An orally bioavailable spleen tyrosine kinase inhibitor delays disease progression and prolongs survival in murine lupus.
OBJECTIVE
To assess whether R788, an orally bioavailable small molecule inhibitor of spleen tyrosine kinase (Syk)-dependent signaling, could modulate disease in lupus-prone (NZB x NZW)F1 (NZB/NZW) mice via inhibition of Fc receptor (FcR) and B cell receptor signaling.


METHODS
R788 was administered to NZB/NZW mice before and after disease onset. Proteinuria, blood urea nitrogen levels, and autoantibody titers were examined periodically, and overall survival and renal pathologic features were assessed following long-term treatment (24-34 weeks). The distribution and immunophenotype of various splenic T cell and B cell subpopulations were evaluated at the time of study termination. Arthus responses in NZB/NZW mice pretreated with R788 or Fc-blocking antibody (anti-CD16/32) were also examined.


RESULTS
When R788 was administered prior to or after disease onset, it delayed the onset of proteinuria and azotemia, reduced renal pathology and kidney infiltrates, and significantly prolonged survival of lupus-prone NZB/NZW mice; autoantibody titers were minimally affected throughout the study. Dose-dependent reductions in the numbers of CD4+ activated T cells expressing high levels of CD44 or CD69 were apparent in spleens from R788-treated mice. Minimal effects on the numbers of naive T cells expressing CD62 ligand and total CD8+ T cells per spleen were observed following long-term drug treatment. R788 pretreatment resulted in reduced Arthus responses in NZB/NZW mice, similar to results obtained in mice pretreated with FcR-blocking antibody.


CONCLUSIONS
We demonstrate that a novel Syk-selective inhibitor prevents the development of renal disease and treats established murine lupus nephritis. These data suggest that Syk inhibitors may be of therapeutic benefit in human lupus and related disorders.
Bahjat
Frances Rena
FR
Rigel Pharmaceuticals, South San Francisco, California, USA.
Pine
Polly R
PR
Reitsma
Andrea
A
Cassafer
Gail
G
Baluom
Muhammad
M
Grillo
Sunny
S
Chang
Betty
B
Zhao
Fei Fei
FF
Payan
Donald G
DG
Grossbard
Elliott B
EB
Daikh
David I
DI
D000284:Administration, Oral; D000631:Aminopyridines; D000818:Animals; D018450:Disease Progression; D008180:Lupus Erythematosus, Systemic / Q000401:mortality / Q000517:prevention & control*; D051379:Mice; D008807:Mice, Inbred BALB C; D008814:Mice, Inbred NZB; D009025:Morpholines; D010078:Oxazines / Q000627:therapeutic use*; D011725:Pyridines / Q000627:therapeutic use*; D011743:Pyrimidines; D015996:Survival Rate; D013997:Time Factors
D000631:Aminopyridines; D009025:Morpholines; D010078:Oxazines; D011725:Pyridines; D011743:Pyrimidines; C523665:fostamatinib