Oral Spleen Tyrosine Kinase Inhibitor Research Articles

Real-world experience with fostamatinib in patients with immune thrombocytopenia: Results of an observational study (FORTE).

e23289 Background: Immune thrombocytopenia (ITP) is an autoantibody-mediated disease in which platelets are prematurely phagocytosed by Fcg-receptor-bearing macrophages in a spleen tyrosine kinase (SYK)-dependent signaling pathway. Corticosteroids (CS) are used to suppress the immune response, but long-term use carries a heavy burden of toxicity. Subsequent treatments for ITP include fostamatinib, a potent oral SYK inhibitor approved in 2018 based on two randomized, placebo-controlled, phase 3 trials. In trial patients, who received fostamatinib as second-line therapy following CS with or without immunoglobulins (IVIG), 25 of 32 (78%) patients achieved a platelet response of ≥50,000/µL, which was sustained for a median of 83% of treatment days. Here, we report real-world experience with fostamatinib as second-line therapy for ITP from a multi-center, prospective, observational study. Methods: The study (FORTE; NCT04904276) enrolled adult patients with ITP and an insufficient response to prior CS and/or IVIG. Patients were treated according to their clinician’s discretion, and data were collected for up to 12 months at clinic visits. Results: Sixteen patients were enrolled, and 15 were treated. Of the 15, 9 (60%) were female and the median age was 48 years (range, 20-92). 12 (80%) patients had prior CS and 6 (40%) prior IVIG. 7 (47%) patients completed the study and 8 discontinued treatment due to adverse events (4), lack of efficacy (2), and patient decision (2). After initiation of fostamatinib, 93% (14/15) of patients achieved ≥1 platelet count ≥50,000/μL. Median platelet count increased over time from 43,000/μL (IQR 19,000-105,000) at baseline to 167,000/μL (IQR 96,000-180,000) at Month 12. The median cumulative duration of elevated platelet count was 32 weeks (IQR 6.4-49.4). Concomitant CS were used by 7 (47%) patients at baseline, all of whom were able to taper as early as Month 1 and discontinue their dose by Month 3 in 4 patients, Month 6 in 2 patients, and Month 9 in 1 patient. Five patients had ITP-related AEs (4 Grade 1 and 1 Grade 2): gingival bleeding (2), mucosal haemorrhage (2), fatigue (1), contusion (3), headache (1) and epistaxis (1). There were 3 serious AEs in 2 patients: Grade 3 diarrhea in 1 and Grade 2 dyspnea and chills in 1. Overall safety results were consistent with previous studies of fostamatinib. Conclusions: Real world use of fostamatinib as documented in this observational study demonstrated efficacy and safety as second-line therapy for ITP. Fostamatinib allowed successful tapering and discontinuation of CS while maintaining platelet counts above 50,000/μL. Clinical trial information: NCT04904276 .

Human dermal fibroblast subpopulations and epithelial mesenchymal transition signals in hidradenitis suppurativa tunnels are normalized by spleen tyrosine kinase antagonism in vivo.

Hidradenitis Suppurativa is a chronic inflammatory disease of which the pathogenesis is incompletely understood. Dermal fibroblasts have been previously identified as a major source of inflammatory cytokines, however information pertaining to the characteristics of subpopulations of fibroblasts in HS remains unexplored. Using in silico-deconvolution of whole-tissue RNAseq, Nanostring gene expression panels and confirmatory immunohistochemistry we identified fibroblast subpopulations in HS tissue and their relationship to disease severity and lesion morphology. Gene signatures of SFRP2+ fibroblast subsets were increased in lesional tissue, with gene signatures of SFRP1+ fibroblast subsets decreased. SFRP2+ and CXCL12+ fibroblast numbers, measured by IHC, were increased in HS tissue, with greater numbers associated with epithelialized tunnels and Hurley Stage 3 disease. Pro-inflammatory CXCL12+ fibroblasts were also increased, with reductions in SFRP1+ fibroblasts compared to healthy controls. Evidence of Epithelial Mesenchymal Transition was seen via altered gene expression of SNAI2 and altered protein expression of ZEB1, TWIST1, Snail/Slug, E-Cadherin and N-Cadherin in HS lesional tissue. The greatest dysregulation of EMT associated proteins was seen in biopsies containing epithelialized tunnels. The use of the oral Spleen tyrosine Kinase inhibitor Fostamatinib significantly reduced expression of genes associated with chronic inflammation, fibroblast proliferation and migration suggesting a potential role for targeting fibroblast activity in HS.

Randomized Trial on the Effect of an Oral Spleen Tyrosine Kinase Inhibitor in the Treatment of IgA Nephropathy

We reported increased spleen tyrosine kinase (SYK) expression in kidney biopsies of patients with IgA nephropathy (IgAN) and that inhibition of SYK reduces inflammatory cytokines production from IgA stimulated mesangial cells. This study was a double-blind, randomized, placebo-controlled phase 2 trial of fostamatinib (an oral SYK inhibitor) in 76 patients with IgAN. Patients were randomized to receive placebo, fostamatinib at 100 mg or 150 mg twice daily for 24 weeks on top of maximum tolerated dose of renin-angiotensin system inhibitors. The primary end point was reduction of proteinuria. Secondary end points included change from baseline in estimated glomerular filtration rate (eGFR) and kidney histology. Although we could not detect significant reduction in proteinuria with fostamatinib overall, in a predetermined subgroup analysis, there was a trend for dose-dependent reduction in median proteinuria (from baseline to 24 weeks by 14%, 27%, and 36% in the placebo, fostamatinib 100 mg, and 150 mg groups, respectively) in patients with baseline urinary protein-to-creatinine ratios (UPCR) more than 1000 mg/g. Kidney function (eGFR) remained stable in all groups. Fostamatinib was well-tolerated. Side effects included diarrhea, hypertension, and increased liver enzymes. Thirty-nine patients underwent repeat biopsy showing reductions in SYK staining associated with therapy at low dose (-1.5 vs. 1.7 SYK+ cells/glomerulus in the placebo group, P< 0.05). There was a trend toward reduction in proteinuria with fostamatinib in a predefined analysis of high risk patients with IgAN despite maximal care, as defined by baseline UPCR greater than 1000 mg/g. Further study may be warranted.

