Brentuximab vedotin is an antibody drug conjugate (ADC) that delivers an antineoplastic agent that results in apoptotic cell death selectively in CD30-expressing tumour cells. Nonclinical data suggest that the biological activity of brentuximab vedotin results from a multi-step process. Binding of the ADC to CD30 on the cell surface initiates internalisation of the ADC-CD30 complex, which then traffics to the lysosomal compartment. Within the cell, a single defined active species, MMAE, is released via proteolytic cleavage. Binding of MMAE to tubulin disrupts the microtubule network within the cell, induces cell cycle arrest and results in apoptotic death of the CD30-expressing tumour cell.
Classical HL, sALCL and subtypes of CTCL (including MF and pcALCL) express CD30 as an antigen on the surface of their malignant cells. This expression is independent of disease stage, line of therapy or transplant status. These features make CD30 a target for therapeutic intervention. Because of the CD30-targeted mechanism of action brentuximab vedotin is able to overcome chemo-resistance as CD30 is consistently expressed in patients who are refractory to multi-agent chemotherapy, irrespective of prior transplant status. The CD30-targeted mechanism of action of brentuximab vedotin, the consistent expression of CD30 throughout the classical HL, sALCL and CD30+ CTCL disease and therapeutic spectrums and clinical evidence in CD30-positive malignancies following multiple lines of treatment provide a biologic rationale for its use in patients with relapsed and refractory classical HL, sALCL with or without prior ASCT and CD30+ CTCL after at least 1 prior systemic therapy.
Contributions to the mechanism of action by other antibody associated functions have not been excluded.
Forty-six (46) patients with CD30-expressing haematologic malignancies were evaluable of the 52 patients who received 1.8 mg/kg of brentuximab vedotin every 3 weeks as part of a phase 1, single-arm, open-label, multicenter cardiac safety study. The primary objective was to evaluate the effect of brentuximab vedotin on cardiac ventricular re-polarization and the predefined primary analysis was the change in QTc from baseline to multiple time points in Cycle 1.
The upper 90% confidence interval (CI) around the mean effect on QTc was <10 msec at each of the Cycle 1 and Cycle 3 post-baseline time points. These data indicate the absence of clinically relevant QT prolongation due to brentuximab vedotin administered at a dose of 1.8 mg/kg every 3 weeks in patients with CD30-expressing malignancies.
The pharmacokinetics of brentuximab vedotin were evaluated in phase 1 studies and in a population pharmacokinetic analysis of data from 314 patients. In all clinical trials, brentuximab vedotin was administered as an intravenous infusion.
Maximum concentrations of brentuximab vedotin ADC were typically observed at the end of infusion or the sampling timepoint closest to the end of infusion. A multiexponential decline in ADC serum concentrations was observed with a terminal half-life of approximately 4 to 6 days. Exposures were approximately dose proportional. Minimal to no accumulation of ADC was observed with multiple doses at the every 3-week schedule, consistent with the terminal half-life estimate. Typical Cmax and AUC of ADC after a single 1.8 mg/kg in a phase 1 study was approximately 31.98 μg/ mL and 79.41 μg/ mL x day respectively.
MMAE is the major metabolite of brentuximab vedotin. Median Cmax, AUC and Tmax of MMAE after a single 1.8 mg/kg of the ADC in a phase 1 study was approximately 4.97 ng/ mL, 37.03 ng/ mL x day and 2.09 days respectively. MMAE exposures decreased after multiple doses of brentuximab vedotin with approximately 50% to 80% of the exposure of the first dose being observed at subsequent doses. MMAE is further metabolised mainly to an equally potent metabolite; however, its exposure is an order of magnitude lower than that of MMAE. Thus, it is not likely to have any substantial contribution to the systemic effects of MMAE.
In the first cycle, higher MMAE exposure was associated with an absolute decrease in neutrophil count.
The pharmacokinetics of brentuximab vedotin in combination with AVD were evaluated in a single phase 3 study in 661 patients. Population pharmacokinetic analysis indicated that the pharmacokinetics of brentuximab vedotin in combination with AVD were consistent to that in monotherapy.
After multiple-dose, IV infusion of 1.2 mg/kg brentuximab vedotin every two weeks, maximal serum concentrations of ADC were observed near the end of the infusion and elimination exhibited a multi-exponential decline with a t1/2z of approximately 4 to 5 days. Maximal plasma concentrations of MMAE were observed approximately 2 days after the end of infusion, and exhibited a mono-exponential decline with a t1/2z of approximately 3 to 4 days.
After multiple-dose, IV infusion of 1.2 mg/kg brentuximab vedotin every two weeks, steady-state trough concentrations of ADC and MMAE were achieved by Cycle 3. Once steady-state was achieved, the PK of ADC did not appear to change with time. ADC accumulation (as assessed by AUC14D between Cycle 1 and Cycle 3) was 1.27-fold. The exposure of MMAE (as assessed by AUC14D between Cycle 1 and Cycle 3) appeared to decrease with time by approximately 50%.
In vitro, the binding of MMAE to human serum plasma proteins ranged from 68-82%. MMAE is not likely to displace or to be displaced by highly protein-bound medicines. In vitro, MMAE was a substrate of P-gp and was not an inhibitor of P-gp at clinical concentrations.
In humans, the mean steady state volume of distribution was approximately 6-10 l for ADC. Based on population PK estimation the typical apparent central volume of distribution of MMAE was 35.5 l.
