A phase 1 study to investigate the absorption, distribution, metabolism and excretion of brepocitinib in healthy males using a 14 C-microdose approach.

AIMS: Brepocitinib is a tyrosine kinase 2/Janus kinase 1 inhibitor being investigated for the treatment of several autoimmune diseases. This study assessed the absorption, distribution, metabolism and excretion of oral brepocitinib, and the absolute oral bioavailability (F) and fraction absorbed (Fa ) using a 14 C microtracer approach. METHODS: This was a phase 1 open-label, nonrandomized, fixed sequence, two-period, single-dose study of brepocitinib in healthy male participants. Participants received a single oral 60 mg dose of 14 C brepocitinib (~300 nCi) in Period A, then an unlabelled oral 60 mg dose followed by an intravenous (IV) 30 µg dose of 14 C labelled brepocitinib (~300 nCi) in Period B. Mass balance, pharmacokinetic parameters and safety were assessed. RESULTS: Six participants were enrolled. Brepocitinib was absorbed rapidly following oral administration. In Period A, total recovery of the oral dose was 96.7% ± 6.3% (88.0% ± 8.0% in urine, 8.7% ± 2.1% in faeces). In Period B, a small fraction (6.0% of the oral dose) was recovered unchanged in urine. F and Fa were 74.6% (90% confidence interval 67.3%, 82.8%) and 106.9%, respectively. Brepocitinib demonstrated an acceptable safety profile and was well tolerated following oral or oral then IV administrations. No deaths, serious adverse events or discontinuations were reported. CONCLUSION: Intestinal absorption of brepocitinib was essentially complete after oral administration, with F ~75%. Drug-related material recovery was high, with the majority excreted in urine. The major route of elimination of brepocitinib was renal excretion as metabolites, whereas urinary elimination of unchanged brepocitinib was minor. NCT: NCT03770039.

Distribution, Metabolism, and Excretion of Gedatolisib in Healthy Male Volunteers After a Single Intravenous Infusion.

In this open-label study (NCT02142920), we investigated the distribution, pharmacokinetics, and metabolism of the pan-class-I isoform phosphatidylinositol 3-kinase/mammalian target of rapamycin inhibitor gedatolisib (PF-05212384), following a single intravenous administration in healthy male subjects. A single, 89-mg, intravenous dose of gedatolisib was associated with a favorable safety profile in the 6 healthy subjects evaluated. Peak plasma concentrations for unchanged gedatolisib and total radioactivity were observed at the end of the 30-minute infusion. The only observed drug-related material in plasma was the parent drug, gedatolisib. Terminal half-life for plasma gedatolisib was ∼37 hours. Following the dose, 66%-73% of drug-related material was recovered in the feces. Metabolism of gedatolisib was trace; only 1 oxidative metabolite, M5, was identified in feces (<1% of total dose). Identification of gedatolisib in feces suggests that biliary and/or intestinal secretion of unchanged parent drug significantly contributes to gedatolisib clearance.

Impact of Acid-Reducing Agents on the Pharmacokinetics of Palbociclib, a Weak Base With pH-Dependent Solubility, With Different Food Intake Conditions.

Palbociclib free base capsule is a weak base drug with highly pH-dependent solubility. In vitro and in vivo studies evaluated the impact of acid-reducing agents on exposure of palbociclib and determined whether the impact, if any, can be mitigated by food. A drug-drug interaction study (study 1) was conducted first under fasted conditions and showed that coadministration of multiple doses of the proton-pump inhibitor rabeprazole substantially reduced palbociclib mean area under the concentration-time curve from time 0 to infinity and maximum observed plasma concentration by 62% and 80%, respectively. In vitro assessment suggested that the presence of bile salt mixed micelles to mimic the fed state can significantly enhance the solubility of palbociclib. Subsequently, study 2 was conducted under fed conditions and demonstrated that coadministration of rabeprazole decreased palbociclib maximum observed plasma concentration by 41% but had limited impact on area under the concentration-time curve from 0 to infinity (13% decrease). This study also showed that the histamine-2 receptor antagonist famotidine and local antacid with staggered dosing had no impact on palbociclib exposure under fed conditions. Food intake effectively mitigated the impact of acid-reducing agents on palbociclib exposure. Palbociclib free base capsule should be taken with food, and acid-reducing agent use does not need to be avoided.

