Ang 2014 — Ketotifen in FM: Phase 1 RCT (NEGATIVE)

One-paragraph summary

The single most consequential negative result for the H2 (Mast-Cell Inflammatory) hypothesis in the project's evidence base. Phase 1 randomized, placebo-controlled trial of the mast cell stabilizer ketotifen (2 mg BID × 8 weeks) vs. placebo in 51 unstratified fibromyalgia patients. The trial was NEGATIVE — no improvement on any FM symptom measure. The authors explicitly discussed three explanations: (1) mast cells are not major contributors to FM pathogenesis; (2) mast cells play a role only in a subset of FM patients (which would justify subtype-stratified retrial rather than abandoning the hypothesis); (3) the degree of mast cell stabilization achieved by 8 weeks of ketotifen at this dose was inadequate. The 2026 Morcos & Theoharides review framed mast cells as "a central contributor" to PASC neuropathy and analogous syndromes; this 2014 trial result establishes that the mast cell hypothesis as 'all FM' is empirically refuted in the only RCT yet conducted. The H2 hypothesis remains tenable as a subtype mechanism, but any future MC-directed FM trial must use subtype stratification (anti-SGC IgG +/-, MC marker +/-) to avoid repeating this null result. The trial is therefore a strong argument for the biomarker-mapping cohort study (Q14/Q19/Q27) before any new MC-directed FM trial.

Claims as triples

• mast_cell — does not modulate → widespread_pain (in unstratified FM) [evidence: phase 1 RCT n=51 negative; confidence: emerging]
• ketotifen — does not modulate → widespread_pain (in unstratified FM) [evidence: same; confidence: emerging]

(Note: both encoded informally — the ontology grammar lacks a clean negative-effect predicate; details captured in the ketotifen entity description and this paper's notes.)

Methods note

Phase 1 RCT. n=51 FM patients. Ketotifen 2 mg BID × 8 weeks vs. placebo. Standard FM outcome measures (FIQ, pain VAS, etc. — full text needed for specifics). Single-site or small multi-site; design intentionally exploratory.

Limitations

• Unstratified FM cohort — the trial enrolled all-comers FM, not MC-active or anti-SGC IgG positive subsets. The negative result therefore does NOT refute "MC stabilization helps a subset of FM" — only "MC stabilization doesn't help unstratified FM."
• Ketotifen mast-cell stabilizing potency is moderate. Other agents (cromolyn, antihistamine combinations, leukotriene antagonists) may have different effect sizes.
• 8-week duration may be insufficient if MC dysfunction has produced downstream effects (e.g., established central sensitization) that don't reverse on the same timescale as MC stabilization.
• Phase 1 — small sample, primarily safety-focused; not powered to detect modest efficacy.
• The trial was 12 years before the 2026 reframing of MC-FM as a subset phenomenon — different conceptual era of the hypothesis.

Open questions raised

• Would ketotifen show effect in MC-active-but-anti-SGC-IgG-negative FM? (This is the H2-dominant cell of the 2×2 matrix; never tested.)
• Would a more potent stabilizer (cromolyn + antihistamine + leukotriene antagonist combination) at higher dose for longer duration show effect in unstratified FM? (Would distinguish "wrong drug/dose" from "wrong patients.")
• What's the smallest stratified-RCT sample size that could detect MC-active-subset response with 80% power? (Critical for any future MC-FM trial design.)

Triangulation notes

• Reshapes the H2 (Mast-Cell) chain status in causal-chain-hypotheses.md. The chain is no longer "candidate parallel mechanism alongside H1" with equal prior weight; it's "candidate parallel mechanism but weakened by null trial in unstratified FM, requiring subtype-stratified retrial before further therapeutic deployment."
• Strengthens the case for the biomarker-mapping cohort. Without subtype identification, MC-directed trials risk repeating the Ang 2014 outcome. The cohort proposed in causal-chain-hypotheses.md Q14/Q19/Q27 becomes the prerequisite gate for any MC-FM trial.
• Compatible with H1 dominance. If H1-dominant patients (anti-SGC IgG positive) constitute ~37% of severe FM (Seefried 2025) and are largely distinct from MC-active patients, then most FM patients in an unstratified cohort are NOT MC-active, and a null MC-stabilization result in unstratified FM is exactly what the matrix predicts.

Bridges

• B6 (post-infectious nociplastic conditions): the analogous question in long COVID and ME/CFS is whether MC-stabilization works in MC-active-stratified post-viral patients. No RCT yet; would test the H2 mechanism in its predicted population.