A Phase I Trial of SYK Inhibition with Fostamatinib in the Prevention and Treatment of Chronic Graft-Versus-Host Disease

Despite the exciting advancement of novel therapies, chronic graft-versus-host disease (cGVHD) remains the most common cause of non-relapse mortality after allogeneic hematopoietic stem cell transplantation (HCT). Frontline treatment of cGVHD involves systemic steroids, which are associated with significant morbidities. We previously found that inhibition of spleen tyrosine kinase (SYK) with fostamatinib preferentially eradicated aberrantly activated B cells in both ex vivo studies of cGVHD patient B cells, as well as in vivo mouse studies. These and other preclinical studies implicated hyper-reactive B-cell receptor signaling and increased SYK expression in the pathogenesis of cGVHD and compelled this first in-human allogeneic HCT clinical trial. We investigated the safety and efficacy of the oral SYK inhibitor, fostamatinib, for both the prevention and treatment of cGVHD. The primary objective was to evaluate the safety of fostamatinib and determine its maximum tolerated dose in the post-HCT setting. Secondary objectives included assessing the efficacy of fostamatinib in preventing and treating cGVHD, as well as examining alterations in B-cell compartments with treatment. This was a single-institution phase I clinical trial that evaluated the use of fostamatinib in allogeneic HCT patients before the development of cGVHD or at the time of steroid-refractory cGVHD (SR-cGVHD). Patients received fostamatinib at one of three dose levels using a continual reassessment algorithm to determine the maximum tolerated dose. Multiparameter flow cytometry was used to evaluate changes in B cell subpopulations over the first year of treatment with fostamatinib. Nineteen patients were enrolled in this phase I trial, with 5 in the prophylaxis arm and 14 in the therapeutic arm. One patient (5%) required discontinuation of therapy for a dose-limiting toxicity. At a median follow-up of over 3 years, no patients had cancer relapse while on fostamatinib treatment, and recurrent malignancy was observed in 1 patient 2 years after the end of therapy. In the prophylaxis arm, 1 of 5 patients (20%) developed cGVHD while on fostamatinib. In the therapeutic arm, the overall response rate was 77%, with a complete response rate of 31%. The median duration of response was 19.3 months and the 12-month failure-free survival was 69% (95% confidence interval, 48-100). Patients were able to reduce their steroid dose by a median of 80%, with 73% remaining on a lower dose at 1 year compared to baseline. There was an early reduction in the proportion of IgD−CD38hi plasmablast-like cells with fostamatinib treatment, particularly in those SR-cGVHD patients who had an eventual response. B-cell reconstitution was not significantly impacted by fostamatinib therapy after allogeneic HCT. Fostamatinib featured a favorable safety profile in the post-HCT setting. Our data suggests an early efficacy signal that was associated with effects on expected cell targets in both the prophylaxis and treatment of cGVHD, providing rationale for a phase II investigation.

SYK Inhibitors, Entospletinib and Lanraplenib, Show Potent Anti-Leukemic Activity in Combination with Targeted Agents

Introduction: Spleen tyrosine kinase (SYK) acts as a key integrator of cellular signaling from surface contact and receptor tyrosine kinase receptors containing an immunoreceptor tyrosine-based activation motif (ITAM). In acute myeloid leukemia (AML), SYK serves as a relay to an oncogenic transcriptional regulatory network (TRN) linked to NPM1, HOXA9, and MEIS1 helping to suppress myeloid progenitor maturation and promote proliferation. The selective, oral SYK inhibitor, entospletinib (ENTO), has demonstrated clinical activity in HOXA9/MEIS1-driven AML with acceptable tolerability when combined with intensive induction chemotherapy. A global phase 3 trial (AGILITY, NCT05020665) is currently underway, evaluating the combination of ENTO with intensive induction/consolidation chemotherapy in patients with treatment-naive NPM1-mutated (NPM1m) AML with measurable residual disease as the primary endpoint. Lanraplenib (LANRA) is a next-generation SYK inhibitor with similar potency, enhanced selectivity, and more favorable pharmacologic properties that is currently being evaluated in combination with gilteritinib in patients with relapsed or refractory (R/R) FLT3-mutated AML (NCT05028751). Results: ENTO exhibits anti-proliferative activity in NPM1m AML with associated HOXA9/MEIS1 dysregulation in ex vivo drug sensitivity studies. We hypothesized that SYK inhibition could synergize with other targeted therapies to enhance anti-leukemic activity at different nodes in this pathway. To address this hypothesis, the FLT3 internal tandem duplication/MLL-rearranged cell lines, MOLM13 and MV411, were treated with increasing doses of either LANRA or ENTO in combination with a small molecule MLL-Menin inhibitor (SNDX5613). Synergistic anti-proliferative effects were observed across a broad range of concentrations. No combinatorial or single-agent SNDX5613 activity was seen in the KASUMI-1 AML cell line, which lacks an MLL rearrangement. Phenotypic studies using flow cytometry were performed to assess the mechanistic response for SYK inhibition with LANRA in combination with SNDX5613. LANRA was found to increase the percentage of CD11b-positive cells and mean fluorescence intensity, while SNDX5613 led to a marked increase in CD14. In contrast to either single agent, the combination triggered early apoptosis and cell death, suggesting a more complete blockade of the HOXA9/MEIS1 transcriptional program through synergistic inhibition by orthogonal mechanisms. Furthermore, treatment of leukemic cells with either ENTO or LANRA inhibited SYK auto-phosphorylation in a dose-dependent manner. We also explored the potential for synergistic activity with gilteritinib (FLT3 inhibitor) and venetoclax (BCL2 inhibitor) using patient-derived AML isolates ex vivo based on the potential for SYK signaling cross talk with FLT3 itself and survival pathways. We found strong synergistic anti-proliferative activity for the combination of LANRA with either gilteritinib or venetoclax. Patient-derived xenograft (PDX) studies also demonstrated deeper reductions in leukemic burden in the peripheral blood, liver, and bone marrow after 28 days of treatment. Follow-up PDX studies assessing overall survival and pharmacodynamic activity are ongoing using an optimized dosing regimen and schedule. Summary/Conclusion: SYK is a promising therapeutic target for genetically defined subsets of AML. Two highly selective SYK inhibitors are currently undergoing clinical testing in different but complementary clinical settings. Given its central role as a modulator of leukemogenic signaling, SYK inhibition has the potential to synergize with other targeted therapies in AML. In preclinical studies, LANRA-mediated SYK inhibition shows compelling anti-proliferative and pro-apoptotic activity in combination with gilteritinib, venetoclax, and SNDX5613 in genetically defined subsets of AML.

