A Mechanism-Driven Reframing of Therapeutic Development in Post–Acute SARS-CoV-2 Disease

John Murphy, M.D, M.P.H., D.P.H. President COVID Long-haul Foundation

Conceptual Shift and Therapeutic Reclassification

ABSTRACT

For much of the early Long COVID era, clinical management was dominated by supportive care paradigms grounded in symptom palliation, rehabilitation, and exclusion of alternative diagnoses. However, accumulating evidence from observational cohorts, mechanistic studies, and early interventional trials now indicates that post–acute sequelae of SARS-CoV-2 infection (PASC) is not a singular post-viral fatigue syndrome but a biologically heterogeneous condition with multiple potentially targetable pathophysiological pathways.

A major 2026 synthesis of emerging evidence suggests that the therapeutic landscape has expanded substantially beyond supportive care into mechanism-directed experimentation. Investigational therapies now include low-dose naltrexone, antiviral agents, antihistamines, Janus kinase (JAK) inhibitors, vagus nerve stimulation strategies, GLP-1 receptor agonists, anticoagulant and fibrinolytic approaches, intravenous immunoglobulin (IVIG), nicotine receptor modulation via transdermal systems, guanfacine, and colchicine.

This review examines the conceptual transition from empiric symptom management to biologically stratified therapeutic development, emphasizing the implications of endotype heterogeneity for treatment response, clinical trial design, and risk of therapeutic misclassification.

1. INTRODUCTION: FROM THERAPEUTIC NILISM TO MECHANISTIC EXPLORATION

Early in the recognition of Long COVID, clinical practice was largely constrained by uncertainty regarding pathogenesis. In the absence of validated biomarkers or defined disease subtypes, management strategies were predominantly supportive and rehabilitative in nature.

This approach reflected a cautious epistemology:

if mechanism is unknown, intervention must remain non-specific

However, this stance increasingly conflicts with emerging biological evidence demonstrating that Long COVID encompasses multiple overlapping but distinct pathophysiological domains, including immune dysregulation, endothelial injury, autonomic dysfunction, neuroinflammation, and metabolic impairment.¹–³

As mechanistic understanding has expanded, so too has therapeutic ambition.

By 2026, the field has transitioned into a new phase:

empiric symptom management → mechanism-targeted experimental therapeutics

This transition represents one of the most significant shifts in post-viral medicine in modern clinical history.

2. LONG COVID AS A MULTI-PATHWAY THERAPEUTIC TARGET

The expansion of therapeutic strategies reflects a fundamental reinterpretation of Long COVID biology.

Rather than a single disease process, Long COVID is now conceptualized as a multi-endotype syndrome, in which distinct biological processes dominate in different patient subgroups.

Major implicated pathways include:

immune activation and exhaustion-like states
persistent inflammatory signaling
endothelial and microvascular dysfunction
dysautonomia and autonomic instability
neuroimmune dysregulation
metabolic and mitochondrial impairment
thromboinflammatory activation

Each pathway corresponds to a distinct potential therapeutic target class.

3. SHIFT IN THERAPEUTIC PHILOSOPHY

3.1 The supportive care paradigm

The initial treatment framework emphasized:

graded rehabilitation
cognitive behavioral strategies
sleep optimization
symptomatic pharmacologic relief
exclusion of alternative diagnoses

While appropriate in early uncertainty, this framework implicitly assumes:

uniformity of underlying disease mechanism

3.2 The emerging mechanistic paradigm

Current evidence contradicts this assumption. Instead, therapeutic research increasingly assumes:

heterogeneous biology requires heterogeneous treatment strategies

This has enabled a rapid expansion of investigational therapies targeting specific biological pathways.

4. EXPANDED THERAPEUTIC LANDSCAPE (2026 SYNTHESIS)

A growing body of clinical literature and early interventional data has identified multiple candidate therapeutic classes under active investigation.

These are not yet universally validated but represent a transition from theoretical plausibility to empirical testing.

5. IMMUNE MODULATION STRATEGIES

5.1 Low-dose naltrexone (LDN)

LDN has emerged as a candidate immunomodulatory agent due to proposed effects on:

microglial activation
cytokine signaling modulation
neuroimmune interface stabilization

Preliminary observational studies suggest potential benefit in fatigue and pain-dominant phenotypes, though randomized controlled evidence remains limited.⁴

5.2 JAK inhibitors

Janus kinase inhibitors target intracellular cytokine signaling pathways implicated in inflammatory states.

