Search

Acalabrutinib is a covalent Bruton tyrosine kinase (BTK) inhibitor approved for relapsed/refractory mantle cell lymphoma and chronic lymphocytic leukemia/small lymphocytic lymphoma. A major metabolite of acalabrutinib (M27, ACP-5862) was observed in human plasma circulation. Subsequently, the metabolite was purified from an in vitro biosynthetic reaction and shown by nuclear magnetic resonance spectroscopy to be a pyrrolidine ring-opened ketone/amide. Synthesis confirmed its structure, and covalent inhibition of wild-type BTK was observed in a biochemical kinase assay. A twofold lower potency than acalabrutinib was observed but with similar high kinase selectivity. Like acalabrutinib, ACP-5862 was the most selective toward BTK relative to ibrutinib and zanubrutinib. Because of the potency, ACP-5862 covalent binding properties, and potential contribution to clinical efficacy of acalabrutinib, factors influencing acalabrutinib clearance and ACP-5862 formation and clearance were assessed. rCYP (recombinant cytochrome P450) reaction phenotyping indicated that CYP3A4 was responsible for ACP-5862 formation and metabolism. ACP-5862 formation K

This single 60-mg dose, 4-period crossover study assessed the effect of food and formulation change on navtemadlin (KRT-232) pharmacokinetics (PK) and macrophage inhibitory cytokine-1 (MIC-1) pharmacodynamics. Healthy subjects (N = 30) were randomized to 3 treatment sequences, A: new tablet, fasted (reference, dosed twice); B: new tablet, 30 minutes after a high-fat meal (test 1); C: old tablet, fasted (test 2). PK/pharmacodynamic parameters were measured over 0 to 96 hours. Adverse events were mild without any discontinuations. No serious adverse events or deaths occurred. In treatment A, navtemadlin mean (coefficient of variation) maximum concentration (C

Acalabrutinib received approval for the treatment of adult patients with mantle cell lymphoma who received at least 1 prior therapy and adult patients with chronic lymphocytic leukemia or small lymphocytic lymphoma. This study investigated the impact of hepatic impairment (HI) on acalabrutinib pharmacokinetics (PK) and safety at a single 50-mg dose in fasted subjects. This study was divided into 2 parts: study 1, an open-label, parallel-group study in Child-Pugh class A or B subjects and healthy subjects; and study 2, an open-label, parallel-group study in Child-Pugh class C subjects and healthy subjects. Baseline characteristics and safety profiles were similar across groups. Acalabrutinib exposure (area under the plasma concentration-time curve) increased slightly (1.90- and 1.48-fold) in subjects with mild (Child-Pugh class A) and moderate (Child-Pugh class B) hepatic impairment compared with healthy subjects. In severe hepatic impairment (Child-Pugh class C), acalabrutinib exposure (area under the plasma concentration-time curve and maximum plasma concentration) increased ≈5.0- and 3.6-fold, respectively. Results were consistent across total and unbound exposures. Severe hepatic impairment did not impact total/unbound metabolite (ACP-5862) exposures; the metabolite-to-parent ratio decreased to 0.6 to 0.8 (vs 3.1-3.6 in healthy subjects). In summary, single oral dose of 50-mg acalabrutinib was safe and well tolerated in subjects with mild, moderate, and severe hepatic impairment and in healthy control subjects. In subjects with severe hepatic impairment, mean acalabrutinib exposure increased by up to 5-fold and should be avoided. Acalabrutinib does not require dose adjustment in patients with mild or moderate hepatic impairment.

Acalabrutinib is a targeted, covalent inhibitor of Bruton tyrosine kinase (BTK) with a unique 2-butynamide warhead that has relatively lower reactivity than other marketed acrylamide covalent inhibitors. A human [14C] microtracer bioavailability study in healthy subjects revealed moderate intravenous clearance (39.4 l/h) and an absolute bioavailability of 25.3% ± 14.3% (n = 8). Absorption and elimination of acalabrutinib after a 100 mg [14C] microtracer acalabrutinib oral dose was rapid, with the maximum concentration reached in

Aim: A sensitive method to quantify emixustat and its rapidly formed three major deaminated metabolites in human plasma was necessary to determine exposure in clinical trials. Methods: An LC–MS/MS method was validated for accuracy and precision, linearity, carry over, selectivity, recovery, matrix effects, hematocrit effects and stability. Results: A quantitative procedure for the determination of emixustat, ACU-5116, ACU-5124 and ACU-5149 in human plasma over the concentration range of 0.0500/1.00/1.00/1.00–10.0/1000/1000/1000 ng/ml, was successfully validated and has been used to successfully analyze samples in three clinical trials. Incurred sample reanalysis was performed for all four analytes in each study with >92% of the repeat results and original results within 20% of the mean of the two values.

