Therapeutic options for relapsed/refractory mantle cell lymphoma

SOX11 is a novel binding partner and endogenous inhibitor of SAMHD1 ara-CTPase activity in mantle cell lymphoma

ABSTRACT

Sterile alpha motif and histidine-aspartate (HD) domain-containing protein 1 (SAMHD1) is a deoxynucleoside triphosphate triphosphohydrolase with ara-CTPase activity that confers cytarabine (ara-C) resistance in several hematological malignancies. Targeting SAMHD1's ara-CTPase activity has recently been demonstrated to enhance ara-C efficacy in acute myeloid leukemia. Here, we identify the transcription factor SRY-related HMG-box containing protein 11 (SOX11) as a novel direct binding partner and first known endogenous inhibitor of SAMHD1. SOX11 is aberrantly expressed not only in mantle cell lymphoma (MCL), but also in some Burkitt lymphomas. Coimmunoprecipitation of SOX11 followed by mass spectrometry in MCL cell lines identified SAMHD1 as the top SOX11 interaction partner, which was validated by proximity ligation assay. In vitro, SAMHD1 bound to the HMG box of SOX11 with low-micromolar affinity. In situ crosslinking studies further indicated that SOX11-SAMHD1 binding resulted in a reduced tetramerization of SAMHD1. Functionally, expression of SOX11 inhibited SAMHD1 ara-CTPase activity in a dose-dependent manner resulting in ara-C sensitization in cell lines and in a SOX11-inducible mouse model of MCL. In SOX11-negative MCL, SOX11-mediated ara-CTPase inhibition could be mimicked by adding the recently identified SAMHD1 inhibitor hydroxyurea. Taken together, our results identify SOX11 as a novel SAMHD1 interaction partner and its first known endogenous inhibitor with potentially important implications for clinical therapy stratification.

Front-line and second-line treatment for mantle cell lymphoma in clinical practice: A multicenter retrospective analysis

BACKGROUND

There are few reports of clinical practice treatment patterns and efficacy in mantle cell lymphoma (MCL).

MATERIALS AND METHODS

We retrospectively studied a large, multicenter, cohort of patients with MCL diagnosed between 2000 and 2020 in eight institutions.

RESULTS

536 patients were registered (73% male, median of 70 years). Front-line treatment was based on high-dose cytarabine, bendamustine, and anthracyclines in 42%, 12%, and 15%, respectively. The median PFS for all patients was 45 months; 68, 34, and 30 months for those who received high-dose cytarabine-based, bendamustine-based and anthracycline-based therapy. 204 patients received second-line. Bendamustine-based treatment was the most common second-line regimen (36% of patients). The median second-line PFS (sPFS) for the entire cohort was 14 months; 19, 24, and 31 for bendamustine-, platinum-, and high-dose cytarabine-based regimens, with broad confidence intervals for these latter estimates. Patients treated with cytarabine-based therapies in the front-line and those with front-line PFS longer than 24 months had a substantially superior sPFS.

CONCLUSION

Front-line treatment in this cohort of MCL was as expected and with a median PFS of over 3.5 years. Second-line treatment strategies were heterogeneous and the median second-line PFS was little over 1 year.

State of the Art in CAR-T Cell Therapy for Solid Tumors: Is There a Sweeter Future?

Chimeric antigen receptor (CAR)-T cell therapy has proven to be a powerful treatment for hematological malignancies. The situation is very different in the case of solid tumors, for which no CAR-T-based therapy has yet been approved. There are many factors contributing to the absence of response in solid tumors to CAR-T cells, such as the immunosuppressive tumor microenvironment (TME), T cell exhaustion, or the lack of suitable antigen targets, which should have a stable and specific expression on tumor cells. Strategies being developed to improve CAR-T-based therapy for solid tumors include the use of new-generation CARs such as TRUCKs or bi-specific CARs, the combination of CAR therapy with chemo- or radiotherapy, the use of checkpoint inhibitors, and the use of oncolytic viruses. Furthermore, despite the scarcity of targets, a growing number of phase I/II clinical trials are exploring new solid-tumor-associated antigens. Most of these antigens are of a protein nature; however, there is a clear potential in identifying carbohydrate-type antigens associated with tumors, or carbohydrate and proteoglycan antigens that emerge because of aberrant glycosylations occurring in the context of tumor transformation.