Rationale includes:

suppression of aberrant cytokine signaling
modulation of interferon pathways
potential dampening of chronic immune activation

Their use remains investigational due to immunosuppression risks and need for stratified patient selection.⁵

5.3 Intravenous immunoglobulin (IVIG)

IVIG is under investigation for immune-dysregulated phenotypes based on:

immune recalibration effects
Fc receptor modulation
autoantibody neutralization potential

However, cost, access, and uncertain patient selection remain limiting factors.⁶

6. ANTIVIRAL STRATEGIES AND PERSISTENCE HYPOTHESIS

Antiviral therapies are being explored under the hypothesis that:

viral persistence or antigenic remnants may contribute to ongoing immune activation in subsets of patients

While evidence for active replication in Long COVID remains inconsistent, the possibility of tissue reservoir persistence has driven targeted antiviral trials.⁷

This represents one of the most debated mechanistic domains in the field.

7. HISTAMINE AND MAST CELL–TARGETED STRATEGIES

Antihistamines are being evaluated based on proposed mast cell activation and histaminergic dysregulation in subsets of Long COVID patients.

Mechanistic rationale includes:

mast cell degranulation pathways
neuroimmune signaling via histamine receptors
autonomic nervous system sensitization

Clinical reports suggest symptomatic improvement in select cohorts, though controlled trials remain limited.⁸

8. AUTONOMIC AND NEUROMODULATION THERAPIES

8.1 Vagus nerve stimulation

Neuromodulatory strategies aim to restore autonomic balance through:

parasympathetic activation
inflammatory reflex modulation
heart rate variability stabilization

This reflects a growing recognition of autonomic dysfunction as a central integrative pathway in Long COVID.⁹

8.2 Guanfacine

Guanfacine, an alpha-2A adrenergic agonist, is being studied for:

prefrontal cortical network stabilization
cognitive dysfunction (“brain fog”)
stress-response modulation

Its proposed mechanism is consistent with neurocognitive symptom clustering observed in Long COVID populations.¹⁰

9. METABOLIC AND ENERGETIC INTERVENTIONS

9.1 GLP-1 receptor agonists

Originally developed for metabolic disease, GLP-1 agonists are now being explored due to:

anti-inflammatory signaling properties
metabolic regulation effects
potential neuroprotective mechanisms

This reflects a broader conceptual shift linking metabolism and inflammation in post-viral syndromes.¹¹

10. COAGULATION AND MICROVASCULAR STRATEGIES

10.1 Anticoagulant and fibrinolytic approaches

These strategies target hypothesized:

microvascular clot formation
impaired fibrinolysis
endothelial injury–driven coagulation imbalance

However, they remain highly controversial due to:

bleeding risk
heterogeneous biomarker support
lack of definitive randomized evidence

11. NICOTINIC RECEPTOR MODULATION STRATEGIES

Nicotine patches (transdermal)

Exploratory hypotheses suggest that nicotinic receptor modulation may influence:

neuroinflammatory signaling
autonomic regulation
cholinergic anti-inflammatory pathways

This remains highly investigational and mechanistically speculative.¹²

12. ANTI-INFLAMMATORY REPURPOSING AGENTS

Colchicine

Colchicine is under investigation due to:

inhibition of microtubule-mediated inflammatory activation
suppression of inflammasome signaling pathways
established anti-inflammatory pharmacology in cardiovascular disease

Its role in Long COVID remains exploratory.¹³

13. KEY PARADIGM SHIFT: FROM “NO TREATMENT” TO “MULTI-PATHWAY EXPERIMENTATION”

The most significant transformation in the field is conceptual rather than pharmacologic:

Earlier paradigm:

Long COVID has no targeted treatment; management is supportive

Emerging paradigm:

Long COVID contains multiple biologically distinct subtypes, each potentially treatable through targeted intervention

This shift has enabled:

rapid expansion of clinical trials
repurposing of existing drugs
biomarker-driven hypothesis testing
increased therapeutic experimentation

14. CONCLUSION (PART I)

The treatment landscape for Long COVID has undergone a fundamental transition from supportive care–based management to mechanism-targeted experimental therapeutics. The diversity of candidate interventions now under investigation reflects a growing consensus that Long COVID is not a singular pathological entity but a heterogeneous syndrome comprising multiple overlapping biological endotypes.

