I haven't seen the new Thom et al. publication yet on the Journal of Cerebral Blood Flow and Metabolism website (http://journals.sagepub.com/home/jcb). It should be out soon. On slide 14 of the latest corporate presentation, underneath the graph it stated "Thom, et al. J. Cereb. Blood Flow Metab. 2018 (manuscript accepted)." Thom G has some nice prior publications in the pain research area.

On that slide 14, it shows the excellent brain exposure for the xB3-Ab1 fusion compared to Ab1 alone. The slide indicates that two xB3 fusion proteins were made: xB3-Ab, xB3-Ab-ILXX. I'm pretty sure that this is the MedImmune pain collaboration based on the similarity to the data I review below. We'll have to wait to see the paper for the details. 

Perhaps a clue lies in a previous slide deck from 2017 (pre-Mark Day I believe) that showed data for a MedImmune colloboration using the Mtf AND Mtfp fusions to IgG1-IL1Ra. I'm assuming that this was a rodent pain model. They achieved great brain exposure, as well as fast and prolonged reduction in pain dependent upon delivery across the BBB. Importantly, the IgG1-IL1Ra w/o the Mtf or Mtfp did not elicit the analgesic response.

Summary slide stated: