Mantle Cell Lymphoma Patients Research Articles

Ki-67 Expression of 50% Is the Optimal Cut-Off to Predict Survival Outcomes in Mantle Cell Lymphoma (MCL): A Pooled Analysis from CALGB 50403 (Alliance) and MCL Real-World Study Cohort

Introduction The Ki-67 index has been previously shown to be prognostic, wherein the cut-off of 30% was associated with inferior survival outcomes (Determann O et al, Blood 2008) in newly diagnosed MCL patients (pts). However, this cut-off determination was made in pts treated with CHOP/R-CHOP as the first-line treatment, controlled only for MIPI, and predates the advent of novel agents. Short diagnosis to treatment interval (DTI ≤ 14 days) was recently shown to be prognostic in newly diagnosed MCL but its association with Ki-67 is unknown. We sought to determine the optimal Ki-67 cut-off in MCL and its prognostic relevance in the modern era. Methods This is a pooled analysis of 2 large datasets, one prospective (CALGB 50403) and one retrospective (MCL real world study [MCL-RWS]). CALGB is now part of the Alliance for Clinical Trials in Oncology. CALGB 50403 is a phase II randomized study wherein newly diagnosed MCL pts received intensive induction chemoimmunotherapy (IIC) followed by autologous transplant, and posttransplant rituximab. The MCL-RWS included adult pts (≥18 years [yrs]) with MCL treated from 2000 to 2017 at 12 participating US sites. Pts from sites in the MCL-RWS that enrolled on CALGB 50403 were excluded. Ki-67 was scored by central review in 10% increments in the CALGB 50403 and per institutional standard in the MCL-RWS. We assessed Ki-67 as a continuous variable and used a restricted quadratic spline fit to find an optimal cut-off. We looked at the associations between Ki-67 and other known/ established MCL prognostic markers including MIPI and DTI. The outcome parameters were PFS and OS. Time-to-event endpoints were evaluated by Kaplan-Meier and Cox proportional hazard methods. Results Among the 793 pts (n=666, MCL-RWS and n=127, CALGB 50403) in the pooled analysis, Ki-67 was available in 385 pts (311 from MCL-RWS and 74 from CALGB 50403). The median OS (mOS) and PFS (mPFS) in the entire cohort (n=793) was 11.8 years and 4.7 years, respectively. The two groups (gps), those with and without Ki-67 data, were well balanced including MIPI and DTI. The median age was 62 yrs (range, 32-88), 81% males, 94% with ECOG performance status (PS) 0-1 and 84% with stage 4. We found a Ki-67 cut-off of 50% to be optimal as the relative hazard of death rises after 50%. Pts in the Ki-67 >50% gp had significantly higher proportion with short DTI (36% vs 17%, p<0.001), ECOG PS ≥2 (12% vs 5%, p=0.02), elevated LDH (58% vs 39%, p=0.005), and MIPI ≥6.2 (38% vs 20%, p=0.007) compared to Ki-67 of ≤50%. Ki-67 >50% was associated with significantly inferior PFS with a hazard ratio (HR) of 2.10 (95%CI 1.50-2.92) compared to Ki-67 ≤50% with a mPFS of 2.1 vs 5.3 yrs, respectively, regardless of the age (young [≤65 yrs], 2.6 vs 5.3 yrs or old [>65 yrs], 1.1 vs 5.4 yrs) or receipt of IIC (2.2 vs 5.9 yrs). Figure 1 shows the statistically significant difference in PFS between the Ki-67 gps of ≤10%, >10% to <30%, ≥30 to ≤50%, and >50%. Ki-67 >50% remained prognostic for PFS in multivariable analysis (MVA) after adjusting for significant variables in univariable analysis (UVA) including short DTI, ECOG PS ≥2, stage 4, elevated LDH, and MIPI ≥6.2 with adjusted HR (aHR) 2.19, 95%CI 1.38-3.48, p <0.001. Ki-67 >50% was associated with significantly inferior OS with a HR of 2.10 (95%CI 1.33-3.32) compared to Ki-67 ≤50% with a mOS of 9.4 yrs vs not reached (NR), respectively, regardless of the age or receipt of IIC. Figure 2 shows the statistically significant difference in OS between the Ki-67 gps of ≤10%, >10% to <30%, ≥30 to ≤50%, and >50%. Ki-67 >50% was not prognostic for OS in MVA after adjusting for significant variables in the UVA (MIPI and sex), aHR 1.79, 95% CI 0.92-3.49, p=0.08. Similar findings were seen in multivariable analysis with Ki-67 >30%, which showed no prognostic significance (aHR 1.46, 95%CI 0.82-2.58, p=0.19). Because of disparate datasets, we performed sensitivity analysis looking at the prognostic relevance of in individual datasets (CALGB 50403 and MCL-RWS) and found Ki67 >50% was prognostic for PFS and OS in both of the datasets consistent with the primary analysis. Conclusions This study evaluating the optimal Ki-67 cut off for pts with newly diagnosed MCL in the modern era found that Ki-67 > 50% was prognostic for PFS but not OS in MVA. A potential reason for the lack of prognostic relevance for OS in this more recent dataset is the availability of effective options at relapse. We also found that short DTI was associated with high Ki-67 gp which is a novel finding.

Improvements in Overall Survival in Older Patients with Mantle Cell Lymphoma Are Driven By Improvements across Multiple Lines of Therapy

Introduction Survival rates for people with mantle cell lymphoma (MCL) have improved in recent years. Among the potential factors accounting for this improvement is the approval of multiple new therapies over the past two decades, including bortezomib, bendamustine, ibrutinib, lenalidomide, acalabrutinib, and zanubrutinib. We hypothesized that the availability of multiple agents with non-overlapping mechanisms of action would result in significant improvements in overall survival following first-line therapy. Methods Patients diagnosed with MCL between 2002 and 2017 were identified using the SEER-Medicare linked database. Selected patients were >65 years of age at the time of diagnosis with MCL. Lines of therapy were determined using billing codes, with inpatient/outpatient claims used for traditional agents and Medicare Part D dataset used for oral agents. Next lines of therapy were defined based on claims for new anticancer agents separated from the end of the prior line by some certain number of days. Sensitivity analyses were performed varying the number of days between therapies. Overall survival (OS) was defined as initiation of initial therapy to death, while OS2 was defined as time from initiation of second-line therapy to death. Time to next therapy 1 (TTNT1) was defined as time from start of first-line therapy to death or start of second-line therapy, whichever came first. Cox models and Kaplan-Meier (KM) survival curves were generated for time-to-event analyses. Analyses were stratified by categories of years of first- and second-line therapies corresponding to eras of key drug approvals (e.g., 2002-2005, 2006-2009, 2010-2013, >2013). Results In total, 4,832 patients were included, among whom 3,840 patients (79.5%) had claims for first-line regimens and 1,648 (34.1% of total and 42.9% of patients with first-line regimens) had second-line regimens. Of the 4,832 patients, the majority were male (67.4%), White (94.6%), and non-Hispanic (94.7%), with good performance status (74.8%) and a Charlson Comorbidity Index <2 (64.8%). The median age at diagnosis was 75 (IQR 70-81). Patients with first- and/or second-line regimens did not differ significantly from the entire population of 4,832 patients with MCL in terms of baseline characteristics. In the first-line setting, use of bendamustine-rituximab (BR) increased from 2.3% of patients treated in 2006-2009 to 49.5% in 2014-2017. Similarly, use of single-agent BTK-inhibitors (BTKi) increased from nonexistent in patients treated in 2010-2013 to 13.8% in 2014-2017. In the second-line setting, use of single-agent BTKi similarly increased from 2.6% of those treated in 2010-2013 to 44.9% in 2014-2017. Median OS for the 3,840 patients with fist-line regimens was 4.4 years (95% CI, 4.1-4.5); median OS for those receiving first-line therapy in 2002-2005 was 3.5 years (3.1-3.9), compared to 3.7 (3.4-4.0), 4.5 (4.2-5.0), and not reached (4.8-NR) among those treated in 2006-2009, 2010-2013, and 2014-2017, respectively. Patients treated in 2014-2017 had significantly improved OS compared with those in 2002-2005 (log rank p<0.0001). Median TTNT1 overall was 2.5 years (2.4-2.6); median TTNT1 was 3.2 years (2.9-3.5) vs 2.3 years (2.1-2.6) for patients who received first-line therapy in 2014-2017 compared to 2002-2005 (log rank p<0.0001) ( Figure A). In addition, there was a significant difference across KM curves for OS2 stratified by categories of years of second-line therapy, with median OS2 of 2.5 (2.0-3.2) in patients treated in 2014-2017 compared to median OS2 of 2.1 (1.7-2.5) in 2010-2013 ( Figure B). Discussion In this analysis, we observed improvements survival of MCL patients over time, along with similar improvements in outcomes following first-line therapy, which may correlate with increased BR and BTKi use as first-line agents. Unexpectedly, improvements in survival following first-line therapy were considerably more modest. Potential explanations include lack of data from recent years during which we expect continued increased utilization of oral therapies vs unique impact of repeated therapies in the elderly. Overall, these data support the need for ongoing development of first- and subsequent-line therapies in MCL.

Combined Inhibition of Protein Kinase CSNK2 and BET Proteins As a Novel Therapeutic Strategy for Mantle Cell Lymphoma

Currently available therapeutic approaches for Mantle Cell Lymphoma (MCL), including the Bruton Tyrosine Kinase (BTK) inhibitors ibrutinib, acalabrutinib and zanubrutinib, are not curative. Therefore, the discovery of novel molecules amenable of drug targeting is a research priority in the MCL field. Bromodomain-containing protein 4 (BRD4) is a member of the Bromodomain (B) and extra terminal (ET) (BET) protein family that regulate chromatin modifications and assembly of transcriptional complexes. Inhibition of BET by available compounds have shown promising anticancer effect. In MCL, BET inhibitors, such as INCB054329 or JQ-1, have been shown to increase apoptosis through downregulation of the AKT-mTOR, ERK, and other B Cell Receptor (BCR)-triggered cascades. We and others have previously demonstrated that the S/T kinase CSNK2 supports chronic BCR activation in MCL by upregulating the AKT/PI3K and NF-κB pathways. Inactivation of CSNK2 results in efficacious induction of MCL cell death. Notably, BRD4 activity is regulated by CSNK2 and double inhibition of BRD4 and CSNK2 has shown significant activity in other tumor models. The most effective and tested CSNK2 chemical inhibitor is CX4945 (silmitasertib), but very recently a novel compound, SGC-CK2, has been developed. No data are available on the effects of SGC-CK2 on MCL cells. In this work, we have evaluated the effects of the combined inhibition of CSNK2 and BET proteins on MCL cell growth and survival signaling pathways. CSNK2 inhibitors employed were CX4945 and SGC-CK2. CSNK2 gene silencing was achieved with the generation of anti- CSNK2 short hairpin-RNA IPTG-inducible MCL cell clones. BET inhibitors used were JQ-1 and INCB054329. Cell survival, apoptosis and proliferation were investigated by AnnexinV/PI staining and FACS analysis, by Western blot (WB) detection of PARP cleavage and Mcl1 expression and by other cell proliferation assays. The synergic action of BET and CK2 inhibitors was assessed by the Chou-Talalay combination index method. CK2 expression and survival-related signaling components were analyzed by WB, qRT-PCR and protein expression assays. CX4945 and the novel inhibitor SGC-CK2 displayed a potent anti-tumor activity on MCL cells as judged by the effective induction of apoptosis and proliferation arrest. A synergistic effect of CSNK2 and BET inhibitors was observed in all the MCL cell lines tested, (Jeko-1, Rec-1, including Granta-519 that are known to be much less sensitive to ibrutinib) and with all the inhibitors tested. The same results were obtained in the CSNK2 gene silencing models. Preliminary data showed that the cooperative cytotoxic effect of CK2 inhibition and BET inhibition on MCL apoptosis was observed also in MCL patient derived B cells, but not in healthy B lymphocytes form buffy coat. CSNK2 inactivation was associated with strong down-regulation of c-Myc and Mcl-1 proteins and with hampered activation of NF-κB and PI3K/AKT-dependent signaling. Surprisingly, BET protein inhibition caused increased Mcl-1 protein expression and augmented Ser 529 p65-NF-kB phosphorylation in Granta-519 and Rec-1 cells. Remarkably, CK2 inactivation led to a robust reduction of the BET inhibitor-induced increase of Mcl1, and NF-kB Ser 529 phosphorylation, thus counteracting BET-inhibitors-evoked compensatory pathways that could favor apoptosis resistance. Therefore, combined CSNK2 and BET proteins inhibition could represent an innovative strategy for chemotherapy and BTKi-resistant MCL.

Treatment Patterns in Patients with Mantle Cell Lymphoma: Updated Report of the Asia-Pacific Multinational Retrospective Registry Study

I ntroduction We conducted a multinational, multicenter retrospective registry study to better define the treatment patterns and survival outcomes of newly diagnosed patients with mantle cell lymphoma (MCL) in the Asia-Pacific region. Methods Data were collected from newly diagnosed MCL patients between January 2008 and September 2019 from 27 hospitals in Asian countries, including China, Malaysia, Japan, Singapore, South Korea, Taiwan, and Thailand. The first interim analysis with 191 patients was previously reported. An updated analysis of 381 patients was performed at the data cutoff date of June 20, 2023. Results The median age was 62 years (range, 26-90), and 282 patients were male (74.0%). The majority of the patients had stage 3 or 4 disease (n = 329, 87.1%). Based on the MIPI score, 20.7% (n = 139) were classified as high-risk, while 39.4% (n = 150) were classified as high-risk according to the IPI. The most frequently administered 1 st line regimen was R-CHOP or R-CHOP-like regimens (n = 177, 46.5%), followed by cytarabine-containing regimens (n = 113, 29.7%), including R-Hyper-CVAD (n = 78), and bendamustine-rituximab (n = 27, 6.3%). There was a significant difference in the treatment pattern between young (age < 65, n = 210) versus elderly patients (age ≥ 65, n = 171). A higher proportion of elderly patients received R-CHOP or R-CHOP-like regimens (n = 98, 57.3%) while cytarabine-containing regimens were more frequently administered in young patients (n = 97, 46.2%). The treatment response to 1st line regimens was available in 349 patients. The overall response rate (ORR) and the complete response (CR) rate among these patients were 91.1% and 57.9%, respectively. The response rates (ORR/CR rate) for each regimen were as follows; 91.4%/49.1% for R-CHOP or R-CHOP-like regimens, 93.5%/67.3% for cytarabine-containing regimens, and 96.2%/76.9% for bendamustine-rituximab (BR). With a median follow-up duration of 82.6 months, the median progression-free survival (PFS) was 40.6 months, and the median overall survival (OS) was 86.8 months (Figure). The median PFS was 35.2 months for R-CHOP or R-CHOP-like regimens, 65.8 months for cytarabine-containing regimens, and 57.9 months for BR. The role of upfront ASCT was evaluated in pts who are < 65 years old and achieved at least partial response (PR) to 1 st line treatment (n = 181). No significant differences were observed in baseline characteristics between patients who received upfront ASCT (n = 48) and those who did not (n = 133). There were no significant differences in PFS and OS between the ASCT and non-ASCT groups, with a 5-year PFS rate of 56.3% vs. 48.9% ( P = 0.190) and a 5-year OS rate of 82.1% vs. 76.1% ( P = 0.069), respectively. The role of maintenance treatment was evaluated in patients who achieved PR or better to 1 st line treatment and did not experience disease progression within 3 months after completion of 1 st line treatment (n = 293). A significantly higher proportion of patients in the non-maintenance group (n = 270) was classified as a high-risk group according to the MIPI score compared with those who received rituximab maintenance (n = 23) (20.3% vs. 0.0%, P = 0.043). Rituximab maintenance was associated with significantly better PFS and OS compared with no maintenance group, with a 5-year PFS rate of 67.7% vs. 42.0% ( P = 0.015) and 5-year OS rate of 88.4% vs. 66.7% ( P = 0.008). A total of 192 patients were treated with 2 nd line regimens. The most frequently administered 2 nd line regimen was cytarabine-based chemotherapy (n = 47, 24.5%), followed by ibrutinib (n = 46, 24.0%) and BR (n = 32, 16.7%). The ORR and the CR rate among these patients were 75.5% and 43.4%, respectively. The median 2 nd PFS was 16.8 months. Conclusion Our study demonstrated that the majority of patients with MCL in the Asia-Pacific region were treated with rituximab-based regimens in the contemporary era. However, R-CHOP or R-CHOP-like regimens are still the most commonly used 1 st line treatment. The rate of upfront ASCT and usage of rituximab maintenance was relatively low, and there was no significant difference in survival outcomes according to upfront ASCT. Although rituximab maintenance was associated with improved survival, patients without maintenance treatment had a higher proportion of high-risk patients in the current study. Our contemporary real-world analysis showed improved survival outcomes compared to previous studies.

