Stem Cell Therapies for Aging: Evidence, Regulation, and How to Assess Claims

October 1, 2026

Longevity Interventions & Therapeutics

If you have ever searched online for ways to slow aging, recover lost physical stamina, or protect your joints and brain from biological decline, you have likely encountered clinics advertising stem cell therapy. These marketing pages promise full-body rejuvenation, restored vitality, and cellular repair through simple intravenous infusions or localized injections. The claims are framed with sophisticated scientific vocabulary, but they often leave out critical context about safety, clinical efficacy, and regulatory approval.

This definitive guide provides an evidence-based breakdown of stem cell therapies in the context of aging. It separates validated, indication-specific medical treatments from unproven commercial offerings. You will learn the exact biological mechanisms being tested, how to read clinical trial outcomes in age-related frailty, how regulatory agencies oversee regenerative medicine, and how to spot misleading clinic marketing.

The Distinction Between Biology, Clinical Evidence, and Marketing Claims

Stem cell biology is one of the most promising fields in modern medicine. Scientists are actively investigating how cells maintain tissues, communicate with neighboring cells, and decline in function as organisms grow older. However, a major gap exists between laboratory discoveries and the commercial treatments currently sold to consumers.

A medical treatment can involve living cells, carry a description as regenerative medicine, and be administered by a licensed physician without ever being proven effective for the advertised use. The International Society for Stem Cell Research (ISSCR) explicitly warns that many commercial therapies lack rigorous evidence of safety and clinical efficacy. In some cases, commercial preparations have not even been proven to contain viable stem cells.

To evaluate regenerative therapies objectively, you must separate interventions into three distinct categories:

Established, Indication-Specific Cell Therapies: These are rigorously tested treatments approved by regulatory bodies like the United States Food and Drug Administration (FDA) for narrow, well-defined medical conditions under strict manufacturing standards.
Investigational Cell Therapies: These are experimental treatments currently being evaluated in regulated clinical trials with defined patient populations, specific endpoints, and formal institutional oversight.
Commercial Rejuvenation Offerings: These are direct-to-consumer procedures promoted for broad, poorly defined goals such as anti-aging, systemic wellness, chronic fatigue, or joint restoration without regulatory approval or robust trial evidence.

In the United States, FDA-approved stem cell products are strictly limited to blood-forming hematopoietic progenitor cells derived from umbilical cord blood. These products are approved exclusively for patients with specific disorders affecting the hematopoietic system, such as certain blood cancers or inherited metabolic diseases. They are not general-purpose interventions for aging, physical decline, or longevity.

Regulatory approval for a specific cell product treating a defined blood disorder does not mean that a different cell type, administered via a different route or dose, is safe or effective for aging.

The Spectrum of Cellular Products and Technical Definitions

The phrase "stem cell therapy" is often used as an umbrella term, but it encompasses fundamentally different biological products. Treating these products as interchangeable leads to confusion and masks potential risks.

Cell Lineages and Product Types

Understanding the source material and processing method is essential when assessing any cellular intervention:

Hematopoietic Progenitor Cells: Blood-forming stem cells derived from bone marrow, peripheral blood, or umbilical cord blood. These cells generate red blood cells, white blood cells, and platelets.
Mesenchymal Stem or Stromal Cells (MSCs): Multipotent cells isolated from bone marrow, adipose tissue (fat), umbilical cord tissue (Wharton's jelly), or dental pulp. In clinical aging trials, MSCs are primarily studied for their signaling and immunomodulatory properties rather than their ability to permanently replace worn-out tissues.
Adipose-Derived Regenerative Cells (Stromal Vascular Fraction): A heterogeneous mixture of cells extracted from surgically harvested fat tissue via enzymatic digestion or mechanical separation. This mixture contains some MSCs alongside endothelial cells, immune cells, and vascular smooth muscle cells.
Exosomes and Extracellular Vesicles: Tiny, membrane-bound particles secreted by cells that carry proteins, lipids, and RNA molecules. Although marketed heavily by commercial clinics as cell-free stem cell therapy, unapproved exosome products carry significant regulatory and biological uncertainties.

