The pharmacokinetics (PK) of acalabrutinib was studied in healthy subjects and patients with B-cell malignancies. Acalabrutinib exhibits almost linear PK across a dose range of 75 to 250 mg (0.75 to 2.5 times the approved recommended single dose) and exhibits dose-proportionality. The daily area under the plasma drug concentration over time curve (AUC) was 1111 ng•h/mL and maximum plasma concentration (Cmax) of acalabrutinib was 323 ng/mL.
Absorption
The geometric mean absolute bioavailability of acalabrutinib was 25%. Median time to peak acalabrutinib plasma concentrations (Tmax) was 0.75 hours.
Effect of Food
In healthy subjects, administration of a single 75 mg dose of acalabrutinib (0.75 times the approved recommended single dose) with a high-fat, high-calorie meal (approximately 918 calories, 59 grams carbohydrate, 59 grams fat, and 39 grams protein) did not affect the mean AUC as compared to dosing under fasted conditions. Resulting Cmax decreased by 73% and Tmax was delayed 1-2 hours.
Distribution
Reversible binding of acalabrutinib to human plasma protein was 97.5%. The in vitro mean blood-to-plasma ratio was 0.7. The mean steady-state volume of distribution (Vss) was approximately 34 L.
Elimination
Following a single oral dose of 100 mg acalabrutinib, the median terminal elimination half-life (t1/2) of acalabrutinib was 0.9 (range: 0.6 to 2.8) hours. The t1/2 of the active metabolite, ACP-5862, was 6.9 hours.
Acalabrutinib mean apparent oral clearance (CL/F) was 159 L/hr with similar PK between patients and healthy subjects, based on population PK analysis.
Metabolism
Acalabrutinib is predominantly metabolized by CYP3A enzymes, and to a minor extent, by glutathione conjugation and amide hydrolysis, based on in vitro studies. ACP-5862 was identified as the major active metabolite in plasma with a geometric mean exposure (AUC) that was approximately 2- to 3-fold higher than the exposure of acalabrutinib. ACP-5862 is approximately 50% less potent than acalabrutinib with regard to BTK inhibition.
Excretion
Following administration of a single 100 mg radiolabeled acalabrutinib dose in healthy subjects, 84% of the dose was recovered in the feces and 12% of the dose was recovered in the urine, with less than 1% of the dose excreted as unchanged acalabrutinib.
Specific Populations
Age, Race, and Body Weight
Age (42 to 90 years), sex, race (Caucasian, African American), and body weight did not have clinically meaningful effects on the PK of acalabrutinib, based on population PK analysis.
Renal Impairment
Acalabrutinib undergoes minimal renal elimination. Based on population PK analysis, no clinically relevant PK difference was observed in 368 patients with mild or moderate renal impairment (eGFR ≥ 30 mL/min/1.73m2, as estimated by MDRD (modification of diet in renal disease equation)). Acalabrutinib PK has not been evaluated in patients with severe renal impairment (eGFR < 29 mL/min/1.73m2, MDRD) or renal impairment requiring dialysis.
Hepatic Impairment
Acalabrutinib is metabolized in the liver. In a hepatic impairment study, compared to subjects with normal liver function (n=6), acalabrutinib exposure (AUC) was increased by less than two-fold in subjects with mild (n=6) (Child-Pugh A) and moderate (n=6) (Child-Pugh B) hepatic impairment, respectively. Based on a population PK analysis, no clinically relevant PK difference was observed in subjects with mild (n=41) or moderate (n=3) hepatic impairment (total bilirubin between 1.5 to 3 times the upper limit of normal [ULN] and any AST) relative to subjects with normal (n=527) hepatic function (total bilirubin and AST within ULN). Acalabrutinib PK has not been evaluated in patients with severe hepatic impairment (Child-Pugh C or total bilirubin between 3 and 10 times ULN and any AST).
Drug Interaction Studies
Effect of CYP3A Inhibitors on Acalabrutinib
Co-administration with a strong CYP3A inhibitor (200 mg itraconazole once daily for 5 days) increased the acalabrutinib Cmax by 3.9-fold and AUC by 5.1-fold in healthy subjects.
Physiologically based pharmacokinetic (PBPK) simulations with acalabrutinib and moderate CYP3A inhibitors (erythromycin, fluconazole, diltiazem) showed that co-administration increased acalabrutinib Cmax and AUC increased by 2- to almost 3-fold [see Drug Interactions (7)].
Effect of CYP3A Inducers on Acalabrutinib
Co-administration with a strong CYP3A inducer (600 mg rifampin once daily for 9 days) decreased acalabrutinib Cmax by 68% and AUC by 77% in healthy subjects [see Drug Interactions (7)].
Gastric Acid Reducing Agents
Acalabrutinib solubility decreases with increasing pH. Co-administration with an antacid (1 g calcium carbonate) decreased acalabrutinib AUC by 53% in healthy subjects. Co-administration with a proton pump inhibitor (40 mg omeprazole for 5 days) decreased acalabrutinib AUC by 43% [see Drug Interactions (7)].
In Vitro Studies
Metabolic Pathways
Acalabrutinib is a weak inhibitor of CYP3A4/5, CYP2C8 and CYP2C9, but does not inhibit CYP1A2, CYP2B6, CYP2C19, and CYP2D6. The active metabolite (ACP-5862) is a weak inhibitor of CYP2C8, CYP2C9 and CYP2C19, but does not inhibit CYP1A2, CYP2B6, CYP2D6 and CYP3A4/5.
Acalabrutinib is a weak inducer of CYP1A2, CYP2B6 and CYP3A4; the active metabolite (ACP-5862) weakly induces CYP3A4.
Based on in vitro data and PBPK modeling, no interaction with CYP substrates is expected at clinically relevant concentrations.
Drug Transporter Systems
Acalabrutinib is a substrate of P-glycoprotein (P-gp) and BCRP. Acalabrutinib is not a substrate of renal uptake transporters OAT1, OAT3, and OCT2, or hepatic transporters OATP1B1, and OATP1B3.
Acalabrutinib does not inhibit P-gp, OAT1, OAT3, OCT2, OATP1B1, and OATP1B3 at clinically relevant concentrations.
Acalabrutinib may increase exposure to co-administered BCRP substrates (e.g., methotrexate) by inhibition of intestinal BCRP.