ABSTRACT
On the basis of the initial success of optimization of a novel series of imidazolopiperazines, a second generation of compounds involving changes in the core piperazine ring was synthesized to improve antimalarial properties. These changes were carried out to further improve the potency and metabolic stability of the compounds by leveraging the outcome of a set of in vitro metabolic identification studies. The optimized 8,8-dimethyl imidazolopiperazine analogues exhibited improved potency, in vitro metabolic stability profile and, as a result, enhanced oral exposure in vivo in mice. The optimized compounds were found to be more efficacious than the current antimalarials in a malaria mouse model. They exhibit moderate oral exposure in rat pharmacokinetic studies to achieve sufficient multiples of the oral exposure at the efficacious dose in toxicology studies.
Subject(s)
Antimalarials/pharmacology , Imidazoles/pharmacology , Malaria, Falciparum/drug therapy , Piperazines/pharmacology , Plasmodium falciparum/drug effects , Animals , Antimalarials/chemical synthesis , Antimalarials/chemistry , Antimalarials/pharmacokinetics , Biological Availability , Caco-2 Cells , Humans , Imidazoles/chemical synthesis , Imidazoles/chemistry , Imidazoles/pharmacokinetics , Malaria, Falciparum/parasitology , Mice , Mice, Inbred BALB C , Piperazines/chemical synthesis , Piperazines/chemistry , Piperazines/pharmacokinetics , Plasmodium falciparum/metabolism , Rats , Rats, Wistar , Structure-Activity RelationshipABSTRACT
A microflow CapNMR probe double-tuned for 1H and 13C was installed on a 400-MHz NMR spectrometer and interfaced to an automated liquid handler. Individual samples dissolved in DMSO-d6 are submitted for NMR analysis in vials containing as little as 10 microL of sample. Sets of samples are submitted in a low-volume 384-well plate. Of the 10 microL of sample per well, as with vials, 5 microL is injected into the microflow NMR probe for analysis. For quality control of chemical libraries, 1D NMR spectra are acquired under full automation from 384-well plates on as many as 130 compounds within 24 h using 128 scans per spectrum and a sample-to-sample cycle time of approximately 11 min. Because of the low volume requirements and high mass sensitivity of the microflow NMR system, 30 nmol of a typical small molecule is sufficient to obtain high-quality, well-resolved, 1D proton or 2D COSY NMR spectra in approximately 6 or 20 min of data acquisition time per experiment, respectively. Implementation of pulse programs with automated solvent peak identification and suppression allow for reliable data collection, even for samples submitted in fully protonated DMSO. The automated microflow NMR system is controlled and monitored using web-based software.