Core Characterization Parameters

Whenever an intervention is proposed, scientific rigor requires identifying six specific parameters:

Cell Source: Whether the material originates from bone marrow, adipose tissue, umbilical cord tissue, or peripheral blood.
Autologous vs. Allogeneic: Autologous therapies use the patient's own harvested cells, whereas allogeneic therapies use cells harvested from a qualified donor.
Processing and Manipulation: What laboratory steps occur between tissue harvesting and patient administration, including cell expansion, enzyme digestion, or cryopreservation.
Route and Target: Whether the product is delivered via intravenous (IV) systemic infusion, direct intra-articular joint injection, intrathecal injection into the spinal canal, or intramuscular delivery.
Target Indication: The exact medical diagnosis or clinical condition being targeted, rather than a broad label like aging.
Product Identity and Dosing: The precise cell count, viability percentage, phenotype characterization, and manufacturing protocol.

A clinical trial showing that a specific dose of manufactured, bone-marrow-derived allogeneic MSCs improves a physical test does not validate a clinic injecting uncharacterized fat extracts into an individual's knee or bloodstream. To learn more about how cellular mechanisms interact with the aging process, explore our resources on cellular health and metabolism.

Biological Rationale and Proposed Mechanisms in Aging

Preclinical geroscience has established that aging involves fundamental biological alterations, known as the hallmarks of aging. Among these hallmarks are stem cell exhaustion, altered intercellular communication, and chronic low-grade inflammation, often termed inflammaging.

The Paracrine Signaling Model

Historically, researchers theorized that injected stem cells would migrate to damaged organs, engraft into host tissues, and differentiate into new functional cells to replace aged tissue. While this mechanism occurs in bone marrow transplants for blood disorders, research in non-hematopoietic applications suggests a different mechanism.

Mesenchymal stem and stromal cells primarily function as temporary cellular signaling factories. Rather than permanently integrating into tissues, these cells release bioactive factors that influence the local microenvironment through paracrine signaling. These factors include:

Cytokines and Chemokines: Molecules that alter immune cell behavior, shifting pro-inflammatory M1 macrophages toward an anti-inflammatory, pro-repair M2 phenotype.
Growth Factors: Peptides such as vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) that support local tissue repair and blood vessel maintenance.
Extracellular Vesicles: Membrane packages containing microRNAs and regulatory proteins that modulate stress responses in surrounding cells.

Why Mechanism Does Not Equal Clinical Efficacy

Having a biologically plausible mechanism is a mandatory first step in medical research, but it is not proof that a treatment works in humans. Biological systems are complex and homeostatic.

When living cells are introduced into a complex human body, several unpredictable factors occur:

Cell Clearance: Intravenously infused cells are largely trapped in the capillary beds of the lungs (the pulmonary first-pass effect) and are rapidly cleared by the immune system within hours or days.
Host Tissue Environment: The aged, fibrotic, or inflamed microenvironment of an older individual may degrade or neutralize the signals released by therapeutic cells.
Dose and Timing Discordance: Laboratory petri dishes and rodent models often use cell-to-body-weight ratios that are impossible or dangerous to achieve in human clinical practice.

A proposed biological pathway is a hypothesis to be tested in controlled human trials, not evidence that an intervention will extend human life or restore functional performance. For detailed examinations of how experimental therapeutics are evaluated, consult our coverage of peptides and emerging therapies.

Clinical Evidence in Age-Related Frailty

To understand the legitimate scientific exploration of stem cell interventions for aging, you must examine clinical trials designed around defined medical conditions. Researchers do not study aging as a generalized concept in clinical trials. Instead, they study age-related frailty.

Frailty is a clinically recognized syndrome characterized by decreased physiological reserve, muscle weakness, slow walking speed, low physical activity, self-reported exhaustion, and unintentional weight loss. It places older adults at high risk for falls, hospitalization, disability, and mortality.

Phase 2b Trial Data: Laromestrocel for Aging Frailty

A 2026 published study evaluated an investigational cellular therapy called laromestrocel in people with age-related frailty. This study provides a clear example of how clinical research measures specific endpoints rather than broad claims.

The study was a randomized, blinded, placebo-controlled phase 2b dose-escalation trial involving 148 ambulatory individuals with mild-to-moderate aging frailty. The intervention consisted of an intravenous infusion of allogeneic, bone-marrow-derived mesenchymal stem cells at varying doses, compared directly against a matching placebo.

