Small molecule protein kinase inhibitors approved by regulatory agencies outside of the United States.

Owing to genetic alterations and overexpression, the dysregulation of protein kinases plays a significant role in the pathogenesis of many autoimmune and neoplastic disorders and protein kinase antagonists have become an important drug target. Although the efficacy of imatinib in the treatment of chronic myelogenous leukemia in the United States in 2001 was the main driver of protein kinase inhibitor drug discovery, this was preceded by the approval of fasudil (a ROCK antagonist) in Japan in 1995 for the treatment of cerebral vasospasm. There are 21 small molecule protein kinase inhibitors that are approved in China, Japan, Europe, and South Korea that are not approved in the United Sates and 75 FDA-approved inhibitors in the United States. Of the 21 agents, eleven target receptor protein-tyrosine kinases, eight inhibit nonreceptor protein-tyrosine kinases, and two block protein-serine/threonine kinases. All 21 drugs are orally bioavailable or topically effective. Of the non-FDA approved drugs, sixteen are prescribed for the treatment of neoplastic diseases, three are directed toward inflammatory disorders, one is used for glaucoma, and fasudil is used in the management of vasospasm. The leading targets of kinase inhibitors approved by both international regulatory agencies and by the FDA are members of the EGFR family, the VEGFR family, and the JAK family. One-third of the 21 internationally approved drugs are not compliant with Lipinski's rule of five for orally bioavailable drugs. The rule of five relies on four parameters including molecular weight, number of hydrogen bond donors and acceptors, and the Log of the partition coefficient.

[A transient lymphocytosis after administration of tirabrutinib for leukemic Waldenström macroglobulinemia].

An 85-year-old woman was admitted to our hospital because of leukocytosis. Abnormal lymphocytic leukocytosis, including few plasmacytes, anemia, and thrombocytopenia, were observed. A diagnosis of primary macroglobulinemia was made based on immunoglobulin M-kappa monoclonal gammopathy, FACS of abnormal lymphocytes, and confirmed MYD88 L265P somatic mutation. Abnormal lymphocytes were markedly increased temporarily after the administration of tirabrutinib. However, the patient continued treatment after abdominal computed tomography showed that splenomegaly and lymphadenopathy had improved, and the patient recovered from leukocytosis. There are no reports that leukocytosis is a side effect of tirabrutinib; therefore, this case can be considered unique.

[An elderly patient with lymphoplasmacytic lymphoma successfully treated with low-dose tirabrutinib].

A 93-year-old woman was diagnosed with lymphoplasmacytic lymphoma (LPL) with circulating tumor cells in her peripheral blood after presenting with anemia. LPL progressed eight months later, with anemia worsening and tumor cells increasing to 66% of leukocytes. She began tirabrutinib at a low dose (80 mg daily: 17% of the standard dose) because she preferred to maintain her quality of life (QOL). Within three weeks, she was free of transfusion dependency and had a partial response with the disappearance of peripheral tumor cells. The dosage of tirabrutinib was increased to 240 mg daily because it was well tolerated. She has been on the treatment for 13 months with no adverse effects. Tirabrutinib, a highly selective Bruton's tyrosine kinase inhibitor, has been reported to have promising efficacy for LPL, but it also has a high incidence of dermatological toxicity, which may impair QOL. Low-dose tirabrutinib initiation may be effective and assist elderly patients with LPL in maintaining their QOL.

Safety and efficacy of filgotinib, lanraplenib and tirabrutinib in Sjögren's syndrome: a randomized, phase 2, double-blind, placebo-controlled study.

OBJECTIVE: The aim of this study was to characterize the safety and efficacy of filgotinib, lanraplenib and tirabrutinib in patients with active SS. METHODS: This multicentre, double-blind study randomized patients with active primary or secondary SS [EULAR SS disease activity index (ESSDAI) ≥5) to receive filgotinib 200 mg (Janus kinase-1 inhibitor), lanraplenib 30 mg (spleen tyrosine kinase inhibitor), tirabrutinib 40 mg (Bruton's tyrosine kinase inhibitor), or placebo. The composite primary end point was the week-12 proportion of patients fulfilling protocol-specified improvement criteria (based on CRP and SS-related symptoms). The EULAR SS patient-reported index (ESSPRI) and the ESSDAI change from baseline (CFB) were secondary end points. Exploratory end points included disease-related biomarkers. Treatment-emergent adverse events (AEs) represented safety outcomes. RESULTS: The mean of the baseline ESSDAI was 10.1, and of ESSPRI was 6.2 in the 150 patients who were treated; 125 completed the 24-week placebo-controlled treatment period. At week 12, 43.3% of the filgotinib group achieved the primary end point (P = 0.17 vs placebo) vs 42.3% (P = 0.16), 34.7% (P = 0.33), and 26.7% of lanraplenib, tirabrutinib, and placebo groups, respectively. Neither secondary end point was met. Biomarker reductions included immunoglobulins classically associated with SS disease activity. Filgotinib ESSDAI CFB appeared more pronounced in subgroups with baseline ESSDAI ≥14 or without DMARDs/CSs. Most AEs were Grade 1 or 2. CONCLUSION: Three drugs with disparate mechanisms were tested, but no significant differences vs placebo in primary or secondary end points were observed. These results may be considered hypothesis-generating, given the drug tolerability, subgroup analysis, and biomarker findings. TRIAL REGISTRATION: ClinicalTrials.gov, https://clinicaltrials.gov, NCT03100942.

[Complete response with tirabrutinib for relapsed and refractory Bing-Neel syndrome].

A 62-year-old female patient was diagnosed with Waldenstrom's macroglobulinemia/lymphoplasmacytic lymphoma (WM/LPL) 8 years ago, which was resolved with rituximab (R) monotherapy. Five years ago, she experienced numbness of the lower limbs, followed by diminished lower limb muscle strength and hearing disturbance. PET-CT scans showed accumulations along the peripheral nerves of the upper and lower limbs together with clonal B lymphocytes in the cerebrospinal fluid, thus a diagnosis of relapse with Bing-Neel syndrome (BNS). After a temporal remission by high-dose cytarabine or bendamustine plus R regimens as salvage treatments, WM/LPL recurred for the third time accompanied by gait disturbances due to muscle weakness and urinary retention. Thus, tirabrultinib was started as a subsequent therapy, which significantly improved the neurological condition together with abnormal findings of magnetic resonance imaging or cerebrospinal fluids. This case is valuable since few relapsed BNS was reported in the literature with successful tirabrutinib treatment.

[Bing-Neel syndrome successfully treated with tirabrutinib].

Bing-Neel syndrome (BNS) is a rare disease manifestation of Waldenström's macroglobulinemia characterized by abnormal lymphoplasmacytoid cells infiltration of the central nervous system. In September 2019, a 46-year-old man presented to a previous hospital with hand tremors, nausea, and dysuria. Demyelination of cerebral white matter and the spinal cord was discovered using MRI. Steroid pulse therapy was used to treat inflammatory demyelinating disease, and it provided temporary relief, but the symptoms returned when the steroids were stopped. He was referred to our hospital in June 2020, for further evaluation with the possibility of hematological malignancy. BNS was diagnosed based on the presence of abnormal lymphoplasmacytoid cells in the bone marrow and cerebrospinal fluid (CSF), as well as the presence of the MYD88L265P mutation in the CSF specimen. In July 2020, BR (bendamustine, rituximab) therapy was administered, but it was ineffective. Oral administration of tirabrutinib, which was recently approved for WM, began in August 2020. He has achieved long-term remission and steroid withdrawal, with no notable side effects. This is the second report of successful treatment of BNS with tirabrutinib. More research is needed to confirm tirabrutinib's efficacy in the treatment of BNS.

A multicenter, open-label, phase II study of tirabrutinib (ONO/GS-4059) in patients with Waldenström's macroglobulinemia.

