Therapeutic agent

1. A method for the depletion of a protein population from the plasma of a subject in need of such treatment, which comprises:

(a) administering to the subject a therapeutically effective amount of a nonproteinaceous agent, wherein the agent is a D-proline of the formula:

wherein R is the group

R 1 is hydrogen or halogen;

X is —(CH 2 )n-; —CH(R 2 )(CH 2 ) n —; —CH 2 O(CH 2 ) n —; —CH 2 NH—; benzyl, —C(R 2 ═CH—; —CH 2 CH(OH)—; or thiazol-2,5-diyl;

Y is —S—S—; —(CH. 2 ) n —; —O—; —NH—; —N(R 2 )—; —CH═CH—; —NHC(O)NH—; —N(R 2 )C(O)N(R 2 )—; —N[CH 2 C 6 H 3 (OCH) 2 ]—; —N(CH 2 C. 6 H 5 )—; —N(CH. 2 C 6 H 5 )C(O)N(CH 2 C 6 H 5 )—; —N(alkoxyalkyl)-; N(cycloalkyl-methyl)-; 2,6-pyridyl; 2,5-furanyl; 2,5-thienyl; 1,2-cyclohexyl; 1,3-cyclohexyl; 1,4-cyclohexyl; 1,2-naphthyl; 1,4naphthyl; 1,5-naphthyl; 1,6-naphthyl; biphenylen; or 1,2-phenylen, 1,3-phenylen and 1,4-phenylen, wherein the phenylen groups are optionally substituted by 1-4 substituents, selected from halogen, lower alkyl, lower alkoxy, hydroxy, carboxy, —COO-lower alkyl, nitrilo, 5-tetrazol, (2-carboxylic acid pyrrolidin-1-yl)-2-oxo-ethoxy, N-hydroxycarbamimidoyl, 5-oxo[1,2,4]oxadiazolyl, 2-oxo-[1,2,3,5]oxathiadiazolyl, 5-thioxo[1,2,4]oxadiazolyl and 5-tert-butylsulfanyl-[1,2,4]oxadiazolyl;

X′ is —(CH 2 ) n —; —(CH 2 ) n CH(R 2 )—; —(CH 2 ) n , OCH 2 —; —NHCH 2 —; benzyl, —C═C(R 2 )—;

—CH(OH)CH 2 ; or thiazol-2,5-diyl;

R 2 is lower alkyl, lower alkoxy or benzyl and

n is 0-3,

or a pharmaceutically acceptable salt or mono- or diester thereof;

which agent comprises a plurality of ligands covalently co-linked to permit complexation with a plurality of the proteins in the presence thereof, wherein at least two of the ligands are the same or different and are capable of being bound by ligand binding sites present on the proteins;

(b) binding of at least two of the ligands by the ligand binding sites of the proteins in the plasma;

(c) forming thereby a complex between the agent and a plurality of the proteins, wherein the complex is abnormal to the subject; and

(d) causing the complex to be identified by the physiological mechanisms of the subject and cleared from the plasma; and

(e) monitoring the clearance of the disease-associated protein population from the subject's plasma;

wherein the ligand binding site is from serum amyloid P component (SAP).

2. The method according to claim 1 , wherein the D-proline is (R)-1-[6-(R)-2-Carboxypyrrolidin- 1-yl]-6-oxo-hexanoyl] pyrrolidine-2-carboxylic acid or a pharmaceutically acceptable salt or mono- or diester thereof.

3. The method according to claim 1 , wherein the linker comprises a linear or branched hydrocarbylene in which one or more of the carbon atoms thereof is optionally substituted by a heteroatom.

4. The method according to claim 1 , wherein the agent has two ligands.

5. A method for the depletion of a protein population from the plasma of a subject in need of such treatment, which comprises administering to the subject a therapeutically effective amount of a nonproteinaceous agent, which agent has the general structure Ligand-liniker-Ligand and is capable of forming a complex with a plurality of the disease-associated proteins in the presence thereof, wherein the ligands are capable of being bound by ligand binding sites present on the proteins; and monitoring the clearance of the disease-associated protein population from the subject's plasma; and wherein the agent is a D-proline of the formula:

wherein R is the group

R 1 is hydrogen or halogen;

X is —(CH 2 )n-; —CH(R 2 )(CH 2 ) n —; —CH 2 O(CH 2 ) n —; —CH 2 NH—; benzyl, —C(R 2═CH—; —CH 2 CH(OH)—; or thiazol-2,5-diyl;