The ADC is expected to be catabolised as a protein with component amino acids recycled or eliminated.
In vivo data in animals and humans suggest that only a small fraction of MMAE released from brentuximab vedotin is metabolised. The levels of MMAE metabolites have not been measured in human plasma. At least one metabolite of MMAE has been shown to be active in vitro.
MMAE is a substrate of CYP3A4 and possibly CYP2D6. In vitro data indicate that the MMAE metabolism that occurs is primarily via oxidation by CYP3A4/5. In vitro studies using human liver microsomes indicate that MMAE inhibits only CYP3A4/5 at concentrations much higher than was achieved during clinical application. MMAE does not inhibit other isoforms.
MMAE did not induce any major CYP450 enzymes in primary cultures of human hepatocytes.
The ADC is eliminated by catabolism with a typical estimated CL and half life of 1.5 l/day and 4-6 days respectively.
The elimination of MMAE was limited by its rate of release from ADC, typical apparent CL and half life of MMAE was 19.99 l/day and 3-4 days respectively.
An excretion study was undertaken in patients who received a dose of 1.8 mg/kg of brentuximab vedotin. Approximately 24% of the total MMAE administered as part of the ADC during a brentuximab vedotin infusion was recovered in both urine and faeces over a 1-week period. Of the recovered MMAE, approximately 72% was recovered in the faeces. A lesser amount of MMAE (28%) was excreted in the urine.
Population PK analysis showed that baseline serum albumin concentration was a significant covariate of MMAE clearance. The analysis indicated that MMAE clearance was 2-fold lower in patients with low serum albumin concentrations <3.0 g/dl compared with patients with serum albumin concentrations within the normal range.
A study evaluated the PK of brentuximab vedotin and MMAE after the administration of 1.2 mg/kg of brentuximab vedotin to patients with mild (Child-Pugh A; n=1), moderate (Child-Pugh B; n=5) and severe (Child-Pugh C; n=1) hepatic impairment. Compared to patients with normal hepatic function, MMAE exposure increased approximately 2.3-fold (90% CI 1.27-4.12-fold) in patients with hepatic impairment.
A study evaluated the PK of brentuximab vedotin and MMAE after the administration of 1.2 mg/kg of brentuximab vedotin to patients with mild (n=4), moderate (n=3) and severe (n=3) renal impairment. Compared to patients with normal renal function, MMAE exposure increased approximately 1.9-fold (90% CI 0.85-4.21-fold) in patients with severe renal impairment (creatinine clearance < 30 mL/min). No effect was observed in patients with mild or moderate renal impairment.
The population pharmacokinetics of brentuximab vedotin were examined from several studies, including data from 380 patients up to 87 years old (34 patients ≥65 - <75 and 17 patients ≥75 years of age). Additionally, the population pharmacokinetics of brentuximab vedotin in combination with AVD were examined, including data from 661 patients up to 82 years old (42 patients ≥65 - <75 and 17 patients ≥75 years of age). The influence of age on pharmacokinetics was investigated in each analysis and it was not a significant covariate.
The pharmacokinetics of brentuximab vedotin ADC and MMAE following a 30-minute intravenous infusion of BV administered at 1.4 mg/kg or 1.8 mg/kg given every 3 weeks were evaluated in a phase ½ clinical trial of 36 paediatric patients (7-17 years of age) with r/r HL and sALCL (children aged 7-11 years, n=12 and adolescents aged 12 to 17 years, n=24). The Cmax of ADC was typically observed at the end of infusion or the sampling closest to the end of infusion. A multiexponential decline in ADC serum concentrations was observed with a terminal half-life of approximately 4 to 5 days. Exposures were approximately dose proportional with a trend observed for lower ADC exposures at lower ages/ body weights in the study population.
Median ADC AUC in children and adolescents from this study was approx. 14% and 3% lower than in adult patients, respectively, while MMAE exposures were 53% lower and 13% higher, respectively, than in adult patients. Median Cmax and AUC of ADC after a single 1.8 mg/kg dose were 29.8 µg/ mL and 67.9 µg*day/ mL, respectively, in patients <12 years of age and 34.4 µg/mL and 77.8 µg*day/mL, respectively, in patients ≥12 years of age. Median Cmax, AUC, and Tmax of MMAE after a single 1.8 mg/kg dose were 3.73 ng/mL, 17.3 ng*day/mL, and 1.92 days, respectively, in patients <12 years of age and 6.33 ng/mL, 42.3 ng*day/mL, and 1.82 days, respectively, in patients ≥12 years of age. There was a trend of increased clearance of brentuximab vedotin in paediatric patients confirmed positive for ADAs. No patients aged <12 years (0 of 11) and 2 patients aged ≥12 years (2 of 23) became persistently ADA positive.
MMAE has been shown to have aneugenic properties in an in vivo rat bone marrow micronucleus study. These results were consistent with the pharmacological effect of MMAE on the mitotic apparatus (disruption of the microtubule network) in cells.
The effects of brentuximab vedotin on human male and female fertility have not been studied. However, results of repeat-dose toxicity studies in rats indicate the potential for brentuximab vedotin to impair male reproductive function and fertility. Testicular atrophy and degeneration were partially reversible following a 16-week treatment-free period.
Brentuximab vedotin caused embryo-foetal lethality in pregnant female rats.
In nonclinical studies, lymphoid depletion and reduced thymic weight were observed, consistent with the pharmacologic disruption of microtubules caused by MMAE derived from brentuximab vedotin.
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