Clinical Pharmacology for Rezlidhia
Mechanism Of Action
Olutasidenib is a small-molecule inhibitor of mutated isocitrate dehydrogenase-1 (IDH1). In patients with AML, susceptible IDH1 mutations are defined as those leading to increased levels of 2-hydroxyglutarate (2-HG) in the leukemia cells and where efficacy is predicted by 1) clinically meaningful remissions with the recommended dose of olutasidenib and/or 2) inhibition of mutant IDH1 enzymatic activity at concentrations of olutasidenib sustainable at the recommended dosage according to validated methods. The most common of such mutations in patients with AML are R132H and R132C substitutions.
In vitro, olutasidenib inhibited mutated IDH1 R132H, R132L, R132S, R132G, and R132C proteins; wild-type IDH1 or mutated IDH2 proteins were not inhibited. Olutasidenib inhibition of mutant IDH1 led to decreased 2-HG levels in vitro and in in vivo xenograft models.
Pharmacodynamics
The mean [% coefficient of variation (%CV)] reduction in 2-HG plasma concentration was 59.1% (122%) by pre-dose Cycle 2 and was sustained throughout the treatment period in patients with AML and IDH1 mutations following the approved recommended olutasidenib dosage.
Increased olutasidenib exposure was correlated with the increased probability of differentiation syndrome and Grade ≥3 hepatotoxicity in patients with AML following the approved recommended olutasidenib dosage.
Cardiac Electrophysiology
The largest mean increase in QTc interval was 6.2 msec (upper 90% confidence interval = 9.7 msec) in 33 patients with advanced hematologic malignancies with an IDH1 mutation following a single dose and multiple doses of the approved recommended olutasidenib dosage under fasted conditions. This increase in the QTc interval was concentration dependent.
Increased QT prolongation is expected with increased exposures of olutasidenib under a fed condition compared to that under fasting conditions [see CLINICAL PHARMACOLOGY]. The clinical impact of this increase could not be determined because QTc intervals were not evaluated at higher olutasidenib exposures.
Pharmacokinetics
The pharmacokinetics of olutasidenib have been characterized in patients with AML following the approved recommended dosage, unless otherwise specified.
The mean (%CV) olutasidenib steady-state daily area under the plasma drug concentration over time curve (AUC0-12-h,ss) is 43050 (34.0%) ng•h/mL and steady-state maximum plasma concentration (Cmax,ss) is 3573 (45.6%) ng/mL following the approved recommended dosage.
Olutasidenib Cmax and AUC increase less-than proportionally over a dosage range from 100 mg to 300 mg (0.33 to 1 time the recommended total daily dose); however, this finding should not affect the recommended dosage of REZLIDHIA. Olutasidenib accumulation ratios ranging from 7.7 and 9.5 were observed following the approved recommended dosage. Steady-state plasma levels are reached within 14 days.
Absorption
The median (min, max) time to maximum concentration (tmax) of olutasidenib is approximately 4 (1, 8) hours following a single oral dose of 150 mg.
Effect Of Food
The mean (CV%) of olutasidenib Cmax increased by 191% (20.6%) and AUCinf increased by 83% (18.3%) following administration of a single 150 mg dose of olutasidenib with a high-fat meal (approximately 800 to 1,000 calories, with approximately 50% of total caloric content of the meal from fat) in healthy subjects.
Distribution
The mean (CV%) apparent volume of distribution of olutasidenib is 319 (28.1%) L. The plasma protein binding of olutasidenib is approximately 93%.
Elimination
The mean (CV%) half-life (t.) of olutasidenib is approximately 67 (51.2%) hours and the mean (CV%) apparent oral clearance (CL/F) of olutasidenib is 4 (60.5%) L/h.
Metabolism
Olutasidenib metabolism involves N-dealkylation, demethylation, oxidative deamination followed by oxidation, monooxidation with subsequent glucuronidation. Olutasidenib is primarily (90%) metabolized by cytochrome P450(CYP)3A4, with minor contributions from CYP2C8, CYP2C9, CYP1A2, and CYP2C19.