CAR T cells and time-limited ibrutinib as treatment for relapsed/refractory mantle cell lymphoma: the phase 2 TARMAC study

ABSTRACT

CD19-directed chimeric antigen receptor T cells (CAR-T) achieve high response rates in patients with relapsed/refractory mantle cell lymphoma (MCL). However, their use is associated with significant toxicity, relapse concern, and unclear broad tractability. Preclinical and clinical data support a beneficial synergistic effect of ibrutinib on apheresis product fitness, CAR-T expansion, and toxicity. We evaluated the combination of time-limited ibrutinib and CTL019 CAR-T in 20 patients with MCL in the phase 2 TARMAC study. Ibrutinib commenced before leukapheresis and continued through CAR-T manufacture for a minimum of 6 months after CAR-T administration. The median prior lines of therapy was 2; 50% of patients were previously exposed to a Bruton tyrosine kinase inhibitor (BTKi). The primary end point was 4-month postinfusion complete response (CR) rate, and secondary end points included safety and subgroup analysis based on TP53 aberrancy. The primary end point was met; 80% of patients demonstrated CR, with 70% and 40% demonstrating measurable residual disease negativity by flow cytometry and molecular methods, respectively. At 13-month median follow-up, the estimated 12-month progression-free survival was 75% and overall survival 100%. Fifteen patients (75%) developed cytokine release syndrome; 12 (55%) with grade 1 to 2 and 3 (20%) with grade 3. Reversible grade 1 to 2 neurotoxicity was observed in 2 patients (10%). Efficacy was preserved irrespective of prior BTKi exposure or TP53 mutation. Deep responses correlated with robust CAR-T expansion and a less exhausted baseline T-cell phenotype. Overall, the safety and efficacy of the combination of BTKi and T-cell redirecting immunotherapy appears promising and merits further exploration. This trial was registered at www.ClinicalTrials.gov as #NCT04234061.

Phase 2 study of ibrutinib plus venetoclax in Japanese patients with relapsed/refractory mantle cell lymphoma

BACKGROUND

Despite high response rates to initial therapy, most patients with mantle cell lymphoma (MCL) experience relapsed or refractory (R/R) disease. Here, we report the efficacy, safety, and pharmacokinetics of the Phase 2, single-arm M20-075 study (NCT04477486) of ibrutinib and venetoclax combination therapy in Japanese patients with R/R MCL.

METHODS

Patients received 560 mg ibrutinib and 400 mg venetoclax (after a 5-week ramp-up from 20 mg) once daily for up to 104 weeks. Primary endpoint was complete response (CR) rate by independent review committee (IRC). Secondary endpoints included overall response rate (ORR), duration of response (DOR), undetectable minimal residual disease (uMRD) rate, progression-free survival (PFS), overall survival (OS), safety including dose-limiting toxicity (DLT) assessment in the first six patients, and pharmacokinetic parameters. Full analysis set (FAS) comprised all treated patients. Per protocol set (PPS) excluded treated patients with non-evaluable disease at baseline by IRC.

RESULTS

Thirteen patients were treated (FAS n = 13; PPS, n = 12). Median age was 71 years, patients had a median of two prior treatments. After a median follow-up of 9.6 months, IRC-assessed CR rate and ORR were both 83% (PPS). All six MRD-evaluable patients had uMRD. Median DOR, PFS, and OS were unreached. The most common Grade ≥ 3 treatment-emergent adverse event (TEAE) was neutropenia (23%); 1 patient discontinued due to squamous cell carcinoma of the lung. No DLTs, tumor lysis syndrome, or deaths related to TEAEs were observed.

CONCLUSION

Ibrutinib plus venetoclax exhibited high response rates and a well-tolerated safety profile in Japanese patients with R/R MCL.

SOX11 is a novel binding partner and endogenous inhibitor of SAMHD1 ara-CTPase activity in mantle cell lymphoma

The sterile alpha motif and histidine-aspartate (HD) domain containing protein 1 (SAMHD1) is a deoxynucleoside triphosphate triphosphohydrolase with ara-CTPase activity that confers cytarabine (ara-C) resistance in several haematological malignancies. Targeting SAMHD1's ara-CTPase activity has recently been demonstrated to enhance ara-C efficacy in acute myeloid leukemia. Here, we identify the transcription factor SRY-related HMG-box containing protein 11 (SOX11) as a novel direct binding partner and first known endogenous inhibitor of SAMHD1. SOX11 is aberrantly expressed not only in mantle cell lymphoma (MCL), but also in some Burkitt lymphomas. Co-immunoprecipitation of SOX11 followed by mass spectrometry in MCL cell lines identified SAMHD1 as the top SOX11 interaction partner which was validated by proximity ligation assay. In vitro, SAMHD1 bound to the HMG box of SOX11 with low-micromolar affinity. In situ crosslinking studies further indicated that SOX11-SAMHD1 binding resulted in a reduced tetramerization of SAMHD1. Functionally, expression of SOX11 inhibited SAMHD1 ara-CTPase activity in a dose-dependent manner resulting in ara-C sensitization in cell lines and in a SOX11-inducible mouse model of MCL. In SOX11-negative MCL, SOX11-mediated ara-CTPase inhibition could be mimicked by adding the recently identified SAMHD1 inhibitor hydroxyurea. Taken together, our results identify SOX11 as a novel SAMHD1 interaction partner and its first known endogenous inhibitor with potentially important implications for clinical therapy stratification.

