Klotho, the Aging Protein: Why Keeping It Flowing Is So Hard

A single gene discovered in 1997 has become one of the most talked-about molecules in longevity research. Klotho, named after the Greek Fate who spun the thread of life, acts as a master regulator of aging in mice: when the gene is knocked out, the animals develop a syndrome that strongly resembles premature aging, with shortened lifespans, ectopic calcification, increased arteriosclerosis and osteoporosis. When Klotho is over-expressed, the opposite occurs, with mouse lifespan extending by 20 to 30 percent. A new perspective article published in Frontiers in Aging by Walter H. Gunzburg, Pharon Pawa and Brian Salmons of the University of Veterinary Medicine in Vienna and Austrianova Thailand argues that the real bottleneck for turning this biology into medicine is not understanding what Klotho does, but keeping therapeutic levels of the protein in the body long enough for it to matter.

Klotho exists in two principal forms. One is a membrane-bound co-receptor for fibroblast growth factor 23, a hormone that governs phosphate and calcium balance. The other, soluble Klotho, circulates as an endocrine factor and has been shown to modulate insulin sensitivity, reduce oxidative stress and counteract fibrotic and inflammatory processes. Together these forms orchestrate mineral metabolism while exerting broader systemic effects, positioning Klotho as what the authors call a multifaceted guardian of physiological integrity. Excitement about the protein has surged not only because of its association with anti-aging properties, but because diminished Klotho levels correlate with a long list of conditions that generally arise in later life.

The breadth of those associations is striking. In the kidneys, reduced Klotho expression is linked to chronic and diabetic kidney disease, acute injury and progressive fibrosis. In the cardiovascular system, deficiency contributes to arteriosclerosis, vascular calcification and hypertension, and failing cardiovascular health in turn drives Klotho levels down, accelerating vascular aging and heart failure, whereas protecting cardiovascular health sustains the body’s native Klotho production. Neurodegenerative conditions including Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis have all been associated with diminished Klotho activity. Metabolic decline shows up as sarcopenia, osteoporosis and even chronic obstructive pulmonary disease. In cancer biology, Klotho appears to act as a tumor suppressor, with reduced expression correlating with tumor progression in pancreatic, breast and oral carcinomas.

If those links hold up, restoring Klotho to the levels found in childhood and youth could, in principle, mitigate multiple degenerative pathways at once, making the protein not just a biomarker of aging but a unifying therapeutic target. The obstacle is delivery. The half-life of Klotho in human serum has been measured at around 7.5 hours, and circulating Klotho is rapidly cleared by the kidneys. There is currently no established human standard or FDA-approved dosage for Klotho protein or peptide treatments, and because Klotho co-regulates major metabolic, inflammatory and ion pathways through its interaction with FGF23, managing exposure is a critical aspect of clinical translation, as is long-term safety monitoring.

Gene therapy has been the most visible route forward. Preclinical work using adeno-associated virus vectors such as AAV9 to deliver the Klotho gene to the central nervous system suggests a potential strategy for Alzheimer’s and ALS. In July 2025, Klotho Neurosciences, now Greenland Mines, received Orphan Drug Approval from the US FDA for KLTO-202, an AAV vector carrying soluble Klotho under a muscle-specific promoter. A Phase 1 trial at UCSF opened in early 2025 and is dosing in 2026, using a single ascending dose design in healthy older adults to evaluate safety, pharmacokinetics and a panel of cognitive endpoints over 90 days after a single subcutaneous injection. But AAV vectors are known from other studies to trigger immune responses, which limits how many times they can be administered.

Nonviral approaches face their own constraints. Minicircle has just completed a Phase 1 trial in healthy volunteers in Próspera, Honduras, testing a combination Klotho and follistatin gene therapy delivered by subcutaneous fat injection of plasmid DNA with a transformation agent designed to help the DNA enter the patient’s genome. Early animal studies suggested plasmid expression in muscle could last more than 19 months, and nanoparticle-complexed Klotho plasmid DNA has shown promise in animals, but more recent human studies have reported much shorter transgene expression or detection, often lasting only about a month. Lipid nanoparticles carrying Klotho mRNA are also in clinical testing: Klothea Bio’s randomized, double-blind, placebo-controlled Phase 1b trial of AKL003 at the GARM Clinic in Roatan, Honduras, is designed to increase human lifespan. Yet LNPs face potential toxicity, poor delivery to tissues outside the liver, where 80 to 90 percent of systemically administered particles accumulate, leaving less than 5 percent for intended target tissues, and rapid clearance by the mononuclear phagocytic system.