Tirabrutinib is a second-generation Bruton's tyrosine kinase inhibitor with greater selectivity than ibrutinib. Here, we conducted a multicenter, phase II study of tirabrutinib in patients with treatment-naïve (Cohort A) or with relapsed/refractory (Cohort B) Waldenström's macroglobulinemia (WM). Patients were treated with tirabrutinib 480 mg once daily. The primary endpoint was major response rate (MRR; ≥ partial response). Secondary endpoints included overall response rate (ORR; ≥ minor response), time to major response (TTMR), progression-free survival (PFS), overall survival (OS), and safety. In total, 27 patients (18 in Cohort A; 9 in Cohort B) were enrolled. The median age was 71 y, and the median serum immunoglobulin M level was 3600 mg/dL. Among the patients, 96.2% had the MYD88L265P mutation. MRR and ORR were 88.9% and 96.3%, respectively (Cohort A: MRR, 88.9%; ORR, 94.4%; Cohort B: MRR, 88.9%; ORR, 100%). Median TTMR was 1.87 mo. PFS and OS were not reached with a median follow-up of 6.5 and 8.3 mo for Cohorts A and B, respectively. The most common adverse events (AEs) were rash (44.4%), neutropenia (25.9%), and leukopenia (22.2%), with most AEs classified as grade 1 or 2. Grade ≥ 3 AEs included neutropenia (11.1%), lymphopenia (11.1%), and leukopenia (7.4%). No grade 5 AEs were noted. All bleeding events were grade 1; none were associated with drug-related atrial fibrillation or hypertension. Although the follow-up duration was relatively short, the study met the primary endpoint. Therefore, tirabrutinib monotherapy is considered to be highly effective for both untreated and relapsed/refractory WM with a manageable safety profile. (JapicCTI-173646).

Phase I study of tirabrutinib (ONO-4059/GS-4059) in patients with relapsed or refractory B-cell malignancies in Japan.

We evaluated the safety, efficacy, pharmacokinetics, pharmacodynamics and predictive biomarkers of tirabrutinib, a second-generation, enhanced-selectivity Bruton's tyrosine kinase inhibitor in Japanese patients with relapsed/refractory B-cell non-Hodgkin lymphoma (B-cell NHL) and chronic lymphocytic leukemia (CLL). This was an open-label, multicenter, phase I study. Seventeen patients (male N = 8) with a median age of 70 years were enrolled in 4 dose cohorts (160 mg once daily [N = 3], 320 mg once daily [N = 3], 480 mg once daily [N = 4] and 300 mg twice daily [N = 7]); 4 patients had continued tirabrutinib administration as of 4 January 2018. The maximum tolerated dose was not reached. Pneumonitis (N = 1) was the dose-limiting toxicity for 300 mg twice daily. Common adverse events (AEs) were rash (35.3%) and vomiting (29.4%). Eight patients (47.1%) developed grade ≥3 AEs: neutropenia (23.5%), anemia (11.8%) and leukopenia (11.8%) were frequent. The overall response rate (≥PR) was 76.5% (13/17 patients), including 4 DLBCL patients with no CD79A/B or MYD88 mutations, and 1 CLL patient with a TP53 mutation, providing promising data for future developments. Of 16 patients with measurable lesions during the screening period, 12 showed ≥50% reductions in tumor diameter. In many patients, the tumor size decreased soon after beginning treatment. The maximum serum concentration for tirabrutinib was 611, 1220, 1280 and 886 ng/mL on Day 1 and 484, 971 1940, and 961 ng/mL on Day 28 for Cohorts 1-4, respectively. Tirabrutinib pharmacokinetics were linear, with little accumulation following multiple doses. Tirabrutinib was well tolerated and showed promising efficacy for B-cell NHL/CLL.

Bruton's tyrosine kinase (BTK) inhibitors for the treatment of primary central nervous system lymphoma (PCNSL): current progress and latest advances.

