There is no approved treatment that slows, stops, or reverses Creutzfeldt-Jakob disease. Every drug tested in human trials so far has failed to change the disease’s course. Current care is entirely supportive, focused on managing symptoms like agitation, involuntary muscle jerks, and pain as the disease progresses. That bleak picture, however, is changing in the laboratory. A handful of experimental strategies, from antisense oligonucleotides that silence the prion protein gene to gene-editing tools that permanently shut it down, have produced striking survival extensions in animal models and are edging toward human trials.
Why CJD Is So Hard to Treat
CJD belongs to a family of diseases caused not by a virus or bacterium but by a misfolded version of a protein the brain already makes. The normal prion protein, called PrP, sits on the surface of neurons and performs functions that are still not fully understood. In CJD, PrP refolds into a shape that acts as a template, forcing neighboring copies of the normal protein to misfold as well. The result is a chain reaction that produces clumps of abnormal protein, kills neurons, and riddles the brain with microscopic sponge-like holes. Intermediate misfolded forms of the protein appear to be key drivers of this conversion process.1PubMed Central. Mechanism of misfolding of the human prion protein revealed by a pathological mutation
Several features make this disease especially resistant to treatment. The misfolded protein is not alive, so antibiotics and antivirals are irrelevant. It is extraordinarily durable: prions resist routine sterilization, remain infectious for years when dried, and require extreme measures like incineration or prolonged exposure to strong chemical disinfectants for reliable decontamination.2PubMed Central. Creutzfeldt-Jakob disease and infection control The disease is also rare, with roughly one to two cases per million people per year worldwide. That rarity, combined with rapid cognitive decline once symptoms appear, makes clinical trials extraordinarily difficult to design and run.3PubMed Central. Clinical trials for prion disease: difficult challenges, but hope for the future
About 85 to 90 percent of cases are “sporadic,” meaning they arise without any identifiable cause. The remaining cases are either genetic, linked to inherited mutations in the PRNP gene, or acquired through exposure to contaminated tissue. Genetic forms account for roughly 10 to 15 percent of all CJD and follow an inherited pattern with variable penetrance, meaning not everyone who carries a mutation will develop symptoms.4PubMed. Genetic Creutzfeldt-Jakob disease
Current Symptom Management
Because no disease-modifying therapy exists, treatment today focuses on comfort. Agitation and delirium are common as the disease advances, and clinicians manage them with low-dose antipsychotics and, when needed, sedatives. Involuntary muscle jerks, called myoclonus, are treated with antiepileptic medications such as levetiracetam or valproate. Excess secretions that develop as patients lose the ability to swallow are controlled with medications like scopolamine patches.5PubMed Central. Addressing the Unmet Needs of Patients With Rapidly Progressive Neurological Disease: A Case Report of Palliative Care in Creutzfeldt-Jakob Disease (CJD) All of these are started at the lowest effective dose and adjusted as the patient’s condition changes.
Early involvement of palliative care specialists is strongly encouraged. CJD progresses so quickly that the window for patients to express their preferences about future care can close within weeks of diagnosis. Many people have already lost decision-making capacity by the time a diagnosis is confirmed, making advance care planning conversations both urgent and emotionally fraught.6Age and Ageing. Multidisciplinary recommendations for palliative and supportive care in Creutzfeldt-Jakob disease and related disorders Multidisciplinary teams that include neurologists, palliative care physicians, nurses, social workers, and psychologists are the standard approach at specialized prion disease centers.
Drugs That Have Already Failed
The history of CJD treatment is littered with compounds that showed promise in cell culture or animal models but did nothing meaningful in people. Understanding these failures is important because they illustrate the gap between laboratory results and clinical reality.
Quinacrine, an antimalarial drug, was tested in the largest human prion trial to date, known as PRION-1. The drug was reasonably tolerated at a daily dose of 300 mg, but after adjusting for differences in disease severity between groups, there was no significant difference in survival between patients who took quinacrine and those who did not.7PubMed Central. Safety and efficacy of quinacrine in human prion disease (PRION-1 study): a patient-preference trial A handful of patients showed brief, transient improvements on neurological rating scales, but none experienced lasting benefit.