Resistance to PRMT5-targeted therapy in mantle cell lymphoma

ABSTRACT

Mantle cell lymphoma (MCL) is an incurable B-cell non-Hodgkin lymphoma, and patients who relapse on targeted therapies have poor prognosis. Protein arginine methyltransferase 5 (PRMT5), an enzyme essential for B-cell transformation, drives multiple oncogenic pathways and is overexpressed in MCL. Despite the antitumor activity of PRMT5 inhibition (PRT-382/PRT-808), drug resistance was observed in a patient-derived xenograft (PDX) MCL model. Decreased survival of mice engrafted with these PRMT5 inhibitor-resistant cells vs treatment-naive cells was observed (P = .005). MCL cell lines showed variable sensitivity to PRMT5 inhibition. Using PRT-382, cell lines were classified as sensitive (n = 4; 50% inhibitory concentration [IC50], 20-140 nM) or primary resistant (n = 4; 340-1650 nM). Prolonged culture of sensitive MCL lines with drug escalation produced PRMT5 inhibitor-resistant cell lines (n = 4; 200-500 nM). This resistant phenotype persisted after prolonged culture in the absence of drug and was observed with PRT-808. In the resistant PDX and cell line models, symmetric dimethylarginine reduction was achieved at the original PRMT5 inhibitor IC50, suggesting activation of alternative resistance pathways. Bulk RNA sequencing of resistant cell lines and PDX relative to sensitive or short-term-treated cells, respectively, highlighted shared upregulation of multiple pathways including mechanistic target of rapamycin kinase [mTOR] signaling (P < 10-5 and z score > 0.3 or < 0.3). Single-cell RNA sequencing analysis demonstrated a strong shift in global gene expression, with upregulation of mTOR signaling in resistant PDX MCL samples. Targeted blockade of mTORC1 with temsirolimus overcame the PRMT5 inhibitor-resistant phenotype, displayed therapeutic synergy in resistant MCL cell lines, and improved survival of a resistant PDX.

CAD204520 Targets NOTCH1 PEST Domain Mutations in Lymphoproliferative Disorders

NOTCH1 PEST domain mutations are often seen in hematopoietic malignancies, including T-cell acute lymphoblastic leukemia (T-ALL), chronic lymphocytic leukemia (CLL), splenic marginal zone lymphoma (SMZL), mantle cell lymphoma (MCL), and diffuse large B-cell lymphoma (DLBCL). These mutations play a key role in the development and progression of lymphoproliferative tumors by increasing the Notch signaling and, consequently, promoting cell proliferation, survival, migration, and suppressing apoptosis. There is currently no specific treatment available for cancers caused by NOTCH1 PEST domain mutations. However, several NOTCH1 inhibitors are in development. Among these, inhibition of the Sarco-endoplasmic Ca2+-ATPase (SERCA) showed a greater effect in NOTCH1-mutated tumors compared to the wild-type ones. One example is CAD204520, a benzimidazole derivative active in T-ALL cells harboring NOTCH1 mutations. In this study, we preclinically assessed the effect of CAD204520 in CLL and MCL models and showed that NOTCH1 PEST domain mutations sensitize cells to the anti-leukemic activity mediated by CAD204520. Additionally, we tested the potential of CAD204520 in combination with the current first-line treatment of CLL, venetoclax, and ibrutinib. CAD204520 enhanced the synergistic effect of this treatment regimen only in samples harboring the NOTCH1 PEST domain mutations, thus supporting a role for Notch inhibition in these tumors. In summary, our work provides strong support for the development of CAD204520 as a novel therapeutic approach also in chronic lymphoproliferative disorders carrying NOTCH1 PEST domain mutations, emerging as a promising molecule for combination treatment in this aggressive subset of patients.

