Table 2.

Preclinical data for Bruton’s tyrosine kinase (BTK) inhibitors evaluated in clinical trials for autoimmune disorders

Animal models	Human in vitro studies	References
Acalabrutinib
–	B cells: Inhibition of B-cell activation (CD69 expression)	[160]
BMS-986142
CAIA: Treatment from the start, dose-dependent reduction of clinical scores CIA (mice): Treatment prior to disease onset, dose-dependent reduction of disease severity; treatment start at time of boost (day 21), dose-dependent reduction of disease severity and joint destruction. Enhances efficacy of standard-of-care agents	GPA: Reduced cytokine expression, but not memory cell/ plasma cell formation and antibody production in B cells from active patients. In B cells from patients in remission, these effector functions were inhibited by BMS-986142	[65, 105]
Branebrutinib
CIA (mice): Treatment at immunization, dose-dependent reduction of clinical scores, reduced joint destruction, almost complete protection at highest dose NZB/W: Reduced mortality, dose-dependent reduction of proteinuria, anti-dsDNA, reduced glomerulonephritis (comparable to prednisolone)	Healthy B cells/PBMC: Inhibits BCR-mediated proliferation and activation of B cells, FcR-mediated TNFα production by PBMC	[139]
Elsubrutinib
NP-immunizations: NP-LPS: no significant effect on antibody development; NP-Ficoll: reduced IgM and IgG3; NP-KLH: reduced IgM after boost, high dose reduced IgG1 Vaccine response (pneumococcal, Prevnar): no significant effect on antibody levels CIA (rats): Treatment at onset disease, dose-dependent reduction in clinical score, bone loss IFN-α-accelerated NZB/W F1: Treatment prior to onset proteinuria, dose-dependent reduction in mortality, proteinuria, and anti-dsDNA (only high doses)	Healthy B cells/PBMC/eosinophils: Inhibits BCR-mediated B-cell activation, IgE-mediated histamine release by eosinophils and FcR- and TLR-mediated cytokine production by PBMC	[125]
Evobrutinib
CIA (mice): Treatment before onset of disease, dose-dependent reduction of incidence and severity of arthritis, and histopathological scores of joint inflammation/destruction CIA (rats): treatment at onset of disease, dose-dependent reduction of clinical and histopathological score IFN-α-accelerated NZB/W F1: Dose-dependent reduction of proteinuria and kidney damage, reduced plasma cell numbers and B- and T-cell activation EAE: Before onset: Dose-dependent reduction of disease severity, cytokine expression, reduced B- and T-cell infiltration in CNS, reduced Ag-dependent B-cell differentiation, antigen presentation	Healthy B cells: Inhibition of BCR-induced B-cell activation (comparable to MS B cells), inhibition of BCR- and TLR9-induced cytokine production MS B cells: BTK protein levels increased in memory CD27+ B cells, no differences in BTK phosphorylation with healthy B cells.	[28, 126, 163]
Fenebrutinib
CIA (rats): Treatment started after onset of arthritis, dose-dependent reduction of ankle thickness, inflammation in the joints and joint destruction	Healthy B cells: Inhibits anti-IgM-induced BCR signaling, anti-IgM- and CD40L-induced proliferation Healthy CD14+ monocytes: prevents FcR-mediated TNFα production	[92]
Orelabrutinib
CIA (rats): Dose-dependent reduction in disease score, proinflammatory cytokine production, and histopathological score MRL/lpr: Increased survival of treated mice, reduction in anti-dsDNA antibodies and IFNα levels in serum, urine protein levels	*	¥
Poseltinib
CIA (mice): Treatment started 10 days after boost, reduced weight loss and severity of arthritis, reduced IL-6 and IgG serum levels and reduced bone erosion/bone loss MRL/lpr: Treatment started at 8 weeks of age, reduced B-cell activation, reduced anti-DNA IgG, reduced skin lesions, improved renal function NZB/W F1: Treatment started at 18 weeks of age, reduced GC B-cell/plasma cell formation, improved renal function, increased survival at higher doses	Healthy B-cells: Inhibits signaling and activation Healthy CD14+ Monocytes: dose-dependent inhibition of cytokine production upon FcR and TLR stimulation. Induction of osteoclast formation inhibited.	[103, 130]
Remibrutinib
SRBC Immunization (rats): treatment at time of immunization, dose-dependent reduction in Ag-specific IgM antibodies CIA (rats): Treatment after onset of disease, reduction of clinical score and joint inflammation and destruction	Blood B cells: Reduced BCR-mediated CD69 expression Blood basophils: Reduced FcεR-mediated CD63 expression Human monocyte cell line: Reduced FcγR-mediated IL-8 production	[95]
Rilzabrutinib
Passive arthus reaction (rats): Dose-dependent reduction of intradermal dye extravasation Anti-GBM nephritis: Dose-dependent reduction of kidney inflammation and improvement of kidney function Anti-CD41-mediated ITP: Pretreatment dose dependently reduced platelet loss CIA (rats): Treatment at disease onset, dose-dependent reduction of clinical and histopathological scores; treatment after disease onset, reversal of disease Canine pemphigus: Immediate and rapid clinical improvement	B cells: Reduced BCR-mediated activation and proliferation, reduced CD40/IL-21R- or TLR9-mediated antibody production Monocytes: Reduced FcγR-mediated TNFα production Basophils/mast cells: Reduced FcεR-mediated degranulation and CD63 expression	[132, 164]
Spebrutinib
CIA (mice): Treatment started after onset of arthritis, dose-dependent reduction of disease severity, weight loss, and inflammatory cytokines in serum, reduced inflammation and bone destruction in joints	B cells: Reduced BCR/TLR-mediated activation, proliferation, cytokine production, plasma cell differentiation, and antibody production Macrophages: Reduced FcγR-mediated TNFα production Monocyte-derived DC: Reduced TLR9 mediated CD86 expression Basophils: Reduced FcεR-induced degranulation Osteoclast: Reduced osteoclastogenesis	[104, 134]
TAS5315
CIA (mice): Treatment started after onset, dose-dependent reduction in arthritis scores, inflammation, pannus formation, cartilage and bone damage, induction of bone repair MRL/lpr: Reduced glomerulonephritis, serum BUN, and anti-dsDNA antibody levels	Monocytes: Dose-dependent reduction of TNFα and IL-6 production Osteoclasts: Reduced osteoclast differentiation and bone resorption	[141, 143, 144]
Tirabrutinib
CIA (mice): Start treatment at time of boost, dose-dependent reduction in disease score and joint damage, reduction of MIP-1α, IL-1β, KC, IL-6, RANKL, and MMP-3 production in joints of arthritic mice NZW/B F1: Start treatment at 12 weeks (before onset), reduced proteinuria, reduced GC B cells and plasma cells, reduced anti-dsDNA antibodies in serum	Monocytes: Reduced FcγR- and TLR9-mediated TNFα and IL-6 production Osteoclast (precursors): Reduced M-CSF- and RANK-L-mediated osteoclast differentiation, reduced MIP-1α and RANTES production in bone marrow cultures	[135–138]