Doxycycline, a common antibiotic that had shown anti-prion effects in the lab, went through a randomized, placebo-controlled trial. The trial was stopped early for futility after an interim analysis showed no advantage for doxycycline over placebo, with survival times essentially the same in both groups.8PubMed. Doxycycline in Creutzfeldt-Jakob disease: a phase 2, randomised, double-blind, placebo-controlled trial
Pentosan polysulfate (PPS), delivered directly into the brain through continuous infusion, was tried in a small number of patients in Japan. The treatment did not produce any obvious clinical improvement, though researchers noted the possibility that some patients survived longer than expected.9PubMed. Continuous intraventricular infusion of pentosan polysulfate: clinical trial against prion diseases The invasive delivery method and ambiguous results meant PPS never advanced further.
Antisense Oligonucleotides
The most advanced experimental strategy for CJD focuses on cutting off the disease’s fuel supply. If the misfolded prion protein needs normal PrP to keep propagating, then reducing the amount of normal PrP in the brain should slow the chain reaction. Antisense oligonucleotides, or ASOs, do exactly this. They are short synthetic strands of modified genetic material designed to bind to the messenger RNA that cells use to produce PrP, marking it for destruction before the protein is ever made.
The results in mice have been dramatic. When ASOs targeting PrP were given to prion-infected mice before symptoms appeared, disease onset was delayed by as much as 99 percent and survival extended by up to 98 percent compared to untreated animals. Even when treatment was started after prions had already taken hold in the brain, a single course of ASO treatment extended survival by more than half and stretched out the symptomatic phase of disease from a couple of weeks to nearly two months.10PubMed Central. Antisense oligonucleotides extend survival of prion-infected mice Earlier proof-of-concept work had already demonstrated that a two-week infusion of ASOs directly into the brain could prolong the incubation period by almost two months.11Molecular Therapy – Nucleic Acids. Intracerebral Infusion of Antisense Oligonucleotides Into Prion-infected Mice
Follow-up studies confirmed that PrP lowering acts as a genuine disease-modifying therapy across multiple prion strains, disease stages, and outcome measures.12Nucleic Acids Research. Prion protein lowering is a disease-modifying therapy across prion disease stages, strains and endpoints This broad effectiveness across strains matters because CJD is not one disease: it comes in subtypes that differ in how fast they progress and which brain regions they attack. A treatment that works against only one subtype would have limited utility.
ASOs have already been approved for other neurological conditions and are delivered by periodic injections into the spinal fluid, so the technology platform is not entirely new to regulators. The major open question is whether the magnitude of PrP reduction achievable in the human brain will be enough to make a meaningful clinical difference, and whether treatment can begin early enough in the disease course to preserve brain function that has not yet been lost.
Gene Editing Approaches
While ASOs require repeated dosing to keep PrP levels down, gene editing aims for a more permanent solution. Two recent studies in mice have taken different paths to the same goal: permanently silencing the PRNP gene so the brain stops making prion protein altogether.
One approach used base editing, a technique that chemically changes a single letter in the DNA code without cutting both strands. Researchers delivered the editing machinery to the brain using engineered viruses injected into the bloodstream. In mice that carry the human version of the PRNP gene and were infected with human prions, a single systemic injection installed the desired edit in about 37 percent of target sites, cut PrP levels in the brain by half, and extended lifespan by 52 percent.13Nature Medicine. In vivo base editing extends lifespan of a humanized mouse model of prion disease The approach worked against isolates representing the most common sporadic and genetic subtypes of human prion disease.
A separate team developed an engineered compact epigenetic editor that silences the Prnp gene without altering the DNA sequence itself. Delivered brain-wide by a virus injected into the bloodstream, it effectively abolished PrP expression across the mouse brain.14PubMed Central. Brainwide silencing of prion protein by AAV-mediated delivery of an engineered compact epigenetic editor Epigenetic editing has a conceptual advantage: because it does not permanently change the genetic code, the effect could in theory be reversed if problems arise, though whether that reversibility holds in practice remains to be seen.
Both approaches face significant hurdles before reaching patients. Delivering editing tools to enough brain cells is a challenge, and the long-term safety of permanently reducing a protein expressed throughout the brain is unknown. PrP likely has normal functions that we do not fully understand, and completely eliminating it could carry its own risks.
