Selective Bruton's Tyrosine Kinase Inhibitor Research Articles

Acalabrutinib in chronic lymphocytic leukemia therapy: literature review and experience of the Clinical and Diagnostic Center of the Lapino Clinical hospital

Chronic lymphocytic leukemia (CLL) is a B-cell tumor consisting of small lymphocytes. It develops through a multistage process of a series of genomic events. Bruton’s tyrosine kinase (BTK) plays an important role in signal transduction through constantly active BCR pathway. It participates in all aspects of B cell development including proliferation, maturation, differentiation, and apoptosis. Therefore, it seems reasonable to modulate BTK using pharmaceutical agents with the goal to suppress tumor process. The effect of 1st generation BTK inhibitor ibrutinib on non-target kinases is significant and causes some adverse events which can limit its use in older patients with concomitant pathologies. The results of completed trails have convincingly shown safety advantage and similar effectiveness of highly selective 2nd generation BTK inhibitor acalabrutinib compared to ibrutinib in all subgroups of patients with CLL. Considering the necessity of long term BTK inhibitor therapy (until progression or unacceptable progression), long-term manageable safety profile of acalabrutinib is important. The article discusses clinical pharmacology, effectiveness and safety of acalabrutinib therapy in the context of clinical trials. Analysis of medical histories of patients with CLL treated at the Clinical and Diagnostic Center of the Lapino Clinical Hospital, “Mother and Child” group of companies, in the last year was performed, and indications for treatment using 2nd generation BTK inhibitor were evaluated.

Acalabrutinib in Chinese patients with relapsed/refractory chronic lymphocytic leukemia: Primary analysis from an open-label, multicenter phase 1/2 trial.

Acalabrutinib is a highly selective Bruton tyrosine kinase inhibitor approved in the United States and Europe for chronic lymphocytic leukemia (CLL) based on phase 3 trials with limited representation of Asian populations. This phase 1/2 trial evaluates acalabrutinib in Chinese adults with relapsed/refractory (R/R) CLL receiving acalabrutinib 100mg twice daily in 28-day cycles until disease progression or treatment discontinuation due to adverse events (AEs) presenting substantial clinical risk. The primary endpoint was blinded independent central review (BICR)-assessed overall response rate (ORR). A total of 60 patients from 20 sites in China received acalabrutinib (median age 62years; median 1 prior therapy line; 21.7% with del(17p) and/or TP53 mutation; 51.7% with unmutated IGHV). Median total treatment duration was 19.4months (range 0.6-28.2) with 53 patients (88.3%) receiving acalabrutinib at data cutoff; median study follow-up was 20.2months. BICR-assessed ORR was 85.0% (95% CI, 73.4-92.9). Median duration of response, progression-free survival (PFS), and overall survival (OS) were not reached. Estimated 12-month and 18-month PFS rates were 91.5% (95% CI, 80.9-96.4) and 78.8% (95% CI, 60.9-89.2); OS rates were both 96.7% (95% CI, 87.3-99.2). AEs of grade ≥ 3 occurred in 25 patients (41.7%), most commonly decreased neutrophil count (13.3%, n = 8), pneumonia (6.7%, n = 4), and upper respiratory tract infection (6.7%, n = 4). AEs led to treatment discontinuation in 2 patients (paraneoplastic pemphigus; rectal neoplasm). This study demonstrated high ORR in acalabrutinib-treated Chinese patients with R/R CLL with no unexpected safety concerns. This trial is registered on ClinicalTrials.gov (NCT03932331).

Labeling of Bruton's Tyrosine Kinase (BTK) Inhibitor [11C]BIO-2008846 in Three Different Positions and Measurement in NHP Using PET.

Bruton's tyrosine kinase (BTK) is pivotal in B-cell signaling and a target for potential anti-cancer and immunological disorder therapies. Improved selective reversible BTK inhibitors are in demand due to the absence of direct BTK engagement measurement tools. Promisingly, PET imaging can non-invasively evaluate BTK expression. In this study, radiolabeled BIO-2008846 ([11C]BIO-2008846-A), a BTK inhibitor, was used for PET imaging in NHPs to track brain biodistribution. Radiolabeling BIO-2008846 with carbon-11, alongside four PET scans on two NHPs each, showed a homogeneous distribution of [11C]BIO-2008846-A in NHP brains. Brain uptake ranged from 1.8% ID at baseline to a maximum of 3.2% post-pretreatment. The study found no significant decrease in regional VT values post-dose, implying minimal specific binding of [11C]BIO-2008846-A compared to free and non-specific components in the brain. Radiometabolite analysis revealed polar metabolites with 10% unchanged radioligand after 30 min. The research highlighted strong brain uptake despite minor distribution variability, confirming passive diffusion kinetics dominated by free and non-specific binding.

Discovery and Preclinical Characterization of BIIB129, a Covalent, Selective, and Brain-Penetrant BTK Inhibitor for the Treatment of Multiple Sclerosis.

Multiple sclerosis (MS) is a chronic disease with an underlying pathology characterized by inflammation-driven neuronal loss, axonal injury, and demyelination. Bruton's tyrosine kinase (BTK), a nonreceptor tyrosine kinase and member of the TEC family of kinases, is involved in the regulation, migration, and functional activation of B cells and myeloid cells in the periphery and the central nervous system (CNS), cell types which are deemed central to the pathology contributing to disease progression in MS patients. Herein, we describe the discovery of BIIB129 (25), a structurally distinct and brain-penetrant targeted covalent inhibitor (TCI) of BTK with an unprecedented binding mode responsible for its high kinome selectivity. BIIB129 (25) demonstrated efficacy in disease-relevant preclinical in vivo models of B cell proliferation in the CNS, exhibits a favorable safety profile suitable for clinical development as an immunomodulating therapy for MS, and has a low projected total human daily dose.

A review of Bruton's tyrosine kinase inhibitors in multiple sclerosis.

