Fluge & Mella 2025 — Daratumumab pilot in ME/CFS
One-paragraph summary
Open-label pilot trial of daratumumab (anti-CD38 monoclonal antibody, plasma-cell-depleting) in 10 patients with severe ME/CFS, conducted by the same Norwegian group whose earlier rituximab phase 3 in ME/CFS was negative. 6 of 10 patients were marked responders; mean SF-36 Physical Function score increased from 25.9 to 55.0 at 8-9 months (p=0.002, paired test); DePaul Symptom Questionnaire–Short Form decreased from 72.3 to 43.1 (p=0.002). Multiple patients reached normal physical function. The mechanistic interpretation is highly consequential for FM: rituximab's failure was explained by sparing of plasma cells (which are CD20-negative and continue producing pathogenic IgG); daratumumab's success suggests that plasma-cell depletion, rather than B-cell depletion, is the active mechanism for autoantibody-mediated post-infectious nociplastic syndromes. Phase 2 RCT (n=66) is now underway. For the FM project, this changes the preferred B-lineage agent for BASIS-FM stage 3 from rituximab to daratumumab, and provides cross-condition support for bridge B4 (ME/CFS ↔ FM via post-viral neuroimmune mechanism).
Claims as triples
- fm_autoimmune — responds_to → daratumumab [evidence: bridging from ME/CFS pilot; confidence: bridging]
- IgG_fm — present_in → me_cfs [evidence: clinical response to plasma-cell depletion; confidence: emerging]
- daratumumab — modulates → autoantibody_mediated_pain [evidence: SF-36 PF and DSQ-SF improvement; confidence: emerging]
Methods note
Open-label, single-arm pilot. n=10 severe ME/CFS patients (ICC criteria). Daratumumab 16 mg/kg IV weekly × 8 weeks induction, then biweekly × 8 weeks consolidation. Endpoints: SF-36 PF, DePaul Symptom Questionnaire-Short Form. Follow-up ≥1 year. Norwegian group (Haukeland University Hospital, Bergen) — same investigators as the rituximab-ME/CFS trials.
Limitations
- Open-label, no placebo control. Placebo response in ME/CFS for similar interventions has been documented at ~20-30%; observed 60% response rate is above placebo threshold but not definitively so without RCT.
- Small sample (n=10).
- ME/CFS ≠ FM — direct extrapolation requires the autoantibody mechanism to operate similarly in both conditions, which is a chain B4 claim still being established.
- Daratumumab carries oncology-grade infusion-reaction risk; cost and safety profile would need substantial favorable phase 2 data before FM deployment.
- The 4/10 non-responders weren't characterized for any biomarker that would predict response — subtype-prediction remains open.
Open questions raised
- What predicted response in the 6 responders? Pre-treatment biomarkers were measured but the pilot didn't have power to identify a stratification rule.
- Does daratumumab response track with anti-SGC IgG titer reduction? (Direct mechanistic test — would close part of the H1 chain in vivo.)
- Could a lower-cost / lower-risk plasma-cell-targeting strategy (e.g., bortezomib in shorter course) achieve similar effect without daratumumab's profile?
- Phase 2 RCT (n=66) result expected — when?
Triangulation notes
- Reshapes BASIS-FM stage 3 plans. The original staged research program (in
research-design-Q17-microbiome-igg.md) referenced "B-cell-directed therapy" generally; this paper specifically argues plasma-cell depletion (CD38) over B-cell (CD20). Stage 3 should be daratumumab-anchored. - Cross-condition mechanism support. If plasma-cell depletion works in ME/CFS, the autoantibody-mediated mechanism extends across at least one of the project's bridge-B4 conditions. Closes part of B4.
- Compatible with the Goebel-Krock-Seefried autoimmune-FM lineage at the mechanism level: same reasoning (autoantibodies → SGC activation → symptoms; remove autoantibodies → improvement) but applied at a different B-lineage depletion target.
- Critical caveat for the H2 hypothesis: if daratumumab works in some ME/CFS patients via plasma-cell depletion, the working assumption that all post-viral nociplastic syndromes share an MC-driven mechanism (Morcos & Theoharides 2026) becomes harder to sustain. The autoantibody mechanism may be more dominant in this population than the MC mechanism is.
Bridges
- B3 (CRPS ↔ FM via pathogenic IgG): daratumumab in CRPS is a natural follow-up trial.
- B4 (ME/CFS ↔ FM via post-viral neuroimmune): significantly strengthened — first interventional cross-condition evidence supporting the shared autoantibody mechanism.
- B6 (Predictive-coding / interoceptive-inference failure): if daratumumab improves objective function in ME/CFS but not via interoceptive-deficit reversal, this would suggest H3 is downstream of H1 rather than parallel to it. Worth co-measuring.