The incidence of primary central nervous system lymphoma (PCNSL) has steadily increased, particularly in elderly patients. Although highly responsive to first-line chemotherapy and radiotherapy, approximately 50% of patients relapse or become refractory within 1 year. Prognosis following relapse is dismal and no standard salvage therapy exists. Bruton's tyrosine kinase (BTK), a key regulator of the B-cell receptor (BCR) pathway, has emerged as a promising therapeutic target. The first BTK inhibitor ibrutinib has been evaluated in the relapsed/refractory PCNSL setting, with overall response rates of 51.9%-89.0% and median progression-free survival of 4.6-4.8 months. However, ibrutinib inhibits several kinases in addition to BTK, leading to off-target effects. Second-generation BTK inhibitors have since been developed, which afford greater selectivity for BTK and fewer off-target effects. We review current practices in the diagnosis and evaluation of PCNSL, as well as clinical trials of BTK inhibitors in PCNSL and future developments in PCNSL treatment.

The Pharmacokinetic Interaction of Tirabrutinib with Voriconazole, Itraconazole, and Fluconazole in SD Rats by UPLC-MS/MS.

BACKGROUND: Tirabrutinib is an orally effective, approved, and highly selective second-generation Bruton's tyrosine kinase (BTK) inhibitor for the treatment of recurrent or refractory primary central nervous system lymphoma (PCNSL). OBJECTIVE: This study aimed to develop an ultra-high performance liquid chromatography- tandem mass spectrometry (UPLC-MS/MS) method for the determination of tirabrutinib concentration in rat plasma, where zanubrutinib was used as an internal standard (IS). This method was also applied to study whether tirabrutinib would interact with voriconazole, itraconazole, and fluconazole in rats, providing a reference value for clinical medication guidance. METHODS: In the current study, the organic solvent protein precipitation method was used to treat plasma samples, which is simple and reproducible. Tirabrutinib (m/z 455.32 → 320.21) and zanubrutinib (m/z 472.13 → 455.04) were separated on a Waters Acquity BEH C18 column (2.1 × 50 mm, 1.7 µm) and detected by multiple reaction monitoring (MRM) in positive ionization mode. RESULTS: The method showed good linearity in the range of 5-3000 ng/mL for tirabrutinib with the lower limit of quantification (LLOQ) of 5 ng/mL. The recovery and matrix effects were 85.7-91.0% and 102.0-113.3%, respectively. The accuracy, precision, stability, and carry-over effect were also acceptable. The method could also be used for determining the pharmacokinetic interaction of tirabrutinib in rats. The results showed AUC0→∞ of tirabrutinib to be increased by 139.3% and 83.9% in the presence of voriconazole and fluconazole, respectively, while itraconazole had little effect. CONCLUSION: It is necessary to monitor the concentration of tirabrutinib in patients when it is combined with voriconazole and fluconazole to achieve a better therapeutic effect and reduce the risk of adverse reaction. Further research should be conducted in the future.

Waldenström Macroglobulinemia-Associated Peripheral Neuropathy in the Brachial Plexus With Bing-Neel Syndrome Diagnosed Through Repeated Cerebrospinal Tests.

In Waldenström macroglobulinemia (WM), confirming the presence of Bing-Neel syndrome (BNS) is important because drugs that penetrate the central nervous system (CNS) must be selected. We report the case of a 75-year-old man for whom tirabrutinib, a second-generation Bruton's tyrosine kinase inhibitor (BTKi), was useful in treating WM-associated peripheral neuropathy (PN) with BNS. Numbness and muscle weakness in the fingers occurred three years after the initial treatment of WM. WM-associated PN due to demyelinating disease was diagnosed based on the results of a nerve conduction study and magnetic resonance imaging showing bilateral symmetric swelling of the brachial plexus. The cerebrospinal fluid (CSF) cytology results were initially negative; however, the CSF test was repeated because of extremely high protein levels (984 mg/dL) and slightly elevated leukocyte counts (14/µL). The second test revealed abnormal lymphoplasmacytic cells (189/µL), indicating BNS. Rituximab and high-dose methotrexate-containing chemotherapy were administered. Despite the subsequent negative CSF cytology results, his neurological symptoms persisted but subsided soon after the initiation of tirabrutinib. The therapeutic effects of tirabrutinib persisted for 25 months. This case suggested that a careful search for concurrent BNS is important when lesions are close to the CNS or when atypical CSF findings are obtained in patients with WM-associated PN, especially when BTKi options are available.

