RNA Therapy Reverses Cellular Defects in Hereditary Cardiomyopathy
A group of scientists from the University of Groningen showed in Nature (Signal Transduction and Targeted Therapy) that RNA therapy reduces the aggregation of the toxic protein phospholamban. The treatment restored calcium homeostasis in cardiomyocytes of patients with the PLN R14del mutation, marking a step toward etiotropic therapy for heart failure.
An analytical article from an insider who sees this modest publication in Nature not just as "another therapy," but as the first swallow in the era of etiotropic treatment for "incurable" cardiomyopathies.
Title: The Dutch "Cursed Gene" Has Fallen: Why RNA Therapy Against PLN R14del Is More Than Just a New Drug
Introduction
While everyone is watching the GLP-1 and CAR-T battles, a tectonic shift has occurred in cardiology that almost no one in mainstream media is talking about. On May 27, 2026, a paper from the University of Groningen group led by Dr. Frits Deiman was published in the journal Signal Transduction and Targeted Therapy (Nature Portfolio). Formally, it is about RNA therapy for a rare phospholamban mutation (PLN R14del). Informally, it is the first convincing case where a post-translational "breakdown" in the calcium pump was not just symptomatically corrected but reversed at the phosphoproteome level.
The R14del mutation is the Dutch "cursed gene." It originated in the province of Friesland several centuries ago, and today it is one of the most common causes of inherited dilated cardiomyopathy (DCM) in the Netherlands. About 10-15% of all Dutch patients with DCM or arrhythmogenic cardiomyopathy carry this variant. Previously, we could only watch as young people suddenly died from arrhythmia or lived long enough for a heart transplant. Standard heart failure therapy (beta-blockers, ACE inhibitors, aldosterone antagonists) is virtually useless for this mutation.
Now, the University of Groningen group (UMCG), together with Ionis Pharmaceuticals and AstraZeneca, has not only demonstrated the effectiveness of antisense oligonucleotides (ASOs). They have applied high-resolution phosphoproteomics for the first time to prove that RNA therapy reverses the disease-specific "fingerprint" of signaling. This is not just news. It is a redefinition of how we will treat genetic heart diseases in the era of RNA therapy.
[The Essence]: What Is Really Happening
Behind the beautiful words "reversed cellular defects" lies a complex multi-layered story. The thing is, PLN R14del is not a classic "loss of function" like in many recessive diseases. It is a toxic gain-of-function. The mutant phospholamban protein does not just stop working—it begins to aggregate (clump) in the sarcoplasmic reticulum of cardiomyocytes, forming toxic conglomerates. These aggregates physically block SERCA2a, the calcium pump responsible for heart muscle relaxation.
The UMCG team used a brilliant approach. They did not try to cut out the gene with CRISPR (although such attempts exist at Tenaya Therapeutics). They used antisense oligonucleotides (ASOs) that reduce the amount of all PLN mRNA variants—both mutant and wild-type. As a result, the total amount of toxic protein decreases, aggregates dissolve, and SERCA2a can finally work properly.
But the most important and groundbreaking aspect of this paper is the phosphoproteomics. The researchers analyzed heart tissue from 6 patients carrying R14del and compared it with 10 patients with another form of DCM. It turned out that at the protein level (proteomics), everything looks similar: fibrosis and inflammation everywhere. However, at the phosphorylation level (where molecular "switches" reside), there is a fundamental difference. They found 1507 differentially phosphorylated sites unique to R14del. And, critically, RNA therapy reversed 22 key sites back to normal, including those responsible for the cytoskeleton and actomyosin interactions.
What does this mean practically? For the first time, we have a surrogate molecular marker of therapy response, rather than just waiting for the patient to develop end-stage heart failure. We can take a biopsy, perform phosphoproteomics, and say, "Yes, the drug is working at the molecular level."
[Timeline and Context]
Pay attention to the dates and players. This story has been brewing for years.
June 2021: Niels Grote Beverborg from UMCG receives the Young Investigator Award from the European Society of Cardiology for the first preclinical data on ASO against PLN in mice. Even then, it was clear that ASO extended mouse lifespan from 9 weeks to 28. But those were mice. Humans are not mice.
May 2025: Tenaya Therapeutics reports at the ASGCT conference on its program TN-501—Cas9 editing aimed at inactivating specifically the mutant R14del allele. This is the competitor's approach: not reducing everything, but precisely turning off the "bad" gene copy. They showed improved heart function and survival in mice. The race begins.
March 2026: Defense of Frits Deiman's dissertation at the University of Groningen. It contains all the phosphoproteomics data and proof of pathology reversibility in iPSC-cardiomyocytes from real patients.
May 2026: Publication in Nature STTT. Key innovation: for the first time, data are validated on real human heart tissue (6 explanted hearts). These are not cells in a dish; these are actual fibrotic ventricles from people who received donor hearts. And they showed that ASO works ex vivo on this tissue.
June 2026 (now): A wave of news. But note: not a word about the FDA, not a word about an IND (investigational new drug application). Why? Because the patents on ASO chemistry belong to Ionis Pharmaceuticals (see their applications for modified oligonucleotides), and the rights to the PLN target are shared by UMCG and AstraZeneca. Right now, a "kitchen" battle is underway over who will pay for Phase I.
[Who Wins and Who Loses]
Here, two paradigms collide: RNA therapy (ASO, Ionis) versus gene editing (CRISPR, Tenaya) and classical gene therapy (AAV).
Winner #1: Ionis Pharmaceuticals (NASDAQ: IONS).
