Long acting multi-specific molecules and related methods

A compound of the Formula Ib:

• wherein:
• P is a polyethylene glycol (PEG);
• B is H, a terminal capping group or void, said capping group selected from C1-50 alkyl and aryl, wherein one or more carbons of said alkyl may be replaced with a heteroatom;
• T is a tri-functional linker, wherein the linkage between T and (L1)a and the linkage between T and (L2)b are the same or different;
• wherein said linkage between T and (L1)a or T and (L2)b is derived from hydroxyl, amino, hydrazinyl, carboxyl, thiol, halide, alkene, anhydride, or maleimide;
• or combinations thereof;
• each of L1 and L2 is independently a bifunctional linker;
• a and b are each an integer selected from 1 to 10;
• one of A1 and A2 is a protein encoded by SCACD3 (SEQ ID No:
• 3) and the other is a protein encoded by SCACD19 (SEQ ID No. 4);
• and
• y is 1.