Bruton's tyrosine kinase (BTK) inhibitors are an emerging class of therapeutics in multiple sclerosis (MS). BTK is expressed in B-cells and myeloid cells, key progenitors of which include dendritic cells, microglia and macrophages, integral effectors of MS pathogenesis, along with mast cells, establishing the relevance of BTK inhibitors to diverse autoimmune conditions. First-generation BTK inhibitors are currently utilized in the treatment of B-cell malignancies and show efficacy in B-cell modulation. B-cell depleting therapies have shown success as disease-modifying treatments (DMTs) in MS, highlighting the potential of BTK inhibitors for this indication; however, first-generation BTK inhibitors exhibit a challenging safety profile that is unsuitable for chronic use, as required for MS DMTs. A second generation of highly selective BTK inhibitors has shown efficacy in modulating MS-relevant mechanisms of pathogenesis in preclinical as well as clinical studies. Six of these BTK inhibitors are undergoing clinical development for MS, three of which are also under investigation for chronic spontaneous urticaria (CSU), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Phase II trials of selected BTK inhibitors for MS showed reductions in new gadolinium-enhancing lesions on magnetic resonance imaging scans; however, the safety profile is yet to be ascertained in chronic use. Understanding of the safety profile is developing by combining safety insights from the ongoing phase II and III trials of second-generation BTK inhibitors for MS, CSU, RA and SLE. This narrative review investigates the potential of BTK inhibitors as an MS DMT, the improved selectivity of second-generation inhibitors, comparative safety insights established thus far through clinical development programmes and proposed implications in female reproductive health and in long-term administration.

Resisting the Resistance: Navigating BTK Mutations in Chronic Lymphocytic Leukemia (CLL).

Bruton's tyrosine kinase (BTK) plays a key role in the B-cell receptor (BCR) signaling pathway and confers anti-apoptotic and proliferative properties to malignant B-cells in chronic lymphocytic leukemia (CLL). Small molecule BTK inhibitors were designed to bind BTK's active site and block downstream signaling. These drugs have now been used in the treatment of thousands of patients with CLL, the most common form of leukemia in the western hemisphere. However, adverse effects of early generations of BTK inhibitors and resistance to treatment have led to the development of newer, more selective and non-covalent BTK inhibitors. As the use of these newer generation BTK inhibitors has increased, novel BTK resistance mutations have come to light. This review aims to discuss previously known and novel BTK mutations, their mechanisms of resistance, and their relationship with patient treatment. Also discussed here are future studies that are needed to investigate the underlying cause allowing these mutations to occur and how they incite resistance. New treatments on the horizon that attempt to maneuver around these resistance mutations can be met with new resistance mutations, creating an unmet need for patients with CLL. Novel therapies and combinations that address all forms of resistance are discussed.

Trial in Progress: A Phase 1b Study of AS-1763, an Oral, Potent and Selective Noncovalent BTK Inhibitor, in Patients with Previously Treated Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma or Non-Hodgkin Lymphoma

Background: Covalent Bruton's tyrosine kinase (BTK) inhibitors such as ibrutinib are approved for treating patients with B-cell malignancies, but their long-term efficacy is limited by toxicity related to off-target kinase inhibition and acquired resistance due to BTK C481 mutation. AS-1763 is a potent, highly selective, orally available, and non-covalent BTK inhibitor, equipotent against both wild-type and C481S-mutated BTK with sub-nanomolar IC50 values (Kawahata et al. J Med Chem 2021; 64,14129-14141). In a Phase 1 single-ascending dose study in healthy volunteers, AS-1763 was well tolerated and safe at doses of 5-600 mg and achieved maximum inhibition of B cell activation at doses of 100 mg and above at 1-2 h post-dose and the duration of inhibitory effect increased with dose [Arimura et al. AACR 2022; Cancer Res 2022;82(12_Suppl)]. In preclinical studies, AS-1763 demonstrated a broad spectrum of inhibition against BTK mutations that confer resistance to other non-covalent BTK inhibitors in addition to the C481 mutation. Study Design and Methods: This study is an open-label, multi-center, Phase 1b study of oral AS-1763 in patients with advanced chronic lymphocytic leukemia (CLL)/small lymphocytic leukemia (SLL) and other B-cell non-Hodgkin lymphomas (NHLs) who have failed or are intolerant to at least two prior lines of systemic therapy. Prior therapy with a covalent BTK inhibitor is permitted; prior use of a noncovalent BTK inhibitor is excluded. This study consists of two parts, i.e., dose escalation and expansion parts. The dose escalation part will follow a 3+3 design with a starting dose of 100 mg BID. Each cycle will be 28 days. Three dose levels will be selected for dose expansion part based on a comprehensive review of data from dose escalation. The dose expansion part consists of 2 cohorts, i.e., Cohort 1 for CLL/SLL and Cohort 2 for B-cell NHL. In each cohort, the first 30 patients will be allocated to the 3 dose levels (10 patients for each), then the same provisional recommended Phase 2 Dose (RP2D) will be selected for Cohort 1 and Cohort 2 after 30 patients have enrolled in either cohort. After the provisional RP2D is selected, up to 28 patients in Cohort 1 and up to 15 patients in Cohort 2 may be treated at the provisional RP2D. In this study, up to 110 patients will be enrolled. Treatment will continue for 24 cycles or until disease progression, occurrence of unacceptable toxicity or discontinuation because of other reasons. Eligible patients include CLL/SLL, Waldenstrӧm macroglobulinemia (WM), marginal zone lymphoma (MZL), mantle cell lymphoma (MCL), and follicular lymphoma (FL). Patients with transformed disease (e.g., Richter's transformation) prior to or during screening are not eligible. Key exclusion criteria include CNS involvement by systemic lymphoma, stem cell transplant or CAR-T therapy <30 days, and clinically significant cardiovascular disease. The primary objective of the dose escalation part is to determine the maximum tolerated dose/dose-limiting toxicity. Key secondary endpoints include the evaluation of safety profile and tolerability, pharmacokinetics properties, and preliminary anti-tumor activity based on overall response rate (ORR) by investigator according to iwCLL 2018 for CLL, IWW6 for WM, and Lugano Treatment Response Criteria for MCL, MZL, SLL and FL. The primary objective of the dose expansion part is to assess the preliminary anti-tumor activity based on ORR by the Safety Monitoring Committee (SMC). Key secondary objectives are to investigate safety, tolerability, and pharmacokinetic profiles and to assess the preliminary antitumor activity based on ORR by investigator and best overall response, duration of response, progression-free survival and overall survival by investigator and the SMC. This trial will evaluate several key exploratory objectives including evaluation of minimal residual disease negativity, characterization of patient subsets defined by mutation status of BTK and phospholipase C gamma 2 (PLCG2), and characterize BTK and PLGC2 gene mutation before and after disease progression. Changes in the level of biomarkers such as CCL3 and CCL4 chemokines and B-cell receptor pathway signaling will be evaluated prior to, during therapy, and at time of disease progression. The RP2D will be determined based on all the data generated in the study. The study has been registered on ClinicalTrials.gov (NCT05602363).

