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Ligand-targeted therapeutics have increased in prominence because of their potential for improved potency and reduced toxicity. However, with the advent of personalized medicine, a need for greater versatility in ligand-targeted drug design has emerged, where each tumor-targeting ligand should be capable of delivering a variety of therapeutic agents to the same tumor, each therapeutic agent being selected for its activity on a specific patient's cancer. In this report, we describe the use of a prostate-specific membrane antigen (PSMA)-targeting ligand to deliver multiple unrelated cytotoxic drugs to human prostate cancer (LNCaP) cells. We demonstrate that the PSMA-specific ligand, 2-[3-(1, 3-dicarboxy propyl)ureido] pentanedioic acid, is capable of mediating the targeted killing of LNCaP cells with many different therapeutic warheads. These results suggest that flexibility can be designed into ligand-targeted therapeutics, enabling adaptation of a single targeting ligand for the treatment of patients with different sensitivities to different chemotherapies.

In the mammalian central nervous system (CNS), the action of sodium dependent excitatory amino acid transporters (EAATs) is responsible for termination of glutamatergic neurotransmission by reuptake of ( S) -glutamate (Glu) from the synaptic cleft. Five EAAT subtypes have been identified, of which EAAT1-4 are present in the CNS, while EAAT5 is localized exclusively in the retina. In this study, we have used an enantioselective chemo-enzymatic strategy to synthesize 10 new Glu analogues 2a- k ( 2d is exempt) with different functionalities in the 4 R-position and characterized their pharmacological properties at the human EAAT1-3. In particular, one compound, 2k, displayed a significant preference as inhibitor of the EAAT2 subtype over EAAT1,3. The compound also displayed very low affinities toward ionotropic and metabotropic Glu receptors, making it the most selective EAAT2 inhibitor described so far.

Two representative glutamate carboxypeptidase II (GCP II) inhibitors, 2-(hydroxypentafluorophenylmethyl-phosphinoylmethyl)pentanedioic acid 2 and 2-(3-mercaptopropyl)pentanedioic acid 3, were synthesized in high optical purities (>97%ee). The two enantiomers of 2 were prepared from previously reported chiral intermediates, (R)- and (S)-2-(hydroxyphosphinoylmethyl)pentanedioic acid benzyl esters 8. The synthesis of (R)- and (S)-3 involves the hydrolysis of (R)- and (S)-3-(2-oxo-tetrahydro-thiopyran-3-yl)propionic acids, (R)- and (S)-11, the corresponding optically pure thiolactones delivered by chiral chromatographic separation of the racemic 11. GCP II inhibitory assay revealed that (S)-2 is 40-fold more potent than (R)-2. In contrast, both enantiomers of 3 inhibited GCP II with nearly equal potency. The efficacy observed in subsequent animal studies with these enantiomers correlated well with the inhibitory potency in a GCP II assay.

A series of 2-(thioalkyl)pentanedioic acids were synthesized and evaluated as inhibitors of glutamate carboxypeptidase II (GCP II, EC 3.4.17.21). The inhibitory potency of these thiol-based compounds against GCP II was found to be dependent on the number of methylene units between the thiol group and pentanedioic acid. A comparison of the SAR of the thiol-based inhibitors to that of the phosphonate-based inhibitors provides insight into the role of each of the two zinc-binding groups in GCP II inhibition. The most potent thiol-based inhibitor, 2-(3-mercaptopropyl)pentanedioic acid (IC(50) = 90 nM), was found to be orally bioavailable in rats and exhibited efficacy in an animal model of neuropathic pain following oral administration.

Integrin adhesion receptors frequently recognize a core amino acid sequence, Arg-Gly-Asp, in their target ligands. Inhibitors with the ability to inhibit one or a small subset of such RGD-dependent integrins have been invaluable in defining their biological function. Here, we have characterized low molecular weight inhibitors for their ability to specifically inhibit alphav(beta)6 integrin, a fibronectin/tenascin receptor. As of yet, no nonpeptidic inhibitor of alphav(beta)6 was known. New peptidomimetic and nonpeptidic compounds were examined in isolated integrin binding assays and in cell adhesion assays for their ability to block alphav(beta)6, alphav(beta)3, alphav(beta)5, and alphalIb(beta)3 integrins. The compounds are based on an aromatically substituted beta amino acid or glutaric acid derivative as an acidic center and an aminopyridyl or guanidyl residue as a basic mimetic. We found several classes of inhibitors with different selectivities, especially mono- or biselectivity on the alpha(v)-integrins alphav(beta)6 and alphav(beta)3, and nanomolar activity. Furthermore, nearly all compounds are inactive on alphaIIb(beta)3. Compound 11 is the first specific, peptidomimetic inhibitor of the alphav(beta)6 integrin receptor.

