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1) A new randomized trial in Long Covid patients tested Temelimab, a drug that targets a potentially pathogenic protein (HERV-W ENV) from endogenous retroviruses. Unfortunately, the results are pretty clear: Temelimab had no beneficial effect.

2) Endogenous retroviruses are virus remnants that we inherit and are already inside our genome. Almost all of them are broken and switched off. The hypothesis, however, is that a viral infection such as SARS-CoV-2 may reactivate some of their functions.

4) There were a couple of Long Covid studies that reported increased HERV-W ENV in Long Covid patients. This trial therefore used this as an inclusion criterion in their trial. It focused only on LC patients who were positive for HERV-W ENV in their blood.

5) This was a large placebo-controlled and international trial: it recruited 203 patients from three European countries (Switzerland, Italy, and Spain) involving 14 centers. The primary outcome was the PROMIS Fatigue SF 7a scale.

6) The main result is shown in the figure below. Temelimab had no effect on fatigue, and the same null results were seen for the secondary outcomes, including several cognitive tests and biomarkers.