RN486 [6-cyclopropyl-8-fluoro-2-(2-hydroxymethyl-3-{1-methyl-5-[5-(4-methyl-piperazin-1-yl)-pyridin-2-ylamino]-6-oxo-1,6-dihydro-pyridin-3-yl}-phenyl)-2H-isoquinolin-1-one]
is a potent, selective, reversible inhibitor of Bruton's tyrosine kinase (BTK).
In the enzymatic assay, the compound potently inhibited Btk kinase activity
with an IC50 of 4.0 nM. RN486 binds the enzyme in a competitive
manner as demonstrated in a time-resolved FRET-based competitive binding assay
with an IC50 of 0.3 nM. RN486 was shown to be highly selective when
tested against a panel of 369 kinases in the Kinomescan. In the assay, the
compound exhibited a strong and competitive binding to Btk with a Kd
of 0.31 nM and a high degree of selectivity over almost all other kinases,
including Syk and Janus kinase (JAK, Kd = 5.1 uM). The enzyme that
was most potently inhibited next to Btk was Ste20-like kinase (SLK, Kd
= 0.043 uM), for which the compound showed a 139-fold selectivity [1].
The activity of RN486 is as follows:
IC50 (BTK enzyme
assay) = 4.0 nM; Kd = 0.31 nM
Kd (JAK binding assay)
= 5.1 uM
Kd (SLK binding assay)
= 0.043 uM
Common Name: RN486
Synonyms: RN486;
RN 486; RN-486
IUPAC Name: 6-cyclopropyl-8-fluoro-2-(2-hydroxymethyl-3-{1-methyl-5-[5-(4-methyl-piperazin-1-yl)-pyridin-2-ylamino]-6-oxo-1,6-dihydro-pyridin-3-yl}-phenyl)-2H-isoquinolin-1-one
CAS Number: 1242156-23-5
SMILES: OCc1c(cccc1n1ccc2c(c1=O)c(F)cc(c2)C1CC1)c1cc(Nc2ccc(cn2)N2CCN(CC2)C)c(=O)n( c1)C
Mechanism of Action: Kinase
Inhibitor; BTK Inhibitor
Indication: Various
Cancers; Anti-inflammatory Agents; Treatment for Rheumatoid Arthritis
Development Stage: Pre-Clinical
Company: Hoffmann-la-Roche
The production and effector function of
antibodies are regulated by distinct immunoreceptors on B cells and innate
immune cells. The receptors, termed B cell antigen receptor (BCR) and
activating Fc receptor (FcR), belong to a family of Ig-like immunoreceptors
containing an intracellular immunoreceptor tyrosine-based activation motif
(ITAM). ITAMs act to integrate diverse antigen- or Fc-specific signals into a
common pathway regulated by nonreceptor tyrosine kinases including Lyn, spleen
tyrosine kinase (Syk), and Bruton's tyrosine kinase (Btk) from the sarcoma
kinase, Syk, and Tec kinase families. These kinases relay the signals
sequentially from ITAMs to phospholipase Cγ2 (PLCγ2) and thus play a critical and nonredundant role in the
signal transduction of BCR and FcR. Consequently, loss-of-function mutation in
the Btk gene results in severe B cell immunodeficiency and impaired FcR
function in both patients with X-linked agammaglobulinemia and mutant mice with
X-linked immunodeficiency.
Together, Btk and Syk regulate the signal
transduction of ITAM-containing receptors or adaptors that are critical for
autoantibody production, effector function, and osteoclast differentiation.
Therefore, pharmacological inhibition of these enzymes may affect multiple
steps in the pathogenesis of Rheumatoid arthritis (RA) and represent a useful
approach for the treatment of the disease. Rheumatoid arthritis (RA) is an
autoimmune joint disease characterized by chronic synovial inflammation and
progressive joint destruction. The disease is often associated with the
appearance of autoantibodies in both blood and inflamed joints. Several of
these autoantibodies have emerged as potential arthritogenic factors. For
example, anti-glucose-6 phosphate isomerase and anti-type II collagen
antibodies, both of which are highly arthritogenic in mice, can be detected in
patients with RA. In addition, anticitrullinated protein autoantibodies, the
most prevalent in RA, can bind citrullinated fibrinogen in RA joints to form
immune complexes, which stimulate macrophages to produce inflammatory cytokines
such as TNFα. Lastly, clinical efficacy of B cell-depleting agents in
RA strongly implicates autoantibodies as culprits in the pathogenesis of the
disease.
When tested in the rat and mouse, RN486
exhibited an excellent pharmacokinetic profile. In the rat, it reached the
maximal concentration of 2.5 µM at 4.5 h when dosed orally at 20 mg/kg and
showed a half-life of 9.8 h in the blood when administered intravenously. In
the mouse, the compound reached the maximal concentration of 6.0 µM at 3 h and a
trough concentration of 1.0 µM at 24 h when dosed orally at 30 mg/kg [1].
Important facts about RN486:
a: RN486 Blocks both BCR and FcR Signaling.
b: RN486 Displays a Selective B Cell Inhibitory
Profile in BioMAP Systems.
c: RN486 Displays Efficacy on Immune Arthritis
Induced by both Active and Passive Immunization in Mice.
d: RN486 Inhibits Inflammation and Bone Erosions
in Adjuvant-Induced Arthritis Either Alone or in Combination with Methotrexate.
e: RN486 Reduces Blood Inflammatory Markers in
AIA.
Combination therapy with low-dose
methotrexate is an important treatment option for patients with RA. Researchers
therefore determined the potential of RN486 for combined therapy with
methotrexate. To identify a suboptimal or low dose of methotrexate for
combination study, researchers tested methotrexate alone in the AIA model at doses
ranging from 0.025 to 0.25 mg/kg. Methotrexate displayed a dose-dependent
inhibitory effect on both paw inflammation and splenomegaly in AIA rats,
attenuating paw swelling by ~50 and 100%, respectively, at 0.075 and greater or
equal 0.15 mg/kg. Researchers then tested RN486 and methotrexate at their
respective suboptimal doses, 10 and 0.075 mg/kg, alone or in combination in the
AIA model to assess the combined effect. As in the monotherapy studies, both
RN486 and methotrexate attenuated paw swelling by approximately 50% when tested
alone at the suboptimal doses. When combined, the two compounds completely
eradicated paw swelling, splenomegaly, and histopathogical changes of
inflammation and bone erosions [1].
References:
1. Xu, D.; et. al. RN486, a selective Bruton's
tyrosine kinase inhibitor, abrogates immune hypersensitivity responses and
arthritis in rodents. J Pharmacol Exp Ther 2012,
341(1), 90-103.