The primary endpoint measured in the trial was the change in physical performance as assessed by the Six-Minute Walk Test (6MWT), a validated clinical measure of functional exercise capacity and mobility.

Six-Minute Walk Test (6MWT) Treatment Differences vs. Placebo (200-Million-Cell Dose)
Did not meet threshold for significance
Statistically significant improvement

At month 6, the treatment-placebo difference for the highest dose group (200 million cells) was 41.3 meters, which did not meet the conventional threshold for statistical significance (p=0.0635). However, by month 9, the 200-million-cell group demonstrated a statistically significant improvement of 63.4 meters over placebo (p=0.0077). The trial report also noted a statistically significant overall dose-response relationship across all groups at six months, even though individual dose comparisons against placebo at that interim time point were not significant.

The Full Pattern of Measured Endpoints

Evaluating clinical trial evidence requires looking at all measured endpoints, not just the single most favorable outcome. The phase 2b frailty study evaluated several functional and patient-reported metrics:

Six-Minute Walk Test: Demonstrated a statistically significant improvement at month 9 in the 200-million-cell cohort.
Four-Meter Gait Speed Test: Did not demonstrate a statistically significant improvement compared to placebo.
Grip Strength: Showed no statistically significant improvement compared to placebo.
PROMIS Physical Function: Patient-reported physical function scores showed no statistically significant change versus the placebo group.

This mixed pattern of outcomes is typical of early-to-mid-stage clinical trials. A positive signal in one mobility metric shows that biological activity may be present, but the lack of improvement in gait speed, grip strength, and self-reported physical function shows why broad claims of total rejuvenation are unsupported.

Context from Earlier Phase 2 Clinical Trials

The phase 2b laromestrocel findings built upon earlier clinical work. A 2017 phase II randomized, double-blind, placebo-controlled trial investigated allogeneic mesenchymal stem cells for aging frailty in a smaller cohort. That study reported improvements in physical performance tests in a 100-million-cell group, alongside immunologic changes in both 100-million and 200-million-cell groups.

Subsequent reviews of the clinical trial landscape, including trials registered under identifiers such as NCT03169231 and NCT05284604 on ClinicalTrials.gov, highlight that MSC research in frailty remains an active, investigational area. While these studies provide valuable data regarding dosing, safety profiles, and surrogate mobility markers, they are phase 2 trials. They do not constitute final proof of efficacy or regulatory approval for routine clinical treatment. To understand how clinical evidence is structured across life-extension research, see our overview of longevity science and healthspan.

Study Design, Trial Limitations, and Analytical Uncertainties

Interpreting clinical data requires understanding the limitations and uncertainties inherent to early-phase research. When reading trial reports on cellular therapies, several methodological constraints must be weighed.

Sample Sizes and Subgroup Constraints

Phase 2 clinical trials are designed primarily to evaluate dosing, preliminary signals of efficacy, and adverse event profiles in relatively small groups. In the phase 2b frailty trial:

The overall study cohort consisted of 148 participants, divided across multiple dose-escalation arms and a placebo group.
The 200-million-cell arm, which demonstrated the most pronounced walking distance improvement at nine months, had a relatively small sample size.
Certain demographic and clinical subgroups had limited representation within individual dose tiers.

Small sample sizes increase the risk that unmeasured confounding variables influenced the results. Larger phase 3 confirmatory trials with hundreds or thousands of patients are necessary to confirm whether these mobility improvements can be replicated consistently across broad populations.

Follow-Up Duration and Durability

Aging is a lifelong, chronic process, but clinical trials of stem cell products typically monitor participants for 6 to 12 months. This introduces critical unanswered questions:

How long do improvements in physical performance persist after a single infusion?
Does the therapeutic effect decline as the paracrine signaling molecules are cleared and donor cells are eliminated?
Would repeated cellular administrations maintain the effect, or would they trigger immune sensitization and neutralising antibodies?

Without multi-year follow-up data, scientists cannot determine whether cell therapies alter the long-term trajectory of functional decline or merely provide a transient physiological boost.

Surrogate Endpoints vs. Definitive Clinical Outcomes

Clinical trials in frailty measure surrogate markers of physical capability, such as walking distance or inflammatory cytokine levels. While the Six-Minute Walk Test correlates with functional independence, it is

a surrogate metric.