Effects of Renal Function on Crizotinib Pharmacokinetics: Dose Recommendations for Patients with ALK-Positive Non-Small Cell Lung Cancer.

BACKGROUND AND OBJECTIVES: Crizotinib (250 mg twice daily) is the first anaplastic lymphoma kinase (ALK) inhibitor approved for treatment of ALK-positive non-small-cell lung cancer (NSCLC). The objectives of the current study were to evaluate the effects of mild, moderate, and severe renal impairment on crizotinib pharmacokinetics and to make crizotinib dosing recommendations for ALK-positive NSCLC patients with renal impairment on the basis of the findings. METHODS: The effects of varying degrees of renal impairment on crizotinib pharmacokinetics were evaluated by: (1) analysis of mild and moderate renal impairment on multiple-dose pharmacokinetics of crizotinib in ALK-positive NSCLC patients from the PROFILE 1001 and PROFILE 1005 trials; (2) analysis of severe renal impairment on single-dose pharmacokinetics of crizotinib in volunteers (Study 1020); and (3) prediction of the effect of severe renal impairment on multiple-dose crizotinib pharmacokinetics using a physiologically-based pharmacokinetic model of crizotinib. RESULTS: No clinically relevant changes in plasma crizotinib exposure were observed in NSCLC patients with mild or moderate renal impairment. After a single 250-mg dose, the area under the plasma concentration-time curve (AUC) for crizotinib was 1.8-fold greater in subjects with severe renal impairment than in those with normal renal function. Physiologically-based pharmacokinetic modeling indicated a similar increase in steady-state AUC after multiple dosing. CONCLUSIONS: These results suggest no dose adjustment for patients with mild or moderate renal impairment. The recommended crizotinib dose for patients with severe renal impairment not requiring dialysis is 250 mg once daily.

Discovery of ANA975: an oral prodrug of the TLR-7 agonist isatoribine.

ANA975, a 5-amino-3-beta -D-ribofuranosyl-3H-thiazolo[4,5-d]pyrimidin-2-one derivative, was synthesized in the search of an oral prodrug of isatoribine, a small molecule toll-like receptor 7 (TLR-7) agonist. Several strategies were studied to enable the kilogram-scale synthesis of ANA975. Three general total syntheses are described. In the phase I clinical study of ANA975 against hepatitis C virus (HCV), conversion to isatoribine in plasma was rapid and effective, delivering levels of isatoribine that have been shown to be clinically relevant.

Synthesis of irreversibly binding bicalutamide analogs for imaging studies.

A new synthetic methodology for preparing radioactive androgen receptor binding compounds in order to determine receptor-ligands interactions has been developed.

Pharmacology, pharmacokinetics, and metabolism of acetothiolutamide, a novel nonsteroidal agonist for the androgen receptor.

