Impresses in Clinical Study

In addition to the continued validation of RNAi in Man, the other big winner of 2013 in the field of oligonucleotide therapeutics was single-strand phosphorothioate chemistry in the CNS.  Today, ISIS Pharmaceuticals announced clinical data from the most prominent candidate in that effort, namely ISIS-SMNRx for spinal muscular atrophy (SMA), a genetic muscle-wasting disease.  Following intrathecal administration of the splice modulating oligonucleotide, time- and dose-dependent improvements were observed not only in muscle function, but also in SMN protein production (biomarker), thus laying the foundation for an accelerated approval pathway.

In the open-label phase Ib/IIa study in ~30 children with the ‘less severe’ form of type II and III SMA, functional improvements of 1.5, 2.3, and 3.7 points on the HFMSE scale were seen at the 3mg (3 doses), 6mg (3 doses), and 9mg (2 doses) cohorts, respectively.  The changes were thus largely consistent with results from a previous similar, but single-dose phase I study where a 3.1 point increase could be observed at the 9mg dose.

Despite the generally positive news, the data raise a number of questions.  For example, optimal dosing frequency remains uncertain as there were similar functional improvements regardless of whether a single dose had been given or 2-3 doses.  This could have been due to the  long half-life of the drug and the time it takes from SMN protein production (as a  result of the splice modulation) to impacting motor neuron function.  Similarly, in the prior phase I study no positive changes in HFMSE scores were observed at the 3mg and 6mg doses whereas in the present study, improvements were reported.  Clearly, larger patient numbers are required  to settle on the optimal dose, and in fact this dose may not have been reached yet (note: a 12mg cohort has been initiated and children from the phase Ib/IIa trial are allowed to roll over to an additional dose of 12mg).

Case for accelerated approval?

Possibly foreseeing such issues due to small patient numbers, ISIS Pharmaceuticals and BiogenIdec recently developed an assay that allows them to measure SMN protein abundance in the cerebral spinal fluid (CSF).  It is the results from these measurements that provide a strong case for why ISIS-SMNRx should be made available (pending the 12mg results) before a larger phase III study will have been completed.  This is because the functional improvements were accompanied by increases in the SMN protein which also were dose-dependent with a more than doubling of SMN protein at 9mg.

In SMA, the SMN1 protein is missing due to mutations.  The therapeutic approach of ISIS-SMNRx takes advantage of the fact that humans have a pretty much identical gene to SMN1, SMN2.  The problem with SMN2, however, is that only ~10% of its precursor messenger RNAs is spliced into a functional SMN protein due to a difference in essentially just one nucleotide in exon 7.  The severity of the disease, i.e. whether somebody belongs to type I (most severe), type II, type III, or type IV of the disease depends on the copy number of SMN2 genes: 2 copies in type I, ~3 copies in type II and III, and at least 4 copies in type IV.

Therefore, doubling the protein output for type II and III patients (the patient population in the present phase Ib/IIa study) would appear to put the children into the type IV category in terms of protein output (correponding to ~6 SMN2 copies).  In contrast to type I-III, type IV results in no differences in life-expectancy and only in rare cases causes patients to be wheelchair-bound late in life.  

Severe disease of high unmet need, strong biomarker data with highly suggestive functional results, all dose-proportional…the ingredients for an accelerated approval. 

Just in: ISISis reporting preliminary data from a parallel multi-dose phase II study in the most severe, infant form of SMA (type I).  Although small in numbers, the fact that the 4 babies at the starting 6mg dose are still alive and without permanent respiratory support at an average age of 12.5 months appears to be much better than expected.  According to natural history data, you would have expected 2 babies either dead or on permanent ventilation by month 10.  

And finally...the ISIS-SMNRx results increase the value of Marina Biotech's CRN chemistry.  This chemistry competes with the ISIS 2'MOE chemistry employed in ISIS-SMNRx and appears to be of higher potency/affinity, but much less defined safety.

