IgA multi-specific binding molecules

1. A dimeric bispecific IgA antibody comprising two binding units in end-to-end configuration and a J-chain, wherein each binding unit is bispecific, each having the same two binding specificities, AB, AB, wherein each binding unit comprises two IgA heavy chain constant region sequences each comprising at least a CA3 domain, two light chain constant region sequences, two heavy chain variable region (V H ) sequences, and two light chain variable region (V L ) sequences, wherein the V H and V L combine to form two V H V L antigen-binding regions each binding to a different epitope, wherein an asymmetric interface exists between the two IgA heavy chain constant regions in each binding unit via a knob-into-hole modification comprising:

(a) (i) a knob modification comprising a substitution of L220 with M and T236 with W; and

(ii) a hole modification comprising:

(1) a substitution of L220 with K, R, or W;

(2) a substitution of T236 with G; and/or

(3) a substitution of T282 with I, V, or L;

(b) (i) a knob modification comprising a substitution of L220 with M, H, F, or Y, T236 with F, and T282 with G; and

(ii) a hole modification comprising:

(1) a substitution of L220 with K, R, or W;

(2) a substitution of T236 with V or I; and/or

(3) a substitution of T282 with V;

(c) (i) a knob modification comprising a substitution of L220 with M, T236 with Y, and T282 with G; and

(ii) a hole modification comprising:

(1) a substitution of L220 with K, R, or W; and/or

(2) a substitution of T236 with V;

(d) (i) a knob modification comprising a substitution of L220 with F, Y, or M, T236 with S, L238 with F, and T282 with S; and

(ii) a hole modification comprising:

(1) a substitution of L220 with K, R, or W; and/or

(2) a substitution of T236 with S;

(e) (i) a knob modification comprising a substitution of L220 with W; and

(ii) a hole modification comprising:

(1) a substitution of L220 with K or R; and/or

(2) a substitution of T236 with G; or

(f) (i) a knob modification comprising a substitution of T234 with S and I284 with For W; and

(ii) a hole modification comprising:

(1) a substitution of L220 with K, R, or W;

(2) a substitution of L238 with G or A;

(3) a substitution of A280 with M; and/or

(4) a substitution of T282 with S;

wherein the amino acid numbering corresponds to SEQ ID NO: 2.

2. The dimeric bispecific IgA antibody of claim 1 , wherein the asymmetric interface between the two IgA heavy chain constant regions in each binding unit further comprises a salt-bridge charge modification, wherein the salt-bridge charge modification comprises:

(A) one of the two IgA heavy chain constant regions comprising a substitution of H218 with D or E and the other of the two IgA heavy chain constant regions comprising a substitution of E225 with K or R; or

(B) one of the two IgA heavy chain constant regions comprising a substitution of E225 with K or R, R240 with D or E, or R286 with D or E and the other of the two IgA heavy chain constant regions comprising a substitution of E225 with K or R, R240 with D or E, or R286 with D,

wherein the amino acid numbering corresponds to SEQ ID NO: 2.

3. The dimeric bispecific IgA antibody of claim 1 or claim 2 , wherein the correct association of the light chains and their cognate heavy chains is achieved by exchange of heavy-chain and light-chain domains within the antigen binding fragment (Fab) of one half of each bispecific antibody binding unit via crossover of the VH and VL domains.

4. The dimeric bispecific IgA antibody of claim 1 or claim 2 , wherein the IgA heavy chain constant regions are IgA1 heavy chain constant regions.

5. The dimeric bispecific IgA antibody of claim 1 or claim 2 , wherein the IgA heavy chain constant regions are IgA2 heavy chain constant regions.

6. The dimeric bispecific IgA antibody of claim 1 or claim 2 , wherein the J chain comprises the sequence of SEQ ID NO: 3.

7. The dimeric bispecific IgA antibody of claim 2 , wherein the heavy chain constant regions are human IgA2 constant regions comprising SEQ ID NO: 4 and SEQ ID NO: 5, respectively, and wherein the light chain constant regions each comprise SEQ ID NO: 6.

8. The dimeric bispecific IgA antibody of claim 3 , wherein the heavy chain constant regions are human IgA2 constant regions comprising SEQ ID NO: 4 and SEQ ID NO: 8, respectively, and wherein the light chain constant regions comprise SEQ ID NO: 6 and SEQ ID NO: 9, respectively.

9. The dimeric bispecific IgA antibody of claim 1 or claim 2 , which specifically binds to two different antigens of a respiratory syncytial virus (RSV).

10. The dimeric bispecific IgA antibody of claim 9 , which binds to RSV F and RSV G.

11. The dimeric bispecific IgA antibody of claim 10 , wherein each binding unit comprises the heavy chains SEQ ID NO: 10 and SEQ ID NO: 12, respectively and the light chains SEQ ID NO: 11 and SEQ ID NO: 13, respectively.

12. The dimeric bispecific IgA antibody of claim 1 or claim 2 , which specifically binds to two different hemagglutinin (HA) antigens of influenza A virus.

13. The dimeric bispecific IgA antibody of claim 12 , wherein each binding unit comprises the heavy chains SEQ ID NO: 14 and SEQ ID NO: 16, respectively and the light chains SEQ ID NO: 15 and SEQ ID NO: 17, respectively.

14. The dimeric bispecific IgA antibody of claim 1 or claim 2 , which specifically binds to two different antigens of Clostridium difficile ( C. difficile ).

15. The dimeric bispecific IgA antibody of claim 14 , which binds to Toxin A and Toxin B of C. difficile.

16. The dimeric bispecific IgA antibody of claim 15 , wherein each binding unit comprises the heavy chains SEQ ID NO: 18 and SEQ ID NO: 20, respectively and the light chains SEQ ID NO: 19 and SEQ ID NO: 21, respectively.

17. A pharmaceutical composition comprising an effective amount of the dimeric bispecific IgA antibody of claim 1 or claim 2 in admixture with a pharmaceutically acceptable carrier.