Evaluating fostamatinib disodium as a treatment option for immune thrombocytopenia in adult patients

ABSTRACT Introduction Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized by increased platelet destruction and decreased platelet production, leading to thrombocytopenia with or without bleeding manifestations. The majority of patients experiencing treatment need will eventually need secondary treatment following first-line therapy with steroids. In 2018, the oral spleen tyrosine kinase inhibitor fostamatinib received US Food and Drug Administration approval for ITP patients with an insufficient response to a previous treatment. Areas covered This review outlines pharmacological characteristics of fostamatinib and provides an overview of its efficacy and safety results in phase II and III trials, followed by the expert opinion of the authors. Expert opinion Increasing knowledge on the role of different players and mechanisms in the pathophysiology of autoimmune disorders, in general, and of ITP, in particular, has led to the development of several new treatment options, as illustrated by the introduction of fostamatinib in the treatment of ITP. However, lacking direct comparison with other recent treatment options (in particular, thrombopoietin receptor agonists), its use should be evaluated critically taking into account the unique toxicity and potential drug-drug interaction profile.

561. Phase 3 Trial of Fostamatinib for the Treatment of COVID-19: Repurposing an Immunomodulatory Drug Previously Approved for Immune Thrombocytopenia

BackgroundKey pathologies in severe COVID-19 include immune cell activation, inflammatory cytokine release, and neutrophil extracellular trap release (NETosis), which are mediated by spleen tyrosine kinase (SYK) (Figure 1). Fostamatinib, an oral SYK inhibitor approved for chronic immune thrombocytopenia, has shown activity in vitro using plasma from patients with severe COVID-19, by abrogating the hyperimmune response triggered by anti-spike IgG; 1 inhibiting hyperactivation in platelets; 2 and blocking NETosis in neutrophils.3 R406, active metabolite of fostamatinib, protected against LPS-induced acute lung injury and thrombosis in mice.4,5 In clinical studies, fostamatinib reduced IL-6 in patients with rheumatoid arthritis.6 Therefore, a phase 2 study (NCT04579393) evaluated fostamatinib vs. placebo plus standard of care (SOC) in 59 hospitalized COVID-19 patients (manuscript pending). We initiated a phase 3 clinical study (NCT04629703) of fostamatinib for the treatment of COVID-19. MethodsA double-blind, randomized, placebo-controlled, adaptive design, multi-center, Phase 3 study (NCT04629703) is underway to evaluate the safety and efficacy of fostamatinib in 308 adult patients with COVID-19 (Figure 2). Hospitalized patients without respiratory failure (with or without supplemental oxygen) were included. Patients with ARDS or using extracorporeal membrane oxygenation (ECMO) were excluded. Patients will receive fostamatinib 150 mg BID or placebo for 14 days; both arms receive SOC. The primary outcome will be progression to severe/critical disease (worsening in clinical status score on the 8-point ordinal scale) within 29 days of the first dose of study drug. Fostamatinib is investigational for COVID-19. ResultsBlinded update of trial in progress as of 28 April 2021. 12 patients have been randomized in North and South America. The clinical status score at Baseline was 5 (Hospitalized, requiring supplemental oxygen) in all 12 patients. Five patients had 8 adverse events (AE) (Fig 3). One AE (PE) was serious and is resolving. No deaths have been reported. At least two patients have been discharged (Day 5, Day 13) with continued dosing at home. ConclusionFostamatinib has the potential to provide a treatment option for the hyperimmune complications of COVID-19. Disclosures Ziad Mallat, MD, PhD, Rigel Pharmaceuticals, Inc. (Consultant) Sandra Tong, MD, Rigel Pharmaceuticals, Inc. (Employee, Shareholder)

Preclinical Activity of Selective SYK Inhibitors, Entospletinib and Lanraplenib, Alone or Combined with Targeted Agents in Ex Vivo AML Models with Diverse Mutational Backgrounds