Recent advances in genomics and therapeutics in mantle cell lymphoma

Over the past decades, significant strides have been made in understanding the pathobiology, prognosis, and treatment options for mantle cell lymphoma (MCL). The heterogeneity observed in MCL's biology, genomics, and clinical manifestations, including indolent and aggressive forms, is intricately linked to factors such as the mutational status of the variable region of the immunoglobulin heavy chain gene, epigenetic profiling, and Sox11 expression. Several intriguing subtypes of MCL, such as Cyclin D1-negative MCL, in situ mantle cell neoplasm, CCND1/IGH FISH-negative MCL, and the impact of karyotypic complexity on prognosis, have been explored. Notably, recent immunochemotherapy regimens have yielded long-lasting remissions in select patients. The therapeutic landscape for MCL is continuously evolving, with a shift towards nonchemotherapeutic agents like ibrutinib, acalabrutinib, and venetoclax. The introduction of BTK inhibitors has brought about a transformative change in MCL treatment. Nevertheless, the challenge of resistance to BTK inhibitors persists, prompting ongoing efforts to discover strategies for overcoming this resistance. These strategies encompass non-covalent BTK inhibitors, immunomodulatory agents, BCL2 inhibitors, and CAR-T cell therapy, either as standalone treatments or in combination regimens. Furthermore, developing novel drugs holds promise for further improving the survival of patients with relapsed or refractory MCL. In this comprehensive review, we methodically encapsulate MCL's clinical and pathological attributes and the factors influencing prognosis. We also undertake an in-depth examination of stratified treatment alternatives. We investigate conceivable resistance mechanisms in MCL from a genetic standpoint and offer precise insights into various therapeutic approaches for relapsed or refractory MCL.

Sequencing-based analysis of clonal evolution of 25 mantle cell lymphoma patients at diagnosis and after failure of standard immunochemotherapy

Our knowledge of genetic aberrations, that is, variants and copy number variations (CNVs), associated with mantle cell lymphoma (MCL) relapse remains limited. A cohort of 25 patients with MCL at diagnosis and the first relapse after the failure of standard immunochemotherapy was analyzed using whole-exome sequencing. The most frequent variants at diagnosis and at relapse comprised six genes: TP53, ATM, KMT2D, CCND1, SP140, and LRP1B. The most frequent CNVs at diagnosis and at relapse included TP53 and CDKN2A/B deletions, and PIK3CA amplifications. The mean count of mutations per patient significantly increased at relapse (n = 34) compared to diagnosis (n = 27). The most frequent newly detected variants at relapse, LRP1B gene mutations, correlated with a higher mutational burden. Variant allele frequencies of TP53 variants increased from 0.35 to 0.76 at relapse. The frequency and length of predicted CNVs significantly increased at relapse with CDKN2A/B deletions being the most frequent. Our data suggest, that the resistant MCL clones detected at relapse were already present at diagnosis and were selected by therapy. We observed enrichment of genetic aberrations of DNA damage response pathway (TP53 and CDKN2A/B), and a significant increase in MCL heterogeneity. We identified LRP1B inactivation as a new potential driver of MCL relapse.

Comprehensive scientometrics and visualization study profiles lymphoma metabolism and identifies its significant research signatures

Background

There is a wealth of poorly utilized unstructured data on lymphoma metabolism, and scientometrics and visualization study could serve as a robust tool to address this issue. Hence, it was implemented.

Methods

After strict quality control, numerous data regarding the lymphoma metabolism were mined, quantified, cleaned, fused, and visualized from documents (n = 2925) limited from 2013 to 2022 using R packages, VOSviewer, and GraphPad Prism.

Results

The linear fitting analysis generated functions predicting the annual publication number (y = 31.685x - 63628, R² = 0.93614, Prediction in 2027: 598) and citation number (y = 1363.7x - 2746019, R² = 0.94956, Prediction in 2027: 18201). In the last decade, the most academically performing author, journal, country, and affiliation were Meignan Michel (n = 35), European Journal of Nuclear Medicine and Molecular Imaging (n = 1653), USA (n = 3114), and University of Pennsylvania (n = 86), respectively. The hierarchical clustering based on unsupervised learning further divided research signatures into five clusters, including the basic study cluster (Cluster 1, Total Link Strength [TLS] = 1670, Total Occurrence [TO] = 832) and clinical study cluster (Cluster 3, TLS = 3496, TO = 1328). The timeline distribution indicated that radiomics and artificial intelligence (Cluster 4, Average Publication Year = 2019.39 ± 0.21) is a relatively new research cluster, and more endeavors deserve. Research signature burst and linear regression analysis further confirmed the findings above and revealed additional important results, such as tumor microenvironment (a = 0.6848, R² = 0.5194, p = 0.019) and immunotherapy (a = 1.036, R² = 0.6687, p = 0.004). More interestingly, by performing a "Walktrap" algorithm, the community map indicated that the "apoptosis, metabolism, chemotherapy" (Centrality = 12, Density = 6), "lymphoma, pet/ct, prognosis" (Centrality = 11, Density = 1), and "genotoxicity, mutagenicity" (Centrality = 9, Density = 4) are crucial but still under-explored, illustrating the potentiality of these research signatures in the field of the lymphoma metabolism.