Three-year follow-up analysis of phase 1/2 study on tirabrutinib in patients with relapsed or refractory primary central nervous system lymphoma.

Background: The ONO-4059-02 phase 1/2 study showed favorable efficacy and acceptable safety profile of tirabrutinib, a second-generation Bruton's tyrosine kinase inhibitor, for relapsed/refractory primary central nervous system lymphoma (PCNSL). Here, we report the long-term efficacy and safety after a 3-year follow-up. Methods: Eligible patients were aged ≥ 20 years with histologically diagnosed PCNSL and KPS of ≥ 70. Patients received oral tirabrutinib once daily at 320 or 480 mg, or 480 mg under fasted conditions. Results: Between October 19, 2017, and June 13, 2019, 44 patients were enrolled: 33 and 9 had relapsed and refractory, respectively. The 320, 480, and 480 mg fasted groups included 20, 7, and 17 patients, respectively. The median follow-up was 37.1 months. The overall response rate was 63.6% (95% CI: 47.8-77.6) with complete response (CR), unconfirmed CR, and partial response in 9, 7, and 12 patients, respectively. The median duration of response (DOR) was 9.2 months, with a DOR rate of 19.8%; the median progression-free survival (PFS) and median overall survival (OS) were 2.9 months and not reached, respectively, with PFS and OS rates of 13.9% and 56.7%, respectively. Adverse events occurred in 38 patients (86.4%): grade ≥ 3 in 23 (52.3%) including 1 patient with grade 5 events. KPS and quality of life (QoL) scores were well maintained among patients receiving long-term treatment. Conclusions: The results demonstrated the long-term clinical benefit of tirabrutinib, with deep and durable response in a subset of patients and acceptable safety profile, while KPS and QoL scores were maintained.

Refractory Primary Vitreoretinal Lymphoma Involving the Spinal Cord with a Temporary Complete Response to Tirabrutinib.

Many patients with primary vitreoretinal lymphoma (PVRL) exhibit central nervous system (CNS) involvement either at the diagnosis or during follow-up. The prognosis in the patients of PVRL with relapsed or refractory CNS remains extremely poor. We herein report a patient with refractory PVRL who had recurrence in the spinal cord despite receiving high-dose methotrexate-based chemotherapy and whole-brain radiotherapy. The patient surprisingly responded to tirabrutinib temporarily. We believe that this case suggests the utility of this new target therapy.

Bruton's tyrosine kinase is a possible therapeutic target in microscopic polyangiitis.

