Targeted Therapies in Younger and Older Patients With Mantle Cell Lymphoma

For the first-line treatment of mantle cell lymphoma (MCL), high-dose chemotherapy and autologous stem cell transplantation (ASCT) have been reserved for relatively young and fit patients. Better-tolerated regimens have provided a preferable ratio of risk to benefit for less fit patients, even if the remissions associated with these combinations are less durable. Recent studies with targeted therapies are now challenging the premise that optimal control of MCL is obtained only by regimens that are difficult to tolerate. The relevance of these studies to specific case examples in this review demonstrates the potential of newer therapies across several MCL phenotypes.

Background 

Of the approximately 80,000 individuals diagnosed annually in the United States with a non-Hodgkin lymphoma (NHL), MCL accounts for an estimated 5%.^1,2 At the time of diagnosis, most of these patients have advanced disease. The diagnosis of MCL is made based on characteristic immunophenotype and the presence of (11;14)(q13;q32) translocation resulting in overexpression of cyclin D1.^3,4 Long-term survival has been observed in a small proportion of patients with MCL, but this disease is generally considered incurable.⁵

Except for the approximately 10% of patients with MCL who present with asymptomatic indolent disease, for whom a watch-and-wait approach is generally used,⁶ there are 2 types of treatment strategies. One is applied to people who are fit and relatively young. In these cases, intensive chemotherapy with or without ASCT has been the dominant approach. In patients who are poor candidates for the toxicities associated with aggressive treatment, less intensive approaches are applied. These strategies include not only better-tolerated combinations of cytotoxic chemotherapies, but also various combinations that involve immunomodulators or small molecule enzyme inhibitors. Although less toxic, these regimens are active, often achieving a complete response (CR) and an extended progression-free survival (PFS).³

These 2 pathways of MCL treatment are reflected in guidelines from the National Comprehensive Cancer Network (NCCN), which describe separate first-line algorithms for stage I and stage II non-bulky disease and stage II bulky and advanced stage disease.⁷ For stage II bulky or advanced stage disease, separate pathways are described for indolent, TP53-mutated, and TP53 wild-type MCL and are further divided into pathways for those who are candidates for ASCT and those who are not.

Currently, “chemotherapy-free” therapies, a term that is sometimes used to identify drug combinations with modest or no cytotoxic effects, though inaccurate, are not preferred for first-line therapy in any group in the NCCN guidelines. However, immunomodulators, such as lenalidomide and targeted therapies, such as Bruton tyrosine kinase inhibitors (BTKis) are being actively tested in the front-line setting with promising results. Practical approaches to the application of these agents are described in trials presented or published in the last year, including TRIANGLE and SHINE.^10,11

Rethinking Front-Line MCL Therapy in the Young and Fit

Case Study

A 52-year-old man with a history of smoking presented with shortness of breath and general fatigue. The medical history included no major chronic diseases. The patient, who was referred after a routine examination, reported a recent decrease in body weight of unknown cause. Enlargement of inguinal, axillary, and submaxillary lymph nodes on examination along with laboratory abnormalities, such as anemia, and elevated lymphoid cells in the peripheral blood, raised suspicion of a lymphoproliferative disorder. A diagnosis of MCL was reached based on characteristic lymphoid cell morphology and immunotyping positive for CCND1 on lymph node biopsy. Ki-67 was 50% with wild-type TP53 on next-generation sequencing. The disease was characterized as stage III with intermediate risk MIPI (Mantle Cell Lymphoma International Prognostic Index).

For this presentation, one NCCN-guideline recommendation is a cytarabine-containing intensive chemotherapy regimen with rituximab followed by ASCT with maintenance rituximab in patients who are fit for transplant,⁷ but the recent data from the multicenter open-label TRIANGLE study has challenged this paradigm.¹⁰

In TRIANGLE, 870 treatment-naïve patients younger than age 65 (median age 57 years) were randomized to 1 of 3 study arms.¹⁰ In the control arm, patients received the standard-of-care induction with intensive chemoimmunotherapy (CIT) with ASCT consolidation (CIT + ASCT). In 1 of 2 experimental arms, patients received CIT + ibrutinib followed by ASCT consolidation and 2 years of ibrutinib maintenance (CIT + I + ASCT). In the other experimental arm, patients received CIT + ibrutinib followed by 2 years of ibrutinib maintenance with ASCT omitted (CIT + I). Rituximab maintenance as a single dose administered every 2 months for up to 3 years was permitted in all arms.