This recognition has transformed the field from therapeutic pessimism into structured biological experimentation. However, without robust biomarker stratification and endotype validation, the risk of therapeutic misclassification remains substantial.

art II

(Mechanistic Drug Mapping, Endotype Targeting, and Evidence Stratification)

15. INTRODUCTION TO PART II: WHY DRUG REPURPOSING IN LONG COVID IS NOT “EMPIRICAL CHAOS”

The expansion of Long COVID therapeutics into diverse pharmacologic classes is often mischaracterized as exploratory heterogeneity without direction. In reality, the current therapeutic landscape reflects an increasingly structured attempt to map pharmacologic mechanisms onto biologically inferred endotypes.

However, because Long COVID lacks a single validated biomarker system, this mapping remains probabilistic rather than definitive. As a result, the same drug may appear effective in one subgroup and inert or harmful in another.

This section formalizes a mechanistic framework for understanding why:

therapeutic response in Long COVID is endotype-dependent, not disease-global

16. MECHANISTIC MAPPING FRAMEWORK (MULTI-AXIS MODEL)

We propose that all candidate therapies in Long COVID can be mapped across five dominant biological axes:

Immune activation / immune exhaustion axis
Endothelial / vascular injury axis
Neuroimmune / CNS dysregulation axis
Metabolic / mitochondrial dysfunction axis
Autonomic / regulatory instability axis

Each therapeutic class acts primarily on one or more of these axes.

17. IMMUNE MODULATION STRATEGIES

17.1 Low-dose naltrexone (LDN)

Mechanistic positioning:

LDN is hypothesized to act primarily on the neuroimmune and glial activation axis.

Proposed biological actions:

modulation of microglial activation states
downregulation of pro-inflammatory cytokine signaling
alteration of opioid receptor–mediated immune signaling
attenuation of central neuroinflammatory amplification loops¹

Endotype alignment:

Most consistent with:

neuroimmune-dominant Long COVID
fatigue-predominant phenotypes
pain + cognitive dysfunction clusters

Evidence status:

small observational cohorts
heterogeneous response rates
no definitive large-scale randomized evidence

Interpretation:

LDN response variability likely reflects neuroimmune endotype presence rather than universal efficacy.

17.2 JAK inhibitors

Mechanistic positioning:

JAK inhibitors operate at the intracellular cytokine signaling level, affecting multiple inflammatory cascades.

Biological effects:

inhibition of JAK-STAT signaling pathways
suppression of interferon-mediated transcriptional programs
modulation of inflammatory cytokine amplification loops²

Endotype alignment:

Most plausible in:

immune activation–dominant Long COVID
inflammatory biomarker–positive subgroups

Risk profile:

immunosuppression risk
infection susceptibility
off-target hematologic effects

Interpretation:

JAK inhibitors exemplify the risk of over-targeting inflammation in non-inflammatory endotypes.

17.3 Intravenous immunoglobulin (IVIG)

Mechanistic positioning:

IVIG functions as a broad immune recalibration therapy, not a single-pathway inhibitor.

Proposed mechanisms:

Fc receptor modulation
neutralization of autoantibodies
suppression of pathogenic immune complexes
regulatory T-cell induction³

Endotype alignment:

Most consistent with:

autoimmune-like Long COVID subsets
immune dysregulation phenotypes

Limitation:

extreme heterogeneity in response
cost and access constraints
unclear optimal dosing schedules

Interpretation:

IVIG likely acts as a system-level immune reset rather than pathway-specific intervention.

18. ANTIVIRAL STRATEGIES

18.1 Rationale for antiviral use

Antiviral therapies in Long COVID are based on the hypothesis that:

persistent viral reservoirs or antigenic remnants may sustain immune activation in a subset of patients

Evidence remains inconsistent, but includes:

detection of viral RNA fragments in some tissues
persistent immune activation signatures
serologic and antigenic persistence hypotheses⁴

18.2 Mechanistic positioning

Antivirals act on the putative upstream driver axis:

viral replication suppression
reduction of antigenic stimulation
interruption of immune activation feedback loops

18.3 Endotype alignment

Potentially relevant in:

viral persistence–dominant endotype (hypothetical subset)
early post-acute inflammatory phase

18.4 Key limitation

The central unresolved question is:

whether ongoing viral replication is causal, epiphenomenal, or absent in most Long COVID cases

Without resolution, antiviral therapy remains mechanistically high-uncertainty intervention.

