Pharmacology: Mechanism of Action: Asciminib is an ABL/BCR-ABL1 tyrosine kinase inhibitor. Asciminib inhibits the ABL1 kinase activity of the BCR::ABL1 fusion protein, by binding to the ABL myristoyl pocket. In studies conducted
in vitro or in animal models of CML, asciminib showed activity against wild-type BCR::ABL1 and several mutant forms of the kinase, including the T315I mutation.
Pharmacodynamics: Exposure-Response Relationships: Over asciminib dosages of 10 mg to 200 mg twice daily (0.25 to 5 times the recommended 80 mg daily dosage), a lower exposure was associated with a smaller decrease in BCR::ABL1 level and a lower MMR rate at Week 24.
Over asciminib dosages of 10 mg to 280 mg twice daily (0.25 to 7 times the recommended 80 mg daily dosage), a higher exposure was associated with slightly higher incidence of some adverse reactions (e.g., Grade ≥3 lipase increase, Grade ≥3 hemoglobin decrease, Grade ≥2 ALT increase, Grade ≥2 AST increase, Grade ≥2 bilirubin increase, and any grade lipase increase).
Cardiac Electrophysiology: Asciminib does not cause a large mean increase in QTc interval (i.e., >20 msec) at the maximum recommended clinical dosage (200 mg twice daily). Based on available clinical data, small mean QTc increase (<10 msec) cannot be excluded.
Clinical Studies: Ph+ CML-CP, Previously Treated with Two or More TKIs: The efficacy of SCEMBLIX in the treatment of patients with Ph+ CML in chronic phase (Ph+ CML-CP), previously treated with two or more TKIs was evaluated in the multi-center, randomized, active-controlled, and open-label study ASCEMBL (NCT03106779).
In this study, a total of 233 patients were randomized in a 2:1 ratio and stratified according to major cytogenetic response (MCyR) status to receive either SCEMBLIX 40 mg twice daily (N=157) or bosutinib 500 mg once daily (N=76). Patients continued treatment until unacceptable toxicity or treatment failure occurred.
Patients were 52% female and 48% male with a median age of 52 years (range, 19 to 83 years). Of the 233 patients, 19% were 65 years or older, while 2.6% were 75 years or older. Patients were White (75%), Asian (14%), and Black or African American (4.3%). Of the 233 patients, 81% and 18% had Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1, respectively. Patients who had previously received 2, 3, 4, or 5 or more prior lines of TKIs were 48%, 31%, 15%, and 6%, respectively. The median duration of treatment was 103 weeks (range, 0.1 to 201 weeks) for patients receiving SCEMBLIX and 31 weeks (range, 1 to 188 weeks) for patients receiving bosutinib.
The main efficacy outcomes from ASCEMBL are summarized in Table 1. (See Table 1.)
Click on icon to see table/diagram/image
With a median duration of follow-up of 28 months (range: 1 day to 45 months), the median duration of response for patients treated with SCEMBLIX had not yet been reached.
Ph+ CML-CP with the T315I Mutation: The efficacy of SCEMBLIX in the treatment of patients with Ph+ CML-CP with the T315I mutation was evaluated in a multi-center open-label study CABL001X2101 (NCT02081378). Testing for T315I mutation utilized a qualitative p210 BCR::ABL1 mutation test on peripheral blood using Sanger Sequencing.
Efficacy was based on 45 patients with Ph+ CML-CP with the T315I mutation who received SCEMBLIX at a dose of 200 mg twice daily. Patients continued treatment until unacceptable toxicity or treatment failure occurred.
Of the 45 patients, 80% were male and 20% female; 31% were 65 years or older, while 9% were 75 years or older with a median age of 54 years (range, 26 to 86 years). The patients were White (47%), Asian (27%), and Black or African American (2.2%), and 24% were unreported or unknown. Seventy-three percent and 27% of patients had ECOG performance status 0 and 1, respectively. Patients who had previously received 1, 2, 3, 4, and 5 or more TKIs were 18%,
31%, 36%, 13%, and 2.2%, respectively. MMR was achieved by 24 weeks in 42% (19/45, 95% CI: 28% to 58%) of the 45 patients treated with SCEMBLIX. MMR was achieved by 96 weeks in 49% (22/45, 95% CI: 34% to 64%) of the 45 patients treated with SCEMBLIX. The median duration of treatment was 108 weeks (range, 2 to 215 weeks).
Pharmacokinetics: Asciminib steady-state exposure (AUC and C
max) increase slightly more than dose proportional across the dose range of 10 to 200 mg (0.25 to 5 times the recommended 80 mg daily dosage) administered once or twice daily.