Most (87%) of the patients in TRIANGLE had stage IV disease and most (85%) had low- or intermediate-risk MIPI. The primary endpoint was failure-free survival (FFS). Rates of FFS at 3 years were 72% for the CIT+ ASCT arm, 88% for the CIT + I + ASCT arm, and 86% for the CIT + I arm. Overall survival (OS) at 3 years, during which time the trial was amended to permit rituximab maintenance in all 3 study arms, numerically favored ibrutinib arms (92% for CIT + I and 91% for CIT + I + ASCT), over chemotherapy alone (86% for CIT + ASCT).

The TRIANGLE trial does not yet establish a new standard for the types of patients enrolled, but it does show clearly that the use of ibrutinib with CIT was not inferior to the standard intensive approach integrating ASCT, and most types of adverse events occurred with less frequency in the ibrutinib-only arm.

There are numerous questions to pose and a broader understanding of applicability to be gained as more follow-up of this study and other studies utilizing targeted therapies, including other BTK inhibitors, provide mor data. Of particular interest is whether the presence of minimal residual disease (MRD) and the prognostic implications of MRD are affected by the use of a BTKi and/or ASCT. The E4151 and E4181 clinical trials may collectively provide greater insight here.^12,13

Rethinking Front-Line MCL Therapy in Older Patients

Case Study

A 74-year-old man with a history of cardiovascular disease, including a prior ST-elevated myocardial infarction, presents with nonspecific symptoms, including night sweats, intermittent fevers, and fatigue. Despite his symptoms, he continues to work 3 days per week and participates in a weekly game of doubles tennis. Axillary swelling leads him to seek medical attention. Imaging demonstrates diffuse lymphadenopathy. An axillary lymph node biopsy confirms a diagnosis of MC with FISH (fluorescence in situ hybridization) positive for t(11;14). He is of intermediate risk on MIPI scoring.

Due to his age and concurrent heart disease, he is not a candidate for aggressive chemotherapy and ASCT. Less aggressive therapies including bendamustine plus rituximab (BR),^14,15 lenalidomide plus rituximab (RR),⁸ and rituximab, bendamustine, and cytarabine (R-BAC) are discussed with this patient.¹⁶

Based on STiL data and BRIGHT studies, BR has become a widely used regimen.^14,15 However, attempts are being made to improve upon the BR backbone with the addition of BTK inhibitors.¹¹ In SHINE, BR plus ibrutinib further improved PFS relative to BR alone. SHINE was a 2-arm study, which was restricted to patients 65 years of age or older (median age 71 years); 523 previously untreated patients with good performance status and acceptable organ function were randomized to BR or BR plus ibrutinib. Most patients had intermediate- (~48%) or high- (~34%) risk MIPI. More than 90% had advanced-stage disease. Of patients in whom the TP53 mutation status was established, only about 10% were positive.

In the arm receiving BR alone, the median PFS was 52.9 months. With the addition of 560 mg once-daily ibrutinib to 6 cycles of BR followed by maintenance rituximab and continued ibrutinib, the median PFS, which was the primary endpoint, climbed to a median of 80.6 months. BR plus ibrutini was associated with a 41% reduction in the hazard ratio (HR) for progression or death (HR 0.75; P=.01). When stratified by risk factors, the advantage of BR plus ibrutinib was particularly pronounced in patients with intermediate-risk, (although not high-risk) nonmutated TP53, and less bulky disease.¹¹

There was no significant effect of the addition of ibrutinib on OS at the last analysis, but the longer PFS was achieved with only a modest increase in adverse events (AEs). For AEs of grade 3 or higher, the AE rates for BR plus ibrutinib and BR alone were 81.5% and 77.3%, respectively. Rates of cytopenias, including grade 3 or higher, were similar in the 2 arms. Rash and gastrointestinal AEs, such as diarrhea, nausea, and abdominal pain, occurred more frequently among patients who received ibrutinib.¹¹