19. HISTAMINE / MAST CELL TARGETING STRATEGIES

19.1 Antihistamines

Mechanistic positioning:

Histamine blockade targets the mast cell–neuroimmune interface axis.

Proposed mechanisms:

suppression of histamine-mediated vasodilation
modulation of neuroimmune signaling pathways
reduction of mast cell activation–driven inflammation⁵

Endotype alignment:

allergic/inflammatory overlap phenotypes
autonomic dysfunction with histamine sensitivity
subset of fatigue syndromes

19.2 Biological interpretation

This therapeutic class supports a broader model:

immune dysregulation in Long COVID may include mast cell–driven amplification loops in a subset of patients

20. AUTONOMIC AND NEUROMODULATION THERAPIES

20.1 Vagus nerve stimulation (VNS)

Mechanistic positioning:

VNS targets the inflammatory reflex and autonomic regulatory axis.

Biological effects:

activation of cholinergic anti-inflammatory pathways
modulation of cytokine production
restoration of autonomic balance
improved heart rate variability signaling⁶

Endotype alignment:

dysautonomia-dominant Long COVID
neuroimmune coupling dysfunction

20.2 Interpretation

VNS represents a shift toward:

neuromodulation as immunomodulation

This reflects increasing recognition that immune and nervous systems are tightly integrated regulatory networks.

20.3 Guanfacine

Mechanistic positioning:

Guanfacine acts on prefrontal cortical regulatory circuits and adrenergic signaling systems.

Proposed effects:

enhancement of executive function networks
reduction of stress-mediated cognitive interference
stabilization of prefrontal cortical signaling⁷

Endotype alignment:

cognitive dysfunction (“brain fog”)
neurocognitive-executive impairment phenotype

21. METABOLIC AND ENERGY DYSFUNCTION THERAPIES

21.1 GLP-1 receptor agonists

Mechanistic positioning:

These agents intersect metabolic regulation and inflammatory signaling pathways.

Proposed mechanisms:

modulation of systemic inflammatory tone
improvement in insulin signaling efficiency
potential neuroprotective effects⁸

Endotype alignment:

metabolic-fatigue dominant Long COVID
energy utilization impairment phenotypes

21.2 Interpretation

This represents a major conceptual shift:

metabolic therapies are increasingly viewed as immunomodulatory by indirect mechanism

22. COAGULATION AND MICROVASCULAR INTERVENTIONS

22.1 Anticoagulant and fibrinolytic approaches

Mechanistic positioning:

Target the thromboinflammatory axis.

Proposed mechanisms:

reduction of microvascular fibrin deposition
restoration of fibrinolytic balance
endothelial injury mitigation⁹

Endotype alignment:

vascular dysfunction phenotype
microcirculatory impairment subset

Critical limitation:

bleeding risk
lack of validated diagnostic criteria for microclot pathology in routine care
heterogeneous biomarker reproducibility

22.2 Clinical interpretation

This remains one of the most controversial domains because:

biological plausibility exceeds clinical validation

23. ANTI-INFLAMMATORY REPURPOSING AGENTS

23.1 Colchicine

Mechanistic positioning:

Colchicine targets the inflammasome activation axis.

Biological effects:

inhibition of microtubule assembly
suppression of NLRP3 inflammasome activation
reduction of IL-1β–mediated inflammation¹⁰

Endotype alignment:

inflammatory endotype
vascular-inflammatory overlap phenotype

24. CROSS-THERAPEUTIC INSIGHT: WHY RESPONSE VARIES

Across all therapeutic classes, a consistent pattern emerges:

treatment efficacy is conditional on biological endotype alignment

This explains:

inconsistent clinical trial outcomes
contradictory observational findings
variability in patient-reported response

The failure of uniform efficacy is not evidence of therapeutic ineffectiveness—it is evidence of underlying biological heterogeneity.

25. IMPLICATIONS FOR MODERN CLINICAL TRIAL DESIGN

The mechanistic landscape necessitates a redesign of clinical trial methodology.

25.1 Required shift:

From:

broad inclusion criteria
symptom-based enrollment

To:

biomarker-stratified cohorts
endotype-enriched randomization

25.2 Outcome measurement reform:

Beyond symptom scales:

endothelial function indices
immune signaling normalization
metabolic efficiency markers
autonomic stability metrics

26. CONCLUSION (PART II)

The therapeutic expansion in Long COVID beyond supportive care reflects a fundamental shift in post-viral medicine: from empiric symptom management toward mechanism-targeted experimental therapeutics.

