Clinical Pharmacology for Scemblix
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.
Pharmacokinetics
Asciminib steady-state exposure (AUC and Cmax) 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 Cmax and AUCtau of asciminib at recommended dosages are listed in Table 9.
Table 9: Steady Statea Asciminib Exposure at Recommended Dosages
| Asciminib dosage |
Cmax (ng/mL) |
AUCtaub (ng*h/mL) |
Accumulation ratio |
| 80 mg once daily |
1781 (23%) |
15112 (28%) |
1.30 |
| 40 mg twice daily |
793 (49%) |
5262 (48%) |
1.65 |
| 200 mg twice daily |
5642 (40%) |
37547 (41%) |
1.92 |
a Steady state is achieved within 3 days.
b AUCtau represents AUC0-12h for twice daily dosing and AUC0-24h for once daily dosing. |
Absorption
The median (range) Tmax of asciminib is 2.5 hours (2 to 3 hours).
Effect of Food
The AUC and Cmax 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 m2), 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 AUCinf and Cmax are increased by 57% and 6%, respectively, in subjects with eGFR between 13 to < 30 mL/min/1.73 m2 and not requiring dialysis compared to subjects with normal renal function (eGFR ≥ 90 mL/min/1.73 m2) 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 AUCinf and Cmax 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 AUCinf and Cmax 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 AUCinf and Cmax 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 AUCinf and Cmax 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 AUCinf and Cmax increased by 28% and 11%, respectively, following coadministration of a CYP3A4 substrate (midazolam) with SCEMBLIX 40 mg twice daily. The midazolam AUCinf and Cmax 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 AUCinf and Cmax increased by 41% and 8%, respectively, following coadministration of CYP2C9 substrate (warfarin) with SCEMBLIX at 40 mg twice daily. The S-warfarin AUCinf and Cmax 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) AUCinf and Cmax increased by 8% and 14%, respectively, following coadministration of repaglinide with SCEMBLIX 40 mg twice daily. The repaglinide AUCinf and Cmax 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) AUCinf and Cmax increased by 20% and 3%, respectively, following coadministration of rosiglitazone with SCEMBLIX 40 mg twice daily. The rosiglitazone AUCinf and Cmax 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.
Clinical Studies
Newly Diagnosed Ph+ CML-CP
The efficacy of SCEMBLIX in the treatment of patients with newly diagnosed Ph+ CML in chronic phase (Ph+ CML-CP) was evaluated in the multi-center, randomized, active-controlled, and open-label study ASC4FIRST (NCT04971226).
In this study, a total of 405 patients were randomized in a 1:1 ratio to receive either SCEMBLIX or investigator selected tyrosine kinase inhibitors (IS-TKIs). Prior to randomization, the investigator selected the TKI (imatinib, nilotinib, dasatinib, or bosutinib) to be used in the event of randomization to the comparator arm, based on patient characteristics and comorbidities. Patients were stratified according to EUTOS long-term survival (ELTS) risk group (low, intermediate, high), and pre-randomization selection of TKI (imatinib or other TKIs stratum composed of nilotinib, dasatinib, and bosutinib). Patients received either SCEMBLIX or IS-TKIs, and continued treatment until unacceptable toxicity or treatment failure occurred.
Patients were 37% female and 63% male with median age 51 years (range, 18 to 86 years). Of the 405 patients, 24% were 65 years or older, while 6% were 75 years or older. Patients were White (54%), Asian (44%), Black or African American (1%), and 1% unknown.
Of the 405 patients, 200 received SCEMBLIX, while 201 received IS-TKIs. Of the 201 patients receiving IS-TKIs, 99 received imatinib, 49 received nilotinib, 42 received dasatinib, and 11 received bosutinib. Four patients did not receive any treatment.
The median duration of treatment was 70 weeks (range, 1 to 108 weeks) for patients receiving SCEMBLIX, and 64 weeks (range, 1 to 103 weeks) for patients receiving IS-TKIs. By 48 weeks, 90% of patients on SCEMBLIX, and 81% of patients on IS-TKIs were still receiving treatment.