Without an OS advantage, the SHINE trial does not establish a new standard of care, particularly given that it was voluntarily revoked from the market for the treatment of MCL. However, results are likely to accelerate interest in evaluating other targeted therapies, in combination with other relatively well-tolerated treatments. In patients with MCL unfit for ASCT, there is interest in pursuing other BTK inhibitors, particularly with ibrutinib being revoked as an indication for MCL. including the newer noncovalent pirtobrutinib, which was recently approved for MCL in the relapsed/refractory setting,¹⁷ and bispecific T-cell engagers (BiTEs) such as glofitamab.¹⁸

Rethinking Front-Line in TP53-Mutated MCL

Case Study

A previously healthy 62-year-old woman who presents with rapidly progressing lymphadenopathy and constitutional symptoms is diagnosed with MCL that has multiple adverse features. She has a Ki-67 level higher than 30%, a TP53 mutation, and blastoid morphology.¹⁹

The NCCN guidelines strongly recommend a clinical trial for patients with a TP53 mutation.⁷ Despite various high-intensity combinations to control disease in these patients, the 2017 pooled analysis demonstrated that most patients with TP53 mutations have a poor or no response to chemotherapy with a high side effect burden.¹⁹ In particular, such patients derive little benefit from high-intensity chemotherapy using ASCT.¹⁹

Nonetheless, for TP53-mutated MCL, several regimens have demonstrated activity. Most of these have used highly targeted therapies that offer the potential for low relative rates of toxicity. Two “chemotherapy-free” combinations involving venetoclax, the CD20-targeted obinutuzumab, and BTK inhibitors have completed phase 2 trials with promising results.^20,21 In a study evaluating the BOVen regimen (the second-generation BTK inhibitor zanubrutinib, obinutuzumab, and venetoclax) as time-limited therapy in TP53-mutated patients, 89% of patients achieved MRD at 26 months of follow-up.²⁰

Several novel therapies being tested in the relapsed/refractory setting have generated interest for evaluation in front-line clinical studies. These strategies include the BiTE glofitamab,¹⁸ the antibody-drug conjugate zilovertamab vedotin,²² and the chimeric antigen receptor (CAR) T-cell therapy brexucabtagene autoleucel (brexu-cel).²³ Brexu-cel is already approved in relapsed/refractory MCL.²³ Given the poor response to available treatments seen in patients with TP53 mutations, these novel therapies have the potential to improve outcomes in this population of high unmet need.

Summary

Durable remissions of MCL can be achieved with aggressive combinations of chemotherapy, but recent studies suggest a momentum away from cytotoxic drugs toward therapies with more targeted effects. In at least some patient populations, these therapies can rival the degree and duration of disease control achieved with less well-tolerated treatment. If ongoing trials corroborate the long-term efficacy and safety of these approaches, these therapies may represent an important evolution in MCL management.

Click to read more from 2023 Rare Diseases Report: Cancers

For the first-line treatment of mantle cell lymphoma (MCL), high-dose chemotherapy and autologous stem cell transplantation (ASCT) have been reserved for relatively young and fit patients. Better-tolerated regimens have provided a preferable ratio of risk to benefit for less fit patients, even if the remissions associated with these combinations are less durable. Recent studies with targeted therapies are now challenging the premise that optimal control of MCL is obtained only by regimens that are difficult to tolerate. The relevance of these studies to specific case examples in this review demonstrates the potential of newer therapies across several MCL phenotypes.

Background 

Of the approximately 80,000 individuals diagnosed annually in the United States with a non-Hodgkin lymphoma (NHL), MCL accounts for an estimated 5%.^1,2 At the time of diagnosis, most of these patients have advanced disease. The diagnosis of MCL is made based on characteristic immunophenotype and the presence of (11;14)(q13;q32) translocation resulting in overexpression of cyclin D1.^3,4 Long-term survival has been observed in a small proportion of patients with MCL, but this disease is generally considered incurable.⁵