Preclinical Studies Support the Clinical Development of LP-284 in Relapsed and Refractory B-Cell Lymphomas

Genomic instability, a hallmark of many cancers, often results from corrupted DNA damage response/repair (DDR) pathways. Targeting DDR deficiencies in cancer therapy has been successful in solid tumors with dysfunctional homologous recombination repair (HR). However, while less recognized, lymphomas also carry DDR defects such as HR deficiency (HRD) and can account for approximately 18% of all lymphomas. LP-284 is a fully synthetic DNA-damaging agent that induces double-stranded DNA breaks and displays elevated potency in cancer cells with HRD or transcription-coupled nucleotide excision repair defects, including multiple advanced B-cell lymphomas. In preclinical pharmacology studies, the mantle cell lymphoma (MCL) xenograft tumor mouse model derived from JeKo-1, which has mutated TP53 and checkpoint kinase 2 (CHEK2), an HRD score of 46, and was refractory to ibrutinib and bortezomib, showed near complete response after LP-284 treatment. It is noteworthy that 40~50% of MCL patients may be HRD due to the presence of mutations in the ataxia-telangiectasia mutated (ATM) gene. HRD is also likely to be prevalent in high-grade lymphomas, as IGH/MYC translocation or BCL2 expression has been reported to be associated with HR inhibition. Studies of LP-284 in the MYC/BCL2 dual-translocated OCILY1 tumor xenograft model have shown a robust efficacy profile with an average of 99% tumor growth inhibition. Key pharmacokinetic studies demonstrated that LP-284 is neither a substrate nor modulator of major CYP-450 enzymes, multi-drug resistance transporters, renal drug transporters, or hepatic drug transporters. Safety pharmacology studies indicated that LP-284 does not inhibit hERG potassium channel and has a low potential to affect cardiovascular functions. Toxicology repeat dose studies of LP-284 in Sprague Dawley rats and Beagle dogs, using intravenous infusion on Days 1, 8, and 15 in a 28-day cycle, were generally well tolerated with notable adverse effects in Beagle dogs consisting mainly of reversible hematologic toxicity and testicular toxicity. The highest non-severely toxic dose (HNSTD) in dogs was considered to be 0.4 mg/kg/dose. Overall, based on its impressive preclinical anti-tumor efficacy profile, low drug-drug interaction liability, and findings from toxicological studies, a Phase 1 study is currently planned with LP-284 to assess its safety, tolerability, pharmacokinetics, and clinical activity in patients with relapsed or refractory B-cell lymphoma. Clinical development will be informed by an emphasis on patient selection strategy based on DDR/HR biomarkers.

Predicted Functional Consequences of TP53 Alterations and Prognosis in TP53-Mutated Mantle Cell Lymphoma

Background: Mantle cell lymphoma (MCL) cases with TP53 mutations ( TP53mut) are associated with poor responses to chemoimmunotherapy (Eskelund Blood 2017). Across myeloid and solid tumors, predicted functional consequences and pathogenicity of specific TP53 mutations have been linked to differential patient outcomes (Pollock Breast Cancer Res Treat 2022, Yabe Cancers 2021). We aimed to characterize the impact of these features and associated molecular alterations on treatment outcome in TP53mut MCL patients treated with standard frontline regimens and on the ongoing phase 2 BOVEN trial. The BOVEN trial aims to assess the efficacy of frontline treatment with zanubrutinib, obinutuzumab, and venetoclax in TP53mut MCL (Kumar Blood 2021). Methods: The BOVEN trial enrolled 25 patients with TP53mut MCL. Retrospective chart review was performed for 22 patients with TP53mut MCL treated at frontline with standard chemoimmunotherapy regimens (Joffe Blood 2019). Tumor histology and FISH were obtained for each case. Mutational profiling (SNV/indels, CNA) was obtained prior to therapy with various CLIA-certified targeted sequencing platforms (Cheng J Mol Diagn 2015, Dias-Santagata EMBO Mol Med 2010). Mutations in TP53 were annotated using predicted phenotypes and pathogenicity from the TP53 Database (de Andrade Cell Death Differ 2022) and from phenotypic annotation of TP53 mutations (Giacomelli Nat Genet 2018). The primary outcome measures were overall and progression-free survival (OS/PFS). Results: Each patient included in the BOVEN cohort featured variants in TP53 with 26 SNV/indels across all 25 patients. There were 25 SNV/indels across all 22 patients treated with standard regimens. Within the trial cohort 14/25 cases had evidence of biallelic inactivation of TP53 with co-occurring SNV/indels in the gene and 17p loss by FISH or TP53 copy losses by SNParray; the comparator cohort featured 11/22 cases with biallelic losses. Across cohorts, most mutations were missense (>80% in both), with the majority occurring in the DNA binding domain of the p53 protein (76% and 91%, respectively), and with >30% at known hotspot codons in both cohorts. Most mutations (>70% in both cohorts) were predicted to adversely impact WT p53 function, including nonfunctional transactivation activity and dominant negative effect on the WT allele. The majority were also predicted to be highly pathogenic by bioinformatic methods (AGVGD, SIFT, PolyPhen2, PHANTM, REVEL, BayesDel). However, none of these features correlated with outcome. In the BOVEN cohort the variant allele frequency (VAF) of the TP53 SNV/indels approached significant association with poor PFS (HR 33.2, p=0.05) but not OS (HR 28.6, p=0.09). In contrast, in the comparator cohort TP53 VAF appeared to have an opposite effect direction, though this was not significant for PFS (HR 0.98, p=0.2) or OS (HR 0.97, p=0.06). We next investigated the impact of co-occurring molecular alterations on outcome. Besides TP53, the most frequently mutated genes in the trial cohort were KMT2D (24%), ATM (16%), NOTCH2 (12%), and CCND1 (12%). Alterations in these genes did not correlate with outcome. Within the comparator cohort the recurrently mutated genes were SMARCA4 (23%), ARID1A (18%), ARID1B (14%), ATM (14%), and CCND1 (14%). As described previously in this cohort (Joffe Blood 2019), alterations in SMARCA4 were associated with worse PFS (HR 4.2, p=0.02) but not OS (HR 2.2, p=0.27). Mutational burden (SNV and CNA load) was not prognostic in either 12/25 BOVEN samples sequenced with the same panel or the comparator cohort. There was no significant difference in outcome between patients with single mutations in TP53 vs. those with biallelic losses in TP53 in either cohort. Conclusion: Across patients with TP53mut MCL treated either with standard frontline chemoimmunotherapy or on the BOVEN trial, predictions of intrinsic pathogenicity and functional consequences of the TP53 alterations were not prognostic. The impact of TP53 mutation VAF remains unclear, with seemingly opposite effect directions between the two cohorts, though neither finding was significant. As previously described in the comparator cohort, alterations in SMARCA4 are associated with worse PFS in TP53mut MCL, though this was not observed in the BOVEN cohort. There were no significant differences in outcome among patients with biallelic inactivations in TP53 or with higher burdens of somatic alterations.

Efficacy and safety outcomes of single-agent ibrutinib therapy in chronic lymphocytic leukemia and relapsed/refractory mantle-cell lymphoma

Objectives: We aimed to evaluate patients using ibrutinib for the treatment of chronic lymphocytic leukemia (CLL) and relapsed/refractory mantle-cell lymphoma (MCL), focusing on high-risk subgroups, predictors of efficacy, response levels, and safety profile. Methods: This retrospective cohort study included adult patients diagnosed with CLL and relapsed/refractory MCL who were started on ibrutinib as a single-agent between May 2015 and December 2021 in Bursa Uludag University, Department of Hematology. Results: Of the 45 patients (23 CLL, 22 MCL) started on ibrutinib, the median age was 65 (range: 48-86) years, and 66.7% were male. Del(17p) was present in 47.8% of CLL patients; there was no remarkable difference between del(17p) status and the rates of achieving CR. The median follow-up with ibrutinib treatment in CLL patients was 13.3 (range: 0.3-77.8) months. In univariate analysis, progression-free survival (PFS) and overall survival (OS) were associated with the advanced Eastern Cooperative Oncology Group (ECOG) score (p = 0.003 and p = 0.004, respectively), and > 2 lines treatment regimens before ibrutinib (p = 0.016 and p = 0.050, respectively). In multivariate analysis, the ECOG performance status remained significant for OS. The median use of ibrutinib for MCL patients was 6 (range: 1-48) months, and the proportion of patients who achieved CR was 27.3%. In the univariate analysis of MCL patients, the ECOG performance status for PFS and OS was statistically significant (p = 0.045 and p = 0.016, respectively). Patients' most common non-hematological adverse events were pneumonia and urinary tract infection. Conclusions: Our investigation of patient outcomes treated outside clinical trials confirms ibrutinib's sufficient efficacy and safety profile in CLL and relapsed/refractory MCL.