The main efficacy outcome was major molecular response rate (MMR) at 48 weeks. Efficacy was established based on SCEMBLIX compared to IS-TKIs and SCEMBLIX compared to IS-TKIs within the imatinib stratum. The main efficacy outcomes from ASC4FIRST are summarized in Table 10.
Table 10: Efficacy Results in Patients with Newly Diagnosed Ph+ CML-CP (ASC4FIRST)
SCEMBLIX
80 mg once daily |
IS-TKIsa
100-400 mg once or twice
daily |
Difference
(95% CI)b |
p-value |
All patients
(N = 204) |
Imatinib stratum
(N = 102) |
|
|
| MMR rate, % (95% CI) at 48 weeks |
| All patients (N = 201) |
68
(61, 74) |
49
(42, 56) |
|
19
(10, 28) |
< 0.001c |
| Imatinib stratum (N = 101) |
69
(59, 78) |
|
40
(31, 50) |
30
(17, 42) |
< 0.001d |
Abbreviations: MMR, major molecular response (BCR::ABL1IS ≤ 0.1%); IS-TKIs, investigator selected tyrosine kinase inhibitors.
a IS-TKIs include imatinib (400 mg once daily) and other TKIs of nilotinib (300 mg twice daily), dasatinib (100 mg once daily) or bosutinib (400 mg once daily).
b Estimated using a common risk difference stratified by PRS-TKI and baseline ELTS risk groups.
c Adjusted p-value using a Cochran-Mantel-Haenszel 1-sided test stratified by PRS-TKI and baseline ELTS risk groups.
d Adjusted p-value using a Cochran-Mantel-Haenszel 1-sided test stratified by baseline ELTS risk group |
MMR rates at 48 weeks in patients receiving SCEMBLIX and IS-TKIs within the other TKIs stratum were 66% (95% CI: 56%, 75%) and 58% (95% CI: 48%, 68%), respectively.
Median time to MMR in patients receiving SCEMBLIX, IS-TKIs, and IS-TKIs within the imatinib stratum were: 24 weeks (95% CI: 24 to 25 weeks), 36 weeks (95% CI: 36 to 49 weeks), and 49 weeks (95% CI: 36 to 60 weeks), respectively.
Ph+ CML-CP, Previously Treated With Two Or More TKIs
The efficacy of SCEMBLIX in the treatment of patients with 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 11.
Table 11: Efficacy Results in Patients with Ph+ CML-CP, Previously Treated with Two or More TKIs (ASCEMBL)
|
SCEMBLIX
40 mg
twice daily |
Bosutinib
500 mg
once daily |
Difference
(95% CI) |
p-value |
MMR rate,
% (95% CI)
at 24 weeks |
N = 157
25
(19, 33) |
N = 76
13
(6.5, 23) |
12a
(2.2, 22) |
0.029b |
MMR rate,
% (95% CI)
at 96 weeks |
N = 157
38
(30, 46) |
N = 76
16
(8, 26) |
22a
(11, 33) |
0.001b |
CCyR rate,
% (95% CI)
at 24 weeks |
N = 103c
41
(31, 51) |
N = 62c
24
(14, 37) |
17
(3.6, 31) |
|
CCyR rate,
% (95% CI)
at 96 weeks |
N = 103c
40
(30, 50) |
N = 62c
16
(8, 28) |
24a
(10, 37) |
|
Abbreviations: MMR, major molecular response (BCR::ABL1IS ≤ 0.1%); CCyR, complete cytogenetic response (0% of Philadelphia-positive metaphases in bone marrow aspirate with at least 20 examined).
a Estimated using a common risk difference stratified by baseline major cytogenetic response status.
b Estimated using a Cochran-Mantel-Haenszel two-sided test stratified by baseline major cytogenetic response status.
c CCyR analysis based on patients who were not in CCyR at baseline. |
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).