Except for the approximately 10% of patients with MCL who present with asymptomatic indolent disease, for whom a watch-and-wait approach is generally used,⁶ there are 2 types of treatment strategies. One is applied to people who are fit and relatively young. In these cases, intensive chemotherapy with or without ASCT has been the dominant approach. In patients who are poor candidates for the toxicities associated with aggressive treatment, less intensive approaches are applied. These strategies include not only better-tolerated combinations of cytotoxic chemotherapies, but also various combinations that involve immunomodulators or small molecule enzyme inhibitors. Although less toxic, these regimens are active, often achieving a complete response (CR) and an extended progression-free survival (PFS).³

These 2 pathways of MCL treatment are reflected in guidelines from the National Comprehensive Cancer Network (NCCN), which describe separate first-line algorithms for stage I and stage II non-bulky disease and stage II bulky and advanced stage disease.⁷ For stage II bulky or advanced stage disease, separate pathways are described for indolent, TP53-mutated, and TP53 wild-type MCL and are further divided into pathways for those who are candidates for ASCT and those who are not.

Currently, “chemotherapy-free” therapies, a term that is sometimes used to identify drug combinations with modest or no cytotoxic effects, though inaccurate, are not preferred for first-line therapy in any group in the NCCN guidelines. However, immunomodulators, such as lenalidomide and targeted therapies, such as Bruton tyrosine kinase inhibitors (BTKis) are being actively tested in the front-line setting with promising results. Practical approaches to the application of these agents are described in trials presented or published in the last year, including TRIANGLE and SHINE.^10,11

Rethinking Front-Line MCL Therapy in the Young and Fit

Case Study

A 52-year-old man with a history of smoking presented with shortness of breath and general fatigue. The medical history included no major chronic diseases. The patient, who was referred after a routine examination, reported a recent decrease in body weight of unknown cause. Enlargement of inguinal, axillary, and submaxillary lymph nodes on examination along with laboratory abnormalities, such as anemia, and elevated lymphoid cells in the peripheral blood, raised suspicion of a lymphoproliferative disorder. A diagnosis of MCL was reached based on characteristic lymphoid cell morphology and immunotyping positive for CCND1 on lymph node biopsy. Ki-67 was 50% with wild-type TP53 on next-generation sequencing. The disease was characterized as stage III with intermediate risk MIPI (Mantle Cell Lymphoma International Prognostic Index).

For this presentation, one NCCN-guideline recommendation is a cytarabine-containing intensive chemotherapy regimen with rituximab followed by ASCT with maintenance rituximab in patients who are fit for transplant,⁷ but the recent data from the multicenter open-label TRIANGLE study has challenged this paradigm.¹⁰

In TRIANGLE, 870 treatment-naïve patients younger than age 65 (median age 57 years) were randomized to 1 of 3 study arms.¹⁰ In the control arm, patients received the standard-of-care induction with intensive chemoimmunotherapy (CIT) with ASCT consolidation (CIT + ASCT). In 1 of 2 experimental arms, patients received CIT + ibrutinib followed by ASCT consolidation and 2 years of ibrutinib maintenance (CIT + I + ASCT). In the other experimental arm, patients received CIT + ibrutinib followed by 2 years of ibrutinib maintenance with ASCT omitted (CIT + I). Rituximab maintenance as a single dose administered every 2 months for up to 3 years was permitted in all arms.

Most (87%) of the patients in TRIANGLE had stage IV disease and most (85%) had low- or intermediate-risk MIPI. The primary endpoint was failure-free survival (FFS). Rates of FFS at 3 years were 72% for the CIT+ ASCT arm, 88% for the CIT + I + ASCT arm, and 86% for the CIT + I arm. Overall survival (OS) at 3 years, during which time the trial was amended to permit rituximab maintenance in all 3 study arms, numerically favored ibrutinib arms (92% for CIT + I and 91% for CIT + I + ASCT), over chemotherapy alone (86% for CIT + ASCT).

The TRIANGLE trial does not yet establish a new standard for the types of patients enrolled, but it does show clearly that the use of ibrutinib with CIT was not inferior to the standard intensive approach integrating ASCT, and most types of adverse events occurred with less frequency in the ibrutinib-only arm.