Spleen tyrosine kinase (SYK) is a non-receptor tyrosine kinase that mediates integrin and Fc receptor signaling in myeloid cells. SYK has been implicated as an oncogenic driver in acute myeloid leukemia (AML) with aberrant expression of HOXA9 and MEIS1 and cooperates with FLT3 internal tandem duplication to drive leukemogenesis. The oral SYK inhibitor entospletinib (ENTO) has demonstrated clinical activity in HOXA9/MEIS1 driven AML and is currently being investigated in a phase 3 trial of previously untreated patients with nucleophosmin1-mutated (NPM1 mut) AML. Lanraplenib (LANRA) is a next generation oral SYK inhibitor with potency and selectivity comparable to ENTO. In healthy volunteers and patients with autoimmune disease, LANRA has shown pharmacokinetic properties that compare favorably with ENTO. To support the clinical development of LANRA for the treatment of AML, ex vivo treatment of patient-derived AML cells was used to compare its activity to that of ENTO, both as a single-agent and in combination with other AML therapies. First, ENTO and LANRA single-agent activities were evaluated in peripheral blood-derived blasts from 15 AML patients, representing different mutational backgrounds including NPM1, FLT3, PTPN11, and NRAS mutations. AML cells were seeded into 96 well plates and treated with ENTO and LANRA for 6 days. Comparable effects on viability were observed across the 15 models with the 2 compounds, and in 11 of the models, the half maximal inhibitory concentration (IC 50) values were within 2-fold of each other. ENTO had a slightly lower IC 50 value than LANRA in the FLT3-mutated models possibly due to the direct FLT3 inhibitory activity of ENTO. Next, we tested the activity of ENTO and LANRA ex vivo in bone marrow-derived AML blasts from 29 AML patients representing diverse mutational backgrounds, including NPM1, IDH1, FLT3, and RAS mutations as well as MLL rearrangements. The models were treated for 9 days with either ENTO or LANRA, and viability was assessed using Annexin V and 7-aminoactinomycin D staining. Again, ENTO and LANRA showed comparable effects on cell viability with no significant differences between the compounds when compared across the different mutational backgrounds. Both studies suggest the potential for anti-leukemic activity in several different genetically defined subsets of AML. Matrix combination assays were performed by combining ENTO or LANRA with either cytarabine (NPM1 mut), gilteritinib (FLT3 mut), or trametinib (RAS mut) with cell viability and death assessed after a 3-day incubation period. Increased cell death in an additive manner was observed in all combinations tested, with results for ENTO and LANRA being similar, indicating the utility of both compounds in combinatorial treatment paradigms. These results support the clinical evaluation of LANRA in genetically defined subsets of AML. A phase 1b/2 study of LANRA in combination with the selective FLT3 inhibitor gilteritinib, in patients with relapsed or refractory FLT3 mut AML is planned for the end of this year. DisclosuresDay: Cyteir Therapeutics: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Heckman: Novartis: Research Funding; Orion Pharma: Research Funding; Celgene/BMS: Research Funding; Oncopeptides: Consultancy, Research Funding; Kronos Bio, Inc.: Research Funding. Schinzel: Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Obholzer: Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Lin: Kronos Bio, Inc.: Current Employment. Kumar: Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company. DiMartino: Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Saffran: Kronos Bio, Inc.: Current Employment, Current equity holder in publicly-traded company.

An Observational Study of Fostamatinib As Second Line Therapy in Adult Patients with Immune Thrombocytopenia (ITP) in Real-World Clinical Practice

Background: In immune thrombocytopenia (ITP), autoantibody-bound platelets are targeted for phagocytosis by Fcγ-receptors on macrophages in a spleen tyrosine kinase (SYK)-dependent signaling pathway. Fostamatinib is a potent oral SYK inhibitor that demonstrated efficacy for the treatment of ITP in two phase 3 randomized, placebo-controlled, double-blind studies and long-term durable responses in the phase 3 open-label extension study. In these studies, 146 patients with ITP were treated with fostamatinib, and 54% had a platelet response (platelet count ≥50,000/µL), which was maintained over a median of 86% of treatment days. These studies led to approval of fostamatinib in the US, Europe, and Canada as a therapy for chronic ITP in adult patients who have had an insufficient response to a prior treatment. Further, a post-hoc analysis showed that, in those who received fostamatinib as second-line therapy (following steroids ± immunoglobulins), 78% achieved a platelet response, which was maintained over a median of 83% of treatment days. 1 Adverse events (AEs) were reported in 72% of second-line patients and 86% of all patients, and common AEs were similar between second-line patients and the total patient population. 1, 2 Bleeding events were reported in 24% of second-line patients vs. 41% of all patients. The results of the post hoc analysis underscored the necessity for further evaluation of fostamatinib as a second-line therapy for ITP.We are conducting a multi-center, prospective, observational, two cohort study of fostamatinib as second-line therapy for the management of ITP in adult patients who have an insufficient response to prior steroids ± immunoglobulins.Aim: This study will evaluate clinical outcomes and safety of fostamatinib as second-line therapy for ITP in adult patients in real-world clinical practice. Patients will also be assessed for quality of life and utilization of health care resources during the study.Methods: The study (FORTE; NCT04904276; O-FOSTA-901) is being conducted at 10 sites across the US and will enroll 45 patients with ITP into 2 cohorts (see Figure). The study is registered at https://clinicaltrials.gov/ct2/show/NCT04904276. The study aims to enroll adult patients with a confirmed diagnosis of ITP and an inadequate response to prior steroids ± immunoglobulins. Patients who have received any prior ITP treatment other than steroids or immunoglobulins will be excluded. Patients who will initiate fostamatinib as second-line therapy at study entry will be enrolled into Cohort 1; patients currently receiving fostamatinib as second-line therapy with the intent to continue treatment will be enrolled in Cohort 2 (historical platelet counts will be retrospectively collected). Patients will be treated by their clinician at the clinician's discretion (not pre-specified by a study protocol).Primary outcome measures will include platelet count over time, duration of platelet count elevation, use of ITP rescue medication, changes in dosing, use of concomitant ITP medications, incidence of serious and ITP-related AEs, and quality of life. Quality of life assessments will utilize the SF-36v2 and ITP-PAQ. All data will be collected at regularly scheduled clinic visits according to the clinician's normal practice for 12 months or until fostamatinib is discontinued.Summary: This ongoing observational study of adult patients with ITP will enable further characterization of the risk/benefit profile of fostamatinib as a second-line treatment for ITP and will provide insight on how clinicians manage ITP in a real-world setting without the constraints of a clinical trial protocol.

Characterization of the mechanism of action of lanraplenib, a novel spleen tyrosine kinase inhibitor, in models of lupus nephritis

