Non-clinical studies in the process of new drug development - Part II: Good laboratory practice, metabolism, pharmacokinetics, safety and dose translation to clinical studies

The process of drug development involves non-clinical and clinical studies. Non-clinical studies are conducted using different protocols including animal studies, which mostly follow the Good Laboratory Practice (GLP) regulations. During the early pre-clinical development process, also known as Go/No-Go decision, a drug candidate needs to pass through several steps, such as determination of drug availability (studies on pharmacokinetics), absorption, distribution, metabolism and elimination (ADME) and preliminary studies that aim to investigate the candidate safety including genotoxicity, mutagenicity, safety pharmacology and general toxicology. These preliminary studies generally do not need to comply with GLP regulations. These studies aim at investigating the drug safety to obtain the first information about its tolerability in different systems that are relevant for further decisions. There are, however, other studies that should be performed according to GLP standards and are mandatory for the safe exposure to humans, such as repeated dose toxicity, genotoxicity and safety pharmacology. These studies must be conducted before the Investigational New Drug (IND) application. The package of non-clinical studies should cover all information needed for the safe transposition of drugs from animals to humans, generally based on the non-observed adverse effect level (NOAEL) obtained from general toxicity studies. After IND approval, other GLP experiments for the evaluation of chronic toxicity, reproductive and developmental toxicity, carcinogenicity and genotoxicity, are carried out during the clinical phase of development. However, the necessity of performing such studies depends on the new drug clinical application purpose.

Ação de extratos de plantas medicinais sobre a motilidade do trato gastrointestinal / Action of medicinal plant extracts on the gastrointestinal tract motility

Muitas plantas são utilizadas pela população para o tratamento e a cura de doenças. Entre elas encontram-se a Persea major Kopp, Piper mollicomum Kunth. e Serjania erecta Radlk. as quais são utilizadas para diversas enfermidades, inclusive para tratar distúrbios do trato gastrointestinal. O objetivo deste trabalho foi estudar os efeitos dos extratos dessas três plantas sobre a motilidade gastrointestinal. Camundongos Swiss foram tratados com os extratos pela via oral 1 hora antes da administração de uma solução semisólida de carboximetilcelulose 1,5% e vermelho de fenol 0,05% e, após 15 minutos, o esvaziamento gástrico e o trânsito intestinal avaliados. O extrato hidroalcoólico da P. major (100 a 1000 mg Kg-1, p.o.) e o extrato hidroalcoólico da P. mollicomum (100 e 300 mg Kg-1, p.o.) aumentaram o trânsito intestinal. No entanto, somente o extrato da P. major (100 e 300 mg Kg-1) também aumentou o esvaziamento gástrico. O extrato etanólico da S. erecta (100 a 1000 mg Kg-1, p.o.) não alterou a motilidade gastrointestinal. Estes resultados sugerem que a Persea major e a Piper mollicomum mereçam estudos mais aprofundados em busca de princípios ativos ou matéria vegetal efetiva para o tratamento de distúrbios do trato gastrointestinal como a constipação.

Many plants are popularly used for the treatment and healing of diseases. The Persea major Kopp, Piper mollicomum Kunth. and Serjania erecta Radlk. are used in several illnesses, including the treatment of disorders of the gastrointestinal tract. The aim of this study was to evaluate the effects of the extracts of these plants on the gastrointestinal motility. Swiss mice were orally treated with extracts one hour before the administration of a semisolid solution of 1.5% carboxymethylcellulose and 0.05% phenol red. After 15 minutes, the gastric emptying and intestinal transit were determined. The hydroalcoholic extract of P. major (100 to 1000 mg Kg-1, p.o.) and the hydroalcoholic extract of P. mollicomum (100 and 300 mg Kg-1, p.o.) increased the intestinal transit. However, only the P. major extract (100 and 300 mg Kg-1) increased the gastric emptying. The ethanolic extract of S. erecta (100 to 1000 mg Kg-1, p.o.) did not alter the gastrointestinal motility. These results suggest that Persea major and Piper mollicomum can be of interest for further studies in the search of active principles or effective plant material for the treatment of disorders of the gastrointestinal tract, such as constipation.

Nylon wool column: a tool for obtaining monokine-rich eluates in the absence of serum

Diverse conditions for stimulating human mononuclear cells to release thymocyte costimulatory factors were tested for their contribution to the generation of supernatants high titers of these monokines. Activity titers increased with LPS concentration, reaching a plateau between 1 and 10 microng/ml. Indomethacin did not modify the monokine, but the assay for thymocyte costimulatory activity was substantially affected by inhibitory substances produced by the monocytes in the absence of indomethacin. The use of nylon wool columns to trap the cells was shown to be effective in raising cellular densities without decreasing activity titers. As result, the yield per cell could be maintained even in the absence of serum, an important step toward the goal of purifiying bioactive from crude broths

Jacalin: an excellent lectin for obtaining T cell growth activity from rat spleen cells

The parameters involved in the choice of an optimal T cell growth activity (TCGAc) induction protocol using rat spleen cells simultated with jacalin were studied. In the absence of serum, 5 microng/ml jacalin was sufficient to obtain maximal TCGAc, Supernatants could be harvested at any time between 24 and 72 h since significant consumption of TCGAc was not observed during this interval. TCGAc recovery was increased in the presence of 5% fetal calf serum, with the optimal jacalin dose being about 25 microng/ml. The recommended harvesting time was 24 h to reduce TCGAc loss due to cellular proliferation. Human or rat sera were not suitable since they absorb significant amounts of jacalin, thus shifting the optimal lectin concentration to > 800 microng/ml. Indomethacin (1 microng/ml) had little enchancing effect on TCGAc production by rat cells but rendered conditioned media less inhibitory of cytotoxic T lymphocyte L (CTLL) proliferation. Addition of 50 ng/ml phorbol myristate acetate is not recommended if the supernatants are to be used for T cell line maintenance, since the agent interferes with CTL function, while only doubling TCGAc production. Jacalin-stimulated TCGAc recovery is comparable, in titer, to that obtained with concanavalin A under the best conditions, but the former is less expensive due to the large quantities of lectin recovered from a single jackfruit, besides being less toxic for rat spleen cells

Sugar inhibition of the lectin jacalin: comparison of three assays

1. Three assays were used to test nine sugars for inhibition of jacalin activity prepared from Artocarpus intefrifolia. Rat spleen proliferation was unssuitable since the measurement of the effects of sugars against jacalin binding was complicated by their simultaneous metavolic effects on the cells. 2. Based partly on a sheep red blood cell hemagglutination assay and mainly on human serum protein preciptation, the following potencies in relation to D(+)-galactose (taken as 1) were obtained: 1-0-methyl-alfa-D-galactopyranoside, 40; methyl-alfa-D-mannopyranoside and D(+)-mannose, 0.12; ß-Dd-(-)-fructose, 0.08; alfa - D(+)-glucose and 1 - 0-methyl-ß-D-glucopyranoside, <0.04