A surrogate endpoint must not be confused with definitive, hard clinical outcomes. The phase 2b trial was not designed or powered to determine whether the intervention reduces hospitalizations, prevents nursing home admissions, lowers all-cause mortality, or extends healthy lifespan. Concluding that a walking test improvement equates to extended life expectancy is scientifically invalid.

The Regulatory Framework and Legal Boundaries

Understanding how health authorities regulate cell therapies is essential for protecting yourself against misleading marketing claims. Regulatory frameworks are designed to ensure that biological products are safe, sterile, pure, and genuinely effective before they can be sold to patients.

US FDA Framework: Section 361 vs. Section 351

In the United States, human cells, tissues, and cellular and tissue-based products (HCT/Ps) are governed by the Public Health Service Act and Title 21 of the Code of Federal Regulations (21 CFR Part 1271). The law creates two primary pathways:

Section 361 HCT/Ps (Lower Regulatory Tier)

Products regulated solely under Section 361 do not require pre-market approval, clinical trials, or proof of efficacy before being used in patients. However, to qualify for this narrow exemption, a cellular product must meet four strict criteria:

Minimal Manipulation: The processing of the cells cannot alter the original relevant biological characteristics. For structural tissue, processing cannot alter utility for reconstruction, repair, or cushioning. For cells, processing cannot alter metabolic or biological functions.
Homologous Use Only: The cells must perform the exact same basic function in the recipient as they did in the donor. For example, using fat tissue to cushion a structural defect is homologous, but injecting fat-derived cells into the bloodstream to treat systemic aging or into a joint to repair cartilage is non-homologous.
No Systemic Effect or Drug Combination: The product must not be combined with another drug or device and must not have a systemic metabolic effect, unless it meets specific autologous or reproductive exemptions.
Independent Function: If the product has a systemic metabolic effect, it must be for autologous use or use in a first- or second-degree blood relative.

Section 351 Biologics (Higher Regulatory Tier)

If a cell product involves more than minimal manipulation (such as expanding cells in culture, adding growth factors, or using digestive enzymes to extract cells) or is marketed for a non-homologous use (such as using bone marrow cells or fat cells for brain health, heart disease, or aging), it is classified as a Section 351 biological drug.

A Section 351 biologic cannot be legally marketed or sold without an approved Biologics License Application (BLA). Before obtaining a BLA, the manufacturer must conduct rigorous phase 1, 2, and 3 clinical trials under an active Investigational New Drug (IND) application overseen by the FDA.

Approved Indications vs. Commercial Hype

To date, the only FDA-approved stem cell therapies are hematopoietic progenitor cells derived from umbilical cord blood, such as DUCORD and related products. These are approved exclusively for allogeneic transplantation in patients with specific disorders of the blood-forming system, including certain leukemias, lymphomas, and inherited metabolic diseases.

The FDA has not approved any stem cell therapy, exosome product, or regenerative cellular intervention for:

General anti-aging, longevity, or age reversal
Age-related frailty or muscle weakness
Osteoarthritis or joint rejuvenation
Chronic fatigue, brain fog, or low vitality
Alzheimer's disease, dementia, or cognitive decline
Heart disease, stroke recovery, or lung disease

When a commercial clinic claims its stem cell procedures are legal or compliant, it often relies on an erroneous interpretation of Section 361. Regulatory enforcement letters and judicial decisions have consistently affirmed that processing adipose tissue into stromal vascular fraction or culturing cells for systemic infusion constitutes drug manufacturing that requires full FDA drug approval.

Safety Risks, Adverse Events, and Unregulated Procedures

Because stem cells are living biological materials, their use carries distinct risks that do not apply to conventional pharmaceutical pills or supplements. Unregulated, unapproved cellular interventions pose substantial hazards to human health.

Documented Harms of Unapproved Interventions

A comprehensive systematic review analyzing adverse-event reports from January 2004 through September 2020 identified 360 documented adverse events associated with unapproved stem cell interventions, including 21 reported patient deaths.