Harnessing Btki Therapy By CDK4/6i Control of T Effector Memory Cells and T Cell Surveillance in Mantle Cell Lymphoma

Drug resistance remains a formidable challenge in mantle cell lymphoma (MCL). Cell cycle dysregulation driven by aberrant Cyclin D1 and CDK4 expression is a hallmark for MCL, providing a rationale for targeting the cell cycle in MCL therapy. We have demonstrated in preclinical studies that inhibition of CDK4/6 not only induces early G1 cell cycle arrest, but also reprograms MCL cells for cytotoxic killing. On this basis, we investigated if inhibition of cyclin D1/CDK4 with palbociclib (CDK4/6 inhibitor) could reprogram recurrent MCL to deepen and prolong the ibrutinib (BTK inhibitor) response in a phase I clinical trial, and the resistance mechanism by longitudinal genomic analysis of sequential samples from individual patients in the context of the clinical response. Palbociclib was administered to MCL patients on days 1-21 of a 28-day cycle; ibrutinib was given continuously. For longitudinal genomic analysis, sequential tissue and blood specimens from 27 evaluable MCL patients before and during therapy, and on progression were collected. Single cell RNA-seq (scRNA-seq) of PBMC or the monocytic fractions from bone marrow and lymph node (53 samples) was performed using a unique in house MCL cell-specific library. PBMC from normal donors (n=4) and untreated MCL patients (n=4) served as controls. The data were then subject to multiplex analysis with whole transcriptome sequencing and whole exome sequencing of MCL cells isolated from the same specimens, as well as flowcytometry in conjunction with IHC. Total numbers of MCL and immune cells in each specimen were deduced by integrating complete blood counts (CBC) with differential with scRNA-seq or flowcytometry. CDK4/6 Inhibition appears to deepen and prolong the BTKi response, with a CR rate of 42% and 5 patients (2 CR and 3 PR) remained on therapy for ~ 9 years. Longitudinal scRNA-seq (210,000 cells) revealed that MCL cells comprise 4 major transcriptomically distinct clusters. Cluster 1 (C1) resembles quiescent normal B cells; C2 mimics hyper-activated B cells that are enriched for signatures of BCR and cytokine signaling; C3 represents non-proliferating, long-lived MCL cells; and C4 is highly proliferative. RNA velocity analysis further indicates that having progressed to late G1 after evading CDK4/6 inhibition, MCL cells in C2 are in transit to C4. By contrast, C3 is a terminal node of MCL cells arrested in late G1 with elevated BCL2 expression Primary resistance and progression on therapy were associated with a marked expansion of either long-live non-proliferating C3 MCL cells, or C2 MCL cells that fuel the proliferating C4 MCL cells. Resistance was also associated with a profound reduction in MHC I and MHC II expression on MCL cells in some patients. Moreover, concurrent with disease progression, CD8+ T and CD+T cells were rapidly depleted by different mechanisms ( Figure 1). CD8+ T cells were proliferating and eliminated by exhaustion, as evidenced by the marked expression of LAG3 TIGIT and TIM3, and a failure to maintain CD8+ T effector memory cells. By contrast, CD4+ T cells were not proliferating and appeared die from glucose starvation. Collectively, these data suggest that T cell maintenance and surveillance is pivotal in sustaining a durable clinical response to combined inhibition of CDK4/6 and BTK. Guided by these discoveries, we have now restored BTKi sensitivity ex vivo in MCL cells from resistant patientsby targeting patient-specific expansion of C2 or C3 in vivo. In one resistant patient, this led to the maintenance of CD4+ and CD8+ T effector memory cells and a CR in response to venetoclax plus BTKi for nearly 3 years and continuing. In summary, by integrated longitudinal scRNA-seq analysis of a hypothesis-driven therapy, we have provided the first evidence that 1) MCL cells comprise 4 major transcriptomically distinct clusters; 2) resistance to CDK4/6i is associated with expansion of C2 that fuels the proliferating C4 MCL cells, or the long-lived C3 MCL cells with elevated BCL2 expression; 3) CDK4/6i harnesses BTKi response by promoting the maintenance of effector memory T cells; 4) combined inhibition of BCL2 and BTK overrides resistance to CDK4/6i and BTKi, leading to a durable clinical response; and 5) T cell surveillance is pivotal for a durable response to CDK4/6, BTK or BCL2 inhibition; implicating genome-guided combination therapy to overcome therapy resistance in MCL.

Inhibition of CDC20 Suppressed the Development and Progression of Mantle Cell Lymphoma

Background: Cell division cycle 20 homologue (CDC20) is an important factor regulating the cell mitosis phase. CDC20 is highly expressed in several types of cancers, which is related to the clinicopathological characteristics and prognosis of cancer patients. This study aimed to explore whether CDC20 could affect the development and progression of mantle cell lymphoma (MCL) and the underlying mechanism. Methods: The expression level of CDC20 was detected in peripheral blood mononuclear cells (PBMCs), bone marrow mononuclear cells (BMNCs) and pathological tissues of MCL patients and MCL cell lines (Z138, Mino, Rec1). The CDC20 inhibitor apcin was used to evaluate the effect of CDC20 on the cell phenotypes of MCL cells. The changes in cell proliferation, apoptosis, cell cycle, cell migration and invasion were determined using CCK-8, flow cytometry, and Transwell assays, respectively. The anti-tumor effect of apcin were investigated in vivo in the Z138-driven xenograft tumor model. RNA-seq was performed to explore the pathways that changed in MCL cells after apcin treatment, and then these possible changes were verified in vitro and in vivo by western blot. Results: CDC20 was overexpressed in PBMCs, BMNCs, and pathological tissues of MCL patients and MCL cells compared with their respective control group. In Z138, Mino, and Rec1 cells, apcin could inhibit cell proliferation, migration, and invasion, promote cell apoptosis, and induce cell cycle arrest. Moreover, apcin confirmed its safety and anti-tumor activity in vivo. In apcin-treated MCL cells and mice, the PI3K/AKT pathway was significantly inhibited (Figure 1). Conclusions: This study confirms the essential role of CDC20 in MCL tumorigenesis. Anti-tumor therapy targeting CDC20 is expected to be a powerful treatment strategy for MCL patients.

Trial-in-Progress: A Phase 1/2 Multi-Center Study of Onct-808, a ROR1-Specific CAR T, in Adult Patients with Relapsed/Refractory Aggressive B Cell Lymphoma

BACKGROUND: The therapeutic landscape for B-cell lymphomas (BCL) leverages several modalities, including chemotherapy, targeted agents, adoptive cell therapy, and immunotherapy. While these approaches have shown clinical benefit, challenges remain, such as variable response rates, treatment resistance, and toxicities. ROR1-specific CAR T-cell therapy represents a promising potential advancement in the treatment of aggressive BCL in patients (pts) who have failed previous CD19 CAR T therapy. ROR1-targeted CAR T therapy offers several advantages that could address these challenges. By directing CAR T cells to specifically recognize and eliminate ROR1-expressing tumor cells, it offers a highly targeted approach with the potential for enhanced efficacy. Moreover, ROR1 is often highly expressed on aggressive BCL, making it a suitable therapeutic target. This focused approach may help overcome the limitations associated with current treatments and improve response rates. After birth ROR1 is predominantly expressed on malignant cells; therefore, this selective expression pattern may reduce the risk of toxicities, including off-tumor target elimination and non-specific activation of immune cells. The development of ROR1-specific CAR T holds promise in enhancing the treatment outcomes for patients with aggressive BCL. With targeted action and potential to reduce toxicity, ROR1-specific CAR T cell therapy offers an innovative and novel strategy for improving patient outcomes in BCL. The ROR1 binding moiety for ONCT-808 is derived from zilovertamab. Zilovertamab vedotin showed preliminary evidence of efficacy and no evidence of on-target off-tumor toxicity in patients with advanced B cell malignancies (Wang 2022). METHODS: This is a Phase 1/2, single-arm, open-label, multi-center trial to evaluate the safety and efficacy of ONCT-808 in pts with aggressive BCL, including large B-cell lymphoma (LBCL) and mantle cell lymphoma (MCL) with no approved therapy available. The study comprises two distinct phases: Phase 1 for dose escalation followed by Phase 2 for dose expansion. In Phase 1, a standard 3+3 dose escalation design will be used with 3 provisional dose levels and expected sample size of up to 18 patients. Subjects will receive a conditioning regimen of intravenous (IV) cyclophosphamide and fludarabine, followed by ONCT-808 IV infusion. The dose of ONCT-808 will be sequentially escalated to determine the recommended Phase 2 dose (RP2D) for LBCL and MCL cohorts. Bridging therapy is permitted if clinically indicated. Phase 2 will enroll LBCL and MCL patients into separate dose expansion cohorts at the RP2D determined in Phase 1. ONCT-808 will be administered as a single IV infusion of autologous CAR T cells. The primary outcomes include assessing the incidence, severity, and relationship of Dose Limiting Toxicities (DLT), Treatment Emergent Adverse Events (TEAE), and RP2D selection of ONCT-808. Secondary outcomes include evaluating the Overall Response Rate (ORR), Complete Response (CR) rate, Duration of Response (DOR), pharmacokinetics of ONCT-808, expansion, persistence of ROR1 CAR-positive T cells, overall safety and tolerability. Key inclusion criteria include histologically confirmed aggressive B-cell NHL, measurable lesions per Lugano criteria (Cheson, 2014), and relapsed/refractory (R/R) disease without available therapy (must be previously treated with systemic therapy, progressed after or ineligible for autologous HSCT, and received prior approved anti-CD19 CAR-T at least 6 months prior to enrollment unless refused/ineligible). Key exclusion criteria include previous ROR1-targeted therapy, ongoing immunosuppression, and CNS involvement. The trial is currently active and patients have been treated in the phase 1 dose escalation. Clinical Trial Identifier: NCT05588440