Zanubrutinib and Venetoclax As Initial Therapy for CLL/SLL with Obinutuzumab Triplet Consolidation in Patients with Minimal Residual Disease Positivity (BruVenG)

Background: Bruton's tyrosine kinase inhibitors (BTKi), anti-CD20 antibodies, and B cell lymphoma 2 inhibitors (BCL-2i) are essential therapeutic drug classes in the treatment of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). Clinical synergy of BTKi and BCL-2i combinations have been observed, which allow for an oral regimen, that can be safely administered in a clinic setting for most patients (Tam et al., 2022; Wierda et al., 2021). Still, it remains uncertain if anti-CD20 antibodies meaningfully add to the effectiveness of oral combination therapy. Recent reports of triplet regimens demonstrate modest improvement in minimal residual disease (MRD) negativity with similar response rates when compared to oral doublets (Davids et al., 2021; Soumerai et al., 2021; Wierda et al., 2021). Additionally, anti-CD20 antibody use causes significant B cell depletion resulting in prolonged immune suppression. Recent reports suggest BTKi use may in fact impair clinical activity of anti-CD20 antibodies, which can be mitigated by using selective BTKi and incorporating anti-CD20 later in the treatment course when lower disease burden is present (Da Roit et al., 2015; Flinsenberg et al., 2020; Pavlasova et al., 2016; Rawstron et al., 2018). Therefore, anti-CD20 therapy may not be required for all patients and could be optimized within a response-adapted strategy. This trial has been developed to assess efficacy and safety of a response adapted consolidative treatment approach utilizing obinutuzumab triplet consolidation in CLL/SLL patients who remain MRD positive after an oral doublet fixed duration treatment with zanubrutinib and venetoclax. This approach looks to maximize MRD negative remissions, spare toxicity by limiting anti-CD20 exposure, and provide a finite therapy. This study will utilize once daily zanubrutinib for which there is limited data in regard to safety and efficacy particularly in combination with venetoclax. Study Design and Endpoints: This is a single center, open label, phase II, investigator initiated clinical trial enrolling 50 subjects evaluating the efficacy and safety of zanubrutinib and venetoclax with obinutuzumab triplet consolidation in subjects who remain MRD positive (BruVenG). Eligible patients must have treatment naïve CLL/SLL and treatment indications per the International Workshop on CLL 2018 guidelines. Subjects with Richter's transformation are excluded. Treatment will consist of lead-in, combination, and consolidation phases. All subjects will be treated with a 3-cycle lead-in of 320mg oral, once daily zanubrutinib monotherapy. Venetoclax will be incorporated at cycle 4, per the standard prescriber insert ramp-up schedule. A final dose of 400mg oral, once daily venetoclax, in combination with 320mg oral, once daily zanubrutinib will be used in all subsequent cycles after ramp-up. At cycle 16, MRD will be assessed in the peripheral blood (PB) and bone marrow (BM) via clonoSEQ (Adaptive Biotechnologies). Subjects who are MRD negative (<1x10 -4 ) in both compartments will stop therapy. Subjects who are MRD positive in PB or BM will continue zanubrutinib and venetoclax for an additional 6 cycles. Obinutuzumab will be added to the oral doublet starting at cycle 17. Standard intravenous obinutuzumab lead-in will occur during cycle 17, followed by standard monthly intravenous dosing of 1000mg through cycle 22. Depending on MRD status, subjects will be treated for 16 or 22 cycles. All subjects who receive consolidation will stop treatment at cycle 23 regardless of end of treatment MRD status. The primary endpoint is cycle 16 PB and BM MRD negativity rates. A co-primary endpoint will be cycle 23 PB and BM MRD negativity rates in subjects who were MRD positive at C16 and who went on to receive at least 1 dose of obinutuzumab. Key secondary endpoints will include cycle 16 overall response rate, 36-month progression free survival, 36-month overall survival, 36-month time to next treatment, 24- and 36-month PB MRD negativity rates, tumor lysis risk reduction rates, and safety. Exploratory endpoints will assess the positive predicative value of the ∆400 biomarker (Soumerai et al., 2021) on MRD negativity at cycle 16. This biomarker will be assessed between cycle 4 and 6. The MRD negative rates at cycle 16 and cycle 23 will be estimated with a 90% confidence interval using the Clopper-Pearson method based on exact binomial distribution.

Efficacy and Safety of Orelabrutinib-Containing Regime (TORM) As First-Line Therapy in Primary Central Nervous System Lymphoma (PCNSL): A Retrospective Analysis