There are numerous questions to pose and a broader understanding of applicability to be gained as more follow-up of this study and other studies utilizing targeted therapies, including other BTK inhibitors, provide mor data. Of particular interest is whether the presence of minimal residual disease (MRD) and the prognostic implications of MRD are affected by the use of a BTKi and/or ASCT. The E4151 and E4181 clinical trials may collectively provide greater insight here.^12,13

Rethinking Front-Line MCL Therapy in Older Patients

Case Study

A 74-year-old man with a history of cardiovascular disease, including a prior ST-elevated myocardial infarction, presents with nonspecific symptoms, including night sweats, intermittent fevers, and fatigue. Despite his symptoms, he continues to work 3 days per week and participates in a weekly game of doubles tennis. Axillary swelling leads him to seek medical attention. Imaging demonstrates diffuse lymphadenopathy. An axillary lymph node biopsy confirms a diagnosis of MC with FISH (fluorescence in situ hybridization) positive for t(11;14). He is of intermediate risk on MIPI scoring.

Due to his age and concurrent heart disease, he is not a candidate for aggressive chemotherapy and ASCT. Less aggressive therapies including bendamustine plus rituximab (BR),^14,15 lenalidomide plus rituximab (RR),⁸ and rituximab, bendamustine, and cytarabine (R-BAC) are discussed with this patient.¹⁶

Based on STiL data and BRIGHT studies, BR has become a widely used regimen.^14,15 However, attempts are being made to improve upon the BR backbone with the addition of BTK inhibitors.¹¹ In SHINE, BR plus ibrutinib further improved PFS relative to BR alone. SHINE was a 2-arm study, which was restricted to patients 65 years of age or older (median age 71 years); 523 previously untreated patients with good performance status and acceptable organ function were randomized to BR or BR plus ibrutinib. Most patients had intermediate- (~48%) or high- (~34%) risk MIPI. More than 90% had advanced-stage disease. Of patients in whom the TP53 mutation status was established, only about 10% were positive.

In the arm receiving BR alone, the median PFS was 52.9 months. With the addition of 560 mg once-daily ibrutinib to 6 cycles of BR followed by maintenance rituximab and continued ibrutinib, the median PFS, which was the primary endpoint, climbed to a median of 80.6 months. BR plus ibrutini was associated with a 41% reduction in the hazard ratio (HR) for progression or death (HR 0.75; P=.01). When stratified by risk factors, the advantage of BR plus ibrutinib was particularly pronounced in patients with intermediate-risk, (although not high-risk) nonmutated TP53, and less bulky disease.¹¹

There was no significant effect of the addition of ibrutinib on OS at the last analysis, but the longer PFS was achieved with only a modest increase in adverse events (AEs). For AEs of grade 3 or higher, the AE rates for BR plus ibrutinib and BR alone were 81.5% and 77.3%, respectively. Rates of cytopenias, including grade 3 or higher, were similar in the 2 arms. Rash and gastrointestinal AEs, such as diarrhea, nausea, and abdominal pain, occurred more frequently among patients who received ibrutinib.¹¹

Without an OS advantage, the SHINE trial does not establish a new standard of care, particularly given that it was voluntarily revoked from the market for the treatment of MCL. However, results are likely to accelerate interest in evaluating other targeted therapies, in combination with other relatively well-tolerated treatments. In patients with MCL unfit for ASCT, there is interest in pursuing other BTK inhibitors, particularly with ibrutinib being revoked as an indication for MCL. including the newer noncovalent pirtobrutinib, which was recently approved for MCL in the relapsed/refractory setting,¹⁷ and bispecific T-cell engagers (BiTEs) such as glofitamab.¹⁸

Rethinking Front-Line in TP53-Mutated MCL

Case Study

A previously healthy 62-year-old woman who presents with rapidly progressing lymphadenopathy and constitutional symptoms is diagnosed with MCL that has multiple adverse features. She has a Ki-67 level higher than 30%, a TP53 mutation, and blastoid morphology.¹⁹

The NCCN guidelines strongly recommend a clinical trial for patients with a TP53 mutation.⁷ Despite various high-intensity combinations to control disease in these patients, the 2017 pooled analysis demonstrated that most patients with TP53 mutations have a poor or no response to chemotherapy with a high side effect burden.¹⁹ In particular, such patients derive little benefit from high-intensity chemotherapy using ASCT.¹⁹