Cell therapy, in which stem cells or genetically modified Klotho-producing cells are transplanted into a patient, seems an obvious alternative, but it runs into the same biological headwinds. Klotho produced by cells in culture can have an even shorter half-life than the circulating protein, and implanted cells are often rapidly lost, either eliminated by the immune system within days or physically cleared, so Klotho production is again lost. The authors argue that these converging limitations across viral vectors, plasmids, nanoparticles and naked cell transplants point to the need for a delivery strategy that can sustain Klotho secretion over time without being undermined by immune barriers.

Several sustained-delivery technologies have been explored. Mechanical systems such as mini-osmotic pumps offer controlled dosing but are limited by finite reservoir capacity and the need for refilling; Lionheart Health is developing an implantable Octopus pump filled percutaneously with soluble Klotho, and its KlothoPatch II bioelectronic bioreactor platform combines the pump with a nutrient hydrogel holding Klotho-overexpressing mesenchymal stem cells. Hydrogel depots have shown results in animals: PLGA scaffolds supporting silk fibroin hydrogels containing Klotho protein and stem cells enhanced regeneration of myotendinous junctions in rats, and chitosan hydrogels allowed long-term Klotho release in murine models of renal fibrosis. But polymer microparticles carry a fixed payload, cannot house living cells and provide no immunoprotection. Alginate microcapsules, the most studied cell-encapsulation system, suffer from fibrotic overgrowth, immune responses to the material and mechanical fragility, while chitosan, gelatin and agarose capsules degrade relatively quickly or lack a substantial clinical track record. None of these has yet been tested with Klotho-expressing cells.

The authors’ favored candidate is cellulose sulphate microencapsulation, marketed as Cell-in-a-Box, which they argue combines durability, manufacturability, immune protection and sustained protein production better than the alternatives. Unlike alginate or agarose matrices, where encapsulated cells remain largely static in a sponge-like structure, cells can proliferate within the viscous liquid centre of cellulose sulphate capsules, enabling robust loading while maintaining long-term viability and continuous secretion. The capsules permit diffusion of proteins and small molecules but restrict direct immune cell access. Evidence from studies not involving Klotho suggests encapsulated cells can persist for extended periods: capsules have been reported present for up to two years in human pancreatic cancer trials, intact capsules with viable cells have been retrieved months after implantation in dogs treated for mammary cancer and in rats treated for diabetes, and the system has supported long-term monoclonal antibody production in mice. Two clinical trials in Germany demonstrated safety and feasibility in pancreatic cancer patients, albeit for a drug-activating system rather than Klotho. Klothonova, a joint venture between Austrianova and Avaí Bio, is now encapsulating immortal human cells engineered to stably produce soluble Klotho and reports long-term Klotho production and secretion from the capsules in vitro.

The authors are careful about what has and has not been shown. Most Cell-in-a-Box clinical data come from oncology rather than regenerative or metabolic indications, long-term persistence and secretion dynamics in humans remain incompletely characterized, and local inflammation, device malfunction or variable secretion rates cannot be excluded. They recommend first-in-human trials with a removable implant, with dosing adjusted by selecting suitable cell clones or changing the number of capsules implanted. Encapsulation differs from gene transfer in one potentially decisive respect: a removable encapsulated cell therapy could offer adjustable, reversible long-term Klotho production, whereas viral and DNA-based approaches are difficult to undo once administered. Whether sustained systemic Klotho exposure can translate the protein’s broad biological activities into clinically meaningful outcomes for neurodegenerative, renal and cardiovascular disease remains, the authors conclude, an important open question that will require substantial preclinical and clinical work to define optimal dosing, durability, safety and therapeutic benefit in human populations.

Subject of Research: Therapeutic delivery strategies for the Klotho longevity protein, including encapsulated cell technology

Article Title: Maintaining Klotho: preventing the body from unwinding

Article References: Gunzburg, W. H., Pawa, P., & Salmons, B. (2026). Maintaining Klotho: preventing the body from unwinding. Frontiers in Aging, 7, 1913194. https://doi.org/10.3389/fragi.2026.1913194

Image Credits: AI Generated

DOI: 10.3389/fragi.2026.1913194

Keywords: Klotho, aging, longevity, cell encapsulation, gene therapy, Cell-in-a-Box, soluble Klotho, AAV vectors, lipid nanoparticles, stem cells, neurodegenerative disease, regenerative medicine