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Key Clinical Summary: Advancing Pompe Care - Applying Triple-S to Treatment Decisions

This is a micro-learning module summary of a presentation by Prof. Pascal Laforêt which you can find here. Before participating, please read our CME and disclosure information which can be found here.

This activity is supported by an independent medical educational grant from Amicus Therapeutics. This online education program has been designed for healthcare professionals globally (excluding the USA).

Applying the European Triple-S Framework in Late-Onset Pompe Disease (LOPD)
Aligned with Learning Objective 3

Long-term experience with enzyme replacement therapy (ERT) in LOPD demonstrates meaningful early benefit in many patients, but substantial heterogeneity in response and frequent secondary decline over time. These realities demand structured, evidence-informed, and patient-centred decision-making when considering starting, switching, or stopping therapy.

The European Triple-S framework (Start – Switch – Stop) provides a practical structure for these decisions.

1. START: When to Initiate Therapy

Core Principle

Treatment initiation should be guided by evidence of clinical or subclinical disease progression, not symptom severity alone.

Indications to Start

A. Symptomatic patients

  • Skeletal muscle weakness on examination
  • Respiratory involvement detectable on pulmonary function testing (especially sitting and supine VC assessments)

B. Subclinical but progressive disease

  • Progressive diaphragmatic dysfunction (sometimes only detected by supine VC assessment)
  • Increasing fat fraction on muscle MRI
  • Objective decline on timed tests or walk tests

Importantly, patients may lack overt symptoms yet demonstrate measurable structural or respiratory progression. In such cases, MRI fat replacement and supine VC decline can support treatment initiation.

Shared Decision-Making Considerations

When discussing initiation:

  • Expected stabilization (rather than recovery)
  • Treatment burden (biweekly infusions, hospital attendance)
  • Individual disease trajectory
  • Patient priorities and life context

Clinical Insight: In pre-symptomatic or minimally symptomatic patients, structured monitoring data can clarify the tipping point between watchful waiting and proactive treatment.

2. SWITCH: Managing Suboptimal Response

Why Switching Is Considered

Comparative-effectiveness experience shows:

  • Initial stabilization is common
  • Secondary decline may occur after 3–5 years
  • A subset of patients demonstrate persistent deterioration despite therapy

Accepted Reasons to Switch

  • Lack of stabilization or improvement after ≥12 months of treatment
  • Progressive decline in motor and/or respiratory function
  • Severe infusion-associated reactions not manageable with premedication

Evaluating True Treatment Failure

Before switching, assess:

  • Adherence
  • Monitoring consistency
  • Confounding factors (age, comorbidities, sarcopenia)
  • Objective multi-domain decline (not a single metric)

After Switching

  • Close reassessment every 6 months initially
  • Minimum 12-month evaluation period
  • Multimodal monitoring (motor, respiratory, MRI, PROs)

Clinical Insight: Switching should be individualized. Current evidence does not uniformly guarantee superiority of newer agents; careful outcome tracking is essential.

3. STOP: When to Reconsider Continuation

Although less common, discontinuation may be considered when:

  • Advanced, irreversible muscle damage with minimal functional reserve
  • No demonstrable stabilization despite prolonged therapy
  • Patient preference after informed discussion
  • Severe intolerance without alternatives

Stopping therapy should never be automatic. It requires:

  • Documentation of disease trajectory
  • Confirmation of lack of meaningful benefit
  • Thorough discussion of risks and expectations

Ethical Principle: Decisions to discontinue are as complex as decisions to initiate. The patient’s values, quality of life, and treatment burden must remain central.

Integrating Comparative-Effectiveness Evidence

Real-world registry data highlight:

  • High inter-individual variability
  • Absence of predictive factors of response to therapy
  • Nearly half of patients may show limited long-term improvement
  • Secondary decline underscores need for next-generation therapies

This reinforces that:

  • ERT is not uniformly disease-modifying in all patients
  • Monitoring must guide adaptation of treatment strategy
  • Static management is inappropriate in a progressive disease

Applying the Triple-S Framework in Practice

Step 1: Collect Structured Data

  • 6MWT or 2MWT
  • Timed tests
  • Supine and sitting VC
  • Muscle MRI
  • PROs

Step 2: Interpret Longitudinal Trends

  • Stabilization vs. slope of decline
  • Structural progression vs. functional stability
  • Respiratory vs. skeletal trajectory

Step 3: Conduct Shared Decision Discussion

Address:

  • Goals of therapy (stabilization vs improvement)
  • Treatment logistics
  • Risk–benefit balance
  • Emotional and psychological readiness
  • Long-term expectations

Case-Based Learning Themes

Across presented cases:

  • Pre-symptomatic patients required careful monitoring before starting therapy.
  • Long-standing patients with slow progression demonstrated that treatment decisions may be delayed but remain appropriate.
  • Patients with clear motor decline despite stable respiratory function (or vice versa) highlighted the need to consider switching.
  • Reluctant patients emphasized that informed autonomy must be respected.

Practical Algorithm

START when:

  • Objective skeletal or respiratory progression is documented
  • MRI shows meaningful fat replacement
  • Diaphragm decline emerges even without symptoms

SWITCH when:

  • No stabilization after ≥12 months
  • Progressive decline despite adherence
  • Unmanageable infusion reactions

STOP when:

  • No measurable benefit after prolonged reassessment
  • Severe intolerance
  • Patient preference after informed counselling

Take-Home Messages

  • The Triple-S framework transforms treatment decisions from reactive to structured and individualized.
  • Initiation should be based on measurable progression—not symptom severity alone.
  • Switching requires objective evidence of suboptimal response and close post-switch monitoring.
  • Discontinuation decisions demand careful ethical and clinical evaluation.
  • Shared decision-making is central at every stage.

In LOPD, therapy decisions are not one-time events—they are longitudinal, data-driven, and patient-centred processes guided by evolving evidence and structured monitoring.

Content accurate at the time of publication.