Pirtobrutinib, a Non-Covalent (reversible) BTK Inhibitor, in Mantle Cell Lymphoma Patients Previously Treated with a Covalent BTK Inhibitor: Results from a China Phase 2 Study

Background Pirtobrutinib, a highly selective, non-covalent (reversible) Bruton tyrosine kinase inhibitor (BTKi), inhibits both wildtype and C481-mutant BTK and has favorable oral pharmacology that enables continuous BTK inhibition throughout the dosing interval regardless of protein turnover, and shows promising efficacy and favorable safety profile in patients with pre-treated B-cell malignancies including a covalent BTKi (cBTKi). This study (NCT04849416) was a China only phase 2, open-label, multi-center trial aiming to evaluate the safety and efficacy of oral pirtobrutinib as a monotherapy for patients with B-cell malignancies. This abstract summarizes the findings on the efficacy in a cBTKi pre-treated mantle cell lymphoma (MCL) population and safety outcomes among all enrolled patients. Methods Eligible Chinese patients with relapsed/refractory B-cell malignancies were enrolled and assigned to one of three cohorts based on tumor histology and prior treatment history. All enrolled patients received pirtobrutinib monotherapy at a daily dose of 200 mg, until disease progression (PD), unacceptable side effects, or other reasons for discontinuation. The primary analysis set (PAS) comprised patients with centrally confirmed non-blastoid MCL, who received a prior cBTKi, and with measurable lesion(s) at baseline. The efficacy analysis set (EAS) was extended into all MCL patients treated with a prior cBTKi. The safety population included all patients who received at least one dose of pirtobrutinib. The primary objective was to evaluate the effectiveness by assessing the overall response rate (ORR) based on Lugano criteria and was conducted by an independent review committee (IRC). Secondary objectives included duration of response (DOR), progression-free survival (PFS), overall survival (OS) and safety profile. Results As of April 10, 2023, of 39 enrolled MCL patients, 28 were in the PAS and 35 were in the EAS for efficacy analysis. The safety analysis included a total of 87 enrolled patients and the median duration of therapy was 4.2 months. In the PAS population (N=28) with cBTKi pre-treated non-blastoid MCL, patients had a median of 3.0 prior lines of therapy (range, 1-8). The majority received prior chemotherapy (96.4%) and an anti-CD20 antibody (85.7%). The most common reason for discontinuation from the prior cBTKi was PD (85.7%). The IRC-assessed ORR was 71.4% (95% CI, 51.3-86.8), with 4 patients (14.3%) achieving complete responses (CR) and 16 patients (57.1%) achieving partial responses (PR). The median DOR assessed by IRC was not reached at the cut-off date with a 6-month DOR rate of 66.02% (95% CI, 39.29-83.14). The median IRC-assessed PFS was 9.43 months (95% CI: 5.32-not evaluable [NE]), and the median OS was 15.47 months (95% CI, 8.67-NE). The EAS (N=35), demonstrated similar efficacy results with IRC-assessed ORR 62.9% (95% CI, 44.9-78.5) and the 6-month DOR rate was 64.45%. In the safety population (N=87) of all enrolled B-cell malignancy patients, common treatment-emergent adverse events (TEAEs) of any grade included decreased neutrophil count (40.2%*), anemia (31%), and increased bilirubin (23.0%, with 2.3% grade ≥3 and none led to dose modification). The most frequent grade ≥3 TEAE was decreased neutrophil count (25.3%*). All grade hemorrhage was observed in 19.5% patient (n=17, with 2.3% grade ≥3), while all grade hypertension was 5.7% (n=5, with 2.3% grade ≥3), and no patient developed atrial fibrillation/flutter. Three patients (3.4%) stopped treatment due to treatment-related TEAEs, and 2 patients (2.3%) experienced treatment related fatal TEAEs (one infection and one patient with reported tumor lysis syndrome, tumor necrosis, and hemorrhage). Conclusion Pirtobrutinib demonstrated clinically meaningful and durable antitumor activity in a cBTKi pre-treated MCL Chinese population and showed a well-tolerated safety profile in patients with B-cell malignancies. * Aggregate of neutropenia and neutrophil count decreased

A Multicenter Phase 2 Trial of Zanubrutinib, Obinutuzumab, and Venetoclax (BOVen) in Patients with Treatment-Naïve, TP53-Mutant Mantle Cell Lymphoma

Background: TP53-mutant mantle cell lymphoma (MCL) is associated with poor survival outcomes with chemoimmunotherapy (Eskelund, Blood 2017) with median progression-free survival (PFS) of 0.9 years and median overall survival (OS) of 1.8 years. There is no standard frontline treatment for this high-risk subset. The combination of Bruton's tyrosine kinase (BTK) inhibition and BCL2 inhibition were synergistic and active in relapsed, refractory MCL, including in patients with TP53 mutation (Tam, NEJM 2018). Obinutuzumab, ibrutinib, and venetoclax were well tolerated and efficacious in relapsed and untreated MCL patients (Le Gouill, Blood 2021). We hypothesized that treatment with zanubrutinib (Zanu), Obinutuzumab (Obin), and venetoclax (Ven) (BOVen) would be well-tolerated and efficacious in untreated TP53-mutant MCL. Methods:In this multicenter, investigator-initiated phase 2 trial (NCT03824483), eligible patients had previously untreated MCL with TP53 mutation (of any variant allele frequency) and ECOG PS ≤2, ANC >1, PLT >75, HGB ≥9 (unless if due to MCL). BOVen is administered in 28-day cycles: Zanu 160 mg PO BID starting D1; Obin 1000 mg IV D1 or split D1-2, 8, 15 of C1, D1 of C2-8; Ven ramp up initiated C3D1 (target 400 mg QD). Treatment duration is 2 years at minimum and the primary endpoint is 2-year PFS. Response was assessed using Lugano criteria (Cheson, JCO 2014). PFS and OS were estimated using the Kaplan-Meier method. Peripheral blood minimal residual disease (PB-MRD) assessment was performed using the Adaptive clonoSEQ ® assay. After 24 cycles, Zanu and Ven can be discontinued if MRD undetectable (<10 -6) complete remission (CR) is achieved. With subsequent PB-MRD monitoring, patients can be retreated if clinical progression or MRD detectability (>10 -6). Adverse events (AE) were assessed per CTCAE v5. Results: All 25 planned patients have been enrolled (May 15, 2023 data cut). The median age on study was 65 years (range 29 - 82); 76% were male (19/25); various histologic subtypes were included (15 conventional MCL, 5 non-nodal leukemic, and 5 blastoid variant); 100% stage IV (25/25); by MIPI: 68% high risk (17/25), 28% intermediate (7/25), and 4% low risk MIPI score (1/25); 67% Ki67 ≥30% (14/21); 33% Ki67≥50% (7/21); 100% TP53 mutation, and 48% 17p deletion (12/25). Treatment was overall well-tolerated. The most common treatment-related AEs (≥20%) were predominantly low-grade and manageable, including diarrhea (52%), neutropenia (28%), infusion-related reaction (24%), bruising (20%), COVID-19 infection (20%), nausea (20%), thrombocytopenia (20%), and rash (20%). The grade 3 or higher treatment-related AEs were neutropenia (12%), infusion-related reaction (8%), COVID-19 (8%), diarrhea (4%), transaminitis (4%), thrombocytopenia without bleeding (4%), and rash (4%). Detailed toxicity data will be presented in future. Median follow-up was 16.1 months. There were 5 progressions and 4 deaths on study (2 COVID-related, 1 post-operative aspiration pneumonia, 1 unknown cause), see Figure 1. All deaths occurred in patients who were in ongoing response at time of death. The best overall response rate was 95% (24/25) with 88% (22/25) achieving a CR. At C3 post Zanu-Obin, 68% (n=17/25) achieved PET-CR and post cycle 3, 5 patients converted to a PET-CR (Figure 1). The 1-year PFS and overall survival (OS) were 84% (95% CI: 71%, 100%) and 96% (95% CI: 89%, 100), respectively. The 16-month PFS and OS were 75% (95% CI: 60%, 95%) and 87% (95% CI: 75%, 100%), respectively. The 16-month PFS and OS for patients less than 65 years of age (n=9) were both 100%. Seven patients completed 24 treatment cycles. Of these, 71% (5/7 pts) were in CR and MRD undetectable (treatment discontinued) and 29% (2/7 pts) were in CR and MRD detectable (continued treatment). Outcomes post C24 will be presented in future. At 10 -6 MRD sensitivity level, 7 (28%) of 23 patients had undetectable MRD at C3 and 16 (100%) of 16 patients at C13. Conclusions:BOVen is a well-tolerated, outpatient regimen associated with high response rates and high rates of undetectable MRD in untreated TP53-mutant MCL. The early PFS and OS estimates with BOVen compare favorably with historical outcomes of chemoimmunotherapy in this high-risk subset of MCL. Based on this data, BOVen emerges as a promising treatment option for TP53-mutant MCL and, therefore, the study was expanded to include an additional 25 (total 50) TP53-mutant MCL patients.

