Zanubrutinib in Treating Waldenström Macroglobulinemia, the Last Shall Be the First

Treatment of Anti-Myelin-Associated Glycoprotein (MAG) Antibody Neuropathy Using Zanubrutinib in a Patient With Waldenström Macroglobulinemia: A Clinical Vignette

The objective of this paper is to report a case of anti-myelin-associated glycoprotein (anti-MAG) antibody neuropathy treated with zanubrutinib, offering insight into a potential therapeutic avenue for this challenging neurological disorder. A 65-year-old male initially presented with peripheral neuropathy in the lower distal extremities. Hematologic evaluation revealed an elevated M-spike of IgM and a high MAG antibody titer. His initial titer was measured at 1:102400 on February 28, 2023. These findings were consistent with the diagnosis of Waldenström macroglobulinemia (WM) with associated anti-MAG antibody neuropathy. The patient was started on rituximab and reported a slight improvement in symptoms. However, the patient felt the efficacy of rituximab diminished with each subsequent dose. Due to this, the patient was initiated on zanubrutinib. Close monitoring of clinical symptoms and laboratory parameters was conducted to assess treatment response and potential side effects. Following zanubrutinib therapy, the patient exhibited mild improvement in neuropathic symptoms, which have stabilized, although still present. Serologic examination demonstrated a decrease in anti-MAG-antibody titer at 1:25600 in the spring of 2023 and 1:51200 in November of 2023. Patient reports increased fatigue and musculoskeletal pain. This clinical vignette highlights the outcomes of zanubrutinib in the management of anti-MAG antibody neuropathy in a patient with WM. Further research and larger clinical trials are warranted to validate these findings and establish zanubrutinib as a viable therapeutic option for this rare and often challenging neurological disorder.

Post-marketing safety evaluation of zanubrutinib: a real-world pharmacovigilance analysis based on the FAERS database

BACKGROUND

Zanubrutinib has been demonstrated to have significant response rates and promising survival data in clinical trials. However, real-world adverse events still need to be ameliorated to facilitate rational clinical drug use.

RESEARCH DESIGN AND METHODS

Adverse incident reports from October 2019 to March 2024 were extracted from the FDA's Adverse Event Reporting System (FAERS) database. Zanubrutinib-related adverse events were obtained after data cleaning and analysis with SAS 9.4. Four methods were utilized to calculate disproportionality and evaluate AE signals of zanubrutinib.

RESULT

At the system organ class (SOC) level, one SOC met the criteria of the four algorithms. At the preferred term (PT) level, most AEs are those already included in the product monograph, and no unexpected safety signals have been identified. Furthermore, the average time to onset of adverse events was 134.8 days, with a median time of 16.5 days. Adverse events occurred in 57.96% of cases within 1 month.

CONCLUSION

Compared to the adverse events reported in clinical trials and drug labels, no unreported signals were identified. This finding will provide clinicians with a more comprehensive understanding of the clinical application of zanubrutinib and provide valuable insights for future investigations.

New Means and Challenges in the Targeting of BTK

Bruton's tyrosine kinase (BTK) is central to the survival of malignant and normal B lymphocytes and has been a crucial therapeutic target of several generations of kinase inhibitors and newly developed degraders. These new means for targeting BTK have added additional agents to the armamentarium for battling cancers dependent on B-cell receptor (BCR) signaling, including chronic lymphocytic leukemia and other non-Hodgkin lymphomas. However, the development of acquired resistance mutations to each of these classes of BTK inhibitors has led to new challenges in targeting BTK as well as novel insights into BCR signaling. The first-generation covalent BTK inhibitor ibrutinib is susceptible to mutations affecting the covalent binding site, cysteine 481 (C481). Newer noncovalent BTK inhibitors, such as pirtobrutinib, overcome C481 mutation-mediated resistance but are susceptible to other kinase domain mutations, particularly at residues Threonine 474 and Leucine 528. In addition, these novel BTK inhibitor resistance mutations have been shown biochemically and in patients to cause cross-resistance to some covalent BTK inhibitors. Importantly, newer generation covalent BTK inhibitors zanubrutinib and acalabrutinib are susceptible to the same mutations that confer resistance to noncovalent inhibitors. The BTK L528W mutation is of particular interest as it disrupts the kinase activity of BTK, rendering it kinase dead. This observation suggests that BTK may act independently of its kinase activity as a scaffold. Thus, the timely development of BTK degrading proteolysis targeting drugs has allowed for degradation, rather than just enzymatic inhibition, of BTK in B-cell lymphomas, and early clinical trials to evaluate BTK degraders are underway.

Zanubrutinib: past, present, and future

In recent years, Bruton tyrosine kinase (BTK) inhibitors have provided significant advances in the treatment of patients with B-cell malignancies. Ibrutinib was the first BTK inhibitor to be approved, and it changed the standard-of-care treatment for diseases such as chronic lymphocytic leukemia, mantle cell lymphoma, marginal zone lymphoma, and Waldenström macroglobulinemia, improving efficacy outcomes and safety compared to chemotherapy. In this article, we review the development of zanubrutinib, a next-generation BTK inhibitor, from molecular design to patient-related outcomes. We start this journey by providing insights into the discovery of BTK and the physiologic, genetic, and molecular characterization of patients lacking this kinase, together with the brief treatment landscape in the era of chemo-immunotherapies. Zanubrutinib was originally developed by applying a structure-activity strategy to enhance the specificity as well as enzymatic and pharmacokinetic properties. Preclinical studies confirmed greater specificity and better bioavailability of zanubrutinib compared with that of ibrutinib, which supported the initiation of clinical trials in humans. Preliminary clinical results indicated activity in B-cell malignancies together with an improved safety profile, in line with less off-target effects described in the preclinical studies. The clinical program of zanubrutinib has since expanded significantly, with ongoing studies in a wide range of hemato-oncological diseases and in combination with many other therapies. Zanubrutinib currently is approved for various B-cell malignancies in multiple countries. This story highlights the importance of multidisciplinary collaborative research, from bench to bedside, and provides an example of how the commitment to finding improved treatment options should always run parallel to patient care.

Targeted and cellular therapies in lymphoma: Mechanisms of escape and innovative strategies

The therapeutic landscape for lymphomas is quite diverse and includes active surveillance, chemotherapy, immunotherapy, radiation therapy, and even stem cell transplant. Advances in the field have led to the development of targeted therapies, agents that specifically act against a specific component within the critical molecular pathway involved in tumorigenesis. There are currently numerous targeted therapies that are currently Food and Drug Administration (FDA) approved to treat certain lymphoproliferative disorders. Of many, some of the targeted agents include rituximab, brentuximab vedotin, polatuzumab vedotin, nivolumab, pembrolizumab, mogamulizumab, vemurafenib, crizotinib, ibrutinib, cerdulatinib, idelalisib, copanlisib, venetoclax, tazemetostat, and chimeric antigen receptor (CAR) T-cells. Although these agents have shown strong efficacy in treating lymphoproliferative disorders, the complex biology of the tumors have allowed for the malignant cells to develop various mechanisms of resistance to the targeted therapies. Some of the mechanisms of resistance include downregulation of the target, antigen escape, increased PD-L1 expression and T-cell exhaustion, mutations altering the signaling pathway, and agent binding site mutations. In this manuscript, we discuss and highlight the mechanism of action of the above listed agents as well as the different mechanisms of resistance to these agents as seen in lymphoproliferative disorders.