Background: KRT-232 is a potent, selective, orally available, targeted inhibitor of human MDM2 homolog interactions with tumor suppressor protein 53 (p53). KRT-232 is under development for treatment of myeloproliferative neoplasms, acute myeloid leukemia and Merkel cell carcinoma. KRT-232 is a highly permeable 568.6 g/mol, monoprotic carboxylic acid (pKa 4.35); elimination involves primarily biliary-fecal excretion of an acyl glucuronide metabolite (M1) and enteric glucuronide hydrolysis with enterohepatic recirculation of parent drug. M1 is a 744.7 g/mol monoprotic acid with pKa 3.32 and 1/5th the MDM2 inhibitory potency of KRT-232. Plasma protein binding (fup) of KRT-232 and M1 were ~0.026 and ~0.006, respectively. Static model drug-drug interaction (DDI) calculations (FDA-CDER. 2020) indicated a potential minor DDI with substrates of cytochrome P450s (CYP) CYP3A4 and CYP2C8, UGT1A1, P-glycoprotein 1 (P-gp) and OATP1B1/3. Here, a 'fit-for-purpose' PBPK model for KRT-232 was developed using physicochemical, preclinical (in vitroandin vivo) and clinical pharmacokinetic (PK) data (KartosData on file; Ye et al.Xenobiotica. 2015; Gluck et al.Invest New Drugs. 2020 [Study A]). Methods:Simcyp Simulator V17 (release 1; 27/11/2017; 17.0.90.0) was used. In vitro kinetic parameters: In vitroKi for competitive inhibition of CYP2C8 was 3.8 and 0.17 µM for KRT-232 and M1, respectively.In vitroKI and kinact for mechanism-based inhibition of CYP3A4 by KRT-232 were 28 µM and 4.14 h-1, respectively. Estimatedin vitroKi values for KRT-232-mediated inhibition of UGT1A1, P-gp, OATP1B1 and OATP1B3, were 1.9, 14.8, 4.9 and 6.9 µM. For M1-mediated inhibition of UGT1A1, OATP1B1 and OATP1B3, values were 2.3, 0.393 and 0.606 µM. Model development and verification:KRT-232 absorption was described by a first-order process; fraction absorbed was assumed to be 100% and the absorption rate constant was manually optimized using observed mean plasma concentration data from Part 1 of Study A. KRT-232 clearance was based onin vitroformation clearance of M1 in human liver microsomes, scaled up 4-fold based on observed oral clearance of KRT-232 (Wood et al.Drug Metab Dispos. 2017). KRT-232 distribution volume was described by a minimal PBPK model. KRT-232 and M1 DDI parameters were based onin vitrodata. M1 clearance was manually optimized using mean observed data from Study A (Part 1, 240 mg dose), and distribution volume was predicted by the Simulator using Method 1 and a full PBPK model. PBPK simulated data were compared with patient PK data collected during Part 2 of Study A. Model application:The model predicted potential DDI after steady state (SS) 240 mg once daily KRT-232 administration with substrates of CYP3A4, CYP2C8, UGT1A1, P-gp and OATP1B1/3. DDI simulations included 100 virtual subjects assigned to 10 virtual trials (N=10 each). Population estimates of geometric mean and median Cmax and AUC0-∞ ratios were generated. A "worst case" sensitivity analysis was performed by using a 10-fold increase inin vitroCYP3A4 interaction potency (KI, EC50) relative to the measuredin vitrovalue. Results:Figure 1shows simulated SS mean and individual observed KRT-232 and M1 concentration data from Part 2 of Study A. SS KRT-232 Cmax, AUC0-24h and t1/2 were predicted within 0.80-1.25-fold of observed PK data and tmax was under-predicted (0.36-fold) by the model (Table 1). M1 Cmax and AUC0-24h were within 0.80-1.25-fold of observed PK data on Day 1 (not shown). M1 Cmax on Day 7 was within 0.80-1.25-fold of observed PK data and SS AUC0-24h, t1/2, and tmax were underpredicted (0.72, 0.79 and 0.61-fold) relative to observed PK data. In all simulated DDIs, no clinically significant interaction was predicted for SS 240 mg doses of KRT-232 since predicted Cmax and AUC0-∞ geometric mean ratio (GMR) changes were less than 1.25-fold (Table 2). The CYP3A4 DDI simulation gave a population GMR (90% CI) for Cmax and AUC0-∞ of 1.07 (1.06, 1.09) and 1.15 (1.12, 1.17), respectively. In a sensitivity check, predicted midazolam Cmax and AUC0-∞ after a 10-fold reduction ofin vitroKI and EC50 were 1.44-fold and 2.18-fold, respectively. Although unlikely, a weak CYP3A4 DDI could not be definitively excluded. Conclusions: Mean plasma exposure of KRT-232 and M1 and inter-individual variability were adequately described by the PBPK model. No clinically significant DDI were predicted based on Cmax and AUC0-∞ GMR changes of less than 1.25-fold. Disclosures Templeton: Certara UK, LTD.:Current Employment.Podoll:IV/PO, LLC:Consultancy.Krejsa:Kartos Therapeutics:Current Employment;AstraZeneca:Current equity holder in publicly-traded company;Seattle Genetics:Current equity holder in publicly-traded company;Acerta Pharma:Current equity holder in private company.Slatter:Kartos Therapeutics:Current Employment;AstraZeneca:Current equity holder in publicly-traded company;Amgen:Divested equity in a private or publicly-traded company in the past 24 months.

