Increased metabolism is a requirement for tumor cell proliferation. To understand the dependence of tumor cells on fatty acid metabolism, we evaluated various nodes of the fatty acid synthesis pathway. Using RNAi we have demonstrated that depletion of fatty-acid synthesis pathway enzymes SCD1, FASN, or ACC1 in HCT116 colon cancer cells results in cytotoxicity that is reversible by addition of exogenous fatty acids. This conditional phenotype is most pronounced when SCD1 is depleted. We used this fatty-acid rescue strategy to characterize several small-molecule inhibitors of fatty acid synthesis, including identification of TOFA as a potent SCD1 inhibitor, representing a previously undescribed activity for this compound. Reference FASN and ACC inhibitors show cytotoxicity that is less pronounced than that of TOFA, and fatty-acid rescue profiles consistent with their proposed enzyme targets. Two reference SCD1 inhibitors show low-nanomolar cytotoxicity that is offset by at least two orders of magnitude by exogenous oleate. One of these inhibitors slows growth of HCT116 xenograft tumors. Our data outline an effective strategy for interrogation of on-mechanism potency and pathway-node-specificity of fatty acid synthesis inhibitors, establish an unambiguous link between fatty acid synthesis and cancer cell survival, and point toward SCD1 as a key target in this pathway.

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Trypanosomiasis remains a significant disease across the sub-Saharan African continent, with 50,000 to 70,000 individuals infected. The utility of current therapies is limited by issues of toxicity and the need to administer compounds intravenously. We have begun a program to pursue lead optimization around MDL 73811, an irreversible inhibitor of S-adenosylmethionine decarboxylase (AdoMetDC). This compound is potent but in previous studies cleared rapidly from the blood of rats (T. L. Byers, T. L. Bush, P. P. McCann, and A. J. Bitonti, Biochem. J. 274:527-533). One of the analogs synthesized (Genz-644131) was shown to be highly active against Trypanosoma brucei rhodesiense in vitro (50% inhibitory concentration, 400 pg/ml). Enzyme kinetic studies showed Genz-644131 to be approximately fivefold more potent than MDL 73811 against the T. brucei brucei AdoMetDC-prozyme complex. This compound was stable in vitro in rat and human liver microsomal and hepatocyte assays, was stable in rat whole-blood assays, did not significantly inhibit human cytochrome P450 enzymes, had no measurable efflux in CaCo-2 cells, and was only 41% bound by serum proteins. Pharmacokinetic studies of mice following intraperitoneal dosing showed that the half-life of Genz-644131 was threefold greater than that of MDL 73811 (7.4 h versus 2.5 h). Furthermore, brain penetration of Genz-644131 was 4.3-fold higher than that of MDL 73811. Finally, in vivo efficacy studies of T. b. brucei strain STIB 795-infected mice showed that Genz-644131 significantly extended survival (from 6.75 days for controls to >30 days for treated animals) and cured animals infected with T. b. brucei strain LAB 110 EATRO. Taken together, the data strengthen validation of AdoMetDC as an important parasite target, and these studies have shown that analogs of MDL 73811 can be synthesized with improved potency and brain penetration.

The paper extends a previously published report [4] on chemical properties of a -amino nitriles and of members of the C3H,N2 ensemble (Scheme I ) as observed in experiments carried out under non-aqueous conditions. The reactions investigated and the observations made are summarized in some detail in the English footnotes (*) referring to Schemes 1-17 and Fig. 1. Schenw 3 *) QCN H 18 CN QCN NC 19 H NC iN NHz HN flyN HzN 15 21 1 *) Retrosynthetic analysis of the structural relationship between the nitrile form of 1,4-dihydronicotinamide, and the glutamic and aspartic acid dinitriles. The relationship rests on the equivalence of glutamic acid dinitrile and acrolein imine under thermal conditions. *) Uber eine potentiell prabiotische Bildung von Asparaginsaure aus Cyanoacetylen mit HCN, NH3 in H,O vgl. Sanchez et ul. [lo]. 9, Eine Variante der Herstellung von 20 aus 22 und 4-Oxobutannitril ist in [4] beschrieben.Scheme 5 *) 2217 *) Hypothetical reaction paths to products in the FVP of (E/Z)-19 and 20. Within this framework of structural transformations, the nitrile form of 1,4-dihydronicotinamide is at the same oxidation level as the ensemble of the dinitrile forms of glutamic and aspartic acids. e-") Gestutzt wird diese Interpretation der Reaktionsmechanismen durch die Beobachtung, dass auch die hier nicht explizit beschriebene Pyrolyse des strukturvenvandten N-Propenylidenasparagindinitril (3-Azahexa-3,5-dien-1,2-dicarbonitril) zu den gleichen isolierbaren Produkten, ausschliesslich 26 und 27, fuhrt, wahrend die Pyrolyse von N-(I-Cyanoethy1iden)glutamindinitril (cl-Azahex-4-en-l,3,5-tricarbonitril) nur 26 und 29und 5-Methylpyrrol-2-carbonitril liefert (121, S . 62,68, 188, 199).

Chemistry of α‐Aminonitriles I: Introduction and Pathways to Uroporphyrinogen‐octanitriles. An introduction to experimental studies on the chemistry of α‐aminonitriles potentially relevant to the problems of prebiotic chemistry is presented. The framework of conditions wherein the investigation is chosen to be carried out implies both molecular oxygen and ‐ whenever feasible ‐ water to be excluded from reaction conditions. This study focusses on 2‐amino‐2‐propenenitrile (3) (Scheme 6) as central starting material of reaction sequences which aim at the nitrile forms of proteinogenic amino acids as well as at the aza forms of building blocks of biological cofactor molecules as their targets (Scheme 5). Schemes 13,16,23 as well as 25 and 26 summarize reaction sequences by which 3 is transformed within the defined framework of conditions into the thermodynamic (statistically controlled) mixture of the four isomeric uroperphyrinogen‐octanitriles 57–60. HPLC's of such mixtures document the dominance of the least symmetrical isomer whose constitutional pattern of peripheral substituents happens to be the one percent in all biological porphinoids. Preparative procedures for the synthesis of 3(Scheme 9), the β,β‐disubstituted pyrrol‐nitriles 30,53 and 54 (Scheme 19) as well as the porphyrinogenoctakis(propionitrile) and‐octakis(acetonitrile) 65 and 66, respectively (Scheme 24) are given.