The presence of TDP-43 seeding-competent species in CSF of ALS patients reinforces the rational for TDP-43 immunotherapy, using, for example, the high-affinity TDP-43 mAb, ACI-5891.28 To test whether the humanized mAb ACI-5891.9 could prevent seeding in ALS CSF samples, target binding and mAb concentration required to saturate TDP-43 in the CSF was evaluated. The gene discussed is TARDBP; the disease is amyotrophic lateral sclerosis.