Succinyl and 3'-substituted glutaryl betulin derivatives showed stronger anti-HIV activity and higher therapeutic index (TI) values than their dihydrobetulin counterparts, with ratios of 1.2:1 to 15:1 (cf. 7 and 15, 9 and 17, 10 and 18, 11 and 19, and 12 and 20). For various 3'-substituted glutaryl compounds, the order of anti-HIV effects, from strong to weak inhibition, was 3',3'-dimethyl, 3'-methyl, 3'-ethyl-3'-methyl, followed by 3',3'-tetramethylene glutaryl derivatives (10 > 9 > 11 > 12, 18 > 17 > 19 > 20). The most potent compound, 10, has two 3',3'-dimethylglutaryl groups and displays significant anti-HIV potency with an EC50 value of 0.000 66 microM and a TI of 21 515. Results for compounds (22 and 23) without a C-3 acyl group confirmed the importance of the C-3 acyl group to the anti-HIV effect. With 3',3'-tetramethylene glutaryl derivatives, triacyl 29 showed stronger inhibition than diacyl 12; in contrast, 3',3'-dimethylglutaryl compounds displayed opposite results. 3-Keto compounds (35 and 36) and 2,3-dihydro compounds (39 and 40) had EC50 values in the range of 4.3-10.0 microM, suggesting that A ring modification led to decreased potency. The reduced activity of amide (33 and 34), ester (41), and oxime (42) analogues suggested that the orientation and linkage of the C-3 acyl side chain play crucial roles in the potent anti-HIV activity. Finally, replacing the C-28 acyl group with a bulky non-carboxylic group produced a less potent compound (44). In the study of mechanism of action, our results indicated that fusion is not the primary target for the anti-HIV activity of 10. It appears to inhibit HIV replication at a late stage of the viral life cycle, i.e., after viral protein synthesis.

Z and E isomers of 3-methyl-3-(carboxymethyl)hexahydro-1 (3H)-isobenzofuranones (I), lactones of 3-hydroxy-3-(2-carboxycyclohexyl) butyric acids (II), were prepared and tested on cholesterol biosynthesis in vitro. Compound I of the Z series was prepared through its ethyl ester by hydrogenation, over Rh/Al2O3 catalyst, of the phenyl ring of 3-methyl-3-[(ethoxycarbonyl)methyl]-1(3H)-isobenzofuranone. Compound I of the E series was prepared, through its ethyl ester, by Reformatsky reaction from ethyl (E)-2-acetylcyclohexanecarboxylate. 3-Methyl-3-(carboxymethyl)-5,6,7,8-tetrahydro-1(3H)-isobenzofuranone, 3-methyl-3-ethyl-5,6,7,8-tetrahydro-1(3H)-isobenzofuranone, and 3-methyl-3-(carboxymethyl)-1(3H)-isobenzofuranone were also prepared and tested. The above compounds inhibited acetate incorporation in cholesterol and fatty acids in rat liver slices at 5 X 10(-3) M but lack specific inhibitory activity on HMG-CoA reductase.

The synthesis of two new series of dicarboxylic acid dipeptides and two sulfhydryl-containing inhibitors are described. The in vitro enkephalinase inhibition data and some in vivo analgesic data are presented for these compounds. For the dibenzylglutaric acid series structure-activity relationships and in vivo analgesic activity are discussed. The reverse amides, i.e., 4-amino-2,4-dibenzylbutyric acid derivatives, are also discussed. Two sulfhydryl-containing inhibitors showed good in vivo potency in the mouse jump-latency hot-plate test after peripheral administration at moderate low doses.

Glutaryl-S-(8-aminooctyl)-L-cysteinylglycine and glutaryl -S-(10-aminodecyl)-L-cysteinylglycine have been prepared by a seven-step procedure as potential ligands for affinity chromatography purification of mouse liver glyoxalase I. Both compounds exhibited nonlinear, mixed-type inhibition of the enzyme. The decyl derivative was a more effective inhibitor than was the octyl analog.

Derivatives of 3-hydroxy-3-methylglutaric acid (HMG), a portion of the substrate for HMG CoA reductase, were prepared and tested for their inhibitory action against rat liver HMG CoA reductase and for their hypocholesterolemic activity. Structure-dependent competitive inhibition was observed. Optimal structures had a free dicarboxylic acid with an alkyl group of 13-16 carbons at position 3. 3-n-Pentadecyl-3-hydroxyglutaric acid (3j) (IC50 = 50 microM) reduced serum cholesterol in the Triton-treated rat and HMG CoA reductase activity in the 20,25-diazacholesterol-treated rat.