Small Molecules and Immunotherapy
Not all experimental treatments rely on genetic approaches. Anle138b is a small molecule that works by blocking the formation of toxic protein clumps. In prion-infected mice, it doubled survival time and durably suppressed a marker of brain inflammation called astrogliosis.15PubMed Central. Therapeutic Trial of anle138b in Mouse Models of Genetic Prion Disease The compound is notable for its breadth: preclinical testing showed it inhibited all prion strains tested, including those derived from BSE (the agent behind mad cow disease) and human prions.16PubMed Central. Anle138b: a novel oligomer modulator for disease-modifying therapy of neurodegenerative diseases such as prion and Parkinson’s disease Because anle138b is taken by mouth and crosses into the brain on its own, it avoids the spinal injections or brain surgery required by some other strategies. The compound has also been tested against other protein-misfolding diseases.
On the immunotherapy front, a team at University College London developed PRN100, a humanized antibody designed to bind to the normal prion protein on cell surfaces, potentially shielding it from conversion by the misfolded form. A first-in-human safety trial delivered repeated intravenous doses to a small number of patients with sporadic CJD. The antibody was well tolerated, with no clinically significant adverse reactions, and it reached its target concentration in cerebrospinal fluid after 22 to 70 days of dosing.17PubMed. Prion protein monoclonal antibody (PRN100) therapy for Creutzfeldt-Jakob disease: evaluation of a first-in-human treatment programme The trial was not designed to measure whether the antibody slowed disease progression, but the encouraging safety and brain-penetration data have led researchers to call for formal efficacy trials, especially in patients diagnosed at the earliest stages or in people who carry PRNP mutations but have not yet developed symptoms.18The Lancet Neurology. Safety and efficacy of a humanised monoclonal antibody specific for the cellular prion protein (PRN100) in patients with sporadic Creutzfeldt-Jakob disease
Boosting the Brain’s Own Cleanup System
The brain has a built-in waste disposal pathway called autophagy, in which cells engulf and break down damaged components, including misfolded proteins. Researchers have found that prion-infected neurons do activate autophagy in response to the accumulating debris, but the response is incomplete and ultimately overwhelmed.19PubMed Central. Pharmacological activation of autophagy favors the clearing of intracellular aggregates of misfolded prion protein peptide to prevent neuronal death When cells are experimentally stripped of autophagy genes, misfolded prion protein accumulates to even higher levels, confirming that the pathway does contribute to prion clearance.20PubMed Central. Contrasting roles of autophagy in cellular prion infection
Pharmacologically boosting autophagy in cell and animal models has produced anti-prion effects: drugs that enhance the process reduce the buildup of misfolded protein and protect neurons from dying.21PubMed Central. An Update on Autophagy in Prion Diseases The challenge is specificity. Autophagy is a fundamental cellular process involved in everything from fighting infections to recycling organelles. Cranking it up globally could cause unwanted side effects. Researchers are exploring ways to target the enhancement more precisely to prion-affected cells.
Diagnostics That Could Change the Treatment Window
Even the best therapy will fail if it arrives after most of the brain damage is done. One of the biggest obstacles in CJD is that by the time a patient receives a definitive diagnosis, the disease has often progressed significantly. Faster, more sensitive diagnostics could transform the treatment landscape by moving the starting line earlier.
The most important recent advance is a laboratory test called RT-QuIC, which detects the seeding activity of misfolded prion protein in cerebrospinal fluid. In large cohorts of sporadic CJD cases, RT-QuIC achieves roughly 92 to 93 percent sensitivity with 100 percent specificity, meaning it almost never produces a false positive.22PubMed Central. RT-QuIC: a new test for sporadic CJD23Frontiers in Neurology. Diagnostic performance of CSF biomarkers in a well-characterized Australian cohort of sporadic Creutzfeldt-Jakob disease Before RT-QuIC, confirming CJD often required a brain biopsy or autopsy. Having a highly accurate spinal fluid test available during life is a substantial step forward.