BackgroundB cells are critical mediators of systemic lupus erythematosus (SLE) and lupus nephritis (LN), and antinuclear antibodies can be found in the serum of approximately 98% of patients with SLE. Spleen tyrosine kinase (SYK) is a nonreceptor tyrosine kinase that mediates signaling from immunoreceptors, including the B cell receptor. Active, phosphorylated SYK has been observed in tissues from patients with SLE or cutaneous lupus erythematosus, and its inhibition is hypothesized to ameliorate disease pathogenesis. We sought to evaluate the efficacy and characterize the mechanism of action of lanraplenib, a selective oral SYK inhibitor, in the New Zealand black/white (NZB/W) murine model of SLE and LN.MethodsLanraplenib was evaluated for inhibition of primary human B cell functions in vitro. Furthermore, the effect of SYK inhibition on ameliorating LN-like disease in vivo was determined by treating NZB/W mice with lanraplenib, cyclophosphamide, or a vehicle control. Glomerulopathy and immunoglobulin G (IgG) deposition were quantified in kidneys. The concentration of proinflammatory cytokines was measured in serum. Splenocytes were analyzed by flow cytometry for B cell maturation and T cell memory maturation, and the presence of T follicular helper and dendritic cells.ResultsIn human B cells in vitro, lanraplenib inhibited B cell activating factor-mediated survival as well as activation, maturation, and immunoglobulin M production. Treatment of NZB/W mice with lanraplenib improved overall survival, prevented the development of proteinuria, and reduced blood urea nitrogen concentrations. Kidney morphology was significantly preserved by treatment with lanraplenib as measured by glomerular diameter, protein cast severity, interstitial inflammation, vasculitis, and frequency of glomerular crescents; treatment with lanraplenib reduced glomerular IgG deposition. Mice treated with lanraplenib had reduced concentrations of serum proinflammatory cytokines. Lanraplenib blocked disease-driven B cell maturation and T cell memory maturation in the spleen.ConclusionsLanraplenib blocked the progression of LN-like disease in NZB/W mice. Human in vitro and murine in vivo data suggest that lanraplenib may be efficacious in preventing disease progression in patients with LN at least in part by inhibiting B cell maturation. These data provide additional rationale for the use of lanraplenib in the treatment of SLE and LN.

Long-Term Safety Profile of the Oral Spleen Tyrosine Kinase Inhibitor Fostamatinib in Immune Thrombocytopenia (ITP) and Other Diseases

Introduction: Fostamatinib is an oral, potent inhibitor of spleen tyrosine kinase (SYK) with proven efficacy and a manageable safety profile for the treatment of ITP. SYK is situated in an intracellular signaling pathway upstream of Bruton's tyrosine kinase (BTK). Long-term safety data on fostamatinib at various dosing regimens (up to 150 mg BID) has been collected in &amp;gt;4000 patients with ITP, rheumatoid arthritis (RA), and other autoimmune, allergic and neoplastic disorders. The safety and tolerability of fostamatinib were consistent across different patient populations (apart from disease specific events). We present a summary analysis of the fostamatinib safety data from the ITP and RA studies. Methods: Fostamatinib safety data from 2 randomized, double-blind, placebo-controlled, phase 3 studies and the long-term, open-label, extension (OLE) study in ITP were pooled and are based on a starting dose of 200 mg/day, which was increased to 300 mg/day after 4 weeks in 88% of patients. Fostamatinib safety data from 13 phase 2/3 studies in RA were pooled and are based on a dosing regimen of 100-150 mg/day (n=1232) or 200-300 mg/day (n=2205). Results: The pooled data set for ITP included 146 patients; 60% were female, and the median age was 53 years (range 20-88). The mean duration of fostamatinib treatment was 19 months (range &amp;lt;1-62 months), representing 229 patient exposure years. Adverse events (AEs) were reported in 87% of patients, and 63% were mild to moderate. Serious AEs were reported in 31% of patients. The incidence of diarrhea, hypertension, alanine aminotransferase increase (ALT), and aspartate aminotransferase (AST) increase was evaluated in 58 patients who received fostamatinib for ≥1 year. This enabled a comparison of the incidence of these AEs in quartiles over the first year to assess the cumulative effects of fostamatinib. The AEs were reported with decreasing frequency during the second, third, and fourth quarters of fostamatinib treatment compared with the first quarter of the initial year of treatment in the 58 patients (see Figure 1). In the same 58 patients, the use of rescue therapy decreased while median platelet counts increased each quarter of the first year. The pooled data set for RA included 3437 patients who received fostamatinib; 83% were female, and the median age was 54 (range 18 -87). The mean duration of treatment was 18 months (range &amp;lt;1-81) representing 5134 patient exposure years. AEs were reported in 86% of RA patients and were mild to moderate in 73% of RA patients. Serious AEs occurred in 14%. In the placebo-controlled RA studies, 2414 patients received fostamatinib with 823 patient exposure years and 1169 received placebo with 367 patient exposure years. Despite a two-fold (125%) increase in exposure with fostamatinib vs placebo (823 vs 367 patient exposure years), there was only a 26% increase in AEs with fostamatinib vs placebo (68% vs 54%). The most common events in the ITP and RA studies were diarrhea (36% and 24%), hypertension (22% and 19%) and nausea (19% and 8%), apart from disease-related AEs. Epistaxis (19% and 0.5%), petechiae (15% and 0.3%), contusion (12% and 2%), and fatigue (10% and 2%) are associated with ITP and were uncommon in the RA population. Rheumatoid arthritis was reported as an AE in 9% of patients with RA and in none with ITP. Some AEs may be dose-related, and one-third of the RA patients were on lower dosages (100-150 mg/day) than were generally given in the ITP trials (200-300 mg/day). Conclusions: Fostamatinib has been evaluated in &amp;gt;4000 patients across different disease populations. Fostamatinib has a consistent and manageable safety profile. No new safety signals and no cumulative toxicity were observed with up to 81 months (6.8 years) of continuous treatment. Figure 1 Disclosures Tong: Rigel: Current Employment, Current equity holder in publicly-traded company. Numerof:Rigel: Current Employment, Current equity holder in publicly-traded company. Datangel:Rigel: Current Employment, Current equity holder in publicly-traded company. Masuda:Rigel: Current Employment, Current equity holder in publicly-traded company.