BACKGROUND: Bruton's tyrosine kinase (Btk) is an enzyme expressed in leukocytes other than T lymphocytes and plasma cells and involved in B-cell receptor- and Fcγ receptor (FcγR)-mediated signal transduction. Btk inhibitors potentially suppress autoantibody production due to the expected inhibitory ability of B lymphocyte differentiation into antibody-producing plasma cells and reduce FcγR-mediated neutrophil activation, including the release of neutrophil extracellular traps (NETs). Microscopic polyangiitis (MPA) is a systemic small-vessel vasculitis characterized by the pathogenic autoantibody, antineutrophil cytoplasmic antibody (ANCA) that reacts with myeloperoxidase (MPO). MPO and MPO-ANCA immune complex (IC)-induced FcγR-mediated NETs are critically involved in MPA pathogenesis. This study aimed to demonstrate the therapeutic efficacy of the Btk inhibitor tirabrutinib on MPA. METHODS: Various doses of tirabrutinib or vehicle were orally administered to Sprague-Dawley rats daily. Four weeks later, the number of peripheral B lymphocytes was counted, and Btk phosphorylation in B lymphocytes was evaluated by flow cytometry. Human peripheral blood neutrophils were stimulated by MPO and anti-MPO antibody ICs (MPO and anti-MPO-ICs), and Btk and its downstream Vav phosphorylation were assessed by western blotting. The effects of tirabrutinib on MPO and anti-MPO-IC-induced NET formation were examined in vitro. Wistar Kyoto rats were immunized with human MPO to induce experimental MPA and given drug-free or tirabrutinib-containing feed (0.0037% or 0.012%) from day 0 or 28. All rats were euthanized on day 42 for serological and histological evaluation. RESULTS: Tirabrutinib inhibited Btk phosphorylation without decreasing B lymphocytes in vivo. Neutrophil Btk and Vav were phosphorylated when stimulated with MPO and anti-MPO-ICs. Tirabrutinib suppressed MPO and anti-MPO-IC-induced NET formation in vitro and ameliorated experimental MPA in a dose-dependent manner in vivo. Although MPO-ANCA production was not affected, NET-forming neutrophils in the blood were significantly reduced by tirabrutinib. CONCLUSIONS: The Btk inhibitor tirabrutinib suppressed MPO and anti-MPO-IC-induced NET formation in vitro and ameliorated experimental MPA by reducing NET-forming neutrophils but not decreasing MPO-ANCA titer in vivo. This study suggests that Btk is a possible therapeutic target in MPA.

BTK Inhibitors in the Frontline Management of Waldenström Macroglobulinemia.

The discovery of MYD88 (L265P) mutation led to investigating BTK inhibitors in Waldenström macroglobulinemia (WM). Ibrutinib, the first-in-class agent, was approved based on a phase II trial in relapsed/refractory patients. In the phase III iNNOVATE study, the combination of rituximab and ibrutinib was compared with rituximab and placebo in treatment-naïve and relapsed/refractory patients. Second-generation BTK inhibitor, zanubrutinib, was compared with Ibrutinib in MYD88-mutated WM patients in the phase III ASPEN trial, whereas acalabrutinib was investigated in a phase II trial. Here, we discuss the role of BTK inhibitors in treatment-naïve patients with WM based on currently available evidence.

Karnofsky Performance Status and quality of life in patients with relapsed or refractory primary CNS lymphoma from a phase I/II study of tirabrutinib.

Background: Tirabrutinib, a second-generation inhibitor of Bruton's tyrosine kinase, was approved in March 2020 for the treatment of relapsed or refractory primary central nervous system lymphoma (r/r PCNSL) based on phase I/II studies in Japan. We previously reported the overall response rate and safety profile. We describe Karnofsky Performance Status (KPS) and the quality of life (QoL) in patients with r/r PCNSL receiving tirabrutinib based on more than 1-year follow-up data. Methods: Patients with r/r PCNSL, age ≥20 years, and KPS ≥70 were treated with tirabrutinib once daily at a dose of 320, 480, or 480 mg under fasted conditions. QoL was assessed using questionnaires issued by the European Organization for Research and Treatment of Cancer (EORTC), namely EORTC QLQ-C30, EORTC QLQ-BN20, and EuroQol 5 dimensions 3-level (EQ-5D-3L) along with KPS. Results: Forty-four patients (mean age, 60 years [range 29-86]) were enrolled. The median follow-up period was 14.9 months (range, 1.4-27.7). The median KPS of the patients at baseline was 80.0 (range, 70-100), and this remained constant during the treatment. The global health status/QoL in the QLQ-C30 showed significant improvements from baseline through cycles 3-17 and remained relatively constant thereafter until cycle 23. Improvements were also seen in emotional functioning and constipation in the QLQ-C30 segments. Other items of QLQ-C30 and QLQ-BN20, EQ-5D visual analog scales, and EQ-5D index were maintained during the treatment. Conclusions: Tirabrutinib generally maintains KPS and QoL scores with some improvements in specific QoL items in patients with r/r PCNSL.