Reported complications associated with unregulated cell procedures include:

Severe Bacterial and Fungal Infections: Caused by contaminated cell preparations, non-sterile processing environments, or improper handling.
Pulmonary Embolism and Infarction: Intravenously infused cellular clumps or fat particles lodging in the microvasculature of the lungs.
Vision Loss and Permanent Blindness: Reported by the National Eye Institute following unregulated injections of fat-derived stem cells directly into the eyes of patients with macular degeneration.
Tumor Formation and Inappropriate Cell Growth: Undifferentiated or improperly characterized cells forming non-malignant growths or tumors in organs where they do not belong, such as spinal cord tumors following intrathecal injections.
Organ Damage and Cardiac Arrest: Systemic inflammatory reactions, acute kidney injury, and cardiovascular collapse following high-dose uncharacterized infusions.

These documented adverse events represent identified reports, not the total incidence rate. Because unapproved interventions occur outside regulated clinical trial monitoring networks, adverse events are severely underreported. The true number of patients harmed by commercial stem cell procedures is unknown.

The Misleading Use of Regulatory Terminology

Commercial clinics frequently exploit regulatory terms to create a false sense of safety and legitimacy. Knowing how these terms are misused helps you avoid predatory practices:

Regulatory Misconceptions vs. Scientific Reality
Claim: "Our clinic is FDA Registered."
Reality: Establishment registration is a simple administrative notification that a facility handles human tissue. It is not an FDA review, endorsement, or approval of their medical treatments.
Claim: "We have an FDA IND Number."
Reality: An Investigational New Drug (IND) status only permits experimental research in a defined protocol. It is not proof that the drug works or is approved for commercial sale.
Claim: "We are listed on ClinicalTrials.gov."
Reality: ClinicalTrials.gov is a public registry, not a peer-reviewed scientific endorsement. Inclusion does not mean a federal agency has verified the safety or efficacy of the intervention.

If a clinic charges thousands of dollars out of pocket for an experimental procedure while pointing to a clinical trial listing or an IND application as proof of legitimacy, exercise extreme caution. Regulated clinical trials evaluating investigational biologics typically provide the study intervention to qualified research subjects at no cost.

How to Assess Clinic Claims and Avoid Deceptive Marketing

If you are evaluating a clinic offering stem cell treatments, regenerative medicine, or cellular rejuvenation, use this structured, step-by-step verification framework.

1. Identify the Specific Medical Claim

What exact diagnosis or physical outcome is being promised?
Is the clinic claiming to treat a wide array of unrelated conditions (e.g. knee pain, erectile dysfunction, dementia, and anti-aging) with a single biological product? A universal therapy for all degenerative conditions does not exist.
Does the clinic rely on patient video testimonials, celebrity endorsements, or vague promises of renewed energy rather than published, peer-reviewed clinical trial data?

2. Demand Full Product Characterization

What is the exact biological source of the cells (autologous bone marrow, autologous fat, donor umbilical cord)?
How are the cells processed, isolated, and quantified? Ask for the specific cell count, viability percentage, and sterility testing documentation.
Is the product an uncharacterized mixture, or has it been manufactured under strict Current Good Manufacturing Practice (cGMP) standards?

3. Verify Regulatory Status and Oversight

Has this specific product been approved by the FDA for the advertised indication via a Biologics License Application (BLA)?
If the clinic claims the therapy is part of an active clinical trial, ask for the FDA IND number and the written institutional review board (IRB) approval letter.
Contact the trial investigator to verify whether the protocol follows standard clinical trial governance and whether patients are being improperly charged for an unapproved investigational drug.

4. Evaluate Safety Protocols and Follow-Up Care

What formal monitoring plan is in place to track short-term and long-term adverse events?
Does the facility have the emergency medical infrastructure required to manage severe complications like anaphylaxis or pulmonary embolism?
Who is responsible for your medical care if serious complications develop weeks or months after the procedure?

To understand how biological markers are used to assess physiological status without invasive cellular procedures, review our guides on biological age testing and age, biomarkers, and diagnostics resources.

What the Current Evidence Does Not Show

To maintain a grounded, scientific perspective on longevity interventions, you must clearly understand what current research has not demonstrated:

The evidence does not show that stem cell therapies reverse human aging. No clinical trial has demonstrated systemic age reversal, cellular rejuvenation across multiple organ systems, or an extension of maximum human lifespan.
The evidence does not show that results in frail older adults apply to healthy individuals. A clinical signal of improved walking distance in frail, physically compromised individuals does not mean the same therapy will enhance physical performance, stamina, or longevity in healthy, active adults.
The evidence does not show that commercial clinic offerings work. Experimental results achieved with highly controlled, manufactured cell products (such as laromestrocel) cannot be generalized to unapproved treatments sold in commercial medspas or stem cell clinics.
The evidence does not show that autologous cell procedures are free of risk. Harvesting and re-injecting a patient's own cells carries inherent risks of infection, structural tissue damage, unintended cellular differentiation, and systemic inflammation.
The evidence does not show that exosomes are an approved alternative to stem cells. Commercial exosome preparations sold for anti-aging are unapproved biologics with uncertain purity, unverified contents, and significant regulatory concerns.