Fostamatinib for the Treatment of Warm Antibody Autoimmune Hemolytic Anemia (wAIHA): A Phase 3, Randomized, Double-Blind, Placebo-Controlled, Global Study

Fostamatinib for the Treatment of Warm Antibody Autoimmune Hemolytic Anemia (wAIHA): A Phase 3, Randomized, Double-Blind, Placebo-Controlled, Global Study

Fostamatinib for the treatment of diffuse large B-cell lymphoma.

e20067 Background: Diffuse large B-cell lymphoma (DLBCL) is an aggressive and common form of non-Hodgkin’s lymphoma, characterized by marked genetic heterogeneity. The disease is difficult to treat, and patients with relapsed/refractory DLBCL often have poor outcomes. Some subsets of DLBCL have an increased reliance on B-cell receptor (BCR) activity. Spleen tyrosine kinase (SYK) is a signaling molecule essential for BCR activation. Fostamatinib, an oral SYK inhibitor, was evaluated for treatment of relapsed/refractory DLBCL in a phase 2 randomized, placebo-controlled trial1(NCT01499303), and 9 patients had clinical benefit (1 complete response, 1 partial response, and 7 stable disease). The patients with clinical benefit from fostamatinib treatment had DLBCL of germinal center B-cell (GCB) or intermediate cell of origin. We present the clinical outcomes of 2 patients from this trial who continued to benefit from fostamatinib treatment for over 6 years. Methods: Medical records for the 2 patients were retrospectively reviewed for dose regimen, clinical response, and safety data. Results: Patient A, a 63-year-old male patient with DLBCL of GCB origin, had been diagnosed with follicular lymphoma in 1996, transformation in 2002. He had undergone 1 line of treatment for follicular lymphoma and 5 treatments for DLBCL prior to fostamatinib treatment. He started fostamatinib at 100mg BID in Dec 2012, which was reduced to 100mg daily in Apr 2013, and patient continues at 100 mg QD. Patient A has maintained a complete response (CR) for &gt; 5 years. An isolated infra-centimetric suspicious lesion was noted in Patient A in May 2019, which is stable as of January 2020 with a progressive decrease of metabolic activity. Patient B, a male with DLBCL of an intermediate cell of origin, was 69 years old at baseline with 2 DLBCL treatments prior to fostamatinib treatment since his diagnosis in Aug 2012. He started fostamatinib in May 2013 at 200 mg BID with no dose changes over the last 7 years. Patient B had a partial response (PR) per Chesson criteria since December 2014, with a sustained improved metabolic response continuing since ( &gt; 6 years), with all but a single metastatic site no longer visible. The only serious adverse event in these 2 patients was a ventricular fibrillation and grade 4 cardiac arrest at Day 90 in Patient B, necessitating defibrillation insertion. This was deemed unrelated to treatment and resolved. Conclusions: Fostamatinib may provide durable benefit to a small subset of patients with relapsed/refractory DLBCL. 1. Flinn, I.W., et al., Eur J. Cancer 2016; 54:11-17

Safety Profile of Fostamatinib, an Oral Spleen Tyrosine Kinase Inhibitor: A Meta-Analysis of Randomized Controlled Trials

Introduction: Fostamatinib, a spleen tyrosine kinase (Syk) inhibitor has been studied in clinical trials of chronic immunologic conditions such as Rheumatoid Arthritis (RA), chronic immune thrombocytopenic purpura (ITP), IgA nephropathy and certain lymphomas. It has recently been granted FDA approval for the treatment of ITP. Fostamatinib inhibits the Syk pathway which is also involved in platelet activation through collagen receptor and the integrin αIIbβ3, which, in theory, would increases the risk of bleeding. Also, by inhibiting Syk, fostamatinib reduces macrophage phagocytosis and may render them ineffective against certain bacteria, hence increasing the risk of serious infections. We sought to examine the side effect profile of Fostamatinib in published and unpublished studies randomized controlled trials (RCT). Methods: A systematic search of scientific databases, major conference abstracts and clinical trial registries was performed. Only Phase 2 and Phase 3 RCTs with a placebo arm were included. For dosing of fostamatinib, we preferentially used the 100mg BID dosing as this is the dose approved by the FDA for ITP and is the dose determined through the large trials in patients with RA, which strikes a balance between benefits and harms. When the 100mg and 150mg dosing were combined (as in the ITP trials), we used data from that arm for the analysis. All major and minor harms specified in the trials were pooled using a random effects model and the risk ratio (RR) and confidence interval (CI) was determined using the Mantel-Haenszel method. An I2 value of less than ≤ 40% was considered minimal heterogeneity. Results: The search found 12 studies involving 1,444 cases and 1,188 controls. Of these, 9 studies examined the use of fostamatinib for RA whereas 2 studies were on ITP, and 1 study was on IgA nephropathy. Commonly encountered side effects of fostamatinib therapy were diarrhea, headache, nausea and hypertension. When compared to placebo, fostamatinib was associated with 19% higher risk of any adverse event (9 studies, RR = 1.19, CI = 1.07 - 1.33, I2 = 40%). Patients who received fostamatinib had a significantly higher risk of developing neutropenia (ANC &lt; 1500/microL) when compared to placebo (8 studies, RR = 4.34, CI = 1.82 - 10.31, I2 = 30%). There was only 1 case of febrile neutropenia in one of the ITP trials. There were no significant differences between the fostamatinib and placebo groups with regard to upper respiratory tract infections (7 studies, RR = 1.43, CI = 0.61 - 3.36, I2 = 49%), urinary tract infections (4 studies, RR = 1.6, CI = 0.78 - 3.28, I2 = 0%) or serious infections (7 studies, RR = 1.18, CI = 0.42 - 3.30, I2 = 0%). However, when compared to placebo, there was a 2.23 times higher risk of developing diarrhea (10 studies, CI = 1.46 - 3.41, I2 = 45%) and hypertension (9 studies, CI = 1.61 - 3.09, I2 = 13%) in the fostamatinib group. Most patients had hypertension at baseline and few needed either medication initiation or adjustment in the fostamatinib cohorts. Fostamatinib also significantly increased liver enzyme (ALT &gt; 3 ULN) when compared to placebo (9 studies, RR = 2.21, CI = 1.18 - 4.14, I2 = 0%). There were higher bleeding events in the fostamatinib group, but there was no significant difference between the treatment and placebo arms (4 studies, RR = 1.06, CI = 0.16 - 6.94, I2 = 45%). There were no significant differences between the treatment and control groups with regard to serious adverse events and mortality. Treatment discontinuation rates due to adverse events were not significantly different between groups. Conclusions: Fostamatinib tends to have a relatively benign side effect profile, with few serious side effects. In congruence of the theoretical higher bleeding risk with Syk inhibition, the bleeding events were slightly higher in fostamatinib group, however there was no statistically significant difference between the treatment and the placebo groups. Similarly, the incidence of neutropenia, though higher in the Fostamatinib group, was rarely associated with fever (1 event among all 12 trials). The incidence of serious infections did not differ significantly between groups. Gastrointestinal and cardiac side effects were transient and did not lead to significantly more treatment discontinuations when compared to placebo. Larger longitudinal studies are needed to better examine the long-term side effects associated with Fostamatinib. Table Disclosures No relevant conflicts of interest to declare.