Conclusion

This study comprehensively mines valuable information and offers significant predictions about lymphoma metabolism for its clinical and experimental practice.

Soluble CD163 predicts outcome in both chemoimmunotherapy and targeted therapy-treated mantle cell lymphoma

The outcome for patients with mantle cell lymphoma (MCL) has drastically improved with new treatments directed toward the tumor immune microenvironment, where macrophages play an important role. In MCL, the presence of M2 macrophages defined by CD163 expression in diagnostic biopsies has been associated with a worse prognosis. An alternative way to assess the abundance of M2 macrophages is by measuring the level of soluble CD163 in serum (sCD163). We aimed to investigate the prognostic value of sCD163 in 131 patients with MCL. We found that high sCD163 at diagnosis was associated with shorter progression-free survival (PFS) and shorter overall survival (OS) in 81 patients who were newly diagnosed and subsequently treated with chemoimmunotherapy. The same was seen in a cohort of 50 patients with relapsed MCL that were mainly treated within the phase 2 Philemon-trial with rituximab, ibrutinib, and lenalidomide. In patients who were newly diagnosed and had low levels of sCD163, 5-year survival was 97%. There was a moderate correlation between sCD163 and tissue CD163. The association with a poor prognosis was independent of MCL international prognostic index, Ki67, p53 status, and blastoid morphology, as assessed in a multivariable Cox proportional hazards model. In this study, high sCD163 was associated with both shorter PFS and shorter OS, showing that high levels of the M2 macrophage marker sCD163 is an independent negative prognostic factor in MCL, both in the chemoimmunotherapy and ibrutinib/lenalidomide era. In addition, low sCD163 levels identify patients with MCL with a very good prognosis.

Beyond Bruton's tyrosine kinase inhibitors in mantle cell lymphoma: bispecific antibodies, antibody-drug conjugates, CAR T-cells, and novel agents

Mantle cell lymphoma is a B cell non-Hodgkin lymphoma (NHL), representing 2-6% of all NHLs and characterized by overexpression of cyclin D1. The last decade has seen the development of many novel treatment approaches in MCL, most notably the class of Bruton's tyrosine kinase inhibitors (BTKi). BTKi has shown excellent outcomes for patients with relapsed or refractory MCL and is now being studied in the first-line setting. However, patients eventually progress on BTKi due to the development of resistance. Additionally, there is an alteration in the tumor microenvironment in these patients with varying biological and therapeutic implications. Hence, it is necessary to explore novel therapeutic strategies that can be effective in those who progressed on BTKi or potentially circumvent resistance. In this review, we provide a brief overview of BTKi, then discuss the various mechanisms of BTK resistance including the role of genetic alteration, cancer stem cells, tumor microenvironment, and adaptive reprogramming bypassing the effect of BTK inhibition, and then provide a comprehensive review of current and emerging therapeutic options beyond BTKi including novel agents, CAR T cells, bispecific antibodies, and antibody-drug conjugates.

Orelabrutinib for the treatment of relapsed or refractory MCL: a phase 1/2, open-label, multicenter, single-arm study

