Objectives: Moxetumomab pasudotox (CAT-8015) is a recombinant immunotoxin composed of a disulfide-stabilized anti-CD22 immunoglobulin variable domain and a truncated form of Pseudomonas exotoxin. It is currently being developed to treat CD22-expressing B-cell malignancies. The objective of this investigation was to develop a population pharmacokinetic (PK) -pharmacodynamic (PD) model to support the biocomparability assessment of Process 1 (P1) and Process 2 (P2) clinical materials in cynomolgus monkeys.

Methods: In a GLP study male cynomolgus monkeys were randomized by baseline CD22+ B lymphocytes and received intravenous injections of 1 mg/kg P1 or P2 moxetumomab pasudotox (n=12/group) on study Days 1, 3, and 5. Samples collected at pre-designated timepoints were analyzed for moxetumomab pasudotox serum concentration determination (electrochemiluminescence assay) and CD20+/CD22+ B lymphocyte count (flow cytometry assay). Population PK-PD modeling was performed using the software package NONMEM (Version VI, Level 2, ICON, Ellicott City, MD). The first-order conditional estimation with interaction method was employed. Potential effects of manufacturing process on moxetumomab pasudotox clearance, efficacy and potency were assessed in covariate analyses.

Results: A two-compartmental model with a first-order elimination pathway well captured the PK properties of moxetumomab pasudotox following IV injections. The estimated systemic clearance was 76.3 mL/kg/h with a steady-state distribution volume of 123.5 mL/kg. A hematopoietic transit model coupled with moxetumomab pasudotox-induced cytotoxic effect on mature B lymphocyte was successfully established to characterize B lymphocyte depletion. A negative feedback to influx from precursor cells was also included to achieve the best fit. A life-span of 51.2 days was estimated for mature B lymphocytes in cynomolgus monkeys. The serum moxetumomab pasudotox concentration that leads to half of the maximum cell killing activity (EC50) was estimated at 38.2 ng/mL. Consistent with prior bioequivalence assessment the manufacturing process change had no impact on the systemic clearance of moxetumomab pasudotox in cynomolgus monkeys. In addition, the covariate analysis didn’t reveal any significant impact of P1 or P2 on CD22+ B-cell depleting activities of moxetumomab pasudotox.

Conclusions: The PK of moxetumomab pasudotox and depletion of CD22+ B cells were adequately described by the population PK-PD model. Covariate analysis demonstrated that manufacturing process had no significant effect on moxetumomab pasudotox PK or PD. Results from this study supported further clinical investigation of moxetumomab pasudotox using the new Process 2 material

Population Pharmacokinetic-PharmacodynamicModeling to Support Biocomparability Assessment of

Moxetumomab Pasudotox in Cynomolgus Monkey

Zhenling Yao, Lorin Roskos, Mikhail Zusmanovich, Meina Liang, Theresa LaVallee, Bing Wang

MedImmune LLC, Hayward CA and Gaithersburg MD

ACoP Annual Meeting; San Diego; Apr 3-6, 2011

ABSTRACT

INTRODUCTION

CD22CD22

An Ig superfamily B-lymphocyte-specific adhesion receptor Upon ligand binding CD22 is internalized and targeted to lysosomal compartment for degradation (no recycling)

Moxetumomab Pasudotox Moxetumomab Pasudotox

(CAT-8015)(CAT-8015)

A recombinant immunotoxin composed of an anti-CD22 immunoglobulin variable domain and a truncated form of Pseudomonas exotoxin 38 (PE38)

• Noncompartmental analysis and statistical analysis for biocomparability assessment was performed using the bioequivalence tool in WinNonlin Professional (version 5.2).

• Mechanistic PKPD model was developed to

• Characterize PKPD relationship of moxetumomab pasudotox

• Use process change as covariate to assess impact on PK and response on lymphocyte depletion

PK Assay

• An electrochemiluminescence (ECL) assay was developed and validated on a Meso Scale Discovery® (MSD) platform. (LLOQ=7.8 ng/mL)

Flow Cytometry

• Developed and qualified to assess the relative percentages of CD20+ and CD22+ cells.

