Novel naphthoquinonyl derivatives: Potential structural components for the synthesis of cytotoxic peptides

Summary Syntheses and physicochemical properties are described of several novel naphthoquinonyl amino acid derivatives, which are potential components in cytotoxic peptide conjugates. These compounds include N - and N -naphthoquinonyl derivatives of lysine as well as N-naphthoquinonyl-carboxylic derivatives. The former class of compounds can be employed as building blocks in a stepwise peptide synthesis, whereas the latter two are adequate for postpeptide chain-assembly modifications. The ability of the naphthoquinonyl derivatives to produce semiquinone radicals and hydroxyl radicals (OH), using chemical (i.e. NaBH₄) and enzymatic (i.e. NADPH-cytochrome P-450 reductase) routes, respectively, was evaluated employing electron spin resonance spectroscopy.     

Protection Against Developmental Deficiencies by a Lipophilic VIP Analogue

Stearyl-Nle-VIP (SNV) is a novel agonist of vasoactive intestinal peptide (VIP) exhibiting a 100-fold greater potency than the parent molecule and specificity for a receptor associated with neuronal survival. Here, the developmental and protective effects of SNV were investigated in vivo using two models of developmental retardation, hypoxia and cholinergic blockade. In both cases chronic administration of SNV during development provided protective effects. Water maze experiments on the weaned animals have demonstrated a prophylactic action for SNV and enhancement of spatial memory in animals exposed to a cholinotoxin. SNV may act by providing neuroprotection, thereby improving cognitive functions. This work is dedicated to Prof. R.J. Wurtman whose inspiration and leadership in the field of neuroscience and cognition is beyond comparison.     

Clinical evaluation of the simultaneous determination of CA 15-3, CA 125 and sHER2 in breast cancer

Objective We investigated serum levels of CA 15-3, sHER2 and CA 125, and their usefulness in the detection of metastatic disease in breast cancer patients.

Methods The levels of CA 15-3, sHER2 and CA 125 tumour markers were determined in 60 patients, 40 with localized and 20 with metastatic breast carcinoma. The control group consisted of 10 healthy women.

Results We found that, at the time of diagnosis, serum levels of all three tumour markers were elevated in patients with distant metastases, but of minute importance in the detection of any breast cancer. When the data for the individual markers were combined the overall sensitivity of metastases detection with all three markers improved. In this regard, 90% of patients with distant metastases had an increase in serum level of at least one of tested tumour markers. Similar results were obtained using receiver operating characteristic curve (ROC). Moreover, using ROC we defined cut-off values for metastasis detection for each of the tested markers.

Conclusion Our findings indicate that measurement of CA 15-3 serum values in conjunction with sHER2 and CA 15-3 can increase sensitivity in metastasis detection.     

Albumin-insulin conjugate releasing insulin slowly under physiological conditions: a new concept for long-acting insulin

The covalent linkage of peptides or protein drugs to human serum albumin (HSA) greatly prolongs their lifetime in vivo but is pharmacologically irrelevant when it irreversibly inactivates them. We retain drug bioactivity by synthesizing a heterobifunctional reagent (MAL-Fmoc-OSu, 9-hydroxymethyl-2-(amino-3-maleimidopropionate)-fluorene-N-hydroxysuccinimide) that generates HSA-Fmoc-insulin on covalent conjugation to the amino group of insulin and the Cys-34 side chain of HSA. HSA-Fmoc-insulin is water-soluble and, upon incubation in aqueous buffers reflecting normal human serum conditions, slowly, spontaneously, and homogeneously hydrolyzes to release unmodified insulin with a t 1/2 of 25 +/- 2 h. A single subcutaneous or intraperitoneal administration of HSA-Fmoc-insulin to diabetic rodents lowers circulating glucose levels for about 4 times longer than an equipotent dose of Zn2+-free insulin. Following subcutaneous administration, onset of the glucose-lowering effect is delayed 0.5-1 h and persists for 12 h. Thus, we present a prototype insulin formulation possessing three desirable parameters: high aqueous solubility, delayed action following subcutaneous administration, and prolonged therapeutic effect.     

QSAR study of mosquito repellents using Codessa Pro

Protection times provided by 31 synthetic repellents against Aedes aegypti mosquitoes were correlated with the chemical structures of these repellents using Codessa Pro software. Two statistically significant quantitative models with R2 values of ca. 0.80 are presented and discussed.     

Poly(L-histidyl-L-alanyl-α-L-glutamic acid). II. Catalysis of p-nitrophenyl acetate hydrolysis

The hydrolysis of p-nitrophenyl acetate is catalyzed by imidazole, free in solution or as the side chain in poly(His-Ala-Glu). This is based on the observations that the reaction is first order in ester and first order in nonprotonated imidazole. Catalysis of p-nitrophenyl acetate hydrolysis is dependent on solvent conditions. The effect of low concentrations of ethanol, dioxane, and trifluoroethanol were investigated. As the concentration of organic solvent is increased, the second-order rate constant for imidazole catalysis decreases. The decrease, however, is greater for imidazole than for poly(His-Ala-Glu). In 2% trifluoroethanol/water solution, free imidazole has twice the catalytic activity of polymeric imidazole, while in 40% trifluoroethanol/water they have equal activity. Since under the latter solvent conditions poly(His-Ala-Glu) is partially α-helical, the relative improvement in polymeric–imidazole catalysis may be attributed to imidazole hydrogen-bonded to a carboxylate ion. With this assumption the carboxylate–imidazole hydrogen-bonded system has been calculated to have three times the base catalytic activity of imidazole.     

Newly designed modifier prolongs the action of short-lived peptides and proteins by allowing their binding to serum albumin

We found that human serum albumin (HSA) contains a single binding domain for derivatives of long-chain fatty acid (LCFA)-like molecules in which the carboxylate is replaced by sulfonate. Accordingly, we have synthesized 16-sulfo-hexadecanoic acid-N-hydroxysuccinimide ester [HO(3)S-(CH(2))(15)-CONHS], an agent that reacts selectively with the amino side chains of peptides and proteins. A macromolecule containing a single 16-sulfohexadecanoate moiety associating with albumin with a K(a) value of 0.83 ± 0.08 × 10(6) M(-1), a sufficient affinity to extend the actions in vivo of such short-lived peptides and proteins. Subcutaneous administration of insulin-NHCO-(CH(2))(15)-SO(3)(-) into mice facilitated a glucose-lowering effect 4.3 times in duration and 6.6 times in area under the curve (AUC) as compared to an in vitro equipotent amount of Zn(2+)-free insulin. Similarly, subcutaneous and intravenous administration of exendin-4-NHCO-(CH(2))(15)-SO(3)(-) to mice yielded prolonged and stable reduction in glucose level, 5-9-fold longer than that of exendin-4. Also, a single subcutaneous administration of human interferon-α2-[NH-CO-(CH(2))(15)-SO(3)(-)](3) to mice yielded circulating antiviral activity over a period of 40 h. In conclusion, a simple, hydrophilic reagent has been engineered, synthesized, and studied. Its linkage to peptides and proteins in a monomodified fashion yielded hydrophilic, prolonged acting derivatives, due to their acquired ability to associate with serum albumin after administration.