ISIS-CRP Phase I Results: The Decreasing Competitiveness of RNaseH Antisense for Liver Gene Knockdown

To maintain is positive trajectory of the recent comeback, it is important for RNAi Therapeutics to firmly claim gene knockdown in the liver for itself.  This is because liver gene knockdown is the lowest hanging fruit for the technology, yet RNaseH antisense has proven to be capable of gene knockdown there as well.   If RNaseH were to crystallize as the preferred technology, it would jeopardize a considerable portion of the near to midterm market potential of RNAi Therapeutics.  Just think of Alnylam's 5x15(TM) portfolio of drug candidates.

As I have explained before, dose/tissue oligonucleotide concentrations and, related to that, safety/tolerability will determine which technology will win the competition.  Although the odds seem in favor of RNAi Therapeutics, ISIS Pharmaceuticals keeps promising that improved chemistry and screening methods will improve upon the modest potency (~30-35% ApoB knockdown) of and the safety concerns with mipomersen.  Due to the importance of liver gene knockdown to RNAi Therapeutics, this blog will continue to comment on the respective data points as they come in.

RNaseH Antisense CRP Phase I Data

Today, ISIS Pharmaceuticals announced phase I knockdown data from its c-reactive protein (CRP) program, ISIS-CRPRx.   CRP, a gene expressed by the liver, is believed (by some, not all) to act as a central player in a host of inflammatory diseases such as atrial fibrillation and rheumatoid arthritis.  Phase II studies for these indications are ongoing.

The phase I study tested whether ISIS-CRPRx can blunt CRP induction upon inflammatory stress.  Accordingly, healthy volunteers were dosed 6 times over 3 weeks with either 400mg or 600mg of the phosphorothioate antisense molecule against CRP.  Following that, subjects received endotoxin, a common laboratory reagent that is interpreted by the body as an infection.

Subjects treated with placebo saw an approximately 30-fold increase in CRP levels due to endotoxin.  When pre-treated with 400mg and 600mg, however, the induction was reduced by 36% and 63%, respectively.

 

Although the study succeeded in showing that ISIS-CRPRx could blunt CRP induction, it is much less clear whether ISIS-CRPRx makes for a viable therapeutic.  A 63% knockdown knockdown may be OK for some indications, but intuitively one has to wonder whether to stop an acute inflammation in its tracks you need to step much harder on brakes like CRP.  Indeed, the press release proclaimed, as a testament to the specificity of the drug candidate, that ‘other important immune modulators’ were not changed- somewhat puzzling given that CRP is thought to play such a central role in inflammation.

Be that as it may, what the press release did not mention was the side effect profile seen in the ISIS-CRPRx phase I study; to wit, safety and tolerability is the primary objective of any phase I study.  What concerns me is that mipomersen is 200mg weekly and causes injection side reactions, flu-like symptoms, and indications of chronic inflammation which are likely the result of the elevated steady-state tissue concentrations required for RNaseH antisense efficacy.  In the CRP study, 2- to 3-times more phosphorothioate antisense molecules were given.  Although the side effect profile of an RNaseH antisense molecule is also sequence-dependent, doses of 400mg and higher have historically been associated with toxicity/tolerability considered unacceptable outside of cancer.   

My prediction is that due to the poor efficacy-dose relationship, ISIS-CRPRx will not go into phase III.  We have to see whether the gen2.5 cET chemistry brings any significant increases in clinical potencies as inherent molecular potencies as measured in cell culture studies may not take into consideration other pharmacological rate-limiting factors.  If gen2.5 can lower liver tissue concentrations required to obtain 50% gene silencing into the low single-digit microgram/g range, RNaseH would become more interesting again for the liver.  Otherwise, it seems that more fertile hunting grounds for antisense technologies may be found in the areas of noncoding RNAs (e.g. microRNAs and lincRNAs) and therapeutic splice regulation, especially when the target molecules have a long nuclear residence time.  With ISIS about to present phase I data for its spinal muscular atrophy splice modulation drug candidate at next week’s AAN meeting, a next step into that strategic re-direction may be taken.