Seven-year outcomes of venetoclax-ibrutinib therapy in mantle cell lymphoma: durable responses and treatment-free remissions.

In the phase-2 clinical trial (AIM) of venetoclax-ibrutinib, 24 patients with mantle cell lymphoma (MCL; 23 with relapsed/refractory [R/R] disease) received ibrutinib 560mg and venetoclax 400mg both once daily. High complete remission (CR) and measurable residual disease negative (MRD-negative) CR rates were previously reported. With median survivor follow-up now exceeding 7 years, we report long-term results. Treatment was initially continuous, with elective treatment interruption (ETI) allowed after protocol amendment for patients in MRD-negative CR. For R/R MCL, the estimated 7-year progression-free survival (PFS) was 30% [95%CI: 14-49] (median 28 months [95%CI: 13-82]) and overall survival was 43% [95%CI: 23-62] (median 32 months [95%CI: 15-NE]). Eight patients in MRD-negative CR entered ETI for a median of 58 months (95%CI, 37-79), with four experiencing disease recurrence. Two of 3 re-attained CR on retreatment. Time-to-treatment-failure (TTF), which excluded progression in ETI for those reattaining response, was 39% overall and 68% at 7-years for responders. Beyond 56 weeks Grade 3 and serious adverse events were uncommon. Newly emergent or increasing cardiovascular toxicity were not observed beyond 56 weeks. We demonstrate long-term durable responses and acceptable toxicity profile of venetoclax-ibrutinib in R/R MCL and show feasibility of treatment interruption while maintaining ongoing disease control. (NCT02471391).

Treatment approaches for patients with TP53-mutated mantle cell lymphoma.

Mantle cell lymphoma is an uncommon subtype of lymphoma characterised by clinical and biological heterogeneity. Although most patients with mantle cell lymphoma have durable responses after chemoimmunotherapy, there is a need to prospectively identify high-risk subsets of patients for whom disease control with standard chemotherapy will be short lived. Among the available prognostic factors, TP53 mutations are uniquely informative owing to their strong association with early disease progression and death among patients receiving conventional chemoimmunotherapy, with the highest negative prognostic value compared with other established risk indicators, including the mantle cell lymphoma international prognostic index, histological features, elevated Ki-67, and other genetic lesions. The poor outcomes for patients with TP53-mutated mantle cell lymphoma receiving chemoimmunotherapy and second-line Bruton tyrosine kinase inhibitors represent an urgent need for alternative approaches. In this Review, we synthesise the available data to inform the management of this high-risk subset of patients and present a treatment strategy prioritising clinical trials and early use of cellular therapies.

Enrichment of BTK Leu528Trp mutations in patients with CLL on zanubrutinib: potential for pirtobrutinib cross-resistance.

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.

Clonal hematopoiesis, myeloid disorders and BAX-mutated myelopoiesis in patients receiving venetoclax for CLL.

The BCL2 inhibitor venetoclax has established therapeutic roles in chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML). As BCL2 is an important determinant of survival of both myeloid progenitor and B cells, we investigated whether clinical and molecular abnormalities arise in the myeloid compartment during long-term continuous venetoclax treatment of CLL in 89 patients (87 with relapsed/refractory CLL). Over a median follow-up of 75 (range 21-98) months, persistent cytopenias (≥1 of neutropenia, thrombocytopenia, anemia) lasting ≥4 months and unrelated to CLL occurred in 25 patients (28%). Of these patients, 20 (80%) displayed clonal hematopoiesis, including 10 with therapy-related myeloid neoplasms (t-MNs). t-MNs occurred exclusively in patients previously exposed to fludarabine-alkylator combination therapy with a cumulative 5-year incidence of 10.4% after venetoclax initiation, consistent with rates reported for patients exposed to fludarabine-alkylator combination therapy without venetoclax. To determine whether the altered myelopoiesis reflected the acquisition of mutations, we analyzed samples from patients with no or minimal bone marrow CLL burden (n = 41). Mutations in the apoptosis effector BAX were identified in 32% (13/41). In cellular assays, C-terminal BAX mutants abrogated outer mitochondrial membrane localization of BAX and engendered resistance to venetoclax killing. BAX-mutated clonal hematopoiesis occurred independently of prior fludarabine-alkylator combination therapy exposure and was not associated with t-MNs. Single-cell sequencing revealed clonal co-occurrence of mutations in BAX with DNMT3A or ASXL1. We also observed simultaneous BCL2 mutations within CLL cells and BAX mutations in the myeloid compartment of the same patients, indicating lineage-specific adaptation to venetoclax therapy.

