12. CLINICAL PHARMACOLOGY
12.1 Mechanism of Action
Inotuzumab ozogamicin is a CD22-directed antibody-drug conjugate (ADC). Inotuzumab recognizes human CD22. The small molecule, N-acetyl-gamma-calicheamicin, is a cytotoxic agent that is covalently attached to the antibody via a linker. Nonclinical data suggest that the anticancer activity of inotuzumab ozogamicin is due to the binding of the ADC to CD22-expressing tumor cells, followed by internalization of the ADC-CD22 complex, and the intracellular release of N-acetyl-gamma-calicheamicin dimethylhydrazide via hydrolytic cleavage of the linker. Activation of N-acetyl-gamma-calicheamicin dimethylhydrazide induces double-strand DNA breaks, subsequently inducing cell cycle arrest and apoptotic cell death.
During the treatment period, the pharmacodynamic response to BESPONSA was characterized by the depletion of CD22-positive leukemic blasts.
In a randomized clinical study in patients with relapsed or refractory ALL, increases in QTcF of ≥ 60 msec from baseline were measured in 4/162 patients (3%) in the BESPONSA arm and 3/124 patients (2%) in the Investigator's choice of chemotherapy arm. Increases in QTcF of > 500 msec were observed in none of the patients in the BESPONSA arm and 1/124 patients (1%) in the Investigator's choice of chemotherapy arm. Central tendency analysis of the QTcF interval changes from baseline showed that the highest mean (upper bound of the 2-sided 90% CI) for QTcF was 15.3 (21.1) msec, which was observed at Cycle 4/Day 1/1 hour in the BESPONSA arm [see Warnings and Precautions (5.5)].
The mean Cmax of inotuzumab ozogamicin was 308 ng/mL. The mean simulated total AUC per cycle was 100,000 ng∙h/mL. In patients with relapsed or refractory ALL, steady-state drug concentration was achieved by Cycle 4. Following administration of multiple doses, a 5.3 times accumulation of inotuzumab ozogamicin was predicted by Cycle 4.
N-acetyl-gamma-calicheamicin dimethylhydrazide is approximately 97% bound to human plasma proteins in vitro. In humans, the total volume of distribution of inotuzumab ozogamicin was approximately 12 L.
The pharmacokinetics of inotuzumab ozogamicin was well characterized by a 2-compartment model with linear and time-dependent clearance components. In 234 patients with relapsed or refractory ALL, the clearance of inotuzumab ozogamicin at steady state was 0.0333 L/h and the terminal half-life (t½) was 12.3 days. Following administration of multiple doses, a 5.3 times accumulation of inotuzumab ozogamicin was predicted by Cycle 4.
In vitro, N-acetyl-gamma-calicheamicin dimethylhydrazide was primarily metabolized via nonenzymatic reduction. In humans, N-acetyl-gamma-calicheamicin dimethylhydrazide serum levels were typically below the limit of quantitation.
The effect of intrinsic factors on inotuzumab ozogamicin pharmacokinetics was assessed using a population pharmacokinetic analysis unless otherwise specified. Age (18 to 92 years of age), sex, and race (Asian versus non-Asian [Caucasian, Black, and Unspecified]) had no clinically significant effect on the pharmacokinetics of inotuzumab ozogamicin. Body surface area was found to significantly affect inotuzumab ozogamicin disposition. BESPONSA is dosed based on body surface area [see Dosage and Administration (2.1)].
Patients with Renal Impairment
The clearance of inotuzumab ozogamicin in patients with mild renal impairment (creatinine clearance [CLcr; based on the Cockcroft-Gault formula] 60–89 mL/min; n=237), moderate renal impairment (CLcr 30–59 mL/min; n=122), or severe renal impairment (CLcr 15–29 mL/min; n=4) was similar to patients with normal renal function (CLcr ≥90 mL/min; n=402). The safety and efficacy of inotuzumab ozogamicin in patients with end stage renal disease with or without hemodialysis is unknown.
Patients with Hepatic Impairment
The clearance of inotuzumab ozogamicin in patients with mild hepatic impairment (total bilirubin ≤ULN and AST > ULN, or total bilirubin >1.0–1.5 × ULN and AST any level; n=150) was similar to patients with normal hepatic function (total bilirubin/AST ≤ULN; n=611). There is insufficient data in patients with moderate and severe hepatic impairment (total bilirubin >1.5 ULN).
Effect of Metabolic Pathways and Transporter Systems on BESPONSA
N-acetyl-gamma-calicheamicin dimethylhydrazide is a substrate of P-glycoprotein (P-gp).
Effect of BESPONSA on Metabolic Pathways and Transporter Systems
At clinically relevant concentrations, N-acetyl-gamma-calicheamicin dimethylhydrazide had a low potential to:
- Inhibit cytochrome P450 (CYP 450) Enzymes: CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4/5.
- Induce CYP450 Enzymes: CYP1A2, CYP2B6, and CYP3A4.
- Inhibit UGT Enzymes: UGT1A1, UGT1A4, UGT1A6, UGT1A9, and UGT2B7.
- Inhibit Drug Transporters: P-gp, breast cancer resistance protein (BCRP), organic anion transporter (OAT)1 and OAT3, organic cation transporter (OCT)2, and organic anion transporting polypeptide (OATP)1B1 and OATP1B3.
At clinically relevant concentrations, inotuzumab ozogamicin had a low potential to:
- Inhibit CYP450 Enzymes: CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4/5.
- Induce CYP450 Enzymes: CYP1A2, CYP2B6, and CYP3A4.