Zr Study: A Prospective Phase II Study of Zanubrutinib-Rituximab Chemo-Free Therapy with or without Autologous Stem Cell Transplantation in Newly Diagnosed Mantle Cell Lymphoma

Background:Mantle cell lymphoma (MCL) is an incurable B-cell lymphoma with heterogeneous clinical presentation. Frontline intensive chemoimmunotherapy induction with or without autologous stem cell transplantation (ASCT) as consolidation is recommended. However, this approach has the tendency to increase short- and long-term toxicities. Window-1 study demonstrated upfront use of ibrutinib-rituximab induction allowed minimization of chemotherapy exposure, thereby reducing adverse events. Based on favorable response rate and superior safety of zanubrutinib in relapsed/refractory (R/R) MCL patients, combination of zanubrutinib plus rituximab (ZR) might obviate the need for chemotherapy in newly diagnosed MCL patients. Aims:This study aimed to analyze the efficacy and safety of ZR chemo-free therapy with or without ASCT in newly diagnosed MCL patients. Methods:Patients with newly diagnosed MCL were enrolled in this prospective, open-label phase II study (NCT05504603). Patients received oral zanubrutinib(160 mg twice daily) and rituximab (375 mg/m 2 weekly for cycle 1 and then on day 1 of cycles 2-5, 4 weeks per cycle) as induction therapy. Then, patients who achieved complete remission (CR) or partial remission (PR) were followed by zanubrutinib maintenance for elderly (age >70y) or unfit patients until intolerable toxicities or relapsed, while ASCT was given to younger (age ≤70y) and fit patients. The primary endpoints were overall response rate (ORR) and complete response rate (CRR) at the end of cycle 3, cycle 5 and ASCT. The secondary endpoints were 2-year overall survival (OS), 2-year progression free survival (PFS) and safety profiles. Results: Twenty-six patients with a median age of 62 years were enrolled. The majority of patients had intermediate-risk international prognostic index and stage III/IV disease. Next-generation sequencing was performed in 21 patients to detect genetic mutations including ATM (n=9, 42.9%) and TP53 (n=3, 14.3%) mutations. 21 patients completed at least 3 cycles of ZR with 19 patients achieved CR, 1 got PR and 1 got stable disease who was then taken off this trial. The ORR and CRR for a 3-cycle response were 95.5% and 90.9%, respectively. 17 patients completed the planned 5-cycle treatment with 5 patients proceeding to ASCT. Among the 17 patients, all patients achieved CR with 10 patients (58.8%) achieved minimal residue disease negative. Within a median follow-up of 18.7 months, the 2-year OS and PFS were both 100%, and the median OS and PFS were undefined. During the whole treatment, 5 cases experienced transient alanine transaminase elevation, oral mucositis and hematological toxicities, 4 cases showed pyrexia, 2 cases occurred infusion-related response, and 1 case occurred COVID-19-related pneumonia. All toxicities were transient and reversible. No atrial fibrillation and bleeding were observed. Conclusions: This study demonstrates a favorable efficacy and tolerable safety of chemo-free regimen ZR in newly diagnosed MCL patients and expands therapeutic options for newly diagnosed MCL. Keywords: Mantle cell lymphoma; Zanubrutinib; Rituximab; Autologous stem cell transplantation; Therapy.

Phase II Trial of Ibrutinib in Previously Untreated High-Risk Smoldering Mantle Cell Lymphoma

Background: Mantle cell lymphoma (MCL) patients usually require immediate therapy, however about 20% of newly diagnosed MCL patients can be initially observed. A subgroup of patients who are suitable for initial observation but exhibit high-risk features are of particular concern as they have a propensity to progress. We consider these patients as high-risk smoldering MCL (defined below). Generally, these patients are observed without systemic therapy for 18-24 months. We investigated the impact of single-agent ibrutinib on time to progression for these patients who would otherwise be observed. Methods: This is a single center, single arm, investigator-initiated phase 2 clinical trial (NCT03282396). High-risk smoldering MCL included one or more of the following criteria: non-blastoid/pleomorphic variant, Ki-67 of 15-30%, white blood cell count of 15-30 x 10^9/L, lymph nodes ≤5 cm, TP53 mutated or wild type, del17p, MYC positive, complex karyotype, presence of KMT2D, BIRC3, or ≥1 other somatic mutations, and were asymptomatic without any clinical indication to start systemic therapy. Major exclusion criteria included significant disease-related symptoms, blastoid/pleomorphic variants, Ki-67 >30%, bulky tumors >5 cm. Patients received ibrutinib 560 mg P.O. daily in 28-day cycles and continued until progression, transformation, drug intolerance, or up to 5 years. The primary endpoint was progression-free survival (PFS). Secondary endpoints were safety, response rate, and duration of response (DOR). Response was measured using the Lugano criteria. It is expected that the current trial will achieve a median PFS time of about 18 months, which would be an improvement over PFS reported on high-risk patients under a watch and wait approach. The median follow-up time was 23.4 months. Results: Twenty patients were enrolled (Table 1). The median age was 60.5 years (range 38-79). Most were male (n=15/20). At baseline, 13 patients (65%) had bone marrow involvement and 15 patients (75%) had gastrointestinal tract involvement. Seven patients (35%) had TP53 alterations. One patient was not evaluable for response due cessation of therapy after less than 1 cycle due to new onset atrial fibrillation. Among 19 evaluable patients, the best overall response rate was 94.7% (n=18/19). Of those who had a positive PET at baseline and were evaluable for PET response, 92.9% (n=13/14) achieved a PET complete response (CR). Of those with bone marrow involvement at baseline, 30.7% (n=4/13) achieved CR by flow cytometry. Of those with baseline gastrointestinal tract involvement, 33.3% (n=5/15) achieved histologically confirmed CR. The median number of cycles received was 16 (range 0-32). The median PFS and DOR were not reached. Seven patients discontinued therapy: atrial fibrillation (n=3), progressive disease (n=1), infection (n=1), lung cancer (n=1). The most frequent grade 3 toxicities were diarrhea (n=2, 10%), atrial fibrillation (n=1, 5%), infection (n=1, 5%), mucositis (n=1, 5%), and syncope (n=1, 5%). No grade 4 toxicities occurred. No deaths on study occurred. Conclusions: Ibrutinib demonstrated significant efficacy with manageable toxicities in previously untreated patients with high-risk smoldering MCL.

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.