Nonetheless, for TP53-mutated MCL, several regimens have demonstrated activity. Most of these have used highly targeted therapies that offer the potential for low relative rates of toxicity. Two “chemotherapy-free” combinations involving venetoclax, the CD20-targeted obinutuzumab, and BTK inhibitors have completed phase 2 trials with promising results.^20,21 In a study evaluating the BOVen regimen (the second-generation BTK inhibitor zanubrutinib, obinutuzumab, and venetoclax) as time-limited therapy in TP53-mutated patients, 89% of patients achieved MRD at 26 months of follow-up.²⁰

Several novel therapies being tested in the relapsed/refractory setting have generated interest for evaluation in front-line clinical studies. These strategies include the BiTE glofitamab,¹⁸ the antibody-drug conjugate zilovertamab vedotin,²² and the chimeric antigen receptor (CAR) T-cell therapy brexucabtagene autoleucel (brexu-cel).²³ Brexu-cel is already approved in relapsed/refractory MCL.²³ Given the poor response to available treatments seen in patients with TP53 mutations, these novel therapies have the potential to improve outcomes in this population of high unmet need.

Summary

Durable remissions of MCL can be achieved with aggressive combinations of chemotherapy, but recent studies suggest a momentum away from cytotoxic drugs toward therapies with more targeted effects. In at least some patient populations, these therapies can rival the degree and duration of disease control achieved with less well-tolerated treatment. If ongoing trials corroborate the long-term efficacy and safety of these approaches, these therapies may represent an important evolution in MCL management.

Click to read more from 2023 Rare Diseases Report: Cancers

For the first-line treatment of mantle cell lymphoma (MCL), high-dose chemotherapy and autologous stem cell transplantation (ASCT) have been reserved for relatively young and fit patients. Better-tolerated regimens have provided a preferable ratio of risk to benefit for less fit patients, even if the remissions associated with these combinations are less durable. Recent studies with targeted therapies are now challenging the premise that optimal control of MCL is obtained only by regimens that are difficult to tolerate. The relevance of these studies to specific case examples in this review demonstrates the potential of newer therapies across several MCL phenotypes.

Background 

Of the approximately 80,000 individuals diagnosed annually in the United States with a non-Hodgkin lymphoma (NHL), MCL accounts for an estimated 5%.^1,2 At the time of diagnosis, most of these patients have advanced disease. The diagnosis of MCL is made based on characteristic immunophenotype and the presence of (11;14)(q13;q32) translocation resulting in overexpression of cyclin D1.^3,4 Long-term survival has been observed in a small proportion of patients with MCL, but this disease is generally considered incurable.⁵

Except for the approximately 10% of patients with MCL who present with asymptomatic indolent disease, for whom a watch-and-wait approach is generally used,⁶ there are 2 types of treatment strategies. One is applied to people who are fit and relatively young. In these cases, intensive chemotherapy with or without ASCT has been the dominant approach. In patients who are poor candidates for the toxicities associated with aggressive treatment, less intensive approaches are applied. These strategies include not only better-tolerated combinations of cytotoxic chemotherapies, but also various combinations that involve immunomodulators or small molecule enzyme inhibitors. Although less toxic, these regimens are active, often achieving a complete response (CR) and an extended progression-free survival (PFS).³

These 2 pathways of MCL treatment are reflected in guidelines from the National Comprehensive Cancer Network (NCCN), which describe separate first-line algorithms for stage I and stage II non-bulky disease and stage II bulky and advanced stage disease.⁷ For stage II bulky or advanced stage disease, separate pathways are described for indolent, TP53-mutated, and TP53 wild-type MCL and are further divided into pathways for those who are candidates for ASCT and those who are not.

Currently, “chemotherapy-free” therapies, a term that is sometimes used to identify drug combinations with modest or no cytotoxic effects, though inaccurate, are not preferred for first-line therapy in any group in the NCCN guidelines. However, immunomodulators, such as lenalidomide and targeted therapies, such as Bruton tyrosine kinase inhibitors (BTKis) are being actively tested in the front-line setting with promising results. Practical approaches to the application of these agents are described in trials presented or published in the last year, including TRIANGLE and SHINE.^10,11

Rethinking Front-Line MCL Therapy in the Young and Fit

Case Study

A 52-year-old man with a history of smoking presented with shortness of breath and general fatigue. The medical history included no major chronic diseases. The patient, who was referred after a routine examination, reported a recent decrease in body weight of unknown cause. Enlargement of inguinal, axillary, and submaxillary lymph nodes on examination along with laboratory abnormalities, such as anemia, and elevated lymphoid cells in the peripheral blood, raised suspicion of a lymphoproliferative disorder. A diagnosis of MCL was reached based on characteristic lymphoid cell morphology and immunotyping positive for CCND1 on lymph node biopsy. Ki-67 was 50% with wild-type TP53 on next-generation sequencing. The disease was characterized as stage III with intermediate risk MIPI (Mantle Cell Lymphoma International Prognostic Index).

