ADME properties of CHF6366, a novel bi-functional M3-Muscarinic receptor antagonist and ß-2 adrenoceptor agonist (MABA) radiolabeled at both functional moieties

CHF6366, a dual action β₂-receptor agonist and M₃-muscarinic receptor antagonist developed for chronic obstructive pulmonary disease (COPD), was [¹⁴C]-radiolabeled on the two different functional moieties of the molecule (either aminobutanolic or carbamate) to characterize its ADME profile following intravenous (IV), intratracheal (IT) and oral (PO) administration.A very low oral bioavailability and a good balance between absorption and lung retention after IT administration were observed, together with a rapid distribution throughout the body and a complete metabolic transformation of the parent drug without relevant gender difference.CHF6366 was observed fully hydrolyzed to alcohol (CHF6387) and carboxylic acid (CHF6361) in plasma and urine after IV and IT administration, and mainly unchanged in feces only after oral administration. An important number of metabolites containing aminobutanolic moiety was excreted via urine, whereas carbamate-containing derivatives were excreted mainly by bile.The major metabolic routes of the alcoholic moiety (CHF6387) included isomerization (Ma7), conjugation with glucuronic acid and dehydrogenation, while the carboxylic acid moiety (CHF6361) was mainly metabolized through oxidation, glucuronide conjugation and, in both pathways, combinations of those metabolic reactions.No major differences arose also from in vitro metabolism profiles investigated using liver microsomes and hepatocytes of different species.

Autoradioluminography, a powerful and reliable tool for drug development: Accelera's experience

A deeper understanding of the pharmacokinetic and pharmacodynamic properties of a drug candidate is a pivotal component of drug discovery and development. Autoradiography is an excellent technique allowing exploiting the advantages of the use of radioisotopes in the drug disscovery field. The introduction of phosphor imaging technology has revolutionized the handling of drug distribution studies providing high-resolution images. Specifically, quantitative whole-body autoradioluminography is employed for preclinical study where the aim is to obtain information about the route of elimination and tissue distribution of a drug candidate. Autoradioluminography is also the technique of choice pursued to deal with all the issue that it is possible to encounter in all stage of drug development (ie, site-specific drug localization and retention, drug-drug interactions, penetration into specific target, specific tissue binding, crossing of brain blood barrier, and placental transfer). The purpose of this review is to give a picture of how autoradiography is employed in our laboratory as a key tool for advances in the assessment of the drug disposition and to validate new experimental models.

Role of efflux transporters in the absorption, distribution and elimination in rodents of a novel PDE4 inhibitor, CHF6001

CHF6001 is a new and potent PDE4 inhibitor for the treatment of human lung diseases, designed for topical administration by inhalation. In preclinical assessment CHF6001 appeared safe and devoid of emetic effect, which is typical side effect of PDE4 inhibitors in humans. CHF6001 absorption, distribution and excretion were evaluated in rats by PO and IV administration of [14C]CHF6001; additionally the role of transporters was investigated by using transfected cells expressing either human transporters or MDR1 and BCRP KO mice. [14C]CHF6001 intravenously administered as bolus distributed in all the tissues (with very low levels in brain and fetus) and it was mainly eliminated in bile. Following oral administration [14C]CHF6001 about half of the dose was absorbed through the gut. In vitro, CHF6001 was a substrate of human membrane transporters MDR1 and BCRP. In wild and BCRP KO mice CHF6001 was not detectable in brain, whereas it was measurable in Mdr1a/b KO mice. Therefore, in animal species Mdr1a/b plays a significant role in CHF6001 disposition, limiting its distribution into brain and contributing to the safety profile observed in preclinical evaluation. This behavior was confirmed by the results of the first human studies, where CHF6001 was safe and with no emetic effect at all the evaluated doses.

Carbon-14 labelled tribendimidine, a broad-spectrum anthelmintic drug

The preparation of [(14) C]tribendimidine, a broad-spectrum anthelmintic agent related to amidantel, and its use during excretion and metabolism studies in the rat are described in this paper.

