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The enantiomers of the highly lipophilic a-amino acid m-carboranyl-alanine [3-(1.7-dicarba-closo-dodecaborane(12)-1-yl)-2-aminopropanoic acid], a carborane containing analogue of phenylalanine, have been synthesised via hydroxyamination of the N-acyl derivative formed from 3-(m-carboranyl)propionoic acid [3-(1.7-dicarba-closo-dodeca-borane(12)-1-yl)-2-propanoic acid] and Oppolzer's camphor sultam. The enantiomeric excess of both enantiomers of the amino acid was >98%. (S)-Configuration was assigned to the (+)-enantiomer (ch3Oh, 589 nm).

Affibody molecules are a new class of small phage-display selected proteins using a scaffold domain of the bacterial receptor protein A. They can be selected for specific binding to a large variety of protein targets. An affibody molecule binidng with high affinity to a tumor antigen HER2 was recently developed for radionuclide diagnostics and therapy in vivo. The use of hte positron-emitting nuclide 76Br(T½ = 16.2 h) could imporve the sensitivity of detection of HER2-expressing tumors. A site-specific radiobromination o fa cysteine-containing variant of the anti-HER2 affibody, (ZHER2:4)2-Cys, using ((4-hydroxpyphenyl)ethyl)maleimide (HPEM), was evaluated in this study. It was found that HPEM can be radiobrominated with an efficiency of 83+0.4% and thereafter coupled to freshly reduced conjugate to exceed 97%. The label was stable against challenge with large excess of nonlabeled bromide and in a high molar strengt solution. In vitro cell tests demonstraded that radiobrominated affibody binds specifically to the HER2-expressing cel-line, SK-OV-3. Biodistribution studies in nude mice bearing SK-OV-3 xenografts have shown tumor accumulation of 4.8 ? 2.2% IA/g and good tumor-to-normal tissue ratios.

Daunorubicin and doxorubicin are efficient agents for cancer treatment. Their clinical efficacy is, however, hampered by their indiscriminant toxicity. This problem may be circumvented by encapsulating the drugs in liposomes and selectively targeting the tumor cells using tumor targeting agents. Furthermore, the antitumor effect could be enhanced by attaching the Auger electron emitter, 125I, to daunorubicin an ddoxorubicin derivatives. In this context a number of ester, amide, and amine derivatives of daunorubicin an ddoxorubicin were synthesized. Benzoic acid ester derivatives of daunorubicin were synthesized by nucleophilic esterification of the 14-bromodaunorubicin with the potassium salt of the corresponding benzoic acid, resulting in good yields. Nicotinic acids and benzoic acids, activated with a succinimidyl group, were coupled to the amino group of daunorubicien to give the corresponding amide derivatives. Amine derivatives were obtained by the reductive amination of aromatic aldehydes with daunorubicin hydrochloride. The stannylated ester and amide derivatives were uses as precursors for radioiodination. Radiolabeling with 125I was performed using chloroamine-T as an oxidant. The optimized labeling resulted in high radiolabeling yields (85-95%) of the radioiodinated daunorubicin and doxorubicin derivatives. Radioiodination of the amines was conducted at the ortho position of the activated phenyl rings providing moderate radiochemical yields (55-75%).

Reactions of decarborane with various aldehydes in alkaline media were studied. The reactions with HCOH and 2-MeOC6H4-CHO give the corresponding arachno-carboranes [6-R-arachno-CB9H13]-(R=H, C6H4-2-OMe), whereas the reactions with C6H5CHO, 4-BrC6H4CHO, 4-MeCONHC6H4CHO and 2-SC4H3CHO result in the nido-carboranes [6-R-nido-CB9H11]-(R=C6H5, C6H4-4Br, C6H4-4-NHCOMe, 2-SC4H3). Both the arachno- and nido-carboranes can be easily oxidized with elemental iodine in an alkaline aqueous solution giving the corresponding closo-derivatives [2-R-closo-2-CB9H9]-. These closo-2isomers, under heating in solution, undergo rearrangement to more thermodynamically favorable closo-1-isomers [1-R-closo-1-CB9H9]-. The structure of (Bu4N)[1-(4-BrC6H4)-1-CB9H9] was determined using single crystal X-ray diffraction.

Polysaccharides are not degradable by proteolytic enzymes in lysosomes and do not diffuse through cellular membranes. Thus, attached to an internalizing, targeting protein, such polysaccharide linkers, will remain intracellularly after protein degradation. They can be labeled with halogens and provide then a so called residualizing label. Such an approach improves tumor-to-non-tumor radioactivity ratio and, consequently, the results of radionuclide diagnostics and therapy. In this study we present a new approach to obtain a stable halogenation of the polysaccharide dextran using 7-(3-amino-propyl)-7,8-dicarba-nido-undecaborate (-) (ANC). Dextran T10 was partially oxidized by metaperiodate, and ANC was coupled to dextran by reductive amination. The conjugate was then labeled with ¹²⁵I using either Chloramine-T or IodoGen as oxidants. Labeling efficiency was 69-85%. Stability of the label was evaluated in rat liver homogenates. Under these conditions, the ANC-dextran conjugate was found to be more stable than labeled albumin, which was used as a control protein.

The monoclonal humanized anti-HER2 antibody trastuzumab was radiolabeled with the positron emitter (76)Br (T(1/2) =16.2 h). Indirect labeling was performed using the p-isothiocyanatobenzene derivative of the [(76)Br]undecahydro-bromo-7,8-dicarba-nido-undecaborate(1-) ((76)Br-NBI) as a precursor molecule. (76)Br-NBI was prepared by bromination of the 7-(p-isothiocyanato-phenyl)dodecahydro-7,8-dicarba-nido-undecaborate(1-) ion (NBI) with a yield of 93-95% using Chloramine-T (CAT) as an oxidant. Coupling of radiobrominated NBI to antibody was performed without intermediate purification, in an "one pot" reaction. An overall labeling yield of 55.7 +/- 4.8% (mean +/- maximum error) was achieved when 300 microg of antibody was labeled. The label was stable in vitro in physiological and denaturing conditions. In a cell binding test, trastuzumab remained immunoreactive after labeling.

The use of charged linkers in attaching radiohalogens to tumor-seeking biomolecules may improve intracellular retention of the radioactive label after internalization and degradation of targeting proteins. Derivatives of polyhedral boron clusters, such as closo-dodecaborate (2-) anion, might be possible charged linkers. In this study, a bifunctional derivative of closo-dodecaborate, (4-isothiocyanatobenzyl-ammonio)-undecahydro-closo-dodecaborate (DABI) was labeled with positron-emitting nuclide (76)Br (T 1/2 = 16.2 h) and coupled to anti-HER2/neu humanized antibody Trastuzumab. The overall labeling yield at optimized conditions was 80.7 +/- 0.6%. The label was proven to be stable in vitro in physiological and a set of denaturing conditions. The labeled antibody retained its capacity to bind to HER-2/neu antigen expressing cells. The results of the study demonstrated feasibility for using derivatives of closo-dodecaborate in indirect labeling of antibodies for radioimmunoPET.