For this presentation, one NCCN-guideline recommendation is a cytarabine-containing intensive chemotherapy regimen with rituximab followed by ASCT with maintenance rituximab in patients who are fit for transplant,⁷ but the recent data from the multicenter open-label TRIANGLE study has challenged this paradigm.¹⁰

In TRIANGLE, 870 treatment-naïve patients younger than age 65 (median age 57 years) were randomized to 1 of 3 study arms.¹⁰ In the control arm, patients received the standard-of-care induction with intensive chemoimmunotherapy (CIT) with ASCT consolidation (CIT + ASCT). In 1 of 2 experimental arms, patients received CIT + ibrutinib followed by ASCT consolidation and 2 years of ibrutinib maintenance (CIT + I + ASCT). In the other experimental arm, patients received CIT + ibrutinib followed by 2 years of ibrutinib maintenance with ASCT omitted (CIT + I). Rituximab maintenance as a single dose administered every 2 months for up to 3 years was permitted in all arms.

Most (87%) of the patients in TRIANGLE had stage IV disease and most (85%) had low- or intermediate-risk MIPI. The primary endpoint was failure-free survival (FFS). Rates of FFS at 3 years were 72% for the CIT+ ASCT arm, 88% for the CIT + I + ASCT arm, and 86% for the CIT + I arm. Overall survival (OS) at 3 years, during which time the trial was amended to permit rituximab maintenance in all 3 study arms, numerically favored ibrutinib arms (92% for CIT + I and 91% for CIT + I + ASCT), over chemotherapy alone (86% for CIT + ASCT).

The TRIANGLE trial does not yet establish a new standard for the types of patients enrolled, but it does show clearly that the use of ibrutinib with CIT was not inferior to the standard intensive approach integrating ASCT, and most types of adverse events occurred with less frequency in the ibrutinib-only arm.

There are numerous questions to pose and a broader understanding of applicability to be gained as more follow-up of this study and other studies utilizing targeted therapies, including other BTK inhibitors, provide mor data. Of particular interest is whether the presence of minimal residual disease (MRD) and the prognostic implications of MRD are affected by the use of a BTKi and/or ASCT. The E4151 and E4181 clinical trials may collectively provide greater insight here.^12,13

Rethinking Front-Line MCL Therapy in Older Patients

Case Study

A 74-year-old man with a history of cardiovascular disease, including a prior ST-elevated myocardial infarction, presents with nonspecific symptoms, including night sweats, intermittent fevers, and fatigue. Despite his symptoms, he continues to work 3 days per week and participates in a weekly game of doubles tennis. Axillary swelling leads him to seek medical attention. Imaging demonstrates diffuse lymphadenopathy. An axillary lymph node biopsy confirms a diagnosis of MC with FISH (fluorescence in situ hybridization) positive for t(11;14). He is of intermediate risk on MIPI scoring.

Due to his age and concurrent heart disease, he is not a candidate for aggressive chemotherapy and ASCT. Less aggressive therapies including bendamustine plus rituximab (BR),^14,15 lenalidomide plus rituximab (RR),⁸ and rituximab, bendamustine, and cytarabine (R-BAC) are discussed with this patient.¹⁶

Based on STiL data and BRIGHT studies, BR has become a widely used regimen.^14,15 However, attempts are being made to improve upon the BR backbone with the addition of BTK inhibitors.¹¹ In SHINE, BR plus ibrutinib further improved PFS relative to BR alone. SHINE was a 2-arm study, which was restricted to patients 65 years of age or older (median age 71 years); 523 previously untreated patients with good performance status and acceptable organ function were randomized to BR or BR plus ibrutinib. Most patients had intermediate- (~48%) or high- (~34%) risk MIPI. More than 90% had advanced-stage disease. Of patients in whom the TP53 mutation status was established, only about 10% were positive.