Camptothecin poly[n-(2-hydroxypropyl) methacrylamide] copolymers in antitopoisomerase-I tumor therapy: intratumor release and antitumor efficacy

Soluble copolymers of camptothecin (CPT), based on poly[N-(2-hydroxypropyl) methacrylamide] (pHPMA), were obtained by conjugation through the degradable spacers -Gly-Phe-Leu-Gly- or -Gly-6-aminohexanoyl-Gly-. We investigated to what extent passive accumulation and retention of hydroxypropyl methacrylamide copolymer of CPT (pHPMA-CPT) in tumors and modulation of the drug release influence efficacy. Release of CPT in vivo was detected by time-resolved phase-shift fluorescence imaging on tumor specimens, based on the evidence that free and bound drug had different fluorescence lifetimes in solution. HT-29 murine specimens, obtained at several times after treatment with (3)H-labeled free CPT, pHPMA-Gly-Phe-Leu-Gly-CPT, or pHPMA-Gly-6-aminohexanoyl-Gly-CPT, were either imaged for time-resolved phase-shift fluorescence or subjected to autoradiography. Phase shifts of CPT conjugates were equal or longer than those of free CPT, indicating the presence of both free and polymer-bound drug in the tumor, in agreement with autoradiograms. pHPMA-Gly-Phe-Leu-Gly-CPT underwent relevant intratumor hydrolysis during the first 24 h, whereas the hydrolysis of pHPMA-Gly-6-aminohexanoyl-Gly-CPT was slow. The latter showed antitumor activity at doses from 10 to 22.5 mg/kg/day against s.c. HT-29, A2780, M14, and A549 s.c. xenografts. Moreover, inhibition of tumor growth lasted for up to 73-88 days, and cures were observed on mice with orthotopic implanted HT-29; pHPMA-Gly-Phe-Leu-Gly-CPT was 2-fold more potent than pHPMA-Gly-6-aminohexanoyl-Gly-CPT but less tolerated. Our data suggest that the efficacy of pHPMA-CPT copolymers is related to their intratumor accumulation, and in vivo properties of releasing CPT by esterolytic and proteolytic degradation.

Polymer-bound camptothecin: initial biodistribution and antitumour activity studies

Camptothecin (CPT) is a potent, antitumour drug acting mainly through inhibition of topoisomerase I during the S-phase of the cell cycle. Despite its impressive antitumour activity, clinical development was halted for unpredictable toxic events. Two soluble N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers were synthesised to contain CPT (5 wt.% and 10 wt.%). CPT was covalently linked at its alpha-hydroxyl group to the polymers through a Gly-Phe-Leu-Gly- spacer. In-vitro, CPT-conjugates were fairly resistant to hydrolysis in plasma as in buffer at neutral pH (0.2-0. 4% free CPT/h), while elastase and cysteine-proteases were able to release the active drug. Plasma levels in mice after intravenous administration of CPT-conjugates confirmed the modest hydrolysis in plasma. Plasma levels were approximately 5-fold lower than those observed at the highest tolerated dose of CPT administered in classical vehicles. Biodistribution in HT29 human colon carcinoma bearing mice was carried out after i.v. injection of [3H]CPT-conjugate and free [3H]CPT. Radioactivity uptake in tumour was evident only after [3H]CPT-conjugate treatment. Repeated intravenous administration of CPT-conjugates to HT29-bearing mice gave more than 90% tumour inhibition, some complete tumour regressions and no toxic deaths. The improved pharmacological profile on HT29 human colon carcinoma xenografts of the first poly(HPMA)-CPT conjugates might be ascribed to their prolonged intra-tumour retention and sustained release of the active drug.

High affinity and selectivity on 5-HT1A receptor of 1-aryl-4-[1-tetralin)alkyl]piperazines. 2

Several 4-alkyl-1-arylpiperazines that present a tetralin moiety on the terminal part of the side chain were synthesized in order to increase the selectivity on the 5-HT1A versus D-2, alpha 1, sigma, and other 5-HT receptors. Many changes have been effected on previous structures of type 3(1-aryl-4-[3-(1,2-dihydronaphthalen-4-yl)-n-propyl]piperazines). Several synthetic procedures were followed to obtain the final products, depending on the presence or absence of a double bond, as well as of a heteroatom on the side chain. In the first case versatile use of Grignard reaction was made, whereas in the second one usual synthetic ways were applied. Final compounds were evaluated for in vitro activity on dopamine D-1 and D-2, serotonin 5-HT1A, 5-HT1B, 5-HT1C, and 5-HT2, alpha 1 adrenergic, and sigma receptors by radioreceptor binding assay. For the 2-MeO-Ph, 2-pyridyl, and unsubstituted phenyl N-piperazine derivatives, low IC50 values (0.3 nM) on 5-HT1A receptors and high selectivity values were observed.