Introduction: Primary central nervous system lymphoma (PCNSL) is a rare, aggressive extranodal lymphoma with poor prognosis. Currently there is no standard therapeutic strategy for PCNSL, and high-dose methotrexate-based regimens remain the first option (Siegal et al. Acta Haematologica 2019). Recently, studies have shown that Bruton's tyrosine kinase (BTK) plays a crucial part in B cell receptor and Toll-like receptor signaling pathways, which are constitutively active in PCNSL (Shen et al. Front Oncol. 2022). BTK inhibitor has been proven effective in treating chronic lymphocytic leukemia and other B-cell lymphomas (Yoshitaka et al. Neuro-Oncology 2021). Orelabrutinib is a novel and highly selective BTK inhibitor with high cerebrospinal fluid (CSF) concentration, which has demonstrated efficacy and safety in PCNSL (Wu et al. Invest New Drugs. 2022). Thus, we conducted a retrospective study to evaluate the efficacy and safety of the orelabrutinib-containing regimens as first-line therapy for patients (pts) with PCNSL. Methods: This isa retrospective analysis of pts with PCNSL who received TORM regimens (temozolomide 150 mg/m 2 day 2-5; orelabrutinib 150 mg qd day 2-21; rituximab 375 mg/m 2 day 1; methotrexate 3.5 g/m 2 day 2; 3 weeks per cycle) as first-line induction therapy between June 2021 and April 2023. It was proposed to receive autologous stem cells transplantation (ASCT) as consolidation therapy or orelabrutinib monotherapy as maintenance after TORM therapy when deemed necessary. The primary endpoint was overall response rate (ORR) according to the International PCNSL Collaborative Group (IPCG) criteria. Secondary endpoints included progression-free survival (PFS), overall survival (OS), and safety. Results: Twelve pts (8 males) with PCNSL were included, with a median age of 63.5 years (range, 40-77). All pts had a histologically confirmed diffuse large B-cell lymphoma and a history of deep intracranial lesions. 8 pts (66.7%) had non-germinal center B-cell-like subtypes. 5 pts (41.7%) had an Eastern Cooperative Oncology Group performance status of ≥2, and 10 pts (83.3%) had International Extranodal Lymphoma Study Group scores ≥2. 4 pts (33.3%) underwent ASCT after induction therapy and 4 pts (33.3%) received orelabrutinib maintenance monotherapy. As of the cut-off date (July 1, 2023), the median follow-up was 11.7 (range, 1.9-23.0) months, and median treatment cycle was 6 cycles (range, 2-9). All 12 pts were evaluated for the treatment response. An interim evaluation after 3/4 cycles was available for 12 pts, showing complete remission (CR) rate of 83.3% (10/12), partial response (PR) rate of 16.7% (2/12), giving an ORR of 100.0% (12/12, Table 1). At data cutoff, of all 12 evaluable pts, the best ORR was 100.0% (12/12), with all pts achieved CR ( Table 1). The median time to response was 1.7 (range, 0.7-2.4) months. Of 12 responders, 9 had an ongoing response, 2 developed progressive disease, and 1 died of covid-19 infection ( Figure 1). Median PFS was 22.6 months, with a 95% CI of 10.4-not reached (NR). Based one OS event, median OS was 22.6 months (95% CI, NR-NR). The most common AEs were anemia. Reported AEs were generally manageable and resolved soon after supportive treatment. AEs associated with off-target activities such as atrial fibrillation, diarrhea, and major hemorrhage were not reported. Conclusions: TORM regimens demonstrated encouraging efficacy and well-tolerated safety profile among pts with PCNSL in this retrospective study. This orelabrutinib-containing regimens may provide a potential treatment strategy for pts with PCNSL.

Preclinical evidence for the effective use of TL-895, a highly selective and potent second-generation BTK inhibitor, for the treatment of B-cell malignancies

TL-895 (formerly known as M7583) is a potent, highly selective, adenosine triphosphate (ATP)-competitive, second-generation, irreversible inhibitor of Bruton’s tyrosine kinase (BTK). We characterized its biochemical and cellular effects in in vitro and in vivo models. TL-895 was evaluated preclinically for potency against BTK using IC50 concentration–response curves; selectivity using a 270-kinase panel; BTK phosphorylation in Ramos Burkitt’s lymphoma cells by ProteinSimple Wes analysis of one study; anti-proliferative effects in primary chronic lymphocytic leukemia (CLL) blasts; cell viability effects in diffuse large B-cell lymphoma (DLBCL) and mantle-cell lymphoma (MCL) cell lines; effects on antibody-dependent cell-mediated cytotoxicity (ADCC) from Daudi cells and chromium-51 release from human tumor cell lines; and efficacy in vivo using four MCL xenograft model and 21 DLBCL patient-derived xenograft (PDX) models (subtypes: 9 ABC, 11 GCB, 1 Unclassified). TL-895 was active against recombinant BTK (average IC50 1.5 nM) and inhibited only three additional kinases with IC50 within tenfold of BTK activity. TL-895 inhibited BTK auto-phosphorylation at the Y223 phosphorylation site (IC50 1–10 nM). TL-895 inhibited the proliferation of primary CLL blasts in vitro and inhibited growth in a subset of activated DLBCL and MCL cell lines. TL-895 inhibited the ADCC mechanism of therapeutic antibodies only at supra-clinical exposure levels. TL-895 significantly inhibited tumor growth in the Mino MCL xenograft model and in 5/21 DLBCL PDX models relative to vehicle controls. These findings demonstrate the potency of TL-895 for BTK and its efficacy in models of B-cell lymphoma despite its refined selectivity.

A novel Bruton's tyrosine kinase inhibitor JDB175 shows potent efficacy to suppress central nervous system lymphoma.

Patients with central nervous system (CNS) lymphoma face limited treatment options and poor treatment outcomes, emphasizing the urgent need for effective therapeutic strategies. One limiting factor contributing to the suboptimal efficacy is the inadequate penetration of most treatment drugs across the blood-brain barrier (BBB). Recent insights into the pathophysiology of CNS lymphoma have identified the Bruton's tyrosine kinase (BTK) signaling pathway as a potential target. Some clinical trials have shown impressive responses to BTK inhibitors in CNS lymphoma. However, currently approved BTK inhibitors have low BBB penetration rates, limiting their efficacy. In this study, we discovered that JDB175, a novel and highly selective BTK inhibitor, exhibits excellent BBB penetration capabilities and demonstrates favorable activity in a mouse model of CNS lymphoma while showing no significant signs of toxicity. JDB175 effectively inhibits the BTK signaling pathway in human lymphoma cells, suppressing their proliferation, inducing cell cycle arrest, and promoting apoptosis. The significance of this study lies in addressing the critical unmet medical need for effective treatments for CNS lymphoma. This finding indicates a promising avenue for improved treatments in CNS lymphoma, potentially opening doors for further clinical investigation and therapeutic advancements.