Background: KRT-232 is a potent, selective, orally available, small-molecule drug that binds to mouse double minute 2 homolog (MDM2) and inhibits its interactions with tumor suppressor protein p53. KRT-232 is under development for treatment of myeloproliferative neoplasms, acute myeloid leukemia, and Merkel cell carcinoma. Increased serum MIC-1 (pg/mL) is a pharmacodynamic (PD) marker of p53-mediated activity in patients treated with KRT-232 (Allard,HemaSphere, 2020;4:S1, Abstract EP519). The aim of this study was to assess the safety and effect of a high-fat meal on KRT-232 pharmacokinetics (PK) and MIC-1 PD of a new tablet formulation in healthy volunteers. This is the first characterization of a MDM2-inhibitor-induced MIC-1 response in healthy volunteers. Methods: KRT-232-105 was a single-center, open-label, 60-mg single-dose, 3-treatment, 4-period, and 3-sequence study with a partial replicate crossover design. Volunteers (N=30) were randomized to three treatment groups: A: new tablet, fasted (reference, dosed twice in Periods 2-4); B: new tablet, 30 min after a high-fat, high-calorie meal (test 1, dosed once in periods 2-4); C: current tablet, fasted (test 2, period 1 only). Plasma KRT-232, its acyl glucuronide metabolite (M1) and serum MIC-1 concentrations were measured over 0-96 h. Urine from group C was collected over 0-48 h. Doses were one week apart. All volunteers had aH pyloribreath test and were genotyped for UGT1A1*28 polymorphisms. Results: Volunteers were 43% female, 7% African American and 77% Hispanic/Latino. Mean age was 38.1 y (range, 18-54), and mean body mass index was 26.9 kg/m2 (range, 21.4-30.9). No deaths, serious adverse events (SAEs), or discontinuations were reported. Twenty-one treatment-emergent AEs (TEAEs) were observed in 13 (43%) volunteers; constipation was the most frequent AE, followed by headache. All TEAEs were grade 1 (n=17) or grade 2 (n=4: 1 headache event [possibly study drug-related] and 3 events of headache, influenza-like illness, and pharyngitis). Mean (SD) concentration-time plots of KRT-232 and M1 were similar across the 3 groups (Figure 1a and b). A second peak was observed, consistent with enterohepatic recirculation. With a meal (test 1), KRT-232 geometric least-squares mean (GLSM) maximum concentration (Cmax) was similar (431 and 442 ng/mL (GLSM ratio [90% CI], 103% [87.4-121]) and KRT-232 GLSM area under the curve (AUC0-t) decreased from 2858 to 2325 ng∙h/mL (GLSM ratio [90% CI], 81.4 [76.2-86.9]). Median time of Cmax (Tmax) was 2 h fasted and 3 h fed. Geometric mean half life (t1/2) was unchanged (17.0 vs 17.1 h). Under fasting conditions, the current tablet (C, test 2) vs new tablet (A, reference), KRT-232 GLSM Cmax decreased from 431 to 337 ng/mL (GLSM ratio [90% CI], 78.4% [72.0-85.3]) and KRT-232 GLSM AUC0-t had a possible small decrease (2858 and 2455 ng∙h/mL, GLSM ratio [90% CI], 85.9 [80.5-91.7]). Median Tmax (~2 h) and geometric mean t1/2 (17 h) were unchanged. The fraction of the KRT-232 dose in urine as KRT-232 and M1 was negligible at 0.0201% and 0.0220% of dose, respectively. KRT-232 is a carboxylic acid with pH-dependent solubility that increases with increasing pH.H pyloriinfection, which can increase stomach pH, did not have any discernable impact on KRT-232 PK. KRT-232 and M1 exposure in heterozygous UGT1A1*28 poor metabolizers (6/7 TA repeats, N=16) was generally comparable to exposure in wild-type (WT) UGT1A1*28 (6/6 TA repeats, N=12) subjects. MIC-1 concentrations in serum were variable and followed the PK time course with a median Tmax lag of ~8-12 h. Group A: Mean Cmax 2115 pg/mL, C0 (Baseline) 170 pg/mL, AUC0-T 89267 pg*h/mL and mean t1/2 27 h. MIC-1 Cmax and AUC were generally comparable over 96 h across groups (Figure 1c).Figure 1dshows the statistically significant correlation between KRT-232 AUC0-t and MIC-1 AUC0-t. Conclusions: Based on generally comparable PK, KRT-232 can be administered with or without food, and no dose adjustment is warranted with a new tablet formulation. KRT-232 PK was not affected byH pylori, inferring that higher gastric pH did not alter absorption of KRT-232. KRT-232 exposure in UGT1A1*28 heterozygous poor metabolizers was generally comparable to WT UGT1A1*28 wild type healthy volunteers. The 60-mg KRT-232 dose elicited a reproducible and robust MIC-1 response that correlated with KRT-232 exposure, indicating MDM2-p53 target engagement. Disclosures Wong: Kartos Therapeutics:Current Employment;AbbVie Biotherapeutics:Ended employment in the past 24 months.Krejsa:Kartos Therapeutics:Current Employment;AstraZeneca:Current equity holder in publicly-traded company;Seattle Genetics:Current equity holder in publicly-traded company;Acerta Pharma:Current equity holder in private company.Lee:Kartos Therapeutics:Current Employment.Harris:Gilead Sciences:Current equity holder in publicly-traded company;Kartos Therapeutics:Current Employment, Current equity holder in private company;BeiGene:Ended employment in the past 24 months;Clovis:Current equity holder in publicly-traded company, Ended employment in the past 24 months.Simard:Certara:Current Employment;AltaScience:Ended employment in the past 24 months.Wang:Certara:Current Employment.Rubets:Certara:Current Employment.Allard:Certara:Consultancy, Ended employment in the past 24 months;CytomX Therapeutics:Ended employment in the past 24 months;Telios Pharma:Current Employment, Current equity holder in private company.Podoll:IV/PO, LLC:Consultancy.O'Reilly:Celerion:Current Employment.Slatter:Amgen:Divested equity in a private or publicly-traded company in the past 24 months;Kartos Therapeutics:Current Employment;AstraZeneca:Current equity holder in publicly-traded company. OffLabel Disclosure: Yes, KRT-232 is an investigational small molecule MDM2 inhibitor.