Pharmacokinetic parameters are presented as geometric mean (CV%) unless otherwise stated. The steady state C
max and AUC
tau of asciminib at recommended dosages are listed in Table 2. (See Table 2.)
Click on icon to see table/diagram/image
Absorption: The median (range) T
max of asciminib is 2.5 hours (2 to 3 hours).
Effect of Food: The AUC and C
max of asciminib decreased by 62% and 68%, respectively, with a high-fat meal (1000 calories, 50% fat) and by 30% and 35%, respectively, with a low-fat meal (400 calories, 25% fat) compared to the fasted state following administration of SCEMBLIX.
Distribution: The apparent volume of distribution of asciminib at steady state is 151 L (135%). Asciminib is the main circulating component in plasma (93% of the administered dose).
Asciminib is 97% bound to human plasma proteins
in vitro.
Elimination: The total apparent clearance of asciminib is 6.7 L/hour (48%) at 40 mg twice daily and 80 mg once daily, and 4.1 L/hour (38%) at 200 mg twice daily. The terminal elimination half-life of asciminib is 5.5 hours (38%) at 40 mg twice daily and 80 mg once daily, and 9.0 hours (33%) at 200 mg twice daily.
Metabolism: Asciminib is metabolized by CYP3A4-mediated oxidation, UGT2B7- and UGT2B17-mediated glucuronidation.
Excretion: Eighty percent (57% as unchanged) and 11% (2.5% as unchanged) of the asciminib dose were recovered in the feces and in the urine of healthy subjects, respectively, following oral administration of a single 80 mg dose of radio-labeled asciminib.
Asciminib is eliminated by biliary secretion via breast cancer-resistant protein (BCRP).
Specific Populations: No clinically significant differences in the pharmacokinetics of asciminib were observed based on sex, age (20 to 88 years), race (Asian 20%, White 70%, Black/African American 4%), or body weight (42-184 kg), mild to moderate renal impairment (eGFR 30 to 89 mL/min/1.73 m
2), or mild (total bilirubin ≤ULN and AST >ULN or total bilirubin >1 to 1.5 times ULN and any AST) to moderate (total bilirubin >1.5 to 3 times ULN and any AST) hepatic impairment.
Patients with Renal Impairment: Asciminib AUC
inf and C
max are increased by 57% and 6%, respectively, in subjects with eGFR between 13 to <30 mL/min/1.73 m
2 and not requiring dialysis compared to subjects with normal renal function (eGFR ≥90 mL/min/1.73 m
2) following oral administration of a single 40 mg dose of SCEMBLIX. The exposure changes in patients with severe renal impairment are not considered clinically meaningful.
Patients with Hepatic Impairment: Asciminib AUC
inf and C
max are increased by 33% and 4%, respectively, in subjects with severe hepatic impairment (total bilirubin >3 times ULN and any AST), compared to subjects with normal hepatic function (total bilirubin ≤ULN and AST ≤ULN) following oral administration of a single 40 mg dose of SCEMBLIX. The exposure changes are not considered clinically meaningful.
Drug Interaction Studies: Clinical Studies and Model-Informed Approaches: Drugs That Affect Asciminib Plasma Concentration: Strong CYP3A Inhibitors: The asciminib AUC
inf and C
max increased by 36% and 19%, respectively, following coadministration of a single SCEMBLIX dose of 40 mg with a strong CYP3A4 inhibitor (clarithromycin). No clinically significant differences in the pharmacokinetics of asciminib were observed when coadministered with itraconazole, which is also a strong CYP3A4 inhibitor.
Strong CYP3A Inducers: Concomitant use of strong CYP3A inducers with SCEMBLIX has not been fully characterized.
Itraconazole Oral Solution: Coadministration of multiple doses of itraconazole oral solution containing hydroxypropyl-β-cyclodextrin with a single SCEMBLIX dose of 40 mg decreased asciminib AUC
inf and C
max by 40% and 50%, respectively. Concomitant use of oral products containing hydroxypropyl-β-cyclodextrin with SCEMBLIX other than itraconazole oral solution has not been fully characterized.
Imatinib: The asciminib AUC
inf and C
max increase by 108% and 59%, respectively following coadministration of a single SCEMBLIX dose of 40 mg with imatinib (an inhibitor of BCRP, CYP3A4, UGT2B17, and UGT1A3/4). The exposure changes are not considered clinically meaningful. Concomitant use of imatinib with SCEMBLIX at 200 mg twice daily has not been fully characterized.
Other Drugs: No clinically significant differences in the pharmacokinetics of asciminib were observed when coadministered with rabeprazole (acid-reducing agent) and quinidine (P-gp inhibitor).