In the arm receiving BR alone, the median PFS was 52.9 months. With the addition of 560 mg once-daily ibrutinib to 6 cycles of BR followed by maintenance rituximab and continued ibrutinib, the median PFS, which was the primary endpoint, climbed to a median of 80.6 months. BR plus ibrutini was associated with a 41% reduction in the hazard ratio (HR) for progression or death (HR 0.75; P=.01). When stratified by risk factors, the advantage of BR plus ibrutinib was particularly pronounced in patients with intermediate-risk, (although not high-risk) nonmutated TP53, and less bulky disease.¹¹

There was no significant effect of the addition of ibrutinib on OS at the last analysis, but the longer PFS was achieved with only a modest increase in adverse events (AEs). For AEs of grade 3 or higher, the AE rates for BR plus ibrutinib and BR alone were 81.5% and 77.3%, respectively. Rates of cytopenias, including grade 3 or higher, were similar in the 2 arms. Rash and gastrointestinal AEs, such as diarrhea, nausea, and abdominal pain, occurred more frequently among patients who received ibrutinib.¹¹

Without an OS advantage, the SHINE trial does not establish a new standard of care, particularly given that it was voluntarily revoked from the market for the treatment of MCL. However, results are likely to accelerate interest in evaluating other targeted therapies, in combination with other relatively well-tolerated treatments. In patients with MCL unfit for ASCT, there is interest in pursuing other BTK inhibitors, particularly with ibrutinib being revoked as an indication for MCL. including the newer noncovalent pirtobrutinib, which was recently approved for MCL in the relapsed/refractory setting,¹⁷ and bispecific T-cell engagers (BiTEs) such as glofitamab.¹⁸

Rethinking Front-Line in TP53-Mutated MCL

Case Study

A previously healthy 62-year-old woman who presents with rapidly progressing lymphadenopathy and constitutional symptoms is diagnosed with MCL that has multiple adverse features. She has a Ki-67 level higher than 30%, a TP53 mutation, and blastoid morphology.¹⁹

The NCCN guidelines strongly recommend a clinical trial for patients with a TP53 mutation.⁷ Despite various high-intensity combinations to control disease in these patients, the 2017 pooled analysis demonstrated that most patients with TP53 mutations have a poor or no response to chemotherapy with a high side effect burden.¹⁹ In particular, such patients derive little benefit from high-intensity chemotherapy using ASCT.¹⁹

Nonetheless, for TP53-mutated MCL, several regimens have demonstrated activity. Most of these have used highly targeted therapies that offer the potential for low relative rates of toxicity. Two “chemotherapy-free” combinations involving venetoclax, the CD20-targeted obinutuzumab, and BTK inhibitors have completed phase 2 trials with promising results.^20,21 In a study evaluating the BOVen regimen (the second-generation BTK inhibitor zanubrutinib, obinutuzumab, and venetoclax) as time-limited therapy in TP53-mutated patients, 89% of patients achieved MRD at 26 months of follow-up.²⁰

Several novel therapies being tested in the relapsed/refractory setting have generated interest for evaluation in front-line clinical studies. These strategies include the BiTE glofitamab,¹⁸ the antibody-drug conjugate zilovertamab vedotin,²² and the chimeric antigen receptor (CAR) T-cell therapy brexucabtagene autoleucel (brexu-cel).²³ Brexu-cel is already approved in relapsed/refractory MCL.²³ Given the poor response to available treatments seen in patients with TP53 mutations, these novel therapies have the potential to improve outcomes in this population of high unmet need.

Summary

Durable remissions of MCL can be achieved with aggressive combinations of chemotherapy, but recent studies suggest a momentum away from cytotoxic drugs toward therapies with more targeted effects. In at least some patient populations, these therapies can rival the degree and duration of disease control achieved with less well-tolerated treatment. If ongoing trials corroborate the long-term efficacy and safety of these approaches, these therapies may represent an important evolution in MCL management.

Click to read more from 2023 Rare Diseases Report: Cancers