The covalent Bruton’s tyrosine kinase inhibitors (BTKis) are highly effective for the treatment of chronic lymphocytic leukemia (CLL). The dominant resistance mechanism observed with the BTKi ibrutinib is the development of BTK Cys481 codon mutations. Whether a similar resistance mutation profile exists for the newer-generation, more selective BTKi zanubrutinib is unknown. In samples referred for diagnostic next-generation sequencing in patients with progressive CLL, we observed an enrichment in the kinase-dead BTK Leu528Trp mutation in patients treated with zanubrutinib compared with ibrutinib (54%; 7 of 13 vs 4%; 1 of 24, P = .001). We describe 2 patients with BTK Leu528Trp mutations who showed clinical cross-resistance and progressive enrichment of the BTK Leu528Trp mutation over time when treated with the noncovalent BTKi pirtobrutinib. Both patients subsequently responded to venetoclax-based treatment. In summary, we have identified an enrichment of the BTK Leu528Trp mutation arising in patients treated with zanubrutinib that may impart cross-resistance to the noncovalent inhibitor pirtobrutinib and therefore may have implications for sequencing of these treatments in CLL.

Prophylactic high-dose methotrexate (HD-MTX) is often used for diffuse large B-cell lymphoma (DLBCL) patients at high risk of central nervous system (CNS) relapse, despite limited evidence demonstrating efficacy or the optimal delivery method. We conducted a retrospective, international analysis of 1384 patients receiving HD-MTX CNS prophylaxis either intercalated (i-HD-MTX) (n = 749) or at the end (n = 635) of R-CHOP/R-CHOP-like therapy (EOT). There were 78 CNS relapses (3-year rate 5.7%), with no difference between i-HD-MTX and EOT: 5.7% vs 5.8%, P = .98; 3-year difference: 0.04% (−2.0% to 3.1%). Conclusions were unchanged on adjusting for baseline prognostic factors or on 6-month landmark analysis (n = 1253). In patients with a high CNS international prognostic index (n = 600), the 3-year CNS relapse rate was 9.1%, with no difference between i-HD-MTX and EOT. On multivariable analysis, increasing age and renal/adrenal involvement were the only independent risk factors for CNS relapse. Concurrent intrathecal prophylaxis was not associated with a reduction in CNS relapse. R-CHOP delays of ≥7 days were significantly increased with i-HD-MTX vs EOT, with 308 of 1573 (19.6%) i-HD-MTX treatments resulting in a delay to subsequent R-CHOP (median 8 days). Increased risk of delay occurred in older patients when delivery was later than day 10 in the R-CHOP cycle. In summary, we found no evidence that EOT delivery increases CNS relapse risk vs i-HD-MTX. Findings in high-risk subgroups were unchanged. Rates of CNS relapse in this HD-MTX-treated cohort were similar to comparable cohorts receiving infrequent CNS prophylaxis. If HD-MTX is still considered for certain high-risk patients, delivery could be deferred until R-CHOP completion.

The B-cell receptor signalling pathway plays a critical role in development of B-cell malignancies, and the central role of Bruton’s tyrosine kinase (BTK) activation in this pathway provides compelling rationale for BTK inhibition as a therapeutic strategy for these conditions. Covalent BTK inhibitors (BTKi) have transformed the treatment landscape of B-cell malignancies, but adverse events and treatment resistance have emerged as therapeutic challenges, with the majority of patients eventually discontinuing treatment due to toxicity or disease progression. Non-covalent BTKi have alternative mechanisms of binding to BTK than covalent BTKi, and therefore offer a therapeutic alternative for patients with B-cell malignancies, including those who have been intolerant to, or experienced disease progression during treatment with a covalent BTKi. Here, we summarise the clinical data, adverse events and mechanisms of resistance observed with covalent BTKi and describe the emerging data for non-covalent BTKi as a novel treatment for B-cell malignancies.

PURPOSE: CNS progression or relapse is an uncommon but devastating complication of aggressive B-cell lymphoma. There is no consensus regarding the optimal approach to CNS prophylaxis. This study was designed to determine whether high-dose methotrexate (HD-MTX) is effective at preventing CNS progression in patients at high risk of this complication. PATIENTS AND METHODS: Patients age 18-80 years with aggressive B-cell lymphoma and high risk of CNS progression, treated with curative-intent anti–CD20-based chemoimmunotherapy, were included in this international, retrospective, observational study. Cause-specific hazard ratios (HRs) and cumulative risks of CNS progression were calculated according to use of HD-MTX, with time to CNS progression calculated from diagnosis for all patients (all-pts) and from completion of frontline systemic lymphoma induction therapy, for patients in complete response at completion of chemoimmunotherapy (CR-pts). RESULTS: Two thousand four hundred eighteen all-pts (HD-MTX; n = 425) and 1,616 CR-pts (HD-MTX; n = 356) were included. CNS International Prognostic Index was 4-6 in 83.4% all-pts. Patients treated with HD-MTX had a lower risk of CNS progression (adjusted HR, 0.59 [95% CI, 0.38 to 0.90]; P = .014), but significance was not retained when confined to CR-pts (adjusted HR, 0.74 [95% CI, 0.42 to 1.30]; P = .29), with 5-year adjusted risk difference of 1.6% (95% CI, –1.5 to 4.4; all-pts) and 1.4% (95% CI, –1.5 to 4.1; CR-pts). Subgroups were underpowered to draw definitive conclusions regarding the efficacy of HD-MTX in individual high-risk clinical scenarios; however, there was no clear reduction in CNS progression risk with HD-MTX in any high-risk subgroup. CONCLUSION: In this large study, high-risk patients receiving HD-MTX had a 7.2% 2-year risk of CNS progression, consistent with the progression risk in previously reported high-risk cohorts. Use of HD-MTX was not associated with a clinically meaningful reduction in risk of CNS progression.

Effective available treatment options for patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) who relapse after becoming refractory to both a covalent Bruton Tyrosine Kinase inhibitor (cBTKi) and a B cell leukemia/lymphoma 2 inhibitor (BCL2i) remain limited, and prognosis is very poor. Emerging areas of drug development include cellular therapies such as chimeric antigen receptor T-cell therapy and bispecific antibodies. However, cost, accessibility, toxicity, and the need for either prolonged or repeated hospitalization prevent universal application of these therapies. Given this area of unmet clinical need, we present this review article on Bruton Tyrosine Kinase (BTK) degraders in patients with CLL/SLL. We focus on their development as a drug class, the up-to-date clinical data available, as well as future directions. BTK protein degraders are a novel drug class with an alternate mechanism of action (MOA), compared to cBTKis and non-covalent BTKis (ncBTKis), causing ubiquitination of BTK, thereby leading to its degradation through the proteasome. Encouraging pre-clinical data show that this MOA allows BTK protein degraders to overcome common BTK mutations. We focus on four agents which are under investigation in B-cell malignancies in early clinical trials: BGB-16673, NX-2127, NX-5948, and AC676. Preliminary data suggest a comparable safety and toxicity profile between agents across this drug class with many patients on phase 1 trials deriving durable clinical benefit. Optimal sequencing of BTK degraders in the therapeutic landscape of CLL/SLL treatment is yet to be established. Further trials investigating these agents in combination with other targeted CLL agents may help to further understand their applicability. An effective, tolerable oral class of drugs would be invaluable in the treatment of patients with multiply relapsed CLL/SLL.