Long-term safety profile of tirabrutinib: final results of a Japanese Phase I study in patients with relapsed or refractory B-cell malignancies.

Tirabrutinib is a Bruton's tyrosine kinase inhibitor for treating B-cell malignancies. We report the final results of a Phase I study of tirabrutinib in 17 Japanese patients with B-cell malignancies. Patients were administered tirabrutinib at a dose of 160 mg, 320 mg, or 480 mg once daily, or 300 mg twice daily (N = 3, 3, 4, and 7, respectively). Three patients continued tirabrutinib until study completion (November 30, 2020). Adverse events (AEs) occurred in all 17 patients, with Grade 3-4 AEs in 8 (47.1%), serious AEs in 7 (41.2%), drug-related AEs in 16 (94.1%), and Grade 3-4 drug-related AEs in 6 (35.3%). Drug-related AEs reported in 3 or more patients were rash, vomiting, neutropenia, arthralgia, and malaise. One additional serious AE (benign neoplasm of the lung, unrelated to tirabrutinib) occurred after the previous data cutoff (January 4, 2018). Tirabrutinib administration and response assessment were continued for over 4 years in 4 patients. The overall response rate was 76.5% (13/17 patients). The median (range) time to response and duration of response were 0.9 (0.9-5.9) months and 2.59 (0.08-5.45) years, respectively. These findings demonstrate the long-term safety and efficacy of tirabrutinib in Japanese patients with B-cell malignancies.Clinical trial registration: JapicCTI-142682 ( http://www.clinicaltrials.jp/ ).

Refractory immune thrombocytopenic purpura associated with IgM monoclonal gammopathy of undetermined significance: Successful treatment with tirabrutinib plus conventional therapies.

When immune thrombocytopenia (ITP) is secondary to malignant diseases, chemotherapy is expected to improve the platelet count (PC) as well. Herein, we report a case of a 72-year-old man with ITP refractory to standard therapies. IgM monoclonal gammopathy of undetermined significance (MGUS) was determined as an underlying disease. After bendamustine and rituximab (BR) therapy was found inadequately effective, tirabrutinib, a novel Bruton's tyrosine kinase inhibitor, was initiated, and the PC normalised subsequently. Surveillance of underlying diseases with which effective therapies are available may help manage refractory ITP, and IgM-MGUS is potentially a targetable underlying disease with this newly available drug.

Bing-Neel Syndrome Successfully Treated with Tirabrutinib.

Bing-Neel syndrome (BNS) is a rare central nervous system manifestation of lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM). We herein report a 62-year-old man with LPL/WM after multiple chemotherapies. He had weakness of lower extremities and elevated serum IgM levels. A bone marrow examination showed lymphoplasmacytic cells infiltration. Contrast-enhanced magnetic resonance imaging suggested enhancing lesions in the cauda equina roots. He was diagnosed with BNS and started on treatment with tirabrutinib 480 mg daily. Within three months, he showed clinical and radiologic improvement. Tirabrutinib may have utility as an effective treatment for BNS.

Successful bridging therapy with tirabrutinib before ASCT for relapsed primary DLBCL of the CNS complicated with PBC, cirrhosis, and pancytopenia.

The optimal therapy for relapsed primary diffuse large B-cell lymphoma (DLBCL) of the central nervous system (CNS) remains unclear. We herein report a case of relapsed primary DLBCL of the CNS complicated with primary biliary cholangitis, cirrhosis, and pancytopenia that was successfully treated with bridging therapy with tirabrutinib before autologous hematopoietic stem cell transplantation (ASCT). Tirabrutinib is well tolerated and effective for relapsed primary DLBCL of the CNS with comorbidities, including cirrhosis and pancytopenia. Tirabrutinib is a promising option as bridging therapy before ASCT.