Solanezumab, or sola, binds the amyloid-βpeptides that aggregate and form plaques in the brain that are an early pathological feature of Alzheimer's disease. Sola binds the central epitope of monomeric amyloid-β, KLVFFAD, (PDB ID 4XXD) with picomolar affinity. This epitope is known as the nucleation site for Aβ oligomerization, and it is these oligomers of Aβ that are thought to be toxic to neurons.
The two Phase III trials were EXPEDITION 1 and EXPEDITION 2. EXPEDITION 1 didn't meet the predefined assessments. Lilly changed the predefined study goal in EXPEDITION 2, but EXPEDITION 2 didn't meet that goal either.
An ex-FDA official told the Financial Times that solanezumab "does not have a snowball’s chance in a very hot place" of getting conditional approval. To the FDA, missing the primary endpoint in a Phase III trial is "fatal."
^Watt, Andrew D.; Crespi, Gabriela A. N.; Down, Russell A.; Ascher, David B.; Gunn, Adam; Perez, Keyla A.; McLean, Catriona A.; Villemagne, Victor L.; Parker, Michael W.; Barnham, Kevin J.; Miles, Luke A. (2014). "Do current therapeutic anti-Aβ antibodies for Alzheimer's disease engage the target?". Acta Neuropathologica127 (6): 803–10. doi:10.1007/s00401-014-1290-2. PMID24803227.