Blood-based biomarkers are also advancing. Plasma levels of neurofilament light chain (NfL) and total tau are markedly elevated in CJD patients, sometimes dozens of times higher than in healthy controls. NfL in particular is elevated early, even when functional impairment is still mild, making it potentially useful for catching the disease sooner.24Molecular Psychiatry. Evaluation of plasma tau and neurofilament light chain biomarkers in a 12-year clinical cohort of human prion diseases Plasma tau levels, meanwhile, are independently associated with how fast the disease progresses, which gives clinicians a tool for predicting the disease course and could serve as a marker to track treatment response in future clinical trials.25JAMA Neurology. Association of Blood and Cerebrospinal Fluid Tau Level and Other Biomarkers With Survival Time in Sporadic Creutzfeldt-Jakob Disease
The Promise and Difficulty of Treating Before Symptoms
For genetic forms of CJD, where a person’s mutation status is known years or decades before disease onset, there is a theoretical window for preventive treatment. The idea is straightforward: if you can lower PrP levels in the brain before the misfolding cascade begins, you might prevent the disease entirely rather than trying to stop it mid-course.
Recent biomarker studies in people who carry PRNP mutations have shown that the RT-QuIC seeding test can turn positive in cerebrospinal fluid one to more than two years before symptom onset in certain genotypes.26PubMed Central. Biomarker changes preceding symptom onset in genetic prion disease That prodromal window, while short, could be enough to start a treatment like ASOs or gene editing before irreversible brain damage accumulates. Ongoing longitudinal studies are tracking at-risk mutation carriers with serial blood draws and spinal fluid sampling to better define how far in advance biomarkers begin to change.27PubMed Central. Fluid Biomarkers in Individuals at Risk for Genetic Prion Disease up to Disease Conversion
Presymptomatic treatment raises its own ethical questions. PRNP mutations have variable penetrance, so not every carrier will develop disease. Treating someone who might never get sick with a therapy that requires spinal injections or gene editing carries real risks. Deciding who qualifies, when to start, and how to weigh uncertain benefit against certain burden will require careful frameworks that do not yet exist.
Chronic Wasting Disease and the Species Barrier
CJD is not the only prion disease causing concern. Chronic wasting disease (CWD), which affects deer and elk across North America and parts of Scandinavia, has been spreading steadily and prompting questions about whether it could cross into humans. No human case of prion disease caused by CWD has been recorded, and most experimental evidence has suggested the risk is very low.28PubMed Central. The Zoonotic Potential of Chronic Wasting Disease-A Review
However, a recent study complicates that reassuring picture. Researchers inoculated cynomolgus macaques, a primate with biology much closer to ours than a mouse, with CWD prions. Most of the macaques did not develop obvious symptoms, but ultrasensitive tests detected low levels of prions in their tissues. When those tissues were then used to infect other laboratory animals, they produced prion disease with 100 percent transmission rates on serial passage.29PubMed Central. Limited transmission of cervid prions to nonhuman primates provides insights into the zoonotic potential of chronic wasting disease In other words, CWD prions appeared to survive and replicate in primate tissue even without causing classical disease, and that silent infection could still be transmitted onward. The findings do not prove CWD is dangerous to people, but they challenge the assumption that the species barrier is absolute and underscore why public health agencies continue to advise against eating meat from CWD-positive animals. Any treatment platform developed for CJD could become relevant to a broader human prion threat if that barrier ever weakens.
Getting Drugs Into the Brain
A recurring challenge across nearly all experimental CJD therapies is the blood-brain barrier, the tightly sealed lining of blood vessels in the brain that keeps most molecules out. ASOs require direct injection into the spinal fluid. Gene editing tools rely on engineered viruses that have been selected for their ability to cross into brain tissue from the bloodstream. Small molecules like anle138b have an advantage here because they naturally penetrate the barrier, but not all candidate compounds do.
Nanoparticle-based delivery systems are being explored as a way to ferry therapies across this barrier more efficiently. Various formulations, including lipid-based and polymer-based nanoparticles, are being engineered to carry gene therapies, enzyme replacements, and RNA-based treatments for rare neurological diseases, prion diseases among them.15PubMed Central. Therapeutic Trial of anle138b in Mouse Models of Genetic Prion Disease These platforms could eventually allow less invasive dosing routes for treatments that currently require spinal taps or brain surgery, though the technology is still largely preclinical. Surgical instruments that contact brain or spinal cord tissue from CJD patients require special decontamination procedures, and conventional sterilization is not always sufficient.30Clinical Infectious Diseases. Creutzfeldt-Jakob Disease: Recommendations for Disinfection and Sterilization Any treatment that reduces the need for invasive procedures would carry infection-control benefits as well.