Relapsed or refractory (r/r) mantle cell lymphoma (MCL) is an aggressive B-cell malignancy with a poor prognosis. Bruton tyrosine kinase (BTK) is a mediator of B-cell receptor signaling and is associated with the development of B-cell lymphomas. Patients with r/r MCL were enrolled in this phase 1/2 study and treated with orelabrutinib, a novel, highly selective BTK inhibitor. The median number of prior regimens was 2 (range, 1-4). The median age was 62 years (range, 37-73 years). Eligible patients received oral orelabrutinib 150 mg once daily (n = 86) or 100 mg twice daily (n = 20) until disease progression or unacceptable toxicity. A dose of 150 mg once daily was chosen as the preferred recommended phase 2 dose. After a median follow-up duration of 23.8 months, the overall response rate was 81.1%, with 27.4% achieving a complete response and 53.8% achieving a partial response. The median duration of response and progression-free survival were 22.9 and 22.0 months, respectively. The median overall survival (OS) was not reached, and the rate of OS at 24 months was 74.3%. Adverse events (AEs) occurring in >20% of patients were thrombocytopenia (34.0%), upper respiratory tract infection (27.4%), and neutropenia (24.5%). Grade ≥3 AEs were infrequent and most commonly included thrombocytopenia (13.2%), neutropenia (8.5%), and anemia (7.5%). Three patients discontinued treatment because of treatment-related adverse events (TRAEs), but no fatal TRAEs were reported. Orelabrutinib showed substantial efficacy and was well tolerated in patients with r/r MCL. This trial was registered at www.clinicaltrials.gov as #NCT03494179.

Time to progression of disease and outcomes with second-line BTK inhibitors in relapsed/refractory mantle cell lymphoma

Time to progression of disease (POD) after first-line (1L) therapy is prognostic in mantle cell lymphoma (MCL), although studies have included a broad range of 1L, second-line (2L), and subsequent lines of therapy. The purpose of this study was to evaluate the factors predicting outcomes in patients with relapsed/refractory (R/R) MCL exclusively initiating 2L Bruton's tyrosine kinase inhibitors (BTKis) after 1L rituximab-containing therapy. Patients were accrued from 8 international centers (7 main, 1 validation cohort). Multivariable models evaluating the association between time to POD and clinical/pathologic factors were constructed and converted into nomograms and prognostic indexes predicting outcomes in this population. A total of 360 patients were included, including 160 in the main cohort and 200 in the validation cohort. Time to POD, Ki67 ≥ 30%, and MCL International Prognostic Index (MIPI) were associated with progression-free survival (PFS2) and overall survival (OS2) from the start of 2L BTKis. C-indexes were consistently ≥0.68 in both cohorts. Web/application-based calculators based on nomograms and prognostic indexes to estimate PFS2 and OS2 were constructed. The 2L BTKi MIPI identifies 3 groups with distinct 2-year PFS2, including high risk (14%), intermediate risk (50%), and low risk (64%). Time to POD, Ki67, and MIPI are associated with survival outcomes in patients with R/R MCL receiving 2L BTKis. Simple clinical models incorporating these variables may assist in planning for alternative therapies such as chimeric antigen receptor T-cell therapy, allogeneic stem cell transplantation, or novel agents with alternative mechanisms of action.

Post-BTK inhibitor mantle cell lymphoma: When is CAR-T not the answer?

In a large multicentre retrospective real-world analysis, Hess and colleagues describe outcomes in post-Bruton tyrosine kinase inhibitor (BTKi) mantle cell lymphoma patients managed in clinical practice prior to availability of brexucabtagene autoleucel (Tecartus). Outcome data not only provide a useful benchmark for future studies but also highlight the great challenges that still lie ahead in managing this challenging patient cohort. Commentary on: Hess et al. Real-world experience among patients with relapsed/refractory mantle cell lymphoma after Bruton tyrosine kinase inhibitor failure in Europe: The SCHOLAR-2 retrospective chart review study. Br J Haematol 2023;202:749-759.

Real-world experience among patients with relapsed/refractory mantle cell lymphoma after Bruton tyrosine kinase inhibitor failure in Europe: The SCHOLAR-2 retrospective chart review study

Mantle cell lymphoma (MCL) after relapse is associated with poor prognosis. No standard of care exists and available evidence for treatments is limited, particularly in patients who fail Bruton tyrosine kinase inhibitor (BTKi) therapy. This multicentre retrospective chart review study, SCHOLAR-2, addresses this knowledge gap and reports on data collected from 240 patients with relapsed/refractory MCL in Europe who were treated with BTKi-based therapy between July 2012 and July 2018, and had experienced disease progression while on BTKi therapy or discontinued BTKi therapy due to intolerance. The median overall survival (OS) from initiation of first BTKi therapy was 14.6 months (95% confidence interval [CI] 11.6-20.0) in the overall cohort, 5.5 months (95% CI 3.9-8.2) in 91 patients without post-BTKi therapy, and 23.8 months (95% CI 18.9-30.1) in 149 patients who received post-BTKi therapy (excluding chimeric antigen receptor T-cell treatment). In the latter group, patients received a median of one (range, one to seven) line of post-BTKi therapy, with lenalidomide-containing regimens and bendamustine plus rituximab being the most frequently administered; the median OS from initiation of first post-BTKi therapy was 9.7 months (95% CI 6.3-12.7). These results provide a benchmark for survival in patients with R/R MCL receiving salvage therapy after BTKi failure.

