I guess you can sort of call this (below) a mini- and focused-TRAP. However, starting with a series of derivatives of a known substrate is not exactly the spirit of TRAP as it's communicated these days. And, as it's communicated these days, you have at most (1) the insulin sensitizers, and (2) anything that has come out of academic labs at U. Arizona.
Proteins 1997 Jun;28(2):202-16
Ligand-based protein alignment and isozyme specificity of glutathione S-transferase inhibitors.
Koehler RT, Villar HO, Bauer KE, Higgins DL.
Chemistry Department, Terrapin Technologies, South San Francisco, California 94080, USA.
Glutathione S-transferases (GST, E.C.2.5.1.18) comprise a family of detoxification enzymes. Elevated levels of specific GST isozymes in tumor cells are thought responsible for resistance to chemotherapeutics, which renders selective GST inhibitors potentially useful pharmaceutical agents. We discuss the development of a structure activity model that rationalizes the isozyme selectivity observed in a series of 12 glutathione (GSH) analogues. Enzymatic activity data was determined for human P1-1, A1-1, and M2-2 isozymes, and these data were then considered in light of structural features of these three GST proteins. A survey of all GST structures in the PDB revealed that GSH binds to these proteins in a single "bioactive" conformation. To focus on differences between binding sites, we exploited our finding of a common GSH conformation and aligned the GST x-ray structures using bound ligands rather than the backbones of the different proteins. Once aligned, binding site lipophilicity and electrostatic potentials were computed, visualized, and compared. Docking and energy minimization exercises provided additional refinements to a model of selectivity developed initially by visual analysis. Our results suggest that binding site shape and lipophilic character are key determinants of GST isozyme selectivity for close GSH analogues.
J Med Chem 1996 Apr 12;39(8):1736-47
Design, synthesis, and evaluation of latent alkylating agents activated by glutathione S-transferase.
Satyam A, Hocker MD, Kane-Maguire KA, Morgan AS, Villar HO, Lyttle MH.
Terrapin Technologies, Inc., South San Francisco, California 94080, USA.
In search of compounds with improved specificity for targeting the important cancer-associated P1-1 glutathione S-transferase (GST) isozyme, new analogs 4 and 5 of the previously reported glutathione S-transferase (GST)-activated latent alkylating agent gamma-glutamyl-alpha-amino-beta-[[[2-[[bis[bis(2-chloroethyl)amino]ph osp horyl]oxy]ethyl]sulfonyl]propionyl]-(R)-(-)-phenylglycine (3) have been designed, synthesized, and evaluated. One of the diastereomers of 4 exhibited good selectivity for GST P1-1. The tetrabromo analog 5 of the tetrachloro compound 3 maintained its specificity and was found to be more readily activated by GSTs than 3. The GST activation concept was further broadened through design, synthesis, and evaluation of a novel latent urethane mustard 8 and its diethyl ester 9. Interestingly, 8 showed very good specificity for P1-1 GST. Cell culture studies were carried out on 4, 5, 8, and 9 using cell lines engineered to have varying levels of GST P1-1 isozyme. New analogs 4 and 5 exhibited increased toxicity to cell lines with overexpressed GST P1-1 isozyme. The urethane mustard 8 and its diethyl ester 9 were found to be not as toxic. However, they too exhibited more toxicity to a cell line engineered to have elevated P1-1 levels, which was in agreement with the observed in vitro specificity of 8 for P1-1 GST isozyme. Mechanistic studies on alkaline as well as enzyme-catalyzed decomposition of latent mustard 3 provided experimental proof for the hypothesis that 3 breaks down into an active phosphoramidate mustard and a reactive vinyl sulfone. The alkylating nature of the decomposition products was further demonstrated by trapping those transient species as relatively stable diethyldithiocarbamic acid adducts. These results substantially extend previous efforts to develop drugs targeting GST and provide a paradigm for development of other latent drugs.
J Med Chem 1994 Jan 7;37(1):189-94
Isozyme-specific glutathione-S-transferase inhibitors: design and synthesis.
Lyttle MH, Hocker MD, Hui HC, Caldwell CG, Aaron DT, Engqvist-Goldstein A, Flatgaard JE, Bauer KE.
Terrapin Technologies, South San Francisco, California 94080.