Acalabrutinib, a selective, covalent Bruton tyrosine kinase inhibitor, is a CYP3A substrate and weak CYP3A/CYP2C8 inhibitor. A physiologically‐based pharmacokinetic (PBPK) model was developed for acalabrutinib and its active metabolite ACP‐5862 to predict potential drug–drug interactions (DDIs). The model indicated acalabrutinib would not perpetrate a CYP2C8 or CYP3A DDI with the sensitive CYP substrates rosiglitazone or midazolam, respectively. The model reasonably predicted clinically observed acalabrutinib DDI with the CYP3A perpetrators itraconazole (4.80‐fold vs. 5.21‐fold observed) and rifampicin (0.21‐fold vs. 0.23‐fold observed). An increase of two to threefold acalabrutinib area under the curve was predicted for coadministration with moderate CYP3A inhibitors. When both the parent drug and active metabolite (total active components) were considered, the magnitude of the CYP3A DDI was much less significant. PBPK dosing recommendations for DDIs should consider the magnitude of the parent drug excursion, relative to safe parent drug exposures, along with the excursion of total active components to best enable safe and adequate pharmacodynamic coverage.

Emixustat potently inhibits the visual cycle isomerase retinal pigment epithelium protein 65 (RPE65) to reduce the accumulation of toxic bisretinoid by-products that lead to various retinopathies. Orally administered emixustat is cleared rapidly from the plasma, with little excreted unchanged. The hydroxypropylamine moiety that is critical in emixustat’s inhibition of RPE65 is oxidatively deaminated to three major carboxylic acid metabolites that appear rapidly in plasma. These metabolites greatly exceed the plasma concentrations of emixustat and demonstrate formation-rate-limited metabolite kinetics. This study investigated in vitro deamination of emixustat in human vascular membrane fractions, plasma, and recombinant human vascular adhesion protein-1 (VAP-1), demonstrating single-enzyme kinetics for the formation of a stable aldehyde intermediate (ACU-5201) in all in vitro systems. The in vitro systems used herein established sequential formation of the major metabolites with addition of assay components for aldehyde dehydrogenase and cytochrome P450. Reaction phenotyping experiments using selective chemical inhibitors and recombinant enzymes of monoamine oxidase, VAP-1, and lysyl oxidase showed that only VAP-1 deaminated emixustat. In individually derived human vascular membranes from umbilical cord and aorta, rates of emixustat deamination were highly correlated to VAP-1 marker substrate activity (benzylamine) and VAP-1 levels measured by enzyme-linked immunosorbent assay. In donor-matched plasma samples, soluble VAP-1 activity and levels were lower than in aorta membranes. A variety of potential comedications did not strongly inhibit emixustat deamination in vitro.

Acalabrutinib (Calquence®) is a potent, selective, orally administered, covalent inhibitor of Bruton tyrosine kinase (BTK) that received accelerated approval for relapsed/refractory mantle cell lymphoma from the US FDA in October 2017. Profiling of acalabrutinib metabolites in human plasma revealed a late-eluting, +16 Da metabolite circulating at concentrations higher than parent drug. Metabolite regiochemistry could not be determined by mass spectrometry. In vitro metabolism and preparative HPLC was used to generate a pure sample of the metabolite for structural characterization by NMR. Confirmatory chemical synthesis revealed a pyrrolidine ring-opened ketone. The structure of the metabolite, designated ACP-5862, and a smaller -2 Da peak, identified as dehydropyrrolidine, M25, inferred a common carbinolamide intermediate in their genesis. Both metabolites retained the butynamide electrophile responsible for the inactivation of BTK. In vitro studies on the inhibition of BTK and related Tec and Src kinases revealed that ACP-5862 was active against BTK with similar selectivity and potency to acalabrutinib (Kaptein et al, 2019) This work then investigated the in vitro metabolism and drug transport features of acalabrutinib, and the metabolite ACP-5862, to establish the potential for clinical drug-drug interactions (DDI) via CYPs, UGTs and drug transporters. CYP reaction phenotyping indicated CYP3A4 was responsible for both the formation and further metabolism of ACP-5862. Km and Vmax values for the formation of ACP-5862 using rCYP3A4 were 2.78 μM and 4.13 pmol/pmol CYP/min, respectively. The in vitro intrinsic clearance of ACP-5862 was 23.6 μL/min/mg. Acalabrutinib weakly inhibited CYP2C8, CYP2C9 and CYP3A4 in vitro, and ACP-5862 weakly inhibited CYP2C9 and CYP2C19, with no inhibition of CYP1A2, CYP2B6, or CYP2D6. Similarly, UGT1A1, UGT2B7, and aldehyde oxidase were not inhibited. Neither parent or ACP-5862 strongly induced CYP1A2, CYP2B6, or CYP3A4 mRNA. Acalabrutinib and ACP-5862 were substrates of MDR1 and BCRP in vitro, but were not substrates of OATP1B1 or OATP1B3. Acalabrutinib was not a substrate of OAT1, OAT3, and OCT2. Based on static PK model calculations, acalabrutinib may cause a modest increase in exposure to coadministered BCRP substrates by inhibition of intestinal BCRP, but with no inhibition of BCRP at the systemic level. The PK of substrates of MDR1, MATE1, MATE2-K, OATP1B1, OATP1B3, OAT1, OAT3, and OCT2 are not likely to be altered by acalabrutinib or ACP-5862. These data were combined with clinical DDI data (Izumi et al, 2017) to simulate DDI in the presence of CYP3A inhibitors and inducers. PBPK models confirmed that acalabrutinib and ACP-5862 were not likely to perpetrate CYP2C8 or CYP3A4 mediated drug interactions (Zhou et al., 2019). Overall, acalabrutinib and major metabolite, ACP-5862 have a favorable drug interaction profile. Citation Format: Terry Podoll, Paul G. Pearson, Jerry Evarts, Tim Ingallinera, Hao Sun, Stephen Byard, Adrian J. Fretland, J. Greg Slatter. Structure elucidation, metabolism, and drug interaction potential of ACP-5862, an active, major, circulating metabolite of acalabrutinib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 13.

