A conjugate comprising an isolated antibody that specifically binds to the extracellular region of SLC34A2 and one or more D-carrying polymeric scaffolds connected to the isolated antibody, wherein each of the one or more D-carrying polymeric scaffolds independently is of Formula (Ic): wherein: the scaffold comprises poly(1-hydroxymethylethylene hydroxymethyl-formal) having a molecular weight ranging from about 2 kDa to about 40 kDa; each occurrence of D is independently a therapeutic agent having a molecular weight of ≤ 5 kDa; L D1 is a carbonyl-containing moiety; each occurrence of in is independently a first linker that contains a biodegradable bond so that when the bond is broken, D is released in an active form for its intended therapeutic effect; and the in between L D1 and D denotes direct or indirect attachment of D to L D1, each occurrence of is independently a second linker not yet connected to the isolated antibody, in which L P2 is a moiety containing a functional group that is yet to form a covalent bond with a functional group of the isolated antibody, and the between L D1 and L P2 denotes direct or indirect attachment of L P2 to L D1, and each occurrence of the second linker is distinct from each occurrence of the first linker; each occurrence of is independently a third linker that connects each D-carrying polymeric scaffold to the isolated antibody, in which the terminal attached to L P2 denotes direct or indirect attachment of L P2 to the isolated antibody upon formation of a covalent bond between a functional group of L P2 and a functional group of the isolated antibody; and each occurrence of the third linker is distinct from each occurrence of the first linker; m is an integer from 1 to about 300, m 1 is an integer from 1 to about 140, m 2 is an integer from 1 to about 40, m 3 is an integer from 0 to about 18, m 4 is an integer from 1 to about 10; the sum of m, m 1, m 2, m 3, and m 4 ranges from 15 to 300; and the total number of L P2 connected to the isolated antibody is 10 or less. the scaffold comprises poly(1-hydroxymethylethylene hydroxymethyl-formal) having a molecular weight ranging from about 2 kDa to about 40 kDa; each occurrence of D is independently a therapeutic agent having a molecular weight of ≤ 5 kDa; L D1 is a carbonyl-containing moiety; each occurrence of in is independently a first linker that contains a biodegradable bond so that when the bond is broken, D is released in an active form for its intended therapeutic effect; and the in between L D1 and D denotes direct or indirect attachment of D to L D1, each occurrence of is independently a second linker not yet connected to the isolated antibody, in which L P2 is a moiety containing a functional group that is yet to form a covalent bond with a functional group of the isolated antibody, and the between L D1 and L P2 denotes direct or indirect attachment of L P2 to L D1, and each occurrence of the second linker is distinct from each occurrence of the first linker; each occurrence of is independently a third linker that connects each D-carrying polymeric scaffold to the isolated antibody, in which the terminal attached to L P2 denotes direct or indirect attachment of L P2 to the isolated antibody upon formation of a covalent bond between a functional group of L P2 and a functional group of the isolated antibody; and each occurrence of the third linker is distinct from each occurrence of the first linker; m is an integer from 1 to about 300, m 1 is an integer from 1 to about 140, m 2 is an integer from 1 to about 40, m 3 is an integer from 0 to about 18, m 4 is an integer from 1 to about 10; the sum of m, m 1, m 2, m 3, and m 4 ranges from 15 to 300; and the total number of L P2 connected to the isolated antibody is 10 or less.