anti-dsDNA anti-double strand DNA, anti-GBM anti-glomerular basal membrane, BCR B-cell receptor, BUN blood urea nitrogen, CAIA collagen antibody-induced arthritis, CIA collagen-induced arthritis, CNS central nervous system, EAE experimental autoimmune encephalomyelitis, FcR Fc receptor, GC germinal center, GPA granulomatosis with polyangiitis, IFNα interferon α, ITP immune thrombocytopenia, KC keratinocyte-derived chemokine, M-CSF macrophage-colony-stimulating factor, MIP-1α macrophage inflammatory protein α, MRL/lpr Murphy Roths Large lymphoproliferative, MS multiple sclerosis, NP-KLH 4-hydroxy-3-nitrophenylacetyl-keyhole limpet, NP-LPS 4-hydroxy-3-nitrophenylacetyl-lipopolysacharide, PBMC peripheral blood mononuclear cell, RANKL receptor-activator of nuclear factor kappa B ligand, RANTES Regulated upon Activation Normal T Cell Expressed and Presumably Secreted, SRBC sheep red blood cell, TLR toll-like receptor, TNFα tumor necrosis factor α, NZB/W New Zealand black × New Zealand white

*No data available

^¥Unpublished data from company presentation (https://www.innocarepharma.com/media/1419/innocare-pharma-investor-presentation-2019.pdf)