The main objective of the research described in this thesis has been the design and synthesis of inhibitors of the enzyme dihydrofolate reductase (DHFR) intended for local administration and devoid of systemic side-effects. The blocking of the enzymatic activity of DHFR is a key element in the treatment of many diseases, including cancer, bacterial and protozoal infections, and also opportunistic infections associated with AIDS (Pneumocystis carinii pneumonia, PCP). Recent research indicates that the enzyme also is involved in various autoimmune diseases, e.g., rheumatoid arthritis, inflammatory bowel diseases and psoriasis. Many useful antifolates have been developed to date although problems remain with toxicity and selectivity, e.g., the well-established, classical antifolate methotrexate exerts a high activity but also high toxicity. The new antifolates described herein were designed to retain the pharmacophore of methotrexate, but encompassing an ester group, so that they also would serve as substrates for the endogenous hydrolytic enzymes, e.g., esterases. Such antifolates would optimally comprise good examples of soft drugs because they in a controlled fashion would be rapidly and predictably metabolized to non-toxic metabolites after having exerted their biological effect at the site of administration. A preliminary screening of a large series of simpler aromatic esters as model compounds in a biological assay consisting of esterases from different sources was performed. The structural features of the least reactive ester were substituted for the methyleneamino bridge in methotrexate to produce analogues that were chemically stable but potential substrates for DHFR as well as for the esterases. The new inhibitor showed desirable activity towards rat liver DHFR, being only eight times less potent then methotrexate. Furthermore, the derived metabolites were found to be poor substrates for the same enzyme. The new compound showed good activity in a mice colitis model in vivo, but a pharmacokinetic study revealed that the half-life of the new compound was similar to methotrexate. A series of compounds characterized by a high lipophilicity and thus expected to provide better esterase substrates were designed and synthesized. One of these analogues in which three methoxy groups were substituted for the glutamic residue of methotrexate exhibited favorable pharmacokinetics. This compound is structurally similar to another potent DHFR inhibitor, trimetrexate, used in the therapy of PCP (vide supra). The new inhibitor that undergoes a fast metabolism in vivo is suitable as a model to further investigate the soft drug concept.

<p>The main objective of the research described in this thesis has been the design and synthesis of inhibitors of the enzyme dihydrofolate reductase (DHFR) intended for local administration and devoid of systemic side-effects. The blocking of the enzymatic activity of DHFR is a key element in the treatment of many diseases, including cancer, bacterial and protozoal infections, and also opportunistic infections associated with AIDS (<i>Pneumocystis carinii</i> pneumonia, PCP). Recent research indicates that the enzyme also is involved in various autoimmune diseases, e.g., rheumatoid arthritis, inflammatory bowel diseases and psoriasis. Many useful antifolates have been developed to date although problems remain with toxicity and selectivity, e.g., the well-established, classical antifolate methotrexate exerts a high activity but also high toxicity. The new antifolates described herein were designed to retain the pharmacophore of methotrexate, but encompassing an ester group, so that they also would serve as substrates for the endogenous hydrolytic enzymes, e.g., esterases. Such antifolates would optimally comprise good examples of <i>soft drugs</i> because they in a controlled fashion would be rapidly and predictably metabolized to non-toxic metabolites after having exerted their biological effect at the site of administration.</p><p>A preliminary screening of a large series of simpler aromatic esters as model compounds in a biological assay consisting of esterases from different sources was performed. The structural features of the least reactive ester were substituted for the methyleneamino bridge in methotrexate to produce analogues that were chemically stable but potential substrates for DHFR as well as for the esterases.</p><p>The new inhibitor showed desirable activity towards rat liver DHFR, being only eight times less potent then methotrexate. Furthermore, the derived metabolites were found to be poor substrates for the same enzyme. The new compound showed good activity in a mice colitis model <i>in vivo</i>, but a pharmacokinetic study revealed that the half-life of the new compound was similar to methotrexate. A series of compounds characterized by a high lipophilicity and thus expected to provide better esterase substrates were designed and synthesized. One of these analogues in which three methoxy groups were substituted for the glutamic residue of methotrexate exhibited favorable pharmacokinetics. This compound is structurally similar to another potent DHFR inhibitor, trimetrexate, used in the therapy of PCP (<i>vide supra</i>). The new inhibitor that undergoes a fast metabolism <i>in vivo</i> is suitable as a model to further investigate the soft drug concept.</p>

Après plusieurs réformes du Code pénal espagnol, de 1971 à 1995, confortées par la loi du 22 juin 2010, le législateur a voulu établir une distinction entre les drogues : les substances qui causent un grave danger à la santé et les autres. Parallèlement, la doctrine majoritaire et la jurisprudence ont poursuivi cette avancée en consacrant l'impunité du consommateur de "drogues toxiques, de stupéfiants ou de substances psychotropes". Cependant, s'il s'agit d'un drogodélinquant ou d'un consommateur qui diffuserait sa déviance et en particulier à l'encontre d'un mineur ou d'une personne dont les facultés physiques sont altérées, l'impunité est reconsidérée. De même, tout prosélytisme tendant à favoriser la consommation des drogues remet en cause la libéralisation voulue par les autorités espagnoles. Dès lors, certains auteurs prônent la légalisation pour que le principe de l'impunité du consommateur soit effectif. / Between 1971 and 1995, the Spanish code incurred several reforms. On June 22nd 2010, a new law confirmed those reforms, making a distinction between the drugs which jeopardize the public health and the other drugs. In the same time, the main doctrine and case law have gone a little further by asserting that consuming “toxic drugs, narcotics or psychotropic substances” was not unlawful anymore. However it remains unlawful to become a drug delinquent or spread one's deviancy among minors and mentally disturbed persons. Besides, proselytizing in favour of drug consuming goes against the Spanish authorities'will to liberalize the drug laws. Some authors now go so far as to advocate a legislation which would vouch for total consumer impunity. / Después de varias reformas del Código penal español, desde 1971 hasta 1995, confortadas por la ley del 22 junio de 2010, el legislator quiso establecer una distinción entre las drogas : las sustancias que causan grave daño a la salud y las otras. Al mismo tiempo, la doctrina mayoritaria y la jurisprudencia siguieron en esta vía, consagrando la impunidad del consumidor de "drogas tóxicas, de estupefacientes o de sustancias psicotrópicas". Sin embargo, si se trata de un drogodelincuente o de un consumidor que difunde su toxicomanía y particularmente en contra de un menor o de una persone con facultades psíquicas disminuidas, se vuelve a considerar la impunidad. Lo mismo, todo proselitismo que favorezca la consumición de drogas pone en peligro la liberalización deseada por las autoridades españolas. Desde entonces, algunos autores piensan que la legalización del consumo establecerá la efectividad del principio de la impunidad.