Development and application of a biomarker assay for determining the pharmacodynamic activity of an antagonist candidate biotherapeutic antibody to IL21R in whole blood.
BACKGROUND
In preparation for potential clinical development of Ab-01, an antagonistic antibody directed against the IL21R, studies were undertaken to address translational medicine needs that fall into four categories: 1) development of a pharmacodynamic biomarker assay suitable for use in the clinic, 2) demonstration that Ab-01 has the desired biological activity in vitro and in vivo in cynomolgus monkeys, the preferred safety study species, 3) pre-clinical in vivo proof-of-concept that the assay can be used to detect Ab-01 pharmacodynamic (PD) activity in treated subjects, and 4) comprehensive assessment of the agonistic potential of Ab-01 when cross-linked. This report and a recently published companion report address the first three of these needs. The fourth has been addressed in a separate study.


METHODS
Genes that change RNA expression upon ex vivo rhIL21 stimulation of whole blood were identified in human and cynomolgus monkey. The inhibitory effects of exogenously added Ab-01 were measured ex vivo in human and monkey, and the in vivo inhibitory effects of Ab-01 treatment were measured in monkey.


RESULTS
Stimulation of whole human blood for 2 hours with rhIL21 induced robust increases in RNA expression of 6 genes. This response was blocked by Ab-01, indicating that the assay is suitable for measuring Ab-01 activity in blood. rhIL21 induced expression of a similar set of genes in cynomolgus monkey blood. This response was blocked with Ab-01, thus demonstrating that Ab-01 has the desired activity in the species, and that safety studies done in cynomolgus monkeys are relevant. Proof -of-concept for using this assay system to detect PD activity in vivo was generated by measuring the response in monkey blood to ex vivo rhIL21 stimulation before and 5 minutes following in vivo Ab-01 administration.


CONCLUSIONS
A robust PD biomarker assay suitable for clinical use has been developed in human whole blood. The successful adaptation of the assay to cynomolgus monkeys has enabled the demonstration of Ab-01 activity both in vitro and in vivo in monkey, thus validating the use of this species in safety studies and establishing proof-of-concept for using this PD assay system to aid in dose selection in clinical studies.
Arai
Maya
M
Global Biotherapeutic Technologies, Pfizer, Cambridge, MA 02140, USA.
Jain
Sadhana
S
Weaver
Amy A
AA
Hill
Andrew A
AA
Guo
Yongjing
Y
Bree
Andrea G
AG
Smith
Michael F
MF
Allen
Scott W
SW
LaVallie
Edward R
ER
Young
Deborah
D
Bloom
Laird
L
Adkins
Karissa
K
O'Toole
Margot
M
D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology* / Q000627:therapeutic use; D001681:Biological Assay / Q000379:methods*; D015415:Biomarkers / Q000097:blood; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007378:Interleukins / Q000276:immunology; D008252:Macaca fascicularis / Q000276:immunology; D053655:Receptors, Interleukin-21 / Q000037:antagonists & inhibitors* / Q000097:blood* / Q000276:immunology; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D017186:Titrimetry; D000098546:Interleukin-21
D000906:Antibodies; D015415:Biomarkers; D007378:Interleukins; D053655:Receptors, Interleukin-21; D000098546:Interleukin-21