Koo,

You totally put my post you linked into a different context. In that post, I was talking about strategies to bypass the BBB for drugs that are known to be unable to cross the BBB. However, some, but not all, drugs can naturally cross the BBB. This is dependent upon the size of the molecule, the solubility (fat/lipid soluble vs. water soluble) of the molecular, and other molecular properties. Many small, lipid-soluble molecules can cross the BBB by transmembrane diffusion. However, many of these may cross the BBB but get pumped back out by active transport systems (i.e. P-glycoprotein). 

I do not know if apabetalone can cross the BBB. But if it cannot, and if one believes that getting apabetalone into the brain is desirable, then yes one could attach the Mtfp (aka xB3) peptide linker from BTI to apabetalone to attempt to increase the brain exposure to apabetalone. 

BearDownAZ