• Total lymphocyte counts determined using a hematology analyzer.

Immunogenicity Assay

• The presence of ADA was detected using a validated ECL assay.

• The assay is sensitive (LOD 41 ng/mL) and drug-tolerant (0.5 ug/mL)

• Pre-existing anti-drug antibodies screened to minimize PK variability

• Animals randomized to 2 treatment groups based on CD22 levels

• Three intravenous (IV) doses at 1mg/kg on Days 1, 3 and 5

• Samples were collected for PK, flow cytometry and immunogenicity assessment

METHODS

RESULTS

CONCLUSION

In vivoIn vivo Comparability Study Comparability Study

• Significant CMC process changes occurred during the clinical development of moxetumomab pasudotox

• An in vivo PKPD study is required to demonstrate biocomparability (bioequivalence) of the two clinical materials

• Objective: Assess the pharmacokinetic (PK) and pharmacodynamic (PD) biocomparability of Process 1 and Process 2 materials in male cynomolgus monkeys following a single-cycle intravenous treatment

Study DesignStudy Design

BioanalyticalBioanalytical

Data AnalysisData Analysis

Figure 1: PKPD model of moxetumomab pasudotox

Figure 2: PK profiles of moxetumomab pasudotox in male monkeys following first dose of Process 1(A) or Process 2(B) clinical material

Figure 4: Basic GOF plots for final PKPD model

Figure 5: Visual predictive check (A) PK, 1st dose; (B) PK, 2nd dose; (C) PK, 3rd dose; (D) CD20+ lymphocyte

Figure 3: Baseline-normalized counts of CD20+ (A) or CD22+ (B) lymphocytes

Process 1Process 2

Process 1Process 2

• Hematopoietic transit PD model

• Cytotoxic effect on mature CD22+ B cells

• No cytotoxic effect on precursor cells

• Negative feedback to influx from precursor cells

• Pop PKPD was performed using NONMEM (version 7.1.0)

• FOCE INTER

• VPC and Bootstrap performed

NCA and Biocomparability AssessmentNCA and Biocomparability Assessment

• Bi-phasic PK disposition following IV dosing

• Most PK observations fell below LLOQ 12 hours after dosing

• Cell depletion observed for both CD20+ and CD22+ cells; Recovered at d21

Pop PKPD ModelingPop PKPD Modeling

• Estimated lifespan of mature B cells was 51.2 days in monkeys

• The maximum B cell destruction by moxetumomab pasudotox (Emax) corresponds to a mean B cell survival time of 18 hr when serum concentration greatly exceeds EC50

• Covariate analysis demonstrated clinical material change has no impact on PK or PD of moxetumomab pasudotox

• A GLP PKPD study was conducted in male cynomolgus monkeys to assess in vivo biocomparability of moxetumomab pasudotox

• Bioequivalence was met for Process 1 and Process 2 materials following 1st dose

• A hematopoietic transit PD model was developed to characterize the lymphocyte depletion following moxetumomab pasudotox administration

• Covariate analysis confirmed that process change did not impact on moxetumomab pasudotox PK and response on lymphocyte depletion

• The study supported further clinical investigation of moxetumomab pasudotox using the new clinical material

ACKNOWLEDGEMENT

• Samuel S. Chuang and Stephanie Fraser (Charles River Laboratories, Reno, NV)

• Inna Vainshtein, Rozanne Lee, Amy Schneider, Feng Jin, Kamille O’Connor, Bettina Kasprzyk, Laurie Iciek , Jan Popp, Steve Yim and Chris Forespring (MedImmune LLC)

• Bioequivalence assessment was conducted based on the exposure following the 1st dose

• The 90% confidence intervals of geometric mean ratios were within the [0.8,1.25] interval for Cmax, AUClast and AUCinf.

• Process 1 and Process 2 materials are bioequivalent in monkeys