This is their technology platform. They own patents on chemical modifications of ASOs that ensure stability and reduce immunogenicity. If PLN-ASO passes clinical trials, Ionis will receive royalties not only from this product but also strengthen its cardiology portfolio. Their stock has already risen 4% in the week after publication, but the real potential is +30% if they buy back the rights from AstraZeneca.
Loser #1: Tenaya Therapeutics (NASDAQ: TNYA).
They have TN-501—a Cas9 therapy that is supposed to excise the mutant gene copy. This sounds cooler (one-time treatment), but they have problems: AAV delivery, risk of off-target editing, immune response to Cas9 (a bacterial protein). In Tenaya's reports from May 2025, they mention "low anti-Cas9 antibody responses," but that is in mice. In humans, this could be fatal. Ionis's ASO does not edit the genome; it simply reduces expression temporarily—safer for first-in-human. Tenaya is 1.5-2 years behind.
Winner #2: Epigenetics and phosphoproteomics as a service.
This is a non-obvious insight. Deiman's work is the first where phosphoproteomics is used as a primary endpoint of efficacy (not just a research tool). Now, any company developing therapies for complex diseases where rapid regulatory switches are important (heart, neurodegeneration) will buy these services from specialized CROs (e.g., Evotec or Alamar Biosciences). The phosphoproteomics market will grow by 25-30% in the next 12 months.
Loser #2: Manufacturers of standard cardiac drugs (Novartis, Bayer).
They are still selling Entresto (sacubitril/valsartan), which only slows symptom progression. But if PLN-ASO reaches the market, it could make Entresto unnecessary for a whole group of patients with genetic cardiomyopathy. The Swiss and Germans have already sent their scouts to Groningen to understand how fast this will happen.
[What the Media Are Not Saying]
Journalists write "RNA therapy reversed defects." But three details are omitted.
1. The "human is not a mouse" problem, which they have not fully solved.
In the paper, they honestly state that the ASO therapy that worked in mice turned out to be species-specific. They had to develop human ASOs from scratch. And even on iPSC-cardiomyocytes (derived from patient cells), the effect exists but is not complete. Calcium homeostasis restoration was about 60-70% of normal. That is, the cells are still "sick," but no longer fatally sick. The question: is this enough to prevent sudden cardiac death in a 40-year-old patient? There is no answer.
2. Distribution of ASO in the myocardium.
ASO needs to be delivered uniformly to all cardiomyocytes. But a study in pigs (published in March 2026 at the DGK congress) showed that AAV delivery (a similar problem) results in extremely uneven distribution across the ventricle: expression in some areas is 10 times higher than in neighboring areas. For virus-free ASO, the problem is even worse—they are excreted by the kidneys, and their accumulation in the heart is low. Ionis has modified the chemistry (LICA technology), but data on biostatistics in large animals (primates) are not yet available. We could end up with a situation where half the heart is treated and the other half is not, which is itself arrhythmogenic.
3. Playing with fire: reducing wild-type PLN.
PLN normally acts as a brake on SERCA2a. If we completely remove it (knockdown), the calcium pump will work at full capacity without regulation. This would lead to tachycardia and an increased risk of arrhythmias. They used partial knockdown, but dosing is very difficult. Patients with R14del have one normal gene copy and one mutant. ASO does not distinguish between them. By killing the mutant protein, we also kill the normal one. This is a "blunt" strategy. Unlike Tenaya, which tries to edit only the mutant allele, here we sacrifice 50% of normal function. Will the heart tolerate this after 10 years of treatment? There are no clinical data.
[Forecast: Next 30 Days and 90 Days]
Next 30 days (July 2026):
We will see a series of press releases from Ionis Pharmaceuticals. They will announce the formation of a consortium with UMCG and likely the European regulator EMA to discuss the design of Phase I/IIa. This will not be a randomized placebo-controlled trial with hundreds of patients (too expensive and rare), but an N-of-1 or small group of 10-15 R14del carriers with early signs of cardiomyopathy (but without severe heart failure). EMA will likely approve an adaptive trial design.
The cost: the production cost of one ASO course is about $25,000-40,000. Ionis will ask investors for additional funding of $50-75 million to conduct Phase I. IONS shares will rise by 5-7%.
Next 90 days (September-October 2026):
At the American Heart Association (AHA) congress in November 2026, first biopsy data from patients who received ASO will be presented. But I give an 80% probability that the data will be on safety and pharmacokinetics (PK/PD), not efficacy. The main question: how much ASO reaches the cardiomyocytes? If the reduction in PLN is less than 40%, the therapy is pointless—aggregates will continue to form.
Competitive forecast:
Tenaya Therapeutics, seeing the success of the ASO approach, will accelerate its TN-501. They may file an IND with the FDA as early as Q4 2026. The game will shift to a comparison: ASO (requires monthly repeat injections) versus editing (one shot, but risk of cancer from CRISPR). The winner will be the one with a wider therapeutic window.
Main insider takeaway:
Do not view this news as a "cure for heart failure." View it as a platform validation. For the first time, we applied top-down phosphoproteomics to a real human heart and demonstrated pathology reversibility. This means the same approach (ASO + phosphoproteomics) can be applied to MYBPC3 (hypertrophic cardiomyopathy), PKP2 (arrhythmogenic dysplasia), and even some forms of amyloidosis. Groningen is now the global epicenter of precision medicine in cardiology. If you have contacts in the European Network for Cardiogenetics, now is the best time to secure a position there. The bets are placed. The game has begun.
— Editorial Team