Single-cell sequencing demonstrates complex resistance landscape in CLL and MCL treated with BTK and BCL2 inhibitors.

The genomic landscape of resistance to targeted agents (TAs) used as monotherapy in chronic lymphocytic leukemia (CLL) is complex and often heterogeneous at the patient level. To gain insight into the clonal architecture of acquired genomic resistance to Bruton tyrosine kinase (BTK) inhibitors and B-cell lymphoma 2 (BCL2) inhibitors in CLL, particularly in patients carrying multiple resistance mutations, we performed targeted single-cell DNA sequencing of 8 patients who developed progressive disease (PD) on TAs (either class). In all cases, analysis of single-cell architecture revealed mutual exclusivity between multiple resistance mutations to the same TA class, variable clonal co-occurrence of multiple mutations affecting different TAs in patients exposed to both classes, and a phenomenon of multiple independent emergences of identical nucleotide changes leading to canonical resistance mutations. We also report the first observation of established BCL2 resistance mutations in a patient with mantle cell lymphoma (MCL) following PD on sequential monotherapy, implicating BCL2 as a venetoclax resistance mechanism in MCL. Taken together, these data reveal the significant clonal complexity of CLL and MCL progression on TAs at the nucleotide level and confirm the presence of multiple, clonally independent, mechanisms of TA resistance within each individual disease context.

Outcomes of patients with CLL sequentially resistant to both BCL2 and BTK inhibition.

Covalent Bruton tyrosine kinase inhibitors (BTKi's) and the B-cell lymphoma 2 (BCL2) inhibitor venetoclax have significantly improved outcomes for patients with chronic lymphocytic leukemia (CLL), especially those with biologically adverse disease. Patients with CLL resistant to their first targeted agent (TA) can be effectively treated with the alternative class. However, relapses are expected with second-line TA therapy, and the clinical challenge of double class-resistant disease is now emerging with increasing frequency. To define the characteristics and outcomes of patients with double class-resistant disease, we retrospectively analyzed 17 patients who developed progressive disease (PD) on both TA classes for CLL (venetoclax, then BTKi, n=12; BTKi, then venetoclax, n = 5). The cohort was heavily pretreated (median lines of prior therapy, 4) and enriched for adverse disease genetics (complex karyotype, 12 of 12 tested [100%]; del(17p)/TP53 mutations, 15 of 17 [88%]). The median time to progression on prior venetoclax was 24 months (range, 6-94 months) and was 25 months (range, 1-55 months) on prior BTKi. Progression on second-line TA was manifest as progressive CLL in 11 patients and as Richter transformation in 6. The median overall survival after progression on second-line TA was 3.6 months (95% confidence interval, 2-11 months). Patients with double class-resistant CLL have a dismal prognosis, representing a group of high unmet need.

Immune recovery in patients with mantle cell lymphoma receiving long-term ibrutinib and venetoclax combination therapy.

Combination venetoclax plus ibrutinib for the treatment of mantle cell lymphoma (MCL) has demonstrated efficacy in the relapsed or refractory setting; however, the long-term impact on patient immunology is unknown. In this study, changes in immune subsets of MCL patients treated with combination venetoclax and ibrutinib were assessed over a 4-year period. Multiparameter flow cytometry of peripheral blood mononuclear cells showed that ≥12 months of treatment resulted in alterations in the proportions of multiple immune subsets, most notably CD4+ and CD8+ effector and central memory T cells and natural killer cells, and normalization of T-cell cytokine production in response to T-cell receptor stimulation. Gene expression analysis identified upregulation of multiple myeloid genes (including S100 and cathepsin family members) and inflammatory pathways over 12 months. Four patients with deep responses stopped study drugs, resulting in restoration of normal immune subsets for all study parameters except myeloid gene/pathway expression, suggesting long-term combination venetoclax and ibrutinib irreversibly affects this population. Our findings demonstrate that long-term combination therapy is associated with immune recovery in MCL, which may allow responses to subsequent immunotherapies and suggests that this targeted therapy results in beneficial impacts on immunological recovery. This trial was registered at www.clinicaltrials.gov as #NCT02471391.

BTK inhibitor therapy is effective in patients with CLL resistant to venetoclax.