For a broader perspective on research methodologies and therapeutic pipelines across geroscience, see our resource on longevity interventions and therapeutics.

Technical Glossary of Regenerative Medicine Terms

Allogeneic: Biological material harvested from a genetically non-identical donor of the same species and administered to a recipient.
Autologous: Biological material harvested from an individual and administered back to the same individual.
Biologics License Application (BLA): The formal submission process required by the FDA to achieve commercial marketing approval for a biological product, requiring extensive phase 1 to phase 3 clinical trial evidence of safety, purity, and potency.
Current Good Manufacturing Practice (cGMP): Strict quality and manufacturing regulations enforced by regulatory agencies to ensure pharmaceutical and biological products are consistently produced and controlled according to quality standards.
Engraftment: The process by which transplanted or injected stem cells successfully integrate into host tissues, survive, and begin producing specialized cells over an extended period.
Extracellular Vesicles (EVs): Microscopic, membrane-bound structures naturally released by cells that carry proteins, RNA, and lipids to mediate intercellular communication.
Hematopoietic Progenitor Cells: Multipotent blood-forming cells capable of developing into mature red blood cells, white blood cells, and platelets.
Homologous Use: The requirement that a transplanted human tissue or cellular product perform the exact same basic biological function in the recipient that it performed in the donor tissue.
Investigational New Drug (IND): An application filed with the FDA requesting authorization to administer an unapproved, experimental biological product or drug to humans in a structured clinical trial.
Mesenchymal Stem/Stromal Cells (MSCs): Multipotent cells derived from tissues such as bone marrow, umbilical cord, or fat that can differentiate into bone, cartilage, and fat in the laboratory and secrete immunomodulatory cytokines in the body.
Minimal Manipulation: Processing steps that do not alter the original relevant biological or structural characteristics of a tissue or cellular product.
Paracrine Signaling: A form of cell-to-cell communication in which a cell produces signaling molecules that alter the behavior and function of nearby cells without long-term physical engraftment.
Six-Minute Walk Test (6MWT): A standardized, objective clinical test that measures the total distance a person can walk on a hard, flat surface in six minutes, used to assess functional mobility and aerobic endurance.
Stromal Vascular Fraction (SVF): A heterogeneous cellular mixture extracted from adipose tissue through mechanical disruption or collagenase enzyme digestion, containing mesenchymal cells, endothelial cells, and immune cells.

Next Steps for Evaluating Regenerative and Longevity Options

If you are considering therapies to maintain physical function, support cellular health, and optimize your healthspan, use this checklist:

Verify Claims Against Published Trial Registries: If a clinic mentions a study, locate the trial on ClinicalTrials.gov. Check if the study is actively recruiting, what specific phase it is in, who is funding it, and whether the study design includes a randomized placebo control.
Consult Independent Specialists: Discuss any proposed regenerative intervention with a board-certified physician in geriatric medicine, rheumatology, or hematology who is not financially affiliated with the clinic selling the treatment.
Focus on Validated Healthspan Interventions: Prioritize lifestyle and medical interventions with robust, replicated evidence for improving physical function and metabolic health. Structured progressive resistance training, cardiovascular exercise, adequate dietary protein, and sleep optimization have proven benefits for physical stamina and frailty prevention that commercial stem cell therapies have not matched.
Report Suspicious Commercial Practices: If you encounter a commercial facility marketing unapproved stem cell or exosome products for anti-aging, chronic diseases, or cognitive disorders, report the facility to the FDA's MedWatch adverse reporting portal and consult consumer guides from the International Society for Stem Cell Research (ISSCR).

Sources

Stay current with research on aging biology, biomarkers, nutrition, therapeutics, peptides and longevity technology. AgeAmaze reports what the evidence shows, where uncertainty remains and which claims still need stronger data.

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