Acalabrutinib in Chinese Patients (Pts) with Relapsed/Refractory (R/R) Chronic Lymphocytic Leukemia (CLL): 12-Month Efficacy and Safety Results from an Open-Label, Multicenter Phase 1/2 Trial

Background: CLL is a rare, incurable, relapsing disease occurring in approximately 0.3/100,000 individuals in China. Acalabrutinib (acala) is a highly selective Bruton tyrosine kinase inhibitor with minimal off-target activity approved in the US and Europe for treatment of CLL. Pivotal studies supporting acala's approval had limited inclusion of Asian populations. In the first phase 1/2 trial (NCT03932331) in Chinese pts with R/R CLL, acala demonstrated high response rates and acceptable tolerability at the 6-mo follow-up (Yang S et al. HemaSphere, 2023;7(S3):3716). We present 12-mo results from this trial. Methods: Adults with active CLL, Eastern Cooperative Oncology Group (ECOG) performance status ≤2, and who received ≥1 prior systemic therapies for CLL were enrolled to receive acala 100 mg twice daily in 28-day cycles until disease progression or treatment discontinuation due to adverse events (AEs) presenting substantial clinical risk. The primary endpoint was overall response rate (ORR) per 2018 International Workshop on Chronic Lymphocytic Leukemia criteria as assessed by blinded independent central review (BICR). Secondary endpoints included duration of response (DOR) and progression-free survival (PFS) as assessed by BICR; ORR, DOR, and PFS as assessed by investigators (INV); overall survival (OS); and AEs. Results: Sixty pts from 20 sites in China received acala (median age 62 y; 31.7% female; 21.7% with del(17p) and/or TP53 mutation; 51.7% with unmutated IGHV; median 1 prior line of therapy). At the updated data cutoff of December 22, 2022, 53 pts (88.3%) were receiving acala; reasons for acala discontinuation were progressive disease (5.0%; n=3), AEs (3.3%; n=2), pt decision (1.7%; n=1), and other (1.7%; n=1). Median duration of treatment was 19.4 mo (range 0.6-28.2). BICR-assessed ORR was 85.0% (95% CI 73.4, 92.9); no pt had complete response (CR). Median DOR by BICR was not reached (NR). At a median follow-up of 20.2 mo, median PFS by BICR was NR; the estimated 12-mo and 18-mo PFS rates were 91.5% (95% CI 80.9, 96.4) and 78.8% (95% CI 60.9, 89.2), respectively ( Figure). When assessed by INV, ORR was 85.0% (95% CI 73.4, 92.9) with 1 pt having CR, median DOR was NR, and median PFS was NR; estimated 12-mo and 18-mo PFS rates were 95.0% (95% CI 85.2, 98.3) and 87.2% (95% CI 69.1, 95.0), respectively. Median OS was also NR; the estimated 12-mo and 18-mo OS rates were both 96.7% (95% CI 87.3, 99.2). AEs of any grade were reported in 58 pts (96.7%); 25 pts (41.7%) had grade ≥3 AEs, most commonly decreased neutrophil count (13.3%, n=8), pneumonia, and upper respiratory tract infection (each 6.7%, n=4) ( Table). AEs leading to treatment discontinuation included paraneoplastic pemphigus (n=1) and rectal neoplasm (n=1). AEs leading to dose interruption were reported in 13 pts (21.7%), most commonly COVID-19 (5.0%), neutrophil count decreased (3.3%), and platelet count decreased (3.3%). Nine pts (15.0%) had serious AEs (SAEs); only 1 SAE occurred in >1 pt (pneumonia, n=2). Fatal AEs (occurring ≤30 d after last dose) were reported in 1 pt (cardiac arrest in a 73-y-old pt with multiple cardiorespiratory comorbidities on study day 34). Among events of clinical interest, neutropenia was reported in 24 pts (40.0%) and hypertension was reported in 3 pts (5.0%). There were no cases of atrial fibrillation/flutter, major hemorrhage, interstitial lung disease/pneumonitis, second primary malignancies, or tumor lysis syndrome. Conclusions: Twelve-mo data in Chinese pts with R/R CLL treated with acala demonstrated a high ORR, with responses that were durable and clinically meaningful. Continuous treatment with acala was well tolerated with manageable toxicities; no unexpected safety observations were observed in Chinese pts with R/R CLL.

Characterization and Preclinical Evaluation of AS-1763, an Oral, Potent and Selective Noncovalent BTK Inhibitor, in Chronic Lymphocytic Leukemia

Background: Covalent Bruton's tyrosine kinase (BTK) inhibitors (cBTKi) have transformed treatment landscape of chronic lymphocytic leukemia (CLL). These inhibitors bind to C481 residue in the kinase domain of BTK. This is also the site for the most common mutations rendering cells resistant to cBTKi. To circumvent this limitation of the cBTKi, non-covalent BTKi (ncBTKi) such as pirtobrutinib have been developed. Recently, non-C481 BTK mutations have been reported in patients with CLL at the time of disease progression during pirtobrutinib treatment. These observations underscore the need for ncBTKi that can target C481 as well as non-C481 mutations of BTK. AS-1763 is a potent, highly selective, orally available, and ncBTKi, equipotent against both wild-type and C481S-mutated BTK when tested in biochemical assays. In vivo, AS-1763 demonstrated significant antitumor effects in OCI-LY10 tumor xenograft models harboring wild-type or C481S mutant BTK (Kawahata et al. J Med Chem 64:14129, 2021). Study Design and Methods: In the present project, first we used cell free assay systems to evaluate selectivity and potency of AS-1763 by a kinome-wide profiling and inhibitory effect of AS-1763 in enzyme assays using recombinant mutant BTK. Second, we examined dose- and time-dependent inhibition of mutant BTK that is expressed in HEK293 cell line. Third, we tested biological, biochemical, and molecular impact of AS-1763 in primary CLL cells. Fourth, we determined sensitivity of CLL cells to AS-1763 when combined with other targeted agents. Results: AS-1763 showed a highly selective profile for BTK in a panel of 291 kinase assays with >260-fold selectivity except 3 Tec family kinases (BMX, ITK, and TEC). We have generated a total of 17 recombinant BTK mutant proteins (C481, T474, L528 variants and other BTK mutants; Table 1) reported in the literature or predicted by single nucleotide change in the codon, and established assay methods to measure inhibitory potency of BTKi for those BTK mutants (Table 1). AS-1763 showed potent inhibitory activities for those BTK mutants while inhibitory potencies of other cBTKi and ncBTKi were diminished against some BTK mutants such as T474 and/or L528 mutations. AS-1763 exhibited dose-dependent and slow-off rate inhibitions of BTK autophosphorylation (pY223) in HEK293 cells transfected with various BTK mutants. Furthermore, the observed inhibitory effects of AS-1763 on the BTK autophosphorylation (pY223) in HEK293 cells were continued up to 24 h after washing out of AS-1763. In primary CLL samples, AS-1763, pirtobrutinib or ibrutinib induced a modest apoptosis. AS-1763 effectively inhibited the BCR signaling pathway in a dose dependent manner as evidenced by downregulation of pY223-BTK expression which was also observed in cBTKi and ncBTKi relapsed/refractory CLL samples. In vitro incubations with AS-1763 inhibited CLL cell spontaneous migration, decreased CCL3/CCL4 levels in culture supernatant and was accompanied with the inhibition of intracellular calcium release and B-cell activation, as measured by surface CD86 expression. Besides, AS-1763 incubation for 24 hours was shown to modulate the expression of BCL-2 family proteins with the downregulation of MCL-1 and BCL-xl. Interestingly, in vitro treatment of CLL patient samples with AS-1763 demonstrated a notable elevation in cellular ROS and mitochondrial superoxide levels starting at 1 µM, concurrently impacting SOD1 expression in CLL patient samples. Evaluation of drug interaction models utilizing Compusyn and Synergy Finder applications predominantly indicated additive effects between AS-1763 with BCL-2 inhibitor, venetoclax as well as p53 activator APR-246. Consistent with this data, AS-1763 and venetoclax combinations showed high-rates of apoptosis in samples that were relapsed/refractory to cBTKi and ncBTKi. Conclusions: AS-1763 is a selective ncBTKi that inhibits both wild-type and mutant BTKs listed in Table 1. In CLL cells, AS-1763 was effective in inhibiting BCR pathway signaling and sensitized cells to other agents such as venetoclax. Based on these encouraging data we have initiated a clinical trial to test AS-1763 in patients with CLL and other B cell malignancies who have failed or are intolerant to at least two prior lines of systemic therapy, including cBTKi (NCT05602363 Clinical Trials.gov).