The present study characterized the in vitro androgen receptor (AR) binding affinity, in vitro and in vivo pharmacological activity, and in vivo pharmacokinetics and metabolism of acetothiolutamide, a nonsteroidal AR ligand. AR binding was determined by a competitive binding assay. In vitro AR agonist activity was examined by a cotransfection assay. Acetothiolutamide displayed high AR binding affinity (K(i) = 4.9 +/- 0.2 nM) and full agonist activity in the in vitro studies. Next, the androgenic, anabolic, and antiandrogenic activity of acetothiolutamide was evaluated in a castrated immature rat model. In this animal model, acetothiolutamide exhibited an overall negligible androgenic effect, but a statistically significant anabolic effect at high subcutaneous doses. Also, acetothiolutamide demonstrated a noticeable antiandrogenic effect in castrated rats supplemented with testosterone propionate. To understand the causes for the observed disparity between in vitro and in vivo activities, pharmacokinetics and metabolism of acetothiolutamide were studied in male Sprague-Dawley rats. Acetothiolutamide was rapidly cleared from rat plasma (clearance of about 45 ml/min/kg) in a concentration-independent manner after i.v. dosing. Acetothiolutamide was completely absorbed after subcutaneous administration, but not bioavailable after oral dose. In the metabolism study, the unchanged molecule and its metabolites in urine and fecal samples were detected by high-performance liquid chromatography-mass spectrometry. The structures of major metabolites were elucidated with liquid chromatography-tandem mass spectrometry. After i.v. administration, acetothiolutamide was excreted in urine and feces as unchanged drug and a variety of metabolites. Oxidation, hydrolysis, and sulfate conjugation of phase I metabolites were the major metabolic pathways of acetothiolutamide in rats. Overall, the high plasma clearance of acetothiolutamide, due to its extensive hepatic metabolism, likely contributed to its lack of androgenic activity in vivo.

Key structural features of nonsteroidal ligands for binding and activation of the androgen receptor.

The purposes of the present studies were to examine the androgen receptor (AR) binding ability and in vitro functional activity of multiple series of nonsteroidal compounds derived from known antiandrogen pharmacophores and to investigate the structure-activity relationships (SARs) of these nonsteroidal compounds. The AR binding properties of sixty-five nonsteroidal compounds were assessed by a radioligand competitive binding assay with the use of cytosolic AR prepared from rat prostates. The AR agonist and antagonist activities of high-affinity ligands were determined by the ability of the ligand to regulate AR-mediated transcriptional activation in cultured CV-1 cells, using a cotransfection assay. Nonsteroidal compounds with diverse structural features demonstrated a wide range of binding affinity for the AR. Ten compounds, mainly from the bicalutamide-related series, showed a binding affinity superior to the structural pharmacophore from which they were derived. Several SARs regarding nonsteroidal AR binding were revealed from the binding data, including stereoisomeric conformation, steric effect, and electronic effect. The functional activity of high-affinity ligands ranged from antagonist to full agonist for the AR. Several structural features were found to be determinative of agonist and antagonist activities. The nonsteroidal AR agonists identified from the present studies provided a pool of candidates for further development of selective androgen receptor modulators (SARMs) for androgen therapy. Also, these studies uncovered or confirmed numerous important SARs governing AR binding and functional properties by nonsteroidal molecules, which would be valuable in the future structural optimization of SARMs.

Novel nonsteroidal ligands with high binding affinity and potent functional activity for the androgen receptor.

While nonsteroidal androgen receptor (AR) antagonists have been known for many years, and used in the clinic for the treatment of hormone dependent prostate cancer, very little is known about nonsteroidal AR agonists. We designed and synthesized a series of chiral bicalutamide analogs, which bear electron-withdrawing groups (either a cyano or a nitro group at the 4-position and a trifluoromethyl group at the 3-position) in the aromatic A ring, and different substituents at the para position in the aromatic B ring of the parent molecule. We also synthesized a series of racemic bicalutamide analogs, which have a trifluoromethyl group instead of a methyl group at the R(2) position. We examined AR binding affinities of our compounds in a competitive binding assay with a radiolabeled high affinity AR ligand, 3H-mibolerone, and also measured their abilities to stimulate AR-mediated transcriptional activation in a cotransfection assay. These studies demonstrated that (1) nonsteroidal ligands can be structurally modified from known nonsteroidal antiandrogens to generate ligands capable of activating AR-mediated transcriptional activation. (2) R-isomer analogs exhibit higher AR binding affinity and more potent functional activity than their corresponding S-isomers in all cases. (3) All sulphide analogs show higher AR binding affinity and more potent functional activity than their corresponding sulphone analogs, with the exception of ligand R-8. Those ligands which exhibit high AR binding affinity and potent functional activity for human AR may provide effective clinical uses for male fertility, male contraception, and hormone replacement therapy.