A monoclonal antibody molecule comprising a variable region that recognizes a trimeric or tetrameric human Aβ, wherein the variable region comprises a combination of CDRs of antibody NT4X-167 except for up to four substitutions in the combination of CDRs, and: a) wherein the combination of CDRs comprises H-CDR1, H-CDR2, H-CDR3, L-CDR1, L-CDR2, and L-CDR3 as shown in SEQ ID NOs: 9, 10, 11, 12, 13, and 14, respectively (NT4X-167); b) wherein the monoclonal antibody molecule recognizes a conformational epitope of trimeric or tetrameric human Aβ, wherein the epitope is formed by Phe at amino acid position 4 and the amino acids at positions 2 and 3 of said trimeric or tetrameric human Aβ; and wherein the antibody molecule competes with antibody NT4X-167 for the said conformational epitope as determined by pepscan ELISA comprising the steps of precoating with 100 ng Aβ 4-19 and Aβ 5-20, blocking, incubating with 7 μg/ml of said antibody molecule, and detecting said antibody molecule with a labeled secondary antibody; c) wherein said antibody NT4X-167 is deposited under DSM ACC3162;wherein the antibody molecule does not bind human Aβ 1-42 monomers or human Aβ 1-42 dimers, as determined by native Western-blotting comprising the steps of applying 7 μg Aβ 1-42 on a 18% SDS-free polyacrylamide gel, transferring on a 0.45 μm nitrocellulose membrane, blocking, incubating with said antibody molecule in a concentration of not more than 10 μg/ml for 2 h at room temperature, and detecting said antibody molecule with a labeled secondary antibody; d) wherein the antibody molecule inhibits further aggregation of trimeric and tetrameric Aβ oligomers of Aβ 4-X, and/or pyro-Glu-Aβ 3-X, wherein X is 42, 40 or 38, preferably wherein X is 42, when tested in a concentration of 10 μM in 50 mM sodium phosphate buffer, 50 mM NaCl, 20 μM thioflavin T and 0.01 % sodium azide, pH 7.4, at 37°C in a peltier adapter with stirring in a thioflavin T aggregation assay. a) wherein the combination of CDRs comprises H-CDR1, H-CDR2, H-CDR3, L-CDR1, L-CDR2, and L-CDR3 as shown in SEQ ID NOs: 9, 10, 11, 12, 13, and 14, respectively (NT4X-167); b) wherein the monoclonal antibody molecule recognizes a conformational epitope of trimeric or tetrameric human Aβ, wherein the epitope is formed by Phe at amino acid position 4 and the amino acids at positions 2 and 3 of said trimeric or tetrameric human Aβ; and wherein the antibody molecule competes with antibody NT4X-167 for the said conformational epitope as determined by pepscan ELISA comprising the steps of precoating with 100 ng Aβ 4-19 and Aβ 5-20, blocking, incubating with 7 μg/ml of said antibody molecule, and detecting said antibody molecule with a labeled secondary antibody; c) wherein said antibody NT4X-167 is deposited under DSM ACC3162;wherein the antibody molecule does not bind human Aβ 1-42 monomers or human Aβ 1-42 dimers, as determined by native Western-blotting comprising the steps of applying 7 μg Aβ 1-42 on a 18% SDS-free polyacrylamide gel, transferring on a 0.45 μm nitrocellulose membrane, blocking, incubating with said antibody molecule in a concentration of not more than 10 μg/ml for 2 h at room temperature, and detecting said antibody molecule with a labeled secondary antibody; d) wherein the antibody molecule inhibits further aggregation of trimeric and tetrameric Aβ oligomers of Aβ 4-X, and/or pyro-Glu-Aβ 3-X, wherein X is 42, 40 or 38, preferably wherein X is 42, when tested in a concentration of 10 μM in 50 mM sodium phosphate buffer, 50 mM NaCl, 20 μM thioflavin T and 0.01 % sodium azide, pH 7.4, at 37°C in a peltier adapter with stirring in a thioflavin T aggregation assay.