A Prospective Multicenter Phase II Study of Orelabrutinib-Lenalidomide-Rituximab (OLR) in Patients with Untreated Mantle Cell Lymphoma (MCL) in China (POLARIS Study): Preliminary Analysis on Efficacy, Safety, Mutation Spectrum and Impact of Mutation Profiling on Treatment Responses

Background: Recently, the first-line treatment of MCL has been continuously evolving with the introduction of targeted agents and chemo-free regimens. It is well-known that bruton's tyrosine kinase (BTK) inhibitors were effective with MCL patients (pts). Orelabrutinib (O), a novel highly selective BTK inhibitor, has shown high response rates and good tolerability in R/R MCL (Song et al. Blood. 2020). Besides, O combined with rituximab (R) could preserve NK cell mediated ADCC induced by R and enhance the apoptosis of tumor (Yu et al. Mol Ther Oncolytics. 2021). Thus, we hypothesized that OLR would exhibit synergistic antitumor activity in MCL and improve the depth and durability of responses. Here, we reported the preliminary data on efficacy, safety, and mutation spectrum of OLR regimen in untreated MCL from the POLARIS study (NCT05076097). Methods: Pts ≥18 years with untreated MCL were enrolled in this prospective, multicenter, single-arm phase 2 study. All pts received OLR-induction therapy on a 28-day cycle for 6 cycles (O, 150 mg/d; L, 15 mg on days 1-21, then 20 mg of cycles 2-6 if tolerated or 10 mg if not tolerated; R, 375 mg/m 2 on days 1, 8, 15, 22, then day 1 of cycles 3, 5), followed by OLR-maintenance therapy for up to 18 cycles. Primary endpoint was complete response rate (CRR) after 6 cycles of induction treatment. Secondary endpoints included overall response rate (ORR), time to response (TTR), duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety. Exploratory endpoint was to explore the prognostic value of detecting peripheral blood (PB) ctDNA by NGS. Results: As of July 10, 2023,a total of 28 pts (male, 89.3%; median age, 60.0 y [range, 53.0-64.5]) were enrolled. Baseline characteristics included 96.4% Eastern Cooperative Oncology Group performance status of 0-1, 82.1% stage III-IV disease, 57.1% Ki67 index (≥30%), 75.0% low-risk MIPI scores, 42.9% bone marrow involvement, and 60.7% maximum lesion diameter of ≥5 cm. Twenty-one pts (75.0%) who have completed 6 cycles of induction therapy were evaluable for response, 16 (76.2%) had a complete response (CR) and 5 (23.8%) had a partial response (PR), with an ORR of 100% ( Figure 1). In addition, 18 of 21 pts were available for minimal residual disease (MRD) analysis, and PB-MRD and bone marrow MRD (BM-MRD) of the 18 pts were negative. The results of CRR were reported across different subgroups stratified by Ki67 index (<30% vs. ≥30%, 66.7% and 83.3%), MIPI scores (low vs. intermediate, 81.3% and 60.0%), maximum lesion diameter (<5 cm vs. ≥5 cm, 87.5% and 69.2%), and bone marrow involvement (yes vs. no, 83.3% and 73.3%). With a median follow-up of 11.0 months, the median TTR was 3.0 months (range, 2.8-3.4). Median DOR and median PFS were not reached, with the estimated 12-month DOR rate and PFS rate of 90.9% and 92.3%, respectively. Mutationalspectrum (475 panels) was determined in 23 pts. The spectrum of gene mutations is depicted by PB samples and tissue samples at baseline in Figure 2. The most common mutated genes in tissues samples were: ATM (48%), KMT2D (43%), CCND1 (17%), SMARCA4(17%), ARID2 (13%), BCOR (13%), BIRC3 (13%), NFKBIE (13%), NOTCH1 (13%), ACTB (9%), CDK12 (9%), FANCC(9%),FAT1(9%),KLF2(9%),MEF2B(9%),MET(9%),SETD2(9%), TP53 (13%),TERT(9%). The most common mutated genes in PB samples were: ATM (48%), KMT2D (39%), DNMT3A (17%), BIRC3 (13%), CCND1 (13%), TP53 (13%), BCOR (9%), CARD11 (9%), CBLB (9%), CRYBG1 (9%), FAT1(9%), NOTCH1 (9%), GRIN2A (9%), KDM5A (9%), KLHL6(9%), KRAS (9%), MAP3K14 (9%). For all gene mutations, 75.4% (43/57) detected in tissue were also found in PB samples. Further, more additional mutated genes can be detected in plasma. Meanwhile, 4 of 23 pts had a PR, 1 of 4 had multiple gene mutations in PB samples, including BTK and TP53. This suggests that ctDNA detection may potentially predict that these gene mutations are associated with depth of remission. Twenty-six (92.9%) pts experienced adverse events (AEs). The most common AEs (any grades, ≥3 grades) were neutropenia (64.3%, 39.3%), leukopenia (60.7%, 14.3%), thrombocytopenia (35.7%, 7.1%), lymphopenia (35.7%, 3.6%), and COVID-19 infection (28.6%, 7.1%). At the time of data cut-off, 26 pts remained on study. No deaths were observed. Conclusions: The preliminary findings show that the OLR exerted synergistic antitumor activity, with manageable toxicity in untreated MCL. Detection of PB ctDNA by NGS method may help to predict prognosis.

