Absorption, metabolism and excretion of 14C-emvododstat following repeat daily oral dose administration in human volunteers using a combination of microtracer radioactivity and high radioactivity doses.

Emvododstat is a potent inhibitor of dihydroorotate dehydrogenase and is now in clinical development for the treatment of COVID-19 and acute myeloid leukemia. Since the metabolism and pharmacokinetics of emvododstat in humans is time­dependent, a repeat dose study design using a combination of microtracer radioactivity and high radioactivity doses was employed to evaluate the metabolism and excretion of emvododstat near steady state. Seven healthy male subjects each received 16 mg/0.3 µCi 14C-emvododstat daily oral doses for 6 days followed by a 16 mg/100 µCi high radioactivity oral dose on Day 7. Following the last 16 mg/0.3 µCi 14C­emvododstat dose on Day 6, total radioactivity in plasma peaked at 6 h post-dose. Following a high radioactivity oral dose (16 mg/100 µCi) of 14C-emvododstat on Day 7, both whole blood and plasma radioactivity peaked at 6 h, rapidly declined from 6 h to 36 h post-dose, and decreased slowly thereafter with measurable radioactivity at 240 h post-dose. The mean cumulative recovery of the administered dose was 6.0% in urine and 19.9% in feces by 240 h post-dose, and the mean extrapolated recovery to infinity was 37.3% in urine and 56.6% in feces. Similar metabolite profiles were observed after repeat daily microtracer radioactivity oral dosing on Day 6 and after a high radioactivity oral dose on Day 7. Emvododstat was the most abundant circulating component, M443 and O-desmethyl emvododstat glucuronide were the major circulating metabolites; M474 was the most abundant metabolite in urine, while O­desmethyl emvododstat was the most abundant metabolite in feces. Significance Statement This study provides a complete set of the absorption, metabolism and excretion data of emvododstat, a potent inhibitor of dihydroorotate dehydrogenase, at close to steady state in healthy human subjects. Resolution of challenges due to slow metabolism and elimination of a lipophilic compound highlighted in this study can be achieved by repeat daily microtracer radioactivity oral dosing followed by a high radioactivity oral dosing at therapeutically relevant doses.

Strategic, feasibility, economic, and cultural aspects of phase 0 approaches: Is it time to change the drug development process in order to increase productivity?

Research conducted over the past 2 decades has enhanced the validity and expanded the applications of microdosing and other phase 0 approaches in drug development. Phase 0 approaches can accelerate drug development timelines and reduce attrition in clinical development by increasing the quality of candidates entering clinical development and by reducing the time to "go-no-go" decisions. This can be done by adding clinical trial data (both healthy volunteers and patients) to preclinical candidate selection, and by applying methodological and operational advantages that phase 0 have over traditional approaches. The main feature of phase 0 approaches is the limited, subtherapeutic exposure to the test article. This means a reduced risk to research volunteers, and reduced regulatory requirements, timelines, and costs of first-in-human (FIH) testing. Whereas many operational aspects of phase 0 approaches are similar to those of other early phase clinical development programs, they have some unique strategic, regulatory, ethical, feasibility, economic, and cultural aspects. Here, we provide a guidance to these operational aspects and include case studies to highlight their potential impact in a range of clinical development scenarios.

An integrated assessment of the ADME properties of the CDK4/6 Inhibitor ribociclib utilizing preclinical in vitro, in vivo, and human ADME data.

Ribociclib (LEE011, Kisqali ®) is a highly selective small molecule inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6), which has been approved for the treatment of advanced or metastatic breast cancer. A human ADME study was conducted in healthy male volunteers following a single oral dose of 600 mg [14 C]-ribociclib. Mass balance, blood and plasma radioactivity, and plasma ribociclib concentrations were measured. Metabolite profiling and identification was conducted in plasma, urine, and feces. An assessment integrating the human ADME results with relevant in vitro and in vivo non-clinical data was conducted to provide an estimate of the relative contributions of various clearance pathways of the compound. Ribociclib is moderately to highly absorbed across species (approx. 59% in human), and is extensively metabolized in vivo, predominantly by oxidative pathways mediated by CYP3A4 (ultimately forming N-demethylated metabolite M4) and, to a lesser extent, by FMO3 (N-hydroxylated metabolite M13). It is extensively distributed in rats, based on QWBA data, and is eliminated rapidly from most tissues with the exception of melanin-containing structures. Ribociclib passed the placental barrier in rats and rabbits and into milk of lactating rats. In human, 69.1% and 22.6% of the radiolabeled dose were excreted in feces and urine, respectively, with 17.3% and 6.75% of the 14 C dose attributable to ribociclib, respectively. The remainder was attributed to numerous metabolites. Taking into account all available data, ribociclib is estimated to be eliminated by hepatic metabolism (approx. 84% of total), renal excretion (7%), intestinal excretion (8%), and biliary elimination (1%).

Human ADME for YH12852 using wavelength scanning cavity ring-down spectroscopy (WS-CRDS) after a low radioactivity dose.