Pirtobrutinib: First Approval

Pirtobrutinib (Jaypirca^TM), a highly selective, non-covalent, reversible Bruton's tyrosine kinase (BTK) inhibitor, is being developed by Eli Lilly and Company (Lilly) for the treatment of B-cell leukemias and lymphomas. In January 2023, pirtobrutinib was approved in the USA under the Accelerated Approval pathway for the treatment of adult patients with relapsed or refractory mantle cell lymphoma (MCL) after at least two lines of systemic therapy, including a BTK inhibitor. This indication is approved under accelerated approval based on response rate. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial. This article summarizes the milestones in the development of pirtobrutinib leading to this first approval for the treatment of adult patients with relapsed or refractory MCL.

Inhibition of casein kinase 2 sensitizes mantle cell lymphoma to venetoclax through MCL-1 downregulation

BCL-2 family proteins are frequently aberrantly expressed in mantle cell lymphoma (MCL). Recently, the BCL-2-specific inhibitor venetoclax has been approved by the US Food and Drug Administration for chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML). In MCL, venetoclax has shown promising efficacy in early clinical trials; however, a significant subset of patients is resistant. By conducting a kinome-centered CRISPR-Cas9 knockout sensitizer screen, we identified casein kinase 2 (CK2) as a major regulator of venetoclax resistance in MCL. Interestingly, CK2 is over-expressed in MCL and high CK2 expression is associated with poor patient survival. Targeting of CK2, either by inducible short hairpin RNA (shRNA)-mediated knockdown of CK2 or by the CK2-inhibitor silmitasertib, did not affect cell viability by itself, but strongly synergized with venetoclax in both MCL cell lines and primary samples, also if combined with ibrutinib. Furthermore, targeting of CK2 reduced MCL-1 levels, which involved impaired MCL-1 translation by inhibition of eIF4F complex assembly, without affecting BCL-2 and BCL-XL expression. Combined, this results in enhanced BCL-2 dependence and, consequently, venetoclax sensitization. In cocultures, targeting of CK2 overcame stroma-mediated venetoclax resistance of MCL cells. Taken together, our findings indicate that targeting of CK2 sensitizes MCL cells to venetoclax through downregulation of MCL-1. These novel insights provide a strong rationale for combining venetoclax with CK2 inhibition as therapeutic strategy for MCL patients.

Outcomes among Patients with Mantle Cell Lymphoma Post-Covalent BTK Inhibitor Therapy in the United States: A Real-World Electronic Medical Records Study

Purpose

There remains a lack of consensus among experts regarding the optimal therapeutic approach for Mantle cell lymphoma (MCL) after failure of covalent Bruton Tyrosine Kinase inhibitor (cBTKi)-based therapy. This study was designed to examine patient characteristics, current treatment patterns, and clinical outcomes using a real-world database to evaluate how MCL is currently managed post-cBTKi therapy in the U.S.

Methods

A large, deidentified U.S. electronic medical record (EMR) oncology database (ConcertAI) with data from January 2011 to July 2021 was utilized for this study. Eligible patients were adults with MCL who had received at least one cBTKi. Descriptive statistics were used to evaluate patient characteristics and treatment patterns. Time-to-event real-world outcomes of duration of therapy, time to next treatment discontinuation, and overall survival was evaluated using the Kaplan-Meier method.

Results

A total of 946 patients met eligibility criteria. Of these, 739 (78.1%) discontinued cBTKi treatment before the end of the follow-up period, while the remaining 207 (21.9%) were still receiving cBTKi therapy at the end of the follow-up period. Among those who had discontinued the cBTKi, 352 (47.6%, 352/739) received at least one subsequent (post-cBTKi) treatment. The median duration of the immediate post-cBTKi therapy was 2.6 months (n = 352). Among the 739 patients who discontinued cBTKi treatment, the median time from cBTKi discontinuation to next treatment discontinuation or death was 3.9 months and the median overall survival was 10.3 months.

Conclusions

This study demonstrates the poor outcomes experienced by patients after cBTKi therapy. There is an urgent need for safe and effective treatments for patients with recurrent or progressive MCL.