Y is —S—S—; —(CH. 2 ) n —; —O—; —NH—; —N(R 2 )—; —CH═CH—; —NHC(O)NH—; —N(R 2 )C(O)N(R 2 )—; —N[CH 2 C 6 H 3 (OCH) 2 ]—; —N(CH 2 C. 6 H 5 )—; —N(CH. 2 C 6 H 5 )C(O)N(CH 2 C 6 H 5 )—; —N(alkoxyalkyl)-; N(cycloalkyl-methyl)-; 2,6-pyridyl; 2,5-furanyl; 2,5-thienyl; 1,2-cyclohexyl; 1,3-cyclohexyl; 1,4-cyclohexyl; 1,2-naphthyl; 1,4naphthyl; 1,5-naphthyl; 1,6-naphthyl; biphenylen; or 1,2-phenylen, 1,3-phenylen and 1,4-phenylen, wherein the phenylen groups are optionally substituted by 1-4 substituents, selected from halogen, lower alkyl, lower alkoxy, hydroxy, carboxy, —COO-lower alkyl, nitrilo, 5-tetrazol, (2-carboxylic acid pyrrolidin-1-yl)-2-oxo-ethoxy, N-hydroxycarbamimidoyl, 5-oxo[1,2,4]oxadiazolyl, 2-oxo-[1,2,3,5]oxathiadiazolyl, 5-thioxo[1,2,4]oxadiazolyl and 5-tert-butylsulfanyl-[1,2,4]oxadiazolyl;

X′ is —(CH 2 ) n —; —(CH 2 ) n CH(R 2 )—; —CH 2 ) n , OCH 2 —; —NHCH 2 —; benzyl, —C═C(R 2 )—;

—CH(OH)CH 2 ; or thiazol-2,5-diyl;

R 2 is lower alkyl, lower alkoxy or benzyl and

n is 0-3,

or a pharmaceutically acceptable salt or mono- or diester thereof;

wherein the ligand binding site is from serum amyloid P component (SAP).

6. The method according to claim 1 , wherein the dissociation constant for binding of each individual ligand by the target protein is no more than 1 millimolar.

7. A method for the depletion of proteins from the plasma of a subject in need of such treatment, which comprises:

administering to the subject a therapeutically effective amount of a nonproteinaceous agent, which agent comprises a plurality of ligands covalently co-linked to permit complexation with a plurality of the proteins in the presence thereof, wherein at least two of the ligands are the same or different and are capable of being bound by ligand binding sites present on the proteins; and

monitoring the clearance of the disease-associated proteins from the subject's plasma;

wherein the disease-associated protein is serum amyloid P component (SAP); and

wherein the agent is a D-proline of the formula:

wherein R is the group

R 1 is hydrogen or halogen;

X is —(CH 2 )n-; —CH(R 2 )(CH 2 ) n ; —CH 2 O(CH 2 h ) n—; —CH 2 NH—; benzyl, —C(R 2 ═CH—; —CH 2 CH(OH)—; or thiazol-2,5-diyl;

Y is —S—S—; —(CH. 2 ) n —; —O—; —NH—; —N(R 2 )—; —CH═CH—; —NHC(O)NH—; —N(R 2 )C(O)N(R 2 )—; —N[CH 2 C 6 H 3 (OCH) 2 ]—; —N(CH 2 C. 6 H 5 )—; —N(CH. 2 C 6 H 5 )C(O)N(CH 2 C 6 H 5 )—; —N(alkoxyalkyl)-; N(cycloalkyl-methyl)-; 2,6-pyridyl; 2,5-furanyl; 2,5-thienyl; 1,2-cyclohexyl; 1,3-cyclohexyl; 1,4-cyclohexyl; 1,2-naphthyl; 1,4naphthyl; 1,5-naphthyl; 1,6-naphthyl; biphenylen; or 1,2-phenylen, 1,3-phenylen and 1,4-phenylen, wherein the phenylen groups are optionally substituted by 1-4 substituents, selected from halogen, lower alkyl, lower alkoxy, hydroxy, carboxy, —COO-lower alkyl, nitrilo, 5-tetrazol, (2-carboxylic acid pyrrolidin- 1-yl)-2-oxo-ethoxy, N-hydroxycarbamimidoyl, 5oxo[1,2,4]oxadiazolyl, 2-oxo-[1,2,3,5]oxathiadiazolyl, 5-thioxo[1,2,4]oxadiazolyl and 5-tert-butylsulfanyl-[1,2,4]oxadiazolyl;

X′ is —CH 2 ) n ; —(CH 2 ) n CH(R 2 )—; —(CH 2 ) n , OCH 2 —; —NHCH 2 —; benzyl, —C═C(R 2 )—;

—CH(OH)CH 2 ; or thiazol-2,5-diyl;

R 2 is lower alkyl, lower alkoxy or benzyl and

n is 0-3,

or a pharmaceutically acceptable salt or mono- or diester thereof.