Structure–antileukemic activity relationship study of B- and D-ring modified and nonmodified steroidal esters of 4-methyl-3-N,N-bis(2-chloroethyl)amino benzoic acid: a comparative study

Abstract

This study was designed as a rational continuation of our research regarding the functional requirements essential for the antileukemic activity of compounds comprising an alkylating moiety and a modified steroid. The steroidal esteric derivatives of 4-methyl-3-N,N-bis(2-chloroethyl)amino benzoic acid were tested on leukemias P388 and L1210 in vivo and in normal human lymphocytes in vitro. Among them the B-lactamic steroidal esters proved more potent antileukemic agents than the 7-oxidized and those with a simple B-ring, but not more effective inducers of DNA damage and cell cycle arrest in vitro. We speculate that these results indicate a different mechanism of action induced by the lactamized B steroidal ring, in comparison to the 7-keto or the D-lactamic groups, which involves the interaction of the -NHCO- moiety with cellularcomponents essential for tumor growth. 4-Methyl-3-N,N-bis(2-chloroethyl)amino benzoic acid proved a more proper module for the B-lactams than chlorambucil and phenyl acetic acid's nitrogen mustard probably because the esteric bond is less cleaved by the esterases, resulting in an increased concentration of the drug in the vinicity of the target site essential for an antineoplasmatic response.

Steroidal esters of the aromatic nitrogen mustard 2-[4-N,N-bis(2-chloroethyl)amino-phenyl]butanoic acid (2-PHE-BU)

“…Among the tested compounds, derivative 7g was the most toxic; derivatives 7a, 7b, 7d, 7h, 7i, 7j, and 7k showed moderate toxicity, whereas derivatives 7c, 7e, and 7f showed low toxicity values. These results are in agreement with those of previous studies [19,20,[33][34][35], indicating that the conjugation of aromatic nitrogen mustards either on simple or modified steroidal skeletons results in the limitation of their undesired or toxic effects, possibly because of the enhancement of their lipophilicity and effective transport through the cell membranes to the nucleus, close to DNA-specific sites. Table 1 Toxicity and antitumor activity of 2-PHE-BU and steroidal esters 7a-k on P388-leukemia-bearing mice LD 50 values were estimated graphically, where the percentage of deaths because of the toxicity of each dose is shown in the ordinate, whereas the doses administered are indicated on the abscissae on semilogarithmic paper.…”

“…As we have reported elsewhere, the modification of the B ring into a seven-membered lactam ring induces conformational changes in the steroidal part, which enhances the genotoxic and cytotoxic activity [36] as well as the invivo antileukemic potency [15] of the target steroidal esters. Especially, B,D-bilactam derivatives have shown diverse in-vivo toxicity and moderate to excellent antileukemic activity depending on the structural features of the conjugated nitrogen mustard [16,20,37]. These results possibly indicate an alternative mechanism of action for the B-lactamic steroidal esters that does not involve indispensably the interaction of the endocyclic -NHCO -group in the B-ring with cellular sites crucial for tumor growth, but with other specific binding sites that are able to induce antileukemic responses.…”

“…2) with enhanced activity and reduced toxicity compared with the corresponding nitrogen mustards against in-vitro and in-vivo experimental tumors [15,16]. Extensive structure-activity relationship (SAR) studies have shown unique structural features of both the steroidal part and the nitrogen mustard, which contribute positively to the bioactivity of the target steroidal esters [16][17][18][19][20]. Furthermore, recent 3D QSAR/CoMFA and CoMSIA studies have led to the generation of related models that indicate the influence of stereoelectronic and physicochemical parameters on the antileukemic activity of target compounds [21].…”

Steroid Conjugates as Potential Anti-Cancer Agents

“…Согласно современным представлениям, стероидная часть конъюгата не только является биологическим вектором для направленной доставки алкилирующего фрагмента, но и обеспечивает образование специфических комплексов с ДНК и препятствует действию ферментов репарации. Конъюгаты проявляли противоопухолевый эффект, отличающийся от такового и для стероида, и для алкилирующего агента [31][32][33][34][35][36].…”

Σχεδιασμός, Σύνθεση Και Αποτίμηση Βιολογικής Δραστικότητας Νέων Στεροειδών Εστέρων Με Τροποποιημένους Αλκυλιωτικούς Παράγοντες

“…Όπως και παλιότερα έχει αναφερθεί από την ερευνητική μας ομάδα, η τροποποίηση του Β δακτυλίου σε έναν επταμελή λακταμικό δακτύλιο επιφέρει διαμορφωτικές αλλαγές στο στεροειδικό τμήμα του μορίου, γεγονός που ενισχύει τη γενοτοξική, την κυτταροτοξική170 , αλλά και την αντιλευχαιμική δραστικότητα 153 του στεροειδικού εστέρα. Ειδικότερα, τα Β,Δ-διλακταμικά παράγωγα, παρουσίασαν διάφορες τιμές in vivo τοξικότητας με μια μέτρια έως πολύ καλή αντιλευχαιμική δραστικότητα ανάλογα με τα δομικά χαρακτηριστικά της συζευγμένης μουστάρδας171,172,173 . Μέσα από τα αποτελέσματα αυτἀ, πιθανόν να προτείνεται ένας εναλλακτικός μηχανισμός δράσης για τους Β-λακταμικούς εστέρες, ο οποίος δεν περιλαμβάνει απαραίτητα την αλληλεπίδραση της ενδοκυκλικής ομάδας -NHCO-με σημαντικές για την ανάπτυξη του όγκου κυτταρικές περιοχές, αλλά με άλλες περιόχες (binding sites), ικανές να προκαλέσουν αντιλευχαιμική απάντηση.…”