Excretion
Following a single oral radiolabeled olutasidenib dose of 150 mg to healthy subjects, approximately 75% of olutasidenib was recovered in feces (35% unchanged) and 17% in the urine (1% unchanged).
Specific Populations
No clinically significant differences in the pharmacokinetics of olutasidenib were observed based on age (28 to 90 years), sex, body weight (36 to 145 kg), mild to moderate renal impairment (creatinine clearance [CLcr] 30 to <90mL/min as estimated by Cockcroft-Gault), or mild (total bilirubin ≤ULN and any AST >ULN or total bilirubin >1 to 1.5 times ULN and any AST) or moderate (total bilirubin >1.5 to 3 times ULN and any AST) hepatic impairment.
The effect of severe renal impairment (CLcr 15 to 29 mL/min, as estimated by Cockcroft-Gault), kidney failure (CLcr <15 mL/min, as estimated by Cockcroft-Gault), patients on dialysis, and patients with severe hepatic impairment (total bilirubin >3 x ULN with any AST) on olutasidenib pharmacokinetics is unknown or not fully characterized.
Drug Interaction Studies
Clinical Studies
Strong CYP3A And P-glycoprotein (P-gp) Inhibitors
No clinically significant differences in olutasidenib pharmacokinetics were observed when used concomitantly with multiple doses of a strong CYP3A and P-gp inhibitor (itraconazole).
Strong CYP3A4 Inducers
Olutasidenib Cmax decreased by 43% and AUC by 80% when used concomitantly with multiple doses of a strong CYP3A inducer (rifampin).
In vitro Studies
CYP Enzymes
Olutasidenib induces CYP3A4, CYP2B6, CYP1A2, CYP2C8 and CYP2C9.
Olutasidenib does not inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4/5.
Transporter Systems
Olutasidenib is not a substrate of BCRP, BSEP, MRP2, MRP3, or MRP4.
Olutasidenib is an inhibitor of P-gp, BCRP, OATP1B1, OATP1B3, OAT3, OCT2, MATE1, and MATE2K. Olutasidenib does not inhibit BSEP, MRP2, MRP3, MRP4, or OAT1.
Animal Toxicology And/Or Pharmacology
Olutasidenib was phototoxic in vitro and in vivo. In pigmented rats, oral administration of olutasidenib for 3 consecutive days followed by exposure to UV light 2 hours after the last dose resulted in skin erythema which persisted for 72 hours.
Clinical Studies
Acute Myeloid Leukemia
The efficacy of REZLIDHIA was evaluated in an open-label, single-arm, multicenter clinical trial (Study 2102-HEM-101, NCT02719574) in 147 adult patients with relapsed or refractory AML with an IDH1 mutation.
IDH1 mutations in blood or bone marrow were confirmed retrospectively using the Abbott RealTime™ IDH1 Assay. REZLIDHIA was given orally at a dose of 150 mg twice daily until disease progression, development of unacceptable toxicity, or hematopoietic stem cell transplantation. Sixteen of the 147 patients (11%) underwent stem cell transplantation following REZLIDHIA treatment.
The baseline demographic and disease characteristics are shown in Table 4.