Potentiation of apoptosis in drug-resistant mantle cell lymphoma cells by MCL-1 inhibitor involves downregulation of inhibitor of apoptosis proteins

Bruton’s tyrosine kinase inhibitors (BTKi) and CAR T-cell therapy have demonstrated tremendous clinical benefits in mantle cell lymphoma (MCL) patients, but intrinsic or acquired resistance inevitably develops. In this study, we assessed the efficacy of the highly potent and selective MCL-1 inhibitor AZD5991 in various therapy-resistant MCL cell models. AZD5991 markedly induced apoptosis in these cells. In addition to liberating BAK from the antiapoptotic MCL-1/BAK complex for the subsequent apoptosis cascade, AZD5991 downregulated inhibitor of apoptosis proteins (IAPs) through a BAK-dependent mechanism to amplify the apoptotic signal. The combination of AZD5991 with venetoclax enhanced apoptosis and reduced mitochondrial oxygen consumption capacity in MCL cell lines irrespective of their BTKi or venetoclax sensitivity. This combination also dramatically inhibited tumor growth and prolonged mouse survival in two aggressive MCL patient-derived xenograft models. Mechanistically, the augmented cell lethality was accompanied by the synergistic suppression of IAPs. Supporting this notion, the IAP antagonist BV6 induced dramatic apoptosis in resistant MCL cells and sensitized the resistant MCL cells to venetoclax. Our study uncovered another unique route for MCL-1 inhibitor to trigger apoptosis, implying that the pro-apoptotic combination of IAP antagonists and apoptosis inducers could be further exploited for MCL patients with multiple therapeutic resistance.

Real-World Incidence, Characteristics and Management of Cytokine Release Syndrome Induced By Chimeric Antigen Receptor T-Cell Therapy across Hematologic Malignancies

Background: Cytokine release syndrome (CRS) is a potentially life-threatening, supraphysiologic response following immunotherapy resulting in the activation or engagement of endogenous or infused T cells and/or other immune effector cells. CRS occurs with varying frequency and severity, depending on the underlying disease and immunotherapy used, such as chimeric antigen receptor T-cell (CAR-T) therapy or off-the-shelf T-cell engaging bispecific antibodies. Limited research exists on the diagnosis and management of CRS in the real world. This study describes the real-world incidence, severity and clinical management of CRS induced by commercially available CAR-T therapies for diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), mantle cell lymphoma (MCL) and multiple myeloma (MM). Methods: Real-world data (RWD) were obtained from the Flatiron Health, US, nationwide electronic health record (EHR)-derived, de-identified database of cancer patients within a network comprised primarily of community cancer practices. The Flatiron Health network also includes practices designated as academic sites by the National Cancer Institute; however, relative proportions of community/academic practices may vary depending on the study cohort. Data as of August 31, 2022, on CAR-T therapy, clinical characteristics and disease outcomes specific to CAR-T therapy, as well as CRS and its clinical management, were abstracted from unstructured documents in EHRs (in addition to routinely available structured data), in a cohort of patients receiving commercial CAR-T therapy. Specifically, data for CRS including treatments and resolution were abstracted based on explicit mention of and attribution to CRS in charts. Results: Table 1 summarizes data by indication. Incidence of CRS ranged from 56% (104/185) in DLBCL to 72% (66/92) in MCL. Excluding categories with small numbers of cases (<15), CRS incidence also varied by individual CAR-T therapy and underlying indication and ranged from 35% for idecabtagene vicleucel in MM to 73% for brexucabtagene autoleucel in MCL. Highest incidence of Grade ≥2 CRS was observed among MCL patients, whereas Grade ≥3 CRS was most commonly observed among FL patients. Time to onset of CRS ranged from 0 to 16 days, with median onset between 3-4 days among lymphoma patients and earlier median onset of 1 day for MM patients. Median time to CRS resolution ranged from 2 to 6 days across indications. While 81-95% of patients received CAR-T therapy at an academic center, 5-14% received CAR-T therapy at a community center. Tocilizumab and corticosteroids were the most commonly used treatments for CRS, including 37-48% use of tocilizumab for Grade 1 CRS (Table 2). Discussion: This study uniquely summarizes RWD on CRS following the use of commercially available CAR-T therapies across multiple hematologic malignancies, based on information from clinical notes abstracted retrospectively from EHRs. Consistent with the timing of approval of commercially available CAR-T therapies, the sample size for MM was limited compared with other malignancies. Safety events are typically under-reported in RWD sources, specifically for CRS when relying on information documented in patients' EHRs, compared with other published literature. In accordance with other RWD on CRS, grading criteria for CRS as well as vasopressor and oxygen use were not consistently reported in patients' EHRs. CAR-T treatments were predominantly administered in academic centers. Limited use in community practices was also observed; however, further information to accurately characterize the size and capabilities of community centers was not available in this database. Data also showed considerable use of tocilizumab to treat low-grade CRS, suggesting the need for additional evidence on its role to treat CRS beyond its current regulatory approval. Increased evidence generation, specifically from usual clinical practice, can contribute to increased awareness and knowledge about CRS diagnosis and management, and in turn realize the maximum potential of T-cell therapeutics.

Pirtobrutinib in Relapsed/Refractory (R/R) Mantle Cell Lymphoma (MCL) Patients with Prior cBTKi: Safety and Efficacy Including High-Risk Subgroup Analyses from the Phase 1/2 BRUIN Study

Background: Despite the efficacy of covalent (c) Bruton tyrosine kinase inhibitors (BTKi) in R/R MCL, disease relapse arises through evolution of resistance mechanisms or development of cBTKi intolerance. Pirtobrutinib, a highly selective, non-covalent (reversible) BTKi has favorable oral pharmacology that enables continuous BTK inhibition throughout the daily dosing interval regardless of the intrinsic rate of BTK turnover. Pirtobrutinib is the first BTKi to demonstrate durable efficacy following prior cBTKi therapy in heavily pre-treated R/R MCL and was well-tolerated with a low frequency of treatment discontinuation due to toxicity (Wang et al., JCO, 2023). Pirtobrutinib is approved in the USA to treat relapsed or refractory MCL after at least two lines of systemic therapy including a prior cBTKi. Here, we report updated results of pirtobrutinib therapy in all patients (pts), including those with biologically high-risk R/R MCL with a median survival follow-up of 24.2 months (range, 18.2-29.8). Methods: Pts with R/R MCL received pirtobrutinib monotherapy in the multicenter Phase 1/2 BRUIN trial (NCT03740529). Efficacy was assessed in all cBTKi pre-treated pts, as well as in cBTKi treatment-naïve pts. Key endpoints included overall response rate (ORR) as assessed by independent review committee per Lugano 2014 criteria, duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety. Pts were included across the dose escalation range and expansion (25-300 mg/day) with 93% (n=141) receiving at least one dose of 200 mg/day, the FDA-approved dose. A data cut of 05 May 2023 was utilized. Results: Among all 152 pts with R/R MCL who received a prior cBTKi, the median age was 70 years (range, 46-88), and 52% had intermediate-risk and 28.3% had high-risk sMIPI scores. Median prior lines of therapy were 3 (range, 1-9), including an anti-CD20 antibody (96.7%), chemotherapy (90.1%), immunomodulator (17.1%), stem cell transplant (21.7%), BCL-2 inhibitor (15.8%), CAR-T cell therapy (8.6%), and PI3K inhibitor (3.9%). Among pts with high-risk biomarker data available, 30/60 (50%) had TP53 mutations and 45/63 (71%) had a Ki-67 index of ≥30%. The ORR for cBTKi pre-treated pts was 49.3% (95% CI, 41.1-57.6), including 15.8% complete responses (n=24) and 33.6% partial responses (n=51), whilst cBTKi naïve pts (n=14) had an ORR of 85.7% (95% CI, 57.2-98.2). The ORR among 128 pts who had discontinued a prior cBTKi due to PD and 21 pts who had discontinued for toxicity/other reasons was 43.0% and 90.5%, respectively. Among the 75 responding cBTKi pre-treated pts, the median DOR was 21.6 months (95% CI, 9.2-27.2) at a median follow-up of 24 months. The 18- and 24-month DOR rates were 51.9% (95% CI, 37-64.8) and 38.9% (95% CI, 22.7-54.8), respectively. ORR and DOR by high-risk subgroups (including blastoid/pleomorphic variants, Ki-67 index ≥30%, and TP53 mutations) are shown in Table 1. The 18- and 24-month DOR rates among 12 responding cBTKi naïve pts were both 90.0% (95% CI, 47.3-98.5). The median PFS and OS for cBTKi pre-treated pts was 5.6 months (95% CI, 5.3-9.2), and 23.5 months (95% CI, 17.1-NE), respectively. In the MCL cohort (n=166), the most frequent treatment-emergent adverse events (TEAEs) were fatigue (31.9%), diarrhea (22.3%), and dyspnea (17.5%). The most common Grade ≥3 TEAE was neutropenia/neutrophil count decreased (13.3%) and the rate of Grade ≥3 infections was (19.9%). Grade ≥3 hemorrhage/hematoma (2.4%) and all-grade atrial fibrillation/flutter (3.6%) were infrequent. Overall, 8 pts (5%) had treatment-related AEs leading to dose reductions and 5 (3%) had treatment-related AEs leading to pirtobrutinib discontinuation. Conclusion: Pirtobrutinib continues to demonstrate durable efficacy and a favorable safety profile in heavily pre-treated R/R MCL pts with prior cBTKi therapy. High ORRs were observed in pts who had PD on a prior cBTKi, and in pts with high-risk disease features including blastoid/pleomorphic variants, elevated Ki-67 index, and TP53 mutations.

