ProQR Therapeutics- an RNA Therapeutics IPO to Be Enjoyed Responsibly

This week, a new RNA Therapeutics company went public: mRNA repair company ProQR Therapeutics.  This Dutch company from genetics hotbed Leiden sets out to cure severe diseases that are caused by small mutations by repairing the mutations at the messenger RNA level.  First on the list is a treatment for Cystic Fibrosis caused by the 508 deletion.

If Only Science Were Always That Way

The repair is thought to be mediated by the provision of at least two synthetic RNA oligonucleotides (CF4 and CF6 in the image above), a long, modified one (~30nt) with complementarity to the area around the mutation, and a shorter (~10nt), 5’ and 3’-phosphorylated, but otherwise unmodified one of the desired sequence.  Add this to living cells, and hocus-pocus, mutant mRNA is converted into good mRNA.

What makes the publication by Zamecnik et al. from 2004 on which PRO-010 for Cystic Fibrosis is based so amazing, is that by just wishing to repair an RNA and without knowledge of an mRNA repair pathway (note: I’ve considered myself an RNA molecular biologist for close to 10 years, but never came across even the notion of such a mechanism), they obtained the desired results wanted.  Unfortunately, this is not how science works—never. 

In fact, even they considered themselves somewhat lucky, as they had initially thought that the repair first required a third oligonucleotide which by acting via RNaseH mechanism would cleave the target mRNA so that it becomes more amenable to repair ligation reactions.  But when they tried it, it did not make a difference (I would have expected a knockdown), so they stuck with the 2 oligo approach.  Equally amusing was the fact that the phosphorylations were just added for good luck, without any investigation on whether they were useful or necessary.  But as they say, never change a winning team.

Molecular Mechanism Supported Only by Tricky PCR

Most bothersome to me was the fact that the claimed mRNA repair could only be supported after trying out a bunch of PCR amplification reactions, with some reactions suggesting that something might have occurred to the target mRNA. 

As anybody who’s ever work with PCR knows, a lot of strange products are generated during most PCR reactions, either in tiny amounts or less tiny amounts (the infamous PCR artefacts that make lab meetings a fun event).  A related problem is that no conclusions can be drawn from end-point PCRs as used in that seminal paper regarding the amount of these products.  This would have answered the question of whether the phenotypic changes that were reported could be explained by the x % of wild-type CFTR mRNA being generated.

At the minimum, the generation of wildtype CFTR mRNA should have been shown through a hybridization method, not PCR.

Biology’s Best-Kept Secret

As you might imagine, the ability to repair mRNAs with simple oligonucleotides would generate a lot of interest, the type of interest for example that the discovery of RNAi received.   In the case of RNAi, the seminal findings by Tuschl and colleagues that RNAi gene silencing worked in mammalian cells were instantly followed by an explosion of publications harnessing this technology.  Strangely, however, according to GoogleScholar, only 9 papers have cited the mRNA repair publication by Zamecnik et al.  This is explained by most scientists just shaking their heads on reading the publication and then move on, with the more gullible ones failing to reproduce the results.

Laughing All the Way to the Bank

I know that as a scientist I have to be open-minded, but as described above my BS-recognition system, is lighting up bright red.  I  am therefore upset that such science was able to raise $90M in the IPO, valuing ProQR Therapeutics at 300 million dollar- US, not Zimbabwean ones!  On the one hand, I should be glad that financial interest in orphan diseases and RNA Therapeutics is so big right now that this was even possible.  And if you invest according to relative valuations, you will probably do quite well in RNA Therapeutics (Regulus e.g. is worth around the same $300M).  On the other hand, I am always afraid about backlashes from the failures of such companies.  It is therefore important to remember that the qualities of RNA technologies differ vastly in quality from company to company.