ABSTRACT
We report a 28-day repeat dose immunotoxicity evaluation of investigational drug MIDD0301, a novel oral asthma drug candidate that targets gamma amino butyric acid type A receptors (GABAA R) in the lung. The study design employed oral administration of mice twice daily throughout the study period with 100 mg/kg MIDD0301 mixed in peanut butter. Compound dosing did not reveal signs of general toxicity as determined by animal weight, organ weight or haematology. Peanut butter plus test drug (in addition to ad libitum standard rodent chow) did not affect weight gain in the adult mice, in contrast to weight loss in 5 mg/kg prednisone-treated mice. Spleen and thymus weights were unchanged in MIDD0301-treated mice, but prednisone significantly reduced the weight of those organs over the 28-day dosing. Similarly, no differences in spleen or thymus histology were observed following MIDD0301 treatment, but prednisone treatment induced morphological changes in the spleen. The number of small intestine Peyer's patches was not affected by MIDD0301 treatment, an important factor for orally administered drugs. Circulating lymphocyte, monocyte and granulocyte numbers were unchanged in the MIDD0301-treated animals, whereas differential lymphocyte numbers were reduced in prednisone-treated animals. MIDD0301 treatment did not alter IgG antibody responses to dinitrophenyl following dinitrophenyl-keyhole limpet haemocyanin immunization, indicating that systemic humoral immune function was not affected. Taken together, these studies show that repeated daily administration of MIDD0301 is safe and not associated with adverse immunotoxicological effects in mice.
Subject(s)
Anti-Inflammatory Agents/administration & dosage , Asthma/drug therapy , Azepines/administration & dosage , Drugs, Investigational/administration & dosage , GABA-A Receptor Agonists/administration & dosage , Heterocyclic Compounds, 3-Ring/administration & dosage , Imidazoles/administration & dosage , Immune Tolerance/drug effects , Adjuvants, Immunologic/administration & dosage , Administration, Oral , Animals , Anti-Inflammatory Agents/adverse effects , Asthma/blood , Asthma/immunology , Azepines/pharmacology , Disease Models, Animal , Drug Evaluation, Preclinical , Drugs, Investigational/adverse effects , Female , GABA-A Receptor Agonists/adverse effects , Hemocyanins/administration & dosage , Hemocyanins/immunology , Heterocyclic Compounds, 3-Ring/adverse effects , Humans , Imidazoles/pharmacology , Leukocyte Count , Male , Mice , Prednisone/administration & dosage , Prednisone/adverse effects , Weight LossABSTRACT
Recent reports indicate that α6ß2/3γ2 GABAAR selective ligands may be important for the treatment of trigeminal activation-related pain and neuropsychiatric disorders with sensori-motor gating deficits. Based on 3 functionally α6ß2/3γ2 GABAAR selective pyrazoloquinolinones, 42 novel analogs were synthesized, and their in vitro metabolic stability and cytotoxicity as well as their in vivo pharmacokinetics, basic behavioral pharmacology, and effects on locomotion were investigated. Incorporation of deuterium into the methoxy substituents of the ligands increased their duration of action via improved metabolic stability and bioavailability, while their selectivity for the GABAAR α6 subtype was retained. 8b was identified as the lead compound with a substantially improved pharmacokinetic profile. The ligands allosterically modulated diazepam insensitive α6ß2/3γ2 GABAARs and were functionally silent at diazepam sensitive α1ß2/3γ2 GABAARs, thus no sedation was detected. In addition, these analogs were not cytotoxic, which render them interesting candidates for treatment of CNS disorders mediated by GABAAR α6ß2/3γ2 subtypes.
Subject(s)
GABA Antagonists/chemical synthesis , GABA Antagonists/pharmacology , Receptors, GABA-A/drug effects , Animals , Anti-Anxiety Agents/chemical synthesis , Anti-Anxiety Agents/pharmacology , Behavior, Animal/drug effects , Biological Availability , Deuterium , Drug Design , Female , GABA Antagonists/pharmacokinetics , HEK293 Cells , Humans , Hypnotics and Sedatives/pharmacology , Male , Maze Learning/drug effects , Mice , Mice, Inbred C57BL , Microsomes, Liver , Motor Activity/drug effects , Muscle Strength/drug effects , Rats , Rats, Wistar , Substrate SpecificityABSTRACT
A series of novel imidazobenzodiazepine analogs of the lead chiral ligand SH-053-2'F-S-CH3 (2), an α2/α3/α5 (Bz)GABA (A)ergic receptor subtype selective ligand, which reversed PCP-induced prepulse inhibition (PPI) of acoustic startle, were synthesized. These chiral (S)-CH3 ligands are targeted for the treatment of schizophrenia and depression. These new ligands were designed by modifying the liable ester functionality in 2 to improve the metabolic stability, cytotoxicity, and activity as compared to 2. Based on the data to date, the most promising ligands are the N-cyclopropyl amide GL-I-55 (8c) and the methyl bioisostere GL-I-65 (9a). The in vitro metabolic stability, cytotoxicity and in vivo locomotor effects are described in this report. Based on these results, 8c and 9a are the most promising for further in vivo pharmacology.