Abstract 819: High response rates with entospletinib in patients with t(v;11q23.3);KMT2A rearranged acute myeloid leukemia and acute lymphoblastic leukemia

Abstract Introduction: Targeted therapy for KMT2A (mixed lineage leukemia [MLL]) rearranged acute leukemia (AL) is lacking. KMT2A regulates leukemic stem cell transcription factors HOXA9 and MEIS1. Spleen tyrosine kinase (SYK) signaling induces MEIS1 in conjunction with HOXA9. We hypothesize that this regulatory loop may be sensitive to SYK inhibition with Entospletinib (ENTO) a highly selective, oral SYK inhibitor. In this analysis, we evaluate the efficacy of ENTO in patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) with t(v;11q23.3) KMT2A/MLL gene rearrangements. Methods: Patients with KMT2A rearranged AL in two different clinical trials were included. AML patients (NCT02343939) received ENTO 400mg BID monotherapy for up to 14 days prior to and with induction chemotherapy (cytarabine 100 mg/m2 for 7 days plus daunorubicin 60 mg/m2 for 3 days) if previously untreated, or ENTO monotherapy alone if relapsed/refractory (R/R). R/R B-ALL patients received ENTO monotherapy for 7 days prior to and with vincristine and dexamethasone in a phase 1 study (NCT02404220). Results: 18 patients with KMT2A rearranged AL were treated. Untreated AML (n=10) patients had a median age of 49 years. One patient was in a morphologic leukemia-free state after ENTO monotherapy (before chemotherapy). After induction chemotherapy plus ENTO, seven patients had morphologic (CR) and cytogenetic (CRc) remission, but two of them had incomplete count recovery (CRi). The composite CR rate (CR/CRi/CRc) was 90%: 5 CRc, 3 CRi (CR/CRc with incomplete count recovery), and 1 CR. Six patients underwent allogeneic stem cell transplantation (SCT) in CR1. After median follow-up of 9.9 months one patient who achieved CR relapsed, with persistence of t (6;11) and an NRAS mutation. Median overall survival and event-free survival have not been reached. In R/R AML (n=6), patients had a median age of 48 years, with 2 median prior therapies. One had CR and one had CRi (but normal cytogenetics) and both received SCT. In all, 3 AML patients (1 newly diagnosed, 2 R/R) responded to ENTO monotherapy alone. In R/R ALL (n=2), median age was 59 years. Both patients had t (4;11) along with other cytogenetic abnormalities with 2 prior therapies. Both patients achieved CR with loss of KMT2A on cytogenetic testing, and one patient received SCT. Overall, ENTO was safe and well tolerated, even in combination with chemotherapy. Conclusions: KMT2A rearranged AL is sensitive to ENTO with CR observed on monotherapy in AML and high response rates in AL patients treated with combination therapy. This represents the first documentation of CR with small molecule monotherapy (n=3) in this genetic subgroup, which typically portends a poor prognosis. Correlative biomarker studies evaluating HOXA9/MEIS1 in patients with t(v;11q23.3) KMT2A rearranged leukemia treated with ENTO are pending. Citation Format: Alison R. Walker, John C. Byrd, William Blum, Tara Lin, Howland E. Crosswell, Danjie Zhang, Jie Gao, Arati V. Rao, Mark D. Minden, Wendy Stock. High response rates with entospletinib in patients with t(v;11q23.3);KMT2A rearranged acute myeloid leukemia and acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 819.

Targeting the tyrosine kinase signalling pathways for treatment of immune-mediated glomerulonephritis: from bench to bedside and beyond.

Glomerulonephritis (GN) affects patients of all ages and is an important cause of morbidity and mortality. Non-selective immunosuppressive drugs have been used in immune-mediated GN but often result in systemic side effects and occasionally fatal infective complications. There is increasing evidence from both preclinical and clinical studies that abnormal activation of receptor and non-receptor tyrosine kinase signalling pathways are implicated in the pathogenesis of immune-mediated GN. Activation of spleen tyrosine kinase (SYK), Bruton's tyrosine kinase (BTK), platelet-derived growth factor receptor (PDGFR), epidermal growth factor receptor (EGFR) and discoidin domain receptor 1 (DDR1) have been demonstrated in anti-GBM disease. SYK is implicated in the pathogenesis of ANCA-associated GN. SYK, BTK, PDGFR, EFGR, DDR1 and Janus kinase are implicated in the pathogenesis of lupus nephritis. A representative animal model of IgA nephropathy (IgAN) is lacking. Based on the results from in vitro and human renal biopsy study results, a phase II clinical trial is ongoing to evaluate the efficacy and safety of fostamatinib (an oral SYK inhibitor) in high-risk IgAN patient. Various tyrosine kinase inhibitors (TKIs) have been approved for cancer treatment. Clinical trials of TKIs in GN may be justified given their long-term safety data. In this review we will discuss the current unmet medical needs in GN treatment and research as well as the current stage of development of TKIs in GN treatment and propose an accelerated translational research approach to investigate whether selective inhibition of tyrosine kinase provides a safer and more efficacious option for GN treatment.

Femoral Head Growth Plate Dysplasia and Fracture in Juvenile Rabbits Induced by Off-target Antiangiogenic Treatment.