A FOXO1-dependent transcription network is a targetable vulnerability of mantle cell lymphomas

Targeting lineage-defined transcriptional dependencies has emerged as an effective therapeutic strategy in cancer treatment. Through screening for molecular vulnerabilities of mantle cell lymphoma (MCL), we identified a set of transcription factors (TFs) including FOXO1, EBF1, PAX5, and IRF4 that are essential for MCL propagation. Integrated chromatin immunoprecipitation and sequencing (ChIP-Seq) with transcriptional network reconstruction analysis revealed FOXO1 as a master regulator that acts upstream in the regulatory TF hierarchy. FOXO1 is both necessary and sufficient to drive MCL lineage commitment through supporting the lineage-specific transcription programs. We further show that FOXO1, but not its close paralog FOXO3, can reprogram myeloid leukemia cells and induce B-lineage gene expression. Finally, we demonstrate that cpd10, a small molecule identified from an enriched FOXO1 inhibitor library, induces a robust cytotoxic response in MCL cells in vitro and suppresses MCL progression in vivo. Our findings establish FOXO1 inhibition as a therapeutic strategy targeting lineage-driven transcriptional addiction in MCL.

Identification of immune-related genes and development of a prognostic model in mantle cell lymphoma

Background

The immune landscape, prognostic model, and molecular variations of mantle cell lymphoma (MCL) remain unclear. Hence, an integrated bioinformatics analysis of MCL datasets is required for the development of immunotherapy and the optimization of targeted therapies.

Methods

Data were obtained from the Gene Expression Omnibus (GEO) database (GSE32018, GSE45717 and GSE93291). The differentially expressed immune-related genes were selected, and the hub genes were screened by three machine learning algorithms, followed by enrichment and correlation analyses. Next, MCL molecular clusters based on the hub genes were identified by K-Means clustering, the probably approximately correct (PAC) algorithm, and principal component analysis (PCA). The landscape of immune cell infiltration and immune checkpoint molecules in distinct clusters was explored by single-sample gene-set enrichment analysis (ssGSEA) as well as the CIBERSORT and xCell algorithms. The prognostic genes and prognostic risk score model for MCL clusters were identified by least absolute shrinkage and selection operator (LASSO)-Cox analysis and cross-validation for lambda. Correlation analysis was performed to explore the correlation between the screened prognostic genes and immune cells or immune checkpoint molecules.

Results

Four immune-related hub genes (CD247, CD3E, CD4, and GATA3) were screened in MCL, mainly enriched in the T-cell receptor signaling pathway. Based on the hub genes, two MCL molecular clusters were recognized. The cluster 2 group had a significantly worse overall survival (OS), with down-regulated hub genes, and a variety of activated immune effector cells declined. The majority of immune checkpoint molecules had also decreased. An efficient prognostic model was established, including six prognostic genes (LGALS2, LAMP3, ICOS, FCAMR, IGFBP4, and C1QA) differentially expressed between two MCL clusters. Patients with a higher risk score in the prognostic model had a poor prognosis. Furthermore, most types of immune cells and a range of immune checkpoint molecules were positively correlated with the prognostic genes.

Conclusions

Our study identified distinct molecular clusters based on the immune-related hub genes, and showed that the prognostic model affected the prognosis of MCL patients. These hub genes, modulated immune cells, and immune checkpoint molecules might be involved in oncogenesis and could be potential prognostic biomarkers in MCL.

Tipping the balance: toward rational combination therapies to overcome venetoclax resistance in mantle cell lymphoma

Mantle cell lymphoma (MCL), an aggressive, but incurable B-cell lymphoma, is genetically characterized by the t(11;14) translocation, resulting in the overexpression of Cyclin D1. In addition, deregulation of the B-cell lymphoma-2 (BCL-2) family proteins BCL-2, B-cell lymphoma-extra large (BCL-X_L), and myeloid cell leukemia-1 (MCL-1) is highly common in MCL. This renders these BCL-2 family members attractive targets for therapy; indeed, the BCL-2 inhibitor venetoclax (ABT-199), which already received FDA approval for the treatment of chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML), shows promising results in early clinical trials for MCL. However, a significant subset of patients show primary resistance or will develop resistance upon prolonged treatment. Here, we describe the underlying mechanisms of venetoclax resistance in MCL, such as upregulation of BCL-X_L or MCL-1, and the recent (clinical) progress in the development of inhibitors for these BCL-2 family members, followed by the transcriptional and (post-)translational (dys)regulation of the BCL-2 family proteins, including the role of the lymphoid organ microenvironment. Based upon these insights, we discuss how rational combinations of venetoclax with other therapies can be exploited to prevent or overcome venetoclax resistance and improve MCL patient outcome.