Obinutuzumab Versus Rituximab in Transplant Eligible Untreated MCL Patients, a Matching Comparison between the Lyma and Lyma-101 Trials

Aim: Obinutuzumab (O) and Rituximab (R) have never been compared in a prospective randomized trial in mantle cell lymphoma (MCL). The LYMA-101 trial (NCT02896582) investigated the Obinutuzumab-DHAP (O-DHAP) regimen followed by autologous stem cell transplant (O-BEAM, ASCT) plus O maintenance (OM) in transplant eligible patients <66y with untreated MCL (Le Gouill et al, Lancet Hem 2020). The LYMA trial (NCT00921414) used the same regimen with Rituximab instead of Obinutuzumab (Le Gouill et al, NEJM 2017). Herein, we report the long-term outcome of patients enrolled in the LYMA-101 trial and used a propensity score matching (PSM) approach to allow a comparison with patients treated in the LYMA trial (i.e. O versus R group matched comparison). Method: LYMA (n=299 pts, of whom 120 received R Maintenance, RM) is a phase III prospective trial with a median follow-up of 7.5 years (7.4-7.7) from inclusion (Sarkozy et al, ASCO 2023) that randomized, after ASCT, 240 pts between observation and RM. LYMA-101 (n=86) is a prospective single arm phase 2 trial with a median FU of 5.1y (5-5.25) at the time of the present analysis. We first compared minimal residual disease (MRD) at end of induction (EOI), assessed in both trial with quantitative PCR of clonal immunoglobulin gene and used PSM based on clinical characteristics at inclusion (Sex, Ann Arbor stage, MIPI score, B symptoms, blastoid variant, bulky disease) to balance patients' discrepancies between LYMA-101 and LYMA. To compare PFS and OS from inclusion of patients treated with R versus O based regimen, half of the non-randomized LYMA patients (29 out of 58) were randomly reattributed to the RM arm to create an intention to treat RM (RM-ITT) arm including 149 pts (29 non-randomized and 120 randomized) subsequently matched with the 86 LYMA-101 pts. Balance between populations was checked using standardized mean differences (SMD). Results: Eighty-five LYMA-101 pts received the first course of O-DHAP (1 withdrew consent before treatment), 81 (95.3%) completed the 4 cycles and 73 (85.9%) underwent ASCT followed by OM in 69 (81.2%). The estimated 5y PFS and OS since inclusion were 83.4% (95%CI: 73.5-89.8%) and 86.9% (95%CI: 77.6-92.5%) respectively. At EOI, ORR were similar in both studies (89.6% versus 91.8% in LYMA versus LYMA-101 respectively), but within responders, pts treated in LYMA-101 (O-DHAP) had a more frequent MRD negativity than pts treated in LYMA (R-DHAP) both in bone marrow (BM, 82.1% versus 65.3% MRD negativity in O vs R group, Chi2 p=0.011) and blood (95.5% versus 79.2% of MRD negativity in O vs R group, Chi2 p=0.002). These results were confirmed using the propensity score matched populations, with a more frequent MRD negativity in the O versus R group in BM (82.1% vs 63.4%, Chi-2, p=0.01) and blood (95.5% vs 72.9%, Chi-2, p<0.001). To compare PFS and OS since induction, a PSM was performed using the 149 patients treated in the R-group with an RM-ITT and the 85 patients in the O group, resulting in 2 sets of 82 patients with comparable characteristics at inclusion. From treatment initiation, patients treated with O presented a prolonged PFS (p=0.029, figure 1A) and OS (p=0.039, figure 1B) compared to those treated with R, with an estimated 5-year PFS of 82.8% versus 66.6% (HR 1.99, IC95 1.05-3.76) and OS of 86.4% versus 71.4% (HR 2.08, IC95 1.01-4.16) with O and R based regimen respectively. Finally, 37/120 (30.8%) patients in LYMA and 23/69 (33.3%) in LYMA-101 prematurely stopped R and OM respectively (with a similar mean maintenance duration of 29 and 29.4m with R and OM respectively). Reason for maintenance discontinuation were adverse events in 15 cases in R group (12.5% of the population) versus 14 cases in O group (20% of the population), progression or death in 10 (8.3%) versus 3 (4.3%) cases in the R versus O group respectively. Causes of death were comparable in O and R groups, the most common being lymphoma (42% in O and 53% in R group). Infectious deaths in the O group (N=3) were all COVID related (3/12 deaths, 25%), whereas in the R group (LYMA being conducted before the pandemic), 8 deaths were related to infection (8/97 deaths, 8%, including 1 infectious death out of 22 deaths during RM, 5%). Conclusion: O-DHAP followed by OM post ASCT provide prolonged PFS and OS in young patients with MCL. O-based therapy in MCL induce deeper response with increased MRD negativity and seems to outperform R-based therapy in term of PFS and OS, without any significant excess of toxicity.

Validation of POD24 As a Robust Early Clinical End Point of Poor Survival in Mantle Cell Lymphoma from 1280 Patients on Clinical Trials

Background The prognosis of mantle cell lymphoma (MCL) has largely improved in the past decade; however, the disease is characterized by a heterogeneous clinical course. Several retrospective studies identified early progression of disease (i.e. within two years, POD24) as a potential overall survival (OS) surrogate, but this has not been validated in cohorts of patients prospectively included in clinical trials in rituximab maintenance era. Methods We performed a pooled analysis of French patients with MCL included in six randomized clinical trials (EU-MCL younger NCT00209222, LyMA NCT00921414, LyMA101 NCT02896582, EU-MCL elderly NCT00209209, MCL-R2 NCT01865110 and RiBVD NCT01457144). Survival analysis using Landmark approach evaluated the association of POD24 status with post-event OS for all patients: starting from POD24 event or two years for patients without POD24 event. Logistic regression models were used to evaluate the association between POD24 status and (1) clinico-biological factors at diagnosis; (2) autologous stem cell transplantation at end-of-induction (ASCT) and anti-CD20 maintenance (RM) in responding patients after induction only. Results Among 1386 MCL patients, 106 censored for clinical follow-up before 24 months were excluded from the analysis, leading to 1280 patients evaluable for POD24 status: 299 with a POD24 event and 981 without. The 299 (23%) patients with a POD24 event had a post-event median OS of 9.3 months (95% CI 8.4-11.8) versus not reached in patients without POD24 event (95% CI 97.8-NR). Within the 981 non-POD24 patients, 314 presented a late relapse with a post-relapse median OS of 49.4 months (95% CI 30.4-56.8), significantly longer than OS of POD24 patients (HR=0.39; 95%CI 0.31-0.48; p<0.001). Compared to patients without a POD24 event, POD24 patients were older, had more frequently a performance status >1, elevated LDH and higher leucocytes leading to higher MIPI scores (high-risk MIPI 61% vs. 29%; p<0.001), more frequent blastoid variant (24% vs. 9%; p<0.001) and Ki67 > 30% (45% vs. 23%, p<0.001). Regarding treatment, POD24 patients had less frequently received high-dose cytarabine (21% vs. 39%, p<0.001) as well as ASCT (26% vs. 47%, p<0.001). In a final model, including baseline factors and treatment strategies, induction was not associated with risk of POD24, and only baseline variables (age, performance status, LDH, leucocytes and Ki67>30%) remained significantly associated with POD24 status. Within responding patients only (CR/CRu/PR at end-of-induction, n=1000), 150 had a POD24 event, and ASCT or RM were not significantly associated with POD24 status whereas age, LDH and Ki67>30% remained significant. Conclusion Using this large dataset of patients included in clinical trials, we confirm that POD24 can be used as a surrogate for OS in MCL. ASCT as well as RM have not a clear benefit to prevent early relapse within two years after the diagnosis in responding patients at end-of-induction.