Highly active BTK inhibitors (BTKis) and the BCL2 inhibitor venetoclax have transformed the therapeutic landscape for chronic lymphocytic leukemia (CLL). Results of prospective clinical trials demonstrate the efficacy of venetoclax to salvage patients with disease progression on BTKis, but data on BTKi therapy after disease progression on venetoclax are limited, especially regarding durability of benefit. We retrospectively evaluated the records of 23 consecutive patients with relapsed/refractory CLL who received a BTKi (ibrutinib, n = 21; zanubrutinib, n = 2) after stopping venetoclax because of progressive disease. Median progression-free survival (PFS) and median overall survival after BTKi initiation were 34 months (range, <1 to 49) and 42 months (range, 2-49), respectively. Prior remission duration ≥24 months and attainment of complete remission or undetectable measurable residual disease on venetoclax were associated with longer PFS after BTKi salvage (P = .044 and P = .029, respectively). BTKi therapy achieved durable benefit for patients with the BCL2 Gly101Val venetoclax resistance mutation (estimated 24-month PFS, 69%). At a median survivor follow-up of 33 months (range, 2-53), 11 patients remained on BTKi and 12 had stopped therapy because of disease progression (n = 8) or toxicity (n = 4). Our findings indicate that BTKi therapy can provide durable CLL control after disease progression on venetoclax.

Undetectable peripheral blood MRD should be the goal of venetoclax in CLL, but attainment plateaus after 24 months.

The highly selective BCL2 inhibitor venetoclax achieves deep responses in patients with relapsed or refractory (R/R) chronic lymphocytic leukemia (CLL), including undetectable minimal residual disease (uMRD). We retrospectively reviewed 62 patients with CLL treated with venetoclax to investigate the performance of peripheral blood (PB) compared with bone marrow (BM) assessment of MRD; the kinetics, clinicopathological associations, and longer-term outcomes of uMRD attainment and recrudescence; and the ability of venetoclax dose escalation to deepen responses. Among 16 patients who achieved PB uMRD and had contemporaneous BM assessments, 13 (81%) had confirmed BM uMRD, and patients with PB uMRD had outcomes at least as favorable as those with BM uMRD for time to progression, overall survival, and MRD recrudescence. Excluding 2 patients lacking earlier assessment, the median time to PB uMRD was 18 (range, 5-26) months, with 90% of instances achieved by 24 months. There was no new PB uMRD attainment after 24 months without treatment intensification. The dominant association with earlier attainment of uMRD was concurrent rituximab (P = .012). Complex karyotype was associated with inferior uMRD attainment after 12 months of therapy (P = .015), and patients attaining uMRD whose disease harbored TP53 abnormalities demonstrated a trend toward earlier recrudescence (P = .089). Of patients who received venetoclax dose escalations, 4 (27%) of 15 achieved improvements in response. For patients with R/R CLL receiving venetoclax, PB uMRD commonly correlates with BM uMRD and is associated with a comparable longer-term prognosis. Concurrent rituximab augments uMRD attainment, but dose escalation and further treatment beyond 24 months infrequently deepen responses.

Ibrutinib, but not zanubrutinib, induces platelet receptor shedding of GPIb-IX-V complex and integrin αIIbß3 in mice and humans.

The Bruton's tyrosine kinase (Btk) inhibitor ibrutinib has proven to be efficacious in the treatment of B-cell chronic lymphocytic leukemia (B-CLL) and related diseases. However, a major adverse side effect of ibrutinib is bleeding, including major hemorrhages. The bleeding associated with ibrutinib use is thought to be due to a combination of on-target irreversible Btk inhibition, as well as off-target inhibition of other kinases, including EGFR, ITK, JAK3, and Tec kinase. In this study, we investigated the effects of ibrutinib vs zanubrutinib (a more selective Btk inhibitor) on platelet activation, glycoprotein expression, and thrombus formation. Ibrutinib, but not zanubrutinib, induced a time- and dose-dependent shedding of GPIb-IX complex and integrin αIIbß3, but not of GPVI and GPV, from the platelet surface. The shedding of GPIbα and GPIX was blocked by GM6001 and TAPI-2, an ADAM17 inhibitor but not ADAM10 inhibitor. Ibrutinib but not zanubrutinib treatment of human platelets increased ADAM17 activation. Pretreatment of C57BL/6 mice with ibrutinib (10 mg/kg), but not zanubrutinib (10 mg/kg), inhibited ex vivo and in vivo thrombus growth over time. Platelets from ibrutinib-treated patients with CLL showed reduced GPIb-IX complex and integrin αIIbß3 surface expression and reduced ex vivo thrombus formation under arterial flow, which was not observed in zanubrutinib-treated patients. In mice, ibrutinib, but not zanubrutinib, led to increased soluble GPIbα and soluble αIIb levels in plasma. These data demonstrate that ibrutinib induces shedding of GPIbα and GPIX by an ADAM17-dependent mechanism and integrin αIIbß3 by an unknown sheddase, and this process occurs in vivo to regulate thrombus formation.