Zanubrutinib in Mantle Cell Lymphoma Management: A Comprehensive Review.

The pharmacology, pharmacokinetics, pharmacodynamics, clinical efficacy, and safety of zanbrutinib are described. Mantle cell lymphoma (MCL) is a mature B-cell lymphoma that is typically associated with unfavorable outcomes, and virtually all patients with MCL have refractory or relapsed disease despite aggressive treatment. The treatment paradigm for MCL has transformed dramatically over the past decade owing to rapid advancements in immunotherapy and molecular-targeted therapies. Zanubrutinib, a second-generation Bruton's tyrosine kinase inhibitor (BTKI) designated for mature B-cell non-Hodgkin's lymphoma (NHL), has drastically improved the survival outcomes in relapsed/refractory (R/R) MCL patients. This selective BTKI is a small molecule that functions by forming a covalent bond in the active site of BTK. The inhibition of BTK activity is essential for the signaling of B-cell antigen receptor (BCR) and cytokine receptor pathways. In a preclinical study, zanubrutinib inhibited malignant B-cell proliferation and reduced tumor growth. Zanubrutinib was granted FDA-accelerated approval based on the results of Phase I and II trials. The investigator-assessed overall response rate was 83.7%, of which 78% of patients achieved complete response. The median duration of response was 19.5 months, and the median progression-free survival was 22.1 months. The most common (≥20%) all-grade adverse events were low neutrophil count (46.5%), upper respiratory tract infection (38.4%), rash (36.0%), low white blood cell count (33.7%), and low platelet count (32.6%). Zanubrutinib is a selective, next-generation, orally active, irreversible BTK inhibitor. The selectivity of zanubrutinib and its superior efficacy, with a well-tolerated safety profile, have proven to be attractive options for other malignancies.

First interim analysis of a phase 1 study of zanubrutinib (zanu) plus lenalidomide (len) in patients (pts) with relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL).

7557 Background: Effective therapies for R/R DLBCL are limited in China, especially for pts ineligible for high-dose therapy/stem cell transplantation (HDT/SCT). Preclinical data suggest synergy of len with zanu, a potent and selective Bruton tyrosine kinase inhibitor approved for various B-cell malignancies. Here, we present interim analysis results of an ongoing phase 1, open-label, dose-escalation/expansion study of zanu + len in R/R DLBCL (NCT04436107). Methods: Pts with R/R DLBCL ineligible for HDT/SCT with ≥1 prior line of adequate systemic therapy were enrolled. Dose escalation (part 1): Len 15 mg, 20 mg, or 25 mg orally once daily on days 1-21 of each 28-day cycle. Dose expansion (part 2): Len 25 mg. Zanu 160 mg was given orally twice daily continuously in parts 1 and 2. Primary endpoints were safety and recommended phase 2 dose (RP2D) of len (part 1) and overall response rate (ORR) by investigator based on Lugano classification (part 2). Interim analysis was performed when the 19th pt in part 2 completed first tumor assessment. Pts who received len 25 mg (RP2D) in parts 1 and 2 were analyzed separately. Results: As of November 8, 2022, 46 pts were treated and included in interim analysis (27 in part 1; 19 in part 2; 30 at RP2D). Median age was 60 years (range, 29–82), 83% had stage III–IV disease, 37% had refractory disease, 70% had non-germinal center B-cell (non-GCB) like disease; median number of prior systemic therapies was 1 (range, 1–5). Median exposure to zanu and len was 3.9 months (mo) (range 0.4–24.9), median follow-up was 6.6 mo (range 0.5–25.5). ORR was 46% overall (95% CI: 30.9–61.0; complete response [CR]: 24%) and 57% at RP2D (95% CI: 37.4–74.5; CR: 30%). At RP2D, ORR was 61% (95% CI: 38.5–80.3; CR: 35%) for pts with non-GCB disease and 50.0% (95% CI: 11.8–88.2; CR: 17%) for GCB. At RP2D, median duration of response was not reached and 6-mo event-free rate was 59% (95% CI: 23.8–82.8). Median progression-free survival was 5.5 mo (95% CI: 2.8-not estimable) with a 9-mo event-free rate of 37% (95% CI: 17.6–57.4). Overall, 46 (100%) pts experienced ≥1 treatment-emergent adverse event (TEAE). At RP2D, grade ≥3 TEAEs occurred in 60% of pts, most commonly neutrophil count decreased (43%), white blood cell count decreased (23%), and pneumonia (13%). One pt (2%) had febrile neutropenia (grade 3) but recovered within 2 days. TEAEs led to discontinuation of both len and zanu in 2 pts (cardiopulmonary failure unrelated to treatment [part 1, len 20 mg], pulmonary embolism [part 1, len 25 mg]) and discontinuation of len in 2 pts (platelet count decreased [part 1, len 20 mg], rash [part 2]). Two TEAEs leading to death were reported, unrelated to treatment. Conclusions: Zanu 160 mg plus len 25 mg combination showed an acceptable safety profile with promising efficacy. Further evaluation of the combination in a larger sample size is planned in future analysis. Clinical trial information: NCT04436107 .

Diagnosis and management of vitreoretinal lymphoma: present and future treatment perspectives.