However, this expansion also exposes a critical constraint:

without validated endotype stratification, pharmacologic interventions risk systematic misalignment with underlying biology

Thus, the future of Long COVID therapeutics depends not only on drug development, but on biological classification precision.

INTRODUCTION TO PART III: WHY A SAFETY BLUEPRINT IS NECESSARY

The expansion of therapeutic experimentation in Long COVID has outpaced the development of standardized clinical decision frameworks. As mechanism-targeted interventions proliferate across immune, vascular, neurologic, and metabolic domains, clinicians increasingly face a new challenge:

how to combine biologically plausible therapies without amplifying risk in a heterogeneous, incompletely classified disease state

Unlike traditional single-pathway diseases, Long COVID presents a multi-endotype structure, meaning that inappropriate combination therapies may not merely reduce efficacy—they may actively destabilize compensatory biological networks.

This section proposes a clinical algorithm and safety blueprint intended for investigational and specialty-care contexts, not routine primary care use.

28. CORE PRINCIPLE: ENDOTYPE-FIRST MEDICINE

The foundational rule of therapeutic decision-making in Long COVID is:

Treatment selection must follow dominant biological endotype probability, not symptom similarity.

Symptom overlap (fatigue, brain fog, dysautonomia) is not diagnostic of shared mechanism.

29. STEPWISE CLINICAL ALGORITHM (NEJM-STYLE FRAMEWORK)

STEP 1 — CLINICAL PHENOTYPING SCREEN

Classify patient into dominant symptomatic cluster:

A. Fatigue-dominant

post-exertional malaise
energy collapse states
sleep non-restorative patterns

B. Neurocognitive-dominant

attention dysfunction
processing slowing
“brain fog” phenotype

C. Autonomic-dominant

tachycardia
orthostatic intolerance
heart rate variability instability

D. Cardiopulmonary-dominant

dyspnea disproportionate to imaging
exercise intolerance
chest discomfort

E. Mixed systemic phenotype

overlapping multisystem involvement

STEP 2 — RISK STRATIFICATION SCREEN

Before any mechanism-targeted therapy, assess:

2.1 Cardiovascular risk

clotting history
arrhythmia history
baseline BP variability

2.2 Immune risk

recurrent infections
autoimmune disease history
immunosuppressive vulnerability

2.3 Neuropsychiatric vulnerability

cognitive baseline impairment
psychiatric comorbidity
medication sensitivity

STEP 3 — PROVISIONAL ENDOTYPE MAPPING (WEIGHTED MODEL)

Assign probability weights:

Immune activation endotype
Endothelial dysfunction endotype
Neuroimmune dysfunction endotype
Metabolic impairment endotype
Autonomic instability endotype

No patient is assumed to have a single endotype.

STEP 4 — THERAPEUTIC SELECTION MODULE

Select therapy only after dominant endotype estimation.

30. THERAPEUTIC MODULES AND SAFETY RULES

MODULE A — IMMUNE MODULATION PATHWAY

Candidate therapies:

low-dose naltrexone (LDN)
JAK inhibitors
IVIG

INDICATION:

immune activation signature
inflammatory biomarker elevation
autoimmune overlap suspicion

SAFETY RULES:

Avoid combining JAK inhibitors + other systemic immunosuppressants outside trials
Monitor infection risk rigorously
IVIG requires exclusion of hyperviscosity or renal risk

CONTRAINDICATION CLUSTER:

untreated active infection
severe immunodeficiency states
unstable cardiovascular disease (for high-dose IVIG contexts)

MODULE B — NEUROIMMUNE / COGNITIVE MODULE

Candidate therapies:

guanfacine
LDN
vagus nerve stimulation
antihistamines (selective use)

INDICATION:

cognitive dysfunction dominant
executive function impairment
neuroinflammatory symptom cluster

SAFETY RULES:

avoid sedative stacking (antihistamine + central alpha agonists without titration)
monitor hypotension and bradycardia risk (guanfacine + VNS synergy)
cognitive monitoring required before dose escalation

MODULE C — AUTONOMIC DYSREGULATION MODULE

Candidate therapies:

vagus nerve stimulation
beta-blocker–class agents (outside scope here)
behavioral autonomic retraining approaches