Drugs That are Affected by Asciminib: CYP3A4 Substrates: The midazolam AUC
inf and C
max increased by 28% and 11%, respectively, following coadministration of a CYP3A4 substrate (midazolam) with SCEMBLIX 40 mg twice daily. The midazolam AUC
inf and C
max increased by 24% and 17%, respectively, following coadministration with SCEMBLIX at 80 mg once daily and 88% and 58%, respectively, at 200 mg twice daily.
CYP2C9 Substrates: The S-warfarin AUC
inf and C
max increased by 41% and 8%, respectively, following coadministration of CYP2C9 substrate (warfarin) with SCEMBLIX at 40 mg twice daily. The S-warfarin AUC
inf and C
max increased by 52% and 4%, respectively, following coadministration with SCEMBLIX at 80 mg once daily and 314% and 7%, respectively, at 200 mg twice daily.
CYP2C8 Substrates: The repaglinide (substrate of CYP2C8, CYP3A4, and OATP1B) AUC
inf and C
max increased by 8% and 14%, respectively, following coadministration of repaglinide with SCEMBLIX 40 mg twice daily. The repaglinide AUC
inf and C
max increased by 12% and 8%, respectively, following coadministration with SCEMBLIX at 80 mg once daily and 42% and 25%, respectively, at 200 mg twice daily. The rosiglitazone (substrate of CYP2C8 and CYP2C9) AUC
inf and C
max increased by 20% and 3%, respectively, following coadministration of rosiglitazone with SCEMBLIX 40 mg twice daily. The rosiglitazone AUC
inf and C
max increased by 24% and 2%, respectively, following coadministration with SCEMBLIX at 80 mg once daily and 66% and 8%, respectively, at 200 mg twice daily.
P-gp Substrates: Coadministration of SCEMBLIX with a drug that is a substrate of P-gp may result in a clinically relevant increase in the plasma concentrations of P-gp substrates, where minimal concentration changes may lead to serious toxicities.
In Vitro Studies: CYP450 and UGT Enzymes: Asciminib may reversibly inhibit UGT1A1 at plasma concentrations reached at a total daily dose of 80 mg and 200 mg twice daily. In addition, asciminib may reversibly inhibit CYP2C19 at concentrations reached at 200 mg twice daily dose.
Transporter Systems: Asciminib is a substrate of BCRP and P-gp. Asciminib inhibits BCRP, P-gp, OATP1B1, OATP1B3, and OCT1. Asciminib may increase the exposure of OATP1B or BCRP substrates in a dose dependent manner.
Toxicology: Nonclinical Toxicology: Carcinogenesis, Mutagenesis, Impairment of Fertility: In a 2-year carcinogenicity study, rats were administered oral doses of asciminib at 20, 66, and 200 mg/kg/day in males and 10, 30, and 66 mg/kg/day in females. Asciminib induced a statistically significant increase in the incidence of benign Sertoli cell tumors in the ovaries of high-dose females. The exposures to asciminib (AUC) in female rats at 66 mg/kg/day were approximately 8-fold or 6-fold higher than the exposure (AUC) achieved in patients at the dose of 40 mg twice daily or 80 mg once daily, respectively, and equivalent to those achieved in patients at the dose of 200 mg twice daily. The clinical relevance of these findings is currently unknown.
Asciminib was not genotoxic in an
in vitro bacterial mutagenicity (Ames) assay, an
in vitro micronucleus assay in human peripheral blood lymphocytes (HPBL), or an
in vivo rat peripheral blood reticulocyte micronucleus assay.
In a combined male and female fertility and early embryonic development study in rats, animals were administered asciminib doses of 10, 50, or 200 mg/kg/day orally. Male animals were dosed once daily for at least 28 days prior to mating, during the 2-week mating period, and until terminal necropsy (Days 63 to 67). Female animals were dosed once daily for the 2-week premating period, during the 2-week mating period, and through gestation day (GD) 6. Decreased sperm count and motility were observed at 200 mg/kg/day. While there were no effects on fertility indices or conception rates, a decreased mean number of live embryos was observed at 200 mg/kg/day and was attributed to a lower number of implantations and an increased number of early resorptions. Increased early resorptions were also observed in the embryo-fetal development study in rabbits [see Pregnancy under Use in Pregnancy & Lactation].
At the dose of 200 mg/kg, the AUC exposures were approximately 19-fold, 13-fold, or 2-fold higher than those achieved in patients at the 40 mg twice daily, 80 mg once daily, or 200 mg twice daily doses, respectively.