Epiphyseal growth plate dysplasia (chondrodysplasia) might be considered as the pathognomonic feature of antiangiogenic treatment in preclinical species as it is reliably and dose-responsively induced in rodents and monkeys with vascular endothelial growth factor receptor (VEGFR) inhibitors, fibroblast growth factor (FGF) receptor inhibitors, matrix metalloproteinase inhibitors, and vascular targeting agents. Here we report epiphyseal growth plate dysplasia in juvenile rabbits treated with an oral spleen tyrosine kinase inhibitor induced by off-target antiangiogenic inhibition of VEGF and FGF family kinase receptors. Epiphyseal growth plate dysplasia resulted in weakening and fracturing of the femoral head physis in 6 of 10 male and 1 of 10 female animals as well as microfracturing and dysplasia of the distal femoral articular cartilage in 1 male animal. Fracture lines ran through the zone of hypertrophic cartilage (as well as adjacent zones), were orientated parallel to the physeal plane, and often involved displacement of the femoral head. We would suggest that the high prevalence of growth plate fracture in the rabbit may represent a potential additional adverse risk to those already established for children treated with antiangiogenic therapy.

Fostamatinib, an oral spleen tyrosine kinase inhibitor, in the treatment of rheumatoid arthritis: a meta-analysis of randomized controlled trials.

Fostamatinib is a selective inhibitor of spleen tyrosine kinase which has a role in the pathogenesis of RA. Multiple RCTs have been performed to study the effects of fostamatinib. The objective of this study was to perform a meta-analysis to analyze the efficacy and safety of fostamatinib in the management of RA. We searched PubMed, EMBASE and Cochrane CENTRAL through 11/9/15. Random effect model was used to estimate odds ratio (OR) and 95% confidence interval. We measured outcomes with efficacy analysis using ACR20/50/70 response criteria and safety with adverse events. Five studies were included in the meta-analysis with total of 2105 patients including 1419 in fostamatinib group and 686 in placebo. Fostamatinib was effective in achieving ACR20, ACR50 and ACR70 responses compared to placebo (48 vs. 32.8%, OR 1.86, 95% CI 1.32-2.62, P=0.0004, I (2) 63%; 26.4 vs. 12.5%, OR 2.50, 95% CI 1.93-3.23, P<0.00001, I (2) 0% and 12.7 vs. 4.4%, OR 3.00, 95% CI 1.99-4.51, P<0.00001, I (2) 0%, respectively). Response to fostamatinib was rapid and significant effect on ACR20 response was seen by week 1 (OR 3.70, 95% CI 2.33-5.87, P<0.00001, I (2) 42%). Safety analysis showed an increased risk of infection (OR 1.59, 95% CI 1.2-2.11; P=0.001; I (2) 0%), diarrhea (OR 3.54; 95% CI 2.43-5.16; P<0.00001; I (2) 2%), hypertension (OR 2.55, 95% CI 1.54-4.22, P=0.0003; I (2) 42%) and neutropenia (OR 5.68, 95% CI 1.97-16.42, P=0.001, I (2) 35%) and showed a trend toward the increase in ALT ≥3 times ULN (OR 1.76, 95% CI 0.99-3.13; P=0.05; I (2) 0%). This meta-analysis concludes that fostamatinib has moderate effect in the treatment of RA with mostly mild-to-moderate adverse events and dose-dependent, transient neutropenia and hypertransaminasemia.

BI 1002494, a Novel Potent and Selective Oral Spleen Tyrosine Kinase Inhibitor, Displays Differential Potency in Human Basophils and B Cells.

BI 1002494 [(R)-4-{(R)-1-[7-(3,4,5-trimethoxy-phenyl)-[1,6]napthyridin-5-yloxy]-ethyl}pyrrolidin-2-one] is a novel, potent, and selective spleen tyrosine kinase (SYK) inhibitor with sustained plasma exposure after oral administration in rats, which qualifies this molecule as a good in vitro and in vivo tool compound. BI 1002494 exhibits higher potency in inhibiting high-affinity IgE receptor-mediated mast cell and basophil degranulation (IC50 = 115 nM) compared with B-cell receptor-mediated activation of B cells (IC50 = 810 nM). This may be explained by lower kinase potency when the physiologic ligand B-cell linker was used, suggesting that SYK inhibitors may exhibit differential potency depending on the cell type and the respective signal transduction ligand. A 3-fold decrease in potency was observed in rat basophils (IC50 = 323 nM) compared with human basophils, but a similar species potency shift was not observed in B cells. The lower potency in rat basophils was confirmed in both ex vivo inhibition of bronchoconstriction in precision-cut rat lung slices and in reversal of anaphylaxis-driven airway resistance in rats. The different cellular potencies translated into different in vivo efficacy; full efficacy in a rat ovalbumin model (that contains an element of mast cell dependence) was achieved with a trough plasma concentration of 340 nM, whereas full efficacy in a rat collagen-induced arthritis model (that contains an element of B-cell dependence) was achieved with a trough plasma concentration of 1400 nM. Taken together, these data provide a platform from which different estimates of human efficacious exposures can be made according to the relevant cell type for the indication intended to be treated.

A phase II trial to evaluate the efficacy of fostamatinib in patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL)

PurposeTo assess the safety and efficacy of fostamatinib in patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL). Experimental designRelapsed or refractory DLBCL patients originally received the oral spleen tyrosine kinase inhibitor, fostamatinib in a two-arm, randomised, double-blinded manner at either 100 mg twice a day (BID) or 200 mg BID until disease progression or unacceptable toxicity. The primary objective was to assess the overall response rate (ORR). Preliminary analysis showed limited efficacy and all subsequent patients were treated at 200 mg BID. Previously randomised patients were unblinded and given the opportunity to receive 200 mg BID. ResultsSixty-eight patients were treated (47 at 200 mg BID, 21 at 100 mg BID). Cell of origin analysis showed 58% germinal B-cell (GCB) origin, 30% activated B-cell (ABC) origin and 12% with an intermediate cell of origin signature. The most common treatment-related adverse events of all patients were diarrhoea (21% total, 6% grade 3/4), nausea (19% total, 3% grade 3/4), and, fatigue (18% total, 9% grade 3/4). The ORR rate was 3% across both arms and clinical benefit (≥stable disease) was achieved for 13% of all patients. The cell of origin for patients with clinical benefit was GCB (4 patients), intermediate (4 patients) or unknown (1 patient). None of the patients with clinical benefit had ABC genotype. ConclusionsWhile fostamatinib was generally well tolerated in this patient population, efficacy at these doses and schedule was poor. Unlike data with other B-cell antigen receptor pathway inhibitors, responses were not observed in the ABC genotype.