Acalabrutinib is a potent and highly selective, oral covalent inhibitor of Bruton tyrosine kinase (BTK) that received accelerated approval for relapsed/refractory mantle cell lymphoma by the United States Food and Drug Administration in October 2017. ADME studies in humans, rat and dog, revealed extensive metabolism of acalabrutinib. The major circulating metabolite (M27, ACP-5862) was produced by CYP3A oxidation, resulting in a pyrrolidine ring-opened metabolite, with the butynamide electrophile still present. We investigated the on-target BTK inhibition and kinase selectivity profile of ACP-5862 using the same biochemical and cellular assays previously employed to profile acalabrutinib.1 The apparent BTK IC50 was determined over time using the LanthaScreen assay. Results indicate that ACP-5862, like acalabrutinib, is a covalent inhibitor of BTK. Binding kinetics derived from IC50 over time data, indicated that acalabrutinib and ACP-5862 have similar affinity (KI), however the BTK inactivation rate (kinact) for ACP-5862 was half that relative to acalabrutinib. This indicated a covalent BTK inhibition potency for ACP-5862 that was 2-fold lower than acalabrutinib. The overall kinome inhibition profile at 1 µM using KINOMEscan (Eurofins DiscoverX), as well as IC50 determinations on closely related kinases with a Cys in the same position as Cys481 in BTK (ITK, TXK, TEC, BMX, EGFR, ERBB2, ERBB4, BLK, JAK3), both revealed that the kinase selectivity profiles of acalabrutinib and ACP-5862 were similar. On-target inhibition in B cells was investigated measuring inhibition of B-cell antigen receptor-mediated activation of CD69 cell surface expression on human peripheral B cells using human peripheral blood mononuclear cells and human whole blood (hWB). The EC50 for anti-IgD-induced CD69 expression in hWB was 64 ± 6 nM for ACP-5862, compared to 9.2 ± 4.4 nM for acalabrutinib. The hWB EC90, representing near complete inhibition of BTK by acalabrutinib and ACP-5862 was observed at 72 ± 20 nM and 544 ± 376 nM, respectively. In conclusion, the results indicate that ACP-5862, the major metabolite of acalabrutinib, has intrinsic BTK inhibitory activity and a similar kinase selectivity profile as acalabrutinib. The contribution of ACP-5862 to on-target covalent inhibition of BTK in humans is unclear at present, but is most likely limited, since the EC90 in hWB for ACP-5862 approximated observed plasma Cmax in humans dosed with 100 mg acalabrutinib. The relative contribution of acalabrutinib and ACP-5862 to BTK pharmacodynamics is under further investigation. Terry Podoll and J. Greg Slatter are former Acerta Pharma employees. Reference 1. Barf T, Covey T, Izumi R, et al. Acalabrutinib (ACP-196): A covalent Bruton tyrosine kinase inhibitor with a differentiated selectivity and in vivo potency profile. J Pharmacol Exp Ther. 2017;363(2):240-252. Citation Format: Allard Kaptein, Terry Podoll, Gerjan de Bruin, Maaike Emmelot-van Hoek, Anouk de Jong, Bart van Lith, Niels Hoogenboom, Tjeerd Barf, Joseph Ware, J. Greg Slatter. Preclinical pharmacological profiling of ACP-5862, the major metabolite of the covalent BTK inhibitor acalabrutinib, displays intrinsic BTK inhibitory activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2194.

Background: A method to quantify emixustat (an investigational drug agent) in human blood collected using volumetric absorptive microsampling (VAMS) could be more practical for sample collection at sites with limited facilities for processing and storage of plasma. Methods: A LC–MS/MS method was developed and evaluated for accuracy and precision, linearity, carryover, selectivity, recovery, matrix effects, hematocrit effects and stability. Results: Core validation parameters met acceptance criteria within the normal ranges of hematocrit levels for adults (30–55%). Stability of emixustat in blood collected with and without anticoagulant (NaF/KOx) on the VAMS device at ambient, refrigerated and frozen conditions was established. Conclusion: The method has been validated and is suitable for the bioanalysis of emixustat in human blood collected by VAMS.