Aim: Human 14C radiotracer studies provide information-rich data sets that enable informed decision making in clinical drug development. These studies are supported by liquid scintillation counting after conventional-sized 14C doses (50-200 µCi) or complex accelerator mass spectrometry (AMS) after microtracer-sized doses (∼0.1-1 µCi). Mid-infrared laser-based 'cavity ring-down spectroscopy' (CRDS) is an emerging platform for the sensitive quantitation of 14C tracers. Results & methodology: We compared the total 14C concentrations in plasma and urine samples from a microtracer study using both CRDS and AMS technology. The data were evaluated using statistical and pharmacokinetic modeling. Conclusion: The CRDS method closely reproduced the AMS method for total 14C concentrations. With optimization of the automated sample interface and further testing, it promises to be an accessible, robust system for pivotal microtracer investigations.

Metabolism and Excretion of Intravenous, Radio-Labeled Amisulpride in Healthy, Adult Volunteers.

PURPOSE: Intravenous amisulpride, a dopamine D2/D3 antagonist, has recently been shown in trials to be an effective antiemetic at low doses. This study was conducted to investigate the metabolism and elimination of a single dose of intravenous 14C-labeled amisulpride in healthy, adult volunteers. PATIENTS AND METHODS: Six healthy male volunteers aged 18-65 years were given a single 10 mg dose of 14C-labeled amisulpride containing not more than 1.8 MBq of radioactivity, infused over 4 mins. Concentrations of amisulpride and total radioactivity were measured in plasma, whole blood, urine and feces at various time points up to 168 hrs after dosing. Metabolites detected in plasma, urine and feces were characterized using liquid chromatography tandem mass spectrometry (LC-MS/MS) with in-line radiometric detection. RESULTS: The mean recovery of radioactivity in excreta was 96.4% (range 92.0-98.5%), of which 73.6% (range 70.6-79.2%) was recovered from urine and 22.8% (range 18.9-25.7%) from feces. Four metabolites of amisulpride were detected in urine, representing 15.0% of the excreted dose; three of these were also present in feces, representing 6.1% of the excreted dose. No metabolites were detected in plasma. Excretion was initially rapid, with about two-thirds of the drug-related material eliminated within 12 hrs, primarily in the urine. A second, slower phase of excretion was predominantly fecal and was essentially complete by 96 hrs after dosing. The terminal plasma elimination half-life of parent amisulpride was 3.7 hrs and that of total 14C-labeled drug material was 4.2 hrs. CONCLUSION: Intravenous amisulpride undergoes limited metabolism and is excreted primarily via the renal route. CLINICAL TRIAL REGISTRY NUMBER: ClinicalTrials.gov NCT02881840.

A Dual-Administration Microtracer Technique to Characterize the Absorption, Distribution, Metabolism, and Excretion of [14 C]Seletalisib (UCB5857) in Healthy Subjects.

Phosphoinositide 3 kinases are targets for development of small-molecule inhibitors to disrupt progression of immune-inflammatory diseases. This phase 1 open-label study (Eudract 2014-005353-39) evaluated the safety and relative bioavailability of 2 new seletalisib (UCB5857) formulations (A and B) compared with a reference formulation. Absolute bioavailability (period 1a, n = 6) and disposition and metabolism (period 1b, n = 6) of the reference formulation were evaluated: healthy subjects received 30 mg orally plus ∼20 µg of a 14 C-labeled microtracer (intravenously in 1a, orally in 1b). New formulations were evaluated: subjects from periods 1a and 1b were pooled and randomly distributed to receive a single oral dose (30 mg) of formulation A (n = 6) or B (n = 6) in periods 2 and 3, using a crossover design. Absolute oral bioavailability of seletalisib was 97% (90% confidence interval 87, 107). Unchanged [14 C]seletalisib was the predominant radioactive component in plasma (94.8%). After oral dosing, the radioactive dose was primarily recovered in feces (74.6%, geometric coefficient of variation [GeoCV] 18.1%), mostly as metabolites. Seletalisib demonstrated a 24-hour terminal half-life, volume of distribution of 60.9 L (GeoCV 23.8%), and a total plasma clearance of 1.7 L/h (GeoCV 35.4%). Formulations A and B displayed similar or even higher exposure compared with reference seletalisib (areas under the concentration-time curves 19 337 [GeoCV 30.8%], 20 380 [GeoCV 37.7%], and 15 932 [GeoCV 36.4%] h·ng/mL, respectively). New formulations A and B were bioequivalent with each other, and all 3 formulations showed acceptable safety profiles. This radiolabeled microtracer approach successfully informed on the absorption, distribution, metabolism, and excretion of seletalisib and further guided the mechanistic pharmacokinetic modeling.

Opportunities in low-level radiocarbon microtracing: applications and new technology.

14C-radiolabeled (radiocarbon) drug studies are central to defining the disposition of therapeutics in clinical development. Concerns over radiation, however, have dissuaded investigators from conducting these studies as often as their utility may merit. Accelerator mass spectrometry (AMS), originally designed for carbon dating and geochronology, has changed the outlook for in-human radiolabeled testing. The high sensitivity of AMS affords human clinical testing with vastly reduced radiative (microtracing) and chemical exposures (microdosing). Early iterations of AMS were unsuitable for routine biomedical use due to the instruments' large size and associated per sample costs. The situation is changing with advances in the core and peripheral instrumentation. We review the important milestones in applied AMS research and recent advances in the core technology platform. We also look ahead to an entirely new class of 14C detection systems that use lasers to measure carbon dioxide in small gas cells.