Intraocular lymphoma (IOL) is a rare malignant intraocular lymphocytic tumor that mimics uveitis. IOL is anatomically classified into vitreoretinal lymphoma (VRL) and uveal lymphoma; most IOLs are VRLs, while uveal lymphoma is rare. VRL is highly malignant, with 60%-85% of patients developing central nervous system (CNS) lymphoma; primary VRL (PVRL) is an ocular disease with poor prognosis. We aimed to review the management and both current and future treatments for VRL. VRL diagnosis is based on the results of cytopathological examination using vitreous biopsy. However, the positive ratio of vitreous cytology remains 29%-70%. A combination of adjunctive tests may improve diagnostic accuracy, but as yet no gold-standard regimen has been established. Methotrexate intravitreal injections are effective in controlling ocular lesions; however, this treatment allows CNS dissemination. The efficacy of systemic chemotherapy in suppressing CNS dissemination has been recently debated. A multicenter prospective study with a unified treatment protocol is required to clarify this issue. In addition, establishing a treatment protocol for elderly patients and those with poor general health is necessary. Moreover, relapsed/refractory VRL and secondary VRL are more difficult to treat than PVRL because they are prone to recurrence. Ibrutinib, lenalidomide with or without rituximab, and temozolomide are promising treatments for relapsed/refractory VRL. In Japan, Bruton's tyrosine kinase (BTK) inhibitors have been approved for treating refractory CNS lymphoma. Furthermore, a randomized prospective study of tirabrutinib, a highly selective BTK inhibitor, is ongoing for evaluating the suppressing of CNS progression in patients with PVRL.

Discovery of Novel Bruton's Tyrosine Kinase PROTACs with Enhanced Selectivity and Cellular Efficacy.

Bruton's tyrosine kinase (BTK) is a target for treating B-cell malignancies and autoimmune diseases, and several BTK inhibitors are already approved for use in humans. Heterobivalent BTK protein degraders are also in development, based on the premise that proteolysis targeting chimeras (PROTACs) may provide additional therapeutic benefits. However, most BTK PROTACs are based on the BTK inhibitor ibrutinib raising concerns about their selectivity profiles, given the known off-target effects of ibrutinib. Here, we disclose the discovery and in vitro characterization of BTK PROTACs based on the selective BTK inhibitor GDC-0853 and the cereblon recruitment ligand pomalidomide. PTD10 is a highly potent BTK degrader (DC50 0.5 nM) that inhibited cell growth and induced apoptosis at lower concentrations than the two parent molecules, as well as three previously reported BTK PROTACs, and had improved selectivity compared to ibrutinib-based BTK PROTACs.

A Non-Canonical Role for the Glycosyltransferase Enzyme UGT2B17 as a Novel Constituent of the B Cell Receptor Signalosome.

In chronic lymphocytic leukemia (CLL), an elevated glycosyltransferase UGT2B17 expression (UGT2B17HI) identifies a subgroup of patients with shorter survival and poor drug response. We uncovered a mechanism, possibly independent of its enzymatic function, characterized by an enhanced expression and signaling of the proximal effectors of the pro-survival B cell receptor (BCR) pathway and elevated Bruton tyrosine kinase (BTK) phosphorylation in B-CLL cells from UGT2B17HI patients. A prominent feature of B-CLL cells is the strong correlation of UGT2B17 expression with the adverse marker ZAP70 encoding a tyrosine kinase that promotes B-CLL cell survival. Their combined high expression levels in the treatment of naïve patients further defined a prognostic group with the highest risk of poor survival. In leukemic cells, UGT2B17 knockout and repression of ZAP70 reduced proliferation, suggesting that the function of UGT2B17 might involve ZAP70. Mechanistically, UGT2B17 interacted with several kinases of the BCR pathway, including ZAP70, SYK, and BTK, revealing a potential therapeutic vulnerability. The dual SYK and JAK/STAT6 inhibitor cerdulatinib most effectively compromised the proliferative advantage conferred by UGT2B17 compared to the selective BTK inhibitor ibrutinib. Findings point to an oncogenic role for UGT2B17 as a novel constituent of BCR signalosome also connected with microenvironmental signaling.

Abstract A01: Development of a novel BTK inhibitor against resistant acute myeloid leukemia

Abstract Acute myeloid leukemia (AML) is the most common leukemia in adult patients, with a 5-year survival rate of less than 30 percent. Therefore, more effective therapeutic strategies are required to prolong the survival of AML patients. Importantly, anti-apoptotic proteins, especially B-cell lymphoma 2 (Bcl-2), overexpression in AML is associated with uncontrolled growth as well as chemoresistance. Unsurprisingly, Bruton’s tyrosine kinase (BTK) overexpresses in AML and associated with poor prognosis and chemoresistance. The FDA-approved BTK inhibitor, ibrutinib, has been successful in treating other hematologic malignancies, but a proportion of patients relapse mainly because of acquired mutations at Cys481Ser (C481S) in the kinase domain of BTK. If we are to develop effective BTK-based therapeutic regimens, it is critical that we account for these likely mutations and avoid agents that target the kinase domain. To develop a more selective and effective BTK inhibitor, we modified our first-generation BTK inhibitor to avoid the C481S mutation in the BTK kinase domain. This advance allowed us to develop a second-generation BTK inhibitor, KS151, that shows in vitro potency against C481S mutants. Because BTK and Bcl-2 are critical in chemoresistance and poor prognosis, combination therapy targeting BTK and Bcl-2 is a more viable option for AML patients to achieve better therapeutic outcomes. We propose the combination of KS151 with venetoclax (ABT-199) or ABT-737 in resistant AML cells. We employed a panel of three AML cell lines: Kusami-1, U937, and THP-1. Remarkably, KS151 was able to induce AML cell death with an average IC50 of 4 μM. Furthermore, KS151 showed a significant increase in both venetoclax and ABT-737 efficacy against AML cells. Western blot analysis demonstrated that Kusami-1 cells have the highest expression of both BTK and Bcl-2 proteins. Taken further, flow cytometry (Annexin V staining) demonstrated that KS151 combined with inhibition of Bcl-2 by venetoclax synergistically induced apoptosis (approximately 95%) of Kusami-1 cells. Collectively, the combination therapy showed promising and synergistic in vitro anti-leukemic activity against AML cell lines and represents a new viable treatment for AML patients. Future studies will apply the combination strategies in AML-resistant cell lines and include assessment in patient samples and in vivo studies. Citation Format: Nicole K. Schmalbach, Omar S. Al-Odat, Weam Othman Elbezanti, Gabriella Yao, Daniel A. Guirguis, Krishne Gowda, Shantu G Amin, Tulin Budak-Alpdogan, Subash C. Jonnalagadda, Manoj K. Pandey. Development of a novel BTK inhibitor against resistant acute myeloid leukemia [abstract]. In: Proceedings of the AACR Special Conference: Acute Myeloid Leukemia and Myelodysplastic Syndrome; 2023 Jan 23-25; Austin, TX. Philadelphia (PA): AACR; Blood Cancer Discov 2023;4(3_Suppl):Abstract nr A01.