Table 4: Baseline Demographic and Disease Characteristics in Patients with Relapsed or Refractory AML (Study 2102-HEM-101)
| Demographic and Disease Characteristics |
REZLIDHIA (150 mg twice daily)
N=147 |
| Demographics |
| Age (Years) Median (Min, Max) |
71 (32, 87) |
| Age Categories, n (%) |
| <65 years |
37 (25) |
| ≥65 years to <75 years |
65 (44) |
| ≥75 years |
45 (31) |
| Sex, n (%) |
| Male |
74 (50) |
| Female |
73 (50) |
| Race, n (%) |
| White |
67 (46) |
| Black or African American |
5 (3) |
| Asian |
5 (3) |
| Native Hawaiian/Other Pacific Islander |
0 (0) |
| Other/Not provided |
70 (48) |
| Disease Characteristics |
| ECOG PS, n (%) |
| 0 |
45 (31) |
| 1 |
76 (52) |
| 2 |
23 (16) |
| IDH1 Mutation, n (%)1 |
| R132C |
85 (58) |
| R132H |
35 (24) |
| R132G |
12 (8) |
| R132S |
11 (7) |
| R132L |
4 (3) |
| Type of AML, n (%) |
| De novo AML |
97 (66) |
| Secondary AML |
50 (34) |
| Cytogenetic Risk Status2, n (%) |
| Favorable |
6 (4) |
| Intermediate |
107 (73) |
| Poor |
25 (17) |
| Unknown |
9 (6) |
| Relapsed/Refractory Patient Category |
| Primary Refractory |
46 (31) |
| Untreated Relapse3 |
81 (55) |
| Refractory Relapse3 |
20 (14) |
| Relapse Number |
| 0 |
46 (31) |
| 1 |
87 (59) |
| 2 |
11 (8) |
| ≥3 |
3 (2) |
| Prior Stem Cell Transplantation for AML, n (%) |
17 (12) |
| Transfusion Dependent at Baseline4, n (%) |
86 (59) |
| Median Number of Prior Therapies (Min, Max) |
2(1,7) |
1 Using central IDH1 assay testing results.
2 Cytogenetic risk categorization was investigator reported by NCCN or ELN guidelines.
3 May be first or subsequent relapse.
4 Transfusion-Dependent at Baseline is defined as receiving a transfusion within 8 weeks prior to first dose of olutasidenib or noting transfusion dependence prior to coming on study. |
Efficacy was established on the basis of the rate of complete remission (CR) plus complete remission with partial hematologic recovery (CRh), the duration of CR+CRh, and the rate of conversion from transfusion dependence to transfusion independence. The efficacy results are shown in Table 5. The median follow-up was 10.2 months (range: 0.2 to 38.1 months) and median treatment duration was 4.7 months (range: 0.1 to 26.0 months).
Table 5: Efficacy Results in Patients with Relapsed or Refractory AML (Study 2102-HEM-101)
| Endpoint |
REZLIDHIA (150 mg twice daily)
N=147 |
| CR+CRh1,2 n (%) |
51 (35) |
| 95% CI |
(27, 43) |
| Median DOCR+CRh3 (months) |
25.9 |
| 95% CI |
(13.5, NR) |
| CR1 n (%) |
47 (32) |
| 95% CI |
(25, 40) |
| Median DOCR3 (months) |
28.1 |
| 95% CI |
(13.8, NR) |
| CRh1 n (%) |
4(2.7) |
| 95% CI |
(0.7, 6.8) |
| Observed DOCRh3 (months) |
1.8, 5.6, 13.5, 28.5+ |
CI: confidence interval; NR = not reached
1 CR (complete remission) was defined as <5% blasts in the bone marrow, no blasts with Auer rods, no extramedullary disease, and full recovery of peripheral blood counts (platelets >100,000/microliter and absolute neutrophil counts [ANC] >1,000/microliter); CRh (complete remission with partial hematologic recovery) was defined as <5% blasts in the bone marrow, no evidence of disease, and partial recovery of peripheral blood counts (platelets >50,000/microliter and ANC >500/microliter).
2 CR+CRh rate was consistent across all baseline demographic and baseline disease characteristic subgroups with the exception of IDH1 R132H mutation (CR+CRh 17%).
3 Duration of response is defined as the time from the date of the first response to the date of the relapse or death. Patients who did not relapse were censored at the date of last response assessment. + indicates censored observation. |
Of the patients who achieved a CR or CRh, the median time to CR or CRh was 1.9 months (range: 0.9 to 5.6 months). All patients that achieved a best response of CR or CRh did so within 5.6 months of initiating REZLIDHIA.
Overall, among the 86 patients who were dependent on red blood cell (RBC) and/or platelet transfusions at baseline, 29 (34%) became independent of RBC and platelet transfusions during any 56-day post-baseline period. Of the 61 patients who were independent of both RBC and platelet transfusions at baseline, 39 (64%) remained transfusion independent during any 56-day post-baseline period.