IIRC, MUC1 is poorly glycosylated in cancer cells as opposed to normal cells. As a result, MUC1 on cancer cells is supposedly more "exposed".
If proper glycosylation is what makes it work, they’d better make money quickly before the patent runs out and the product goes generic… there’s a company I know that’s pretty good at characterizing stuff like that :- )
If I remember the party line correctly, the low glycosylation of MUC1 was supposed to better expose the amino acid backbone covered by the BLP25 peptide sequence.
So we're talking a super subtle mechanism here.
Regardless, I don't think they really elicit a directed immune response so from my perspective it's not all that interesting.