INDICATION:

orthostatic intolerance
tachycardia syndromes
heart rate variability instability

SAFETY RULES:

avoid aggressive blood pressure suppression in hypoperfusion phenotypes
monitor syncope risk with neuromodulation initiation
avoid combining multiple autonomic suppressors without titration

MODULE D — METABOLIC / ENERGY FAILURE MODULE

Candidate therapies:

GLP-1 receptor agonists (investigational context)
structured metabolic rehabilitation approaches

INDICATION:

exertional intolerance disproportionate to cardiopulmonary findings
post-exertional symptom exacerbation
metabolic signature abnormalities

SAFETY RULES:

monitor for hypoglycemia risk in susceptible individuals
avoid unnecessary weight-loss potentiation in non-metabolic phenotype
ensure nutritional stability before initiation

MODULE E — VASCULAR / COAGULATION MODULE

Candidate therapies:

anticoagulant strategies (carefully selected contexts)
fibrinolytic approaches (highly investigational)

INDICATION:

vascular dysfunction phenotype
suspected microvascular impairment
abnormal coagulation biomarker profile (if validated)

SAFETY RULES (CRITICAL):

high hemorrhage risk category
avoid empiric combination therapy
strict exclusion of bleeding disorders
imaging/biomarker confirmation strongly preferred

MODULE F — MAST CELL / HISTAMINE MODULE

Candidate therapies:

antihistamines (H1/H2 class)

INDICATION:

histamine sensitivity phenotype
flushing, tachycardia, allergic overlap symptoms

SAFETY RULES:

sedation stacking risk with CNS-active agents
caution in autonomic hypotension phenotype
avoid polypharmacy escalation without response monitoring

31. GLOBAL SAFETY BLUEPRINT (NON-NEGOTIABLE PRINCIPLES)

PRINCIPLE 1 — DO NOT TREAT ALL LONG COVID AS INFLAMMATORY

Inflammation is present in some, absent in others. Universal immunosuppression is unsafe.

PRINCIPLE 2 — AVOID MULTI-DRUG MECHANISTIC STACKING WITHOUT ENDOTYPE CONFIRMATION

Stacking increases risk of:

autonomic collapse
immune suppression
metabolic destabilization
neurocognitive worsening

PRINCIPLE 3 — MONOTHERAPY PRIORITY IN EARLY PHASES

Initial intervention should be:

single-mechanism targeting before combinatorial therapy

PRINCIPLE 4 — AVOID ANTICOAGULATION WITHOUT CLEAR VASCULAR SIGNAL

Because:

microvascular hypotheses remain incompletely validated
bleeding risk outweighs speculative benefit in unselected patients

PRINCIPLE 5 — MONITOR RESPONSE AS BIOLOGICAL FEEDBACK, NOT JUST SYMPTOM CHANGE

Key monitored domains:

exertional tolerance
cognitive clarity
autonomic stability
inflammatory markers (when available)

32. CLINICAL DECISION FLOW (TEXTUAL ALGORITHM)

Identify symptom cluster
↓
Screen risk domains
↓
Assign provisional endotype weights
↓
Select single primary therapeutic module
↓
Initiate low-dose, titrated intervention
↓
Monitor multi-system response (not single symptom)
↓
Reclassify endotype weighting after 4–12 weeks
↓
Consider cautious secondary module if stable

33. INTEGRATED CLINICAL INTERPRETATION

The therapeutic landscape in Long COVID is not a linear escalation model. It is a dynamic reclassification system, where:

diagnosis is probabilistic
treatment is adaptive
response informs biology

This represents a departure from classical NEJM-style single-pathway therapeutics and instead aligns with:

systems medicine applied to post-infectious multisystem disease

34. FINAL CONCLUSION

The evolution of Long COVID treatment from supportive care to mechanism-targeted experimentation reflects a fundamental transformation in post-viral medicine. However, this expansion introduces a parallel challenge: therapeutic overextension in the absence of validated endotype boundaries.

This manuscript proposes a structured clinical algorithm and safety blueprint grounded in five principles:

endotype-first treatment selection
single-mechanism initiation strategy
strict avoidance of unsupervised polypharmacy stacking
vascular and immune risk gating
response-guided biological reclassification

Together, these principles aim to reduce harm while preserving therapeutic innovation in a biologically heterogeneous disease landscape.

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