Glutathione-S-transferase (GST) isozyme-selective inhibitors were designed by an empirically guided strategy. In the first phase, literature data were used to select C-terminal modifications which generated maximum variation in the catalytic efficiency (Vmax/Km) for glutathione (GSH) analogs used as substrates with different rat GSTs. Also, on the basis of literature data, the sulfhydryl group was functionalized with a selection of alkyl and aryl groups to maximize potential isozyme specificity. Affinity chromatography sorbents were prepared from these which showed isozyme selectivity for both rat tissue and recombinant human GST isozymes. Some of these compounds also showed selective inhibition of GST activity in catalysis of the reaction of 1-chloro-2,4-dinitrobenzene with GSH. In the second phase, electronic effects were explored through synthesis of an isostructural series of S-benzyl GSH ligands with different substituents on the aromatic ring. GST isozyme specificity for these ligands, measured by binding to derivatized sorbents, varied substantially, with hydrophobic substituents favoring the human GST M1a isozyme and electronegative moieties favoring GST P1. In the third phase, information obtained from testing both series of compounds was combined and used to prepare GSH analogs with chemical features responsible for isozyme specificity at both the C-terminus and the sulfur. This approach gave two new compounds which showed improved potency while still maintaining selectivity in the inhibition of GSTs. A detailed discussion of the logic used in the selection of functional groups for maximum potency and selectivity is included.
Biochem J 1993 Jun 1;292 ( Pt 2):371-7
Glutathione analogue sorbents selectively bind glutathione S-transferase isoenzymes.
Castro VM, Kelley MK, Engqvist-Goldstein A, Kauvar LM.
Terrapin Technologies, South San Francisco, CA 94080.
Novel affinity sorbents for glutathione S-transferases (GSTs) were created by binding glutathione (GSH) analogues to Sepharose 6B. The GSH molecule was modified at the glycine moiety and at the group attached to the sulphur of cysteine. When tested by affinity chromatography in a flow-through microplate format, several of these sorbents selectively bound GST isoenzymes. gamma E-C(Hx)-phi G (glutathione with a hexyl moiety bound to cysteine and phenylglycine substituted for glycine) specifically bound rat GST 7-7, the Pi-class isoenzyme, from liver, kidney and small intestine. gamma E-C(Bz)-beta A (benzyl bound to cysteine and beta-alanine substituted for glycine) was highly selective for rat subunits 3 and 4, which are Mu-class isoenzymes. By allowing purification of the isoenzymes under mild conditions that preserve activity, the novel sorbents should be useful in characterizing the biological roles of GSTs in both normal animal and cancer tissues.
Pept Res 1992 Nov-Dec;5(6):336-42
Construction of affinity sorbents utilizing glutathione analogs.
Lyttle MH, Aaron DT, Hocker MD, Hughes BR.
Terrapin Technologies, South San Francisco, CA 94080.
Solution-phase N-fluorenylmethoxycarbonyl (Fmoc) mediated peptide synthesis has been adapted to the synthesis of glutathione (gamma-glutamyl-cysteinyl-glycine) analogs. A protecting group strategy has been devised in which all of the masking groups are removed with mild base. This allows for the synthesis of acid-sensitive materials and lessens concerns about the alkylation at sulfur by carbocations known to be present in the trifluoroacetic acid mixtures usually employed for deprotection of peptides made by the Fmoc methodology. A series of structurally varied glutathione analogs were prepared by modifying the peptide in two ways. The first involved C-terminal substitution for glycine by one of several different amino acids. The second involved substitution of one of five alkyl or aryl groups onto the cysteine sulfhydryl. The complete set of all combinations would yield 48 reagents, of which 25 have actually been synthesized. Following confirmation of the structures by FAB mass spectrometry, the peptides were immobilize by conjugation to epoxyfunctionalized Sepharose at pH 11-12. The amount and identity of immobilized peptide was assayed by amino acid analysis of acid-hydrolyzed resin. One of the tripeptides was purified by ion-exchange and preparative HPLC.
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So..... you see, Wick isn't lying when he says that 286 was derived from TRAP. But, when he then describes TRAP and it's power from a "platform" or "IPO Prime Time" perspective, it has almost zero relevance to 286 AND 199. He's describing a generalized and iterative technique, where you need know nothing about substrates and active sites, not a 10 year project where analogs of a known substrate were tested on defined isozymes. And all of those collaborative projects with partners? Nada.
Catch 286.
That DOESN'T mean that 286 won't do what it's intended to do. And, again, there's tons of enthusiasm coming from the 286 clinical investigators. It may be a GREAT investment, but I determined that it's not my type of company. Took me awhile. |
