How I use genomics and BTK inhibitors in the treatment of Waldenström macroglobulinemia.

ABSTRACT: Mutations in MYD88 (95%-97%) and CXCR4 (30%-40%) are common in Waldenström macroglobulinemia (WM). TP53 is altered in 20% to 30% of patients with WM, particularly those previously treated. Mutated MYD88 activates hematopoietic cell kinase that drives Bruton tyrosine kinase (BTK) prosurvival signaling. Both nonsense and frameshift CXCR4 mutations occur in WM. Nonsense variants show greater resistance to BTK inhibitors. Covalent BTK inhibitors (cBTKi) produce major responses in 70% to 80% of patients with WM. MYD88 and CXCR4 mutation status can affect time to major response, depth of response, and/or progression-free survival (PFS) in patients with WM treated with cBTKi. The cBTKi zanubrutinib shows greater response activity and/or improved PFS in patients with WM with wild-type MYD88, mutated CXCR4, or altered TP53. Risks for adverse events, including atrial fibrillation, bleeding diathesis, and neutropenia can differ based on which BTKi is used in WM. Intolerance is also common with cBTKi, and dose reduction or switchover to another cBTKi can be considered. For patients with acquired resistance to cBTKis, newer options include pirtobrutinib or venetoclax. Combinations of BTKis with chemoimmunotherapy, CXCR4, and BCL2 antagonists are discussed. Algorithms for positioning BTKis in treatment naïve or previously treated patients with WM, based on genomics, disease characteristics, and comorbidities, are presented.

Ibrutinib and venetoclax as primary therapy in symptomatic, treatment-naïve Waldenström macroglobulinemia.

ABSTRACT: Concurrent Bruton tyrosine kinase and BCL2 inhibition has not yet been investigated in Waldenström macroglobulinemia (WM). We performed an investigator-initiated trial of ibrutinib and venetoclax in symptomatic treatment-naïve patients with MYD88-mutated WM. Patients received ibrutinib 420 mg once daily (cycle 1), followed by a ramp-up of venetoclax to 400 mg daily (cycle 2). The combination was then administered for 22 additional 4-week cycles. The attainment of very good partial response (VGPR) was the primary end point. Forty-five patients were enrolled in this study. The median baseline characteristics were as follows: age 67 years, serum IgM 43 g/L, and hemoglobin 102 g/L. Seventeen patients (38%) carried CXCR4 mutations. Nineteen patients (42%) achieved VGPR. Grade 3 or higher adverse events included neutropenia (38%), mucositis (9%), and tumor lysis syndrome (7%). Atrial fibrillation occurred in 3 (9%), and ventricular arrhythmia in 4 (9%) patients that included 2 grade 5 events. With a median follow-up of 24.4 months, the 24-month progression-free survival (PFS) and overall survival (OS) rates were 76% and 96%, respectively, and were not impacted by CXCR4 mutations. The median time on therapy was 10.2 months, and the median time after the end of therapy (EOT) was 13.3 months. Eleven of the 12 progression events occurred after EOT, and the 12-month PFS rates after EOT were 79%; 93% if VGPR was attained, and 69% for other patients (P = .12). Ibrutinib and venetoclax induced high VGPR rates and durable responses after EOT, although they were associated with a higher-than-expected rate of ventricular arrhythmia in patients with WM, leading to early study treatment termination. This trial was registered at www.clinicaltrials.gov as #NCT04273139.

Optimizing BTK Inhibition in Waldenström Macroglobulinemia.

Bruton tyrosine kinase (BTK) inhibitors have become a standard of care in the treatment of patients with Waldenström macroglobulinemia (WM) and are the only medications approved by the FDA to treat these patients. As more patients with WM are treated with BTK inhibitors in the United States and worldwide, it is essential to optimize this therapy by selecting the patients who are more likely to benefit from it, and by managing the unique adverse effects associated with these agents. Herein, we propose a genomic-driven approach to selecting patients with WM who are more likely to experience fast, deep, and durable responses to BTK inhibitors, and provide practical strategies for managing adverse effects, including BTK inhibitor dose reductions, switching to other BTK inhibitors, and abandoning BTK inhibitor therapy. Ongoing clinical trials are evaluating covalent and noncovalent BTK inhibitors alone and in combination, as well as BTK degraders, with exciting results, making the horizon for BTK-targeting therapies in WM bright and hopeful.

Dose reductions in patients with Waldenström macroglobulinaemia treated with ibrutinib.

Waldenström macroglobulinaemia (WM) is characterized by the presence of a MYD88L265P mutation. This mutation promotes growth and survival of malignant cells through Bruton tyrosine kinase (BTK) activation. Ibrutinib was the first BTK inhibitor approved for WM. Intolerance to ibrutinib frequently leads to dose reductions, though the impact of reducing ibrutinib dosing has not been systematically studied. We performed a retrospective study to determine the frequency and impact of reducing ibrutinib dosing in WM patients. With a median treatment time of 64 months, 96 (27%) of 353 WM patients required a dose reduction due to adverse events such as musculoskeletal symptoms, cardiac events, dermatologic symptoms, cytopenias, and gastrointestinal symptoms. The median time to initial dose reduction was 9.3 months (range, 0.5-74). Dose reductions were more common in those 65 years of age or older versus under 65 [hazard ratio (HR) 2.46, 95% confidence interval (CI) 1.55-3.90; p < 0.001], and in females versus males (HR 2.20, 95% CI 1.41-3.28, p < 0.001). Most patients (65%) had improvement or resolution of adverse effects after initial dose reduction. With a median follow-up of three years from dose reduction, hematologic response sustained or deepened in 79% of patients. These data suggest that dose reduction of ibrutinib is a reasonable treatment approach for patients with intolerable side effects.

Managing Ibrutinib-Intolerant Patients With B-Cell Malignancies.

Ibrutinib is a first-generation inhibitor of Bruton tyrosine kinase (BTK) that is currently approved to treat patients with B-cell malignancies, including Waldenström macroglobulinemia (WM), relapsed/refractory (R/R) mantle cell lymphoma (MCL), R/R marginal zone lymphoma (MZL), and chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). Off-target adverse effects, such as atrial fibrillation, hypertension, and bleeding, have been observed and may limit a patient's tolerance for treatment. Currently, there is no well-established treatment regimen for patients who cannot tolerate ibrutinib. Approaches to address such patients include managing ibrutinib side effects with supportive care or dose reductions, switching to an alternative covalent BTK inhibitor, or abandoning covalent BTK inhibitors for alternative forms of treatment. Here we review the literature and provide guidance on treating ibrutinib-intolerant patients with B-cell malignancies.

Phase 1 study of ibrutinib and the CXCR4 antagonist ulocuplumab in CXCR4-mutated Waldenström macroglobulinemia.

MYD88 and CXCR4 mutations are common in Waldenström macroglobulinemia (WM). Mutated CXCR4 (CXCR4Mut) impacts BTK-inhibitor response. We conducted a phase 1 trial of the CXCR4-antagonist ulocuplumab with ibrutinib in this first-ever study to target CXCR4Mut in WM. Ibrutinib was initiated at 420 mg/d with cycle 1 and continued until intolerance or progression; ulocuplumab was given cycles 1 to 6, with a 3 + 3 dose-escalation design. Each cycle was 4 weeks. Thirteen symptomatic patients, of whom 9 were treatment-naive patients were enrolled. Twelve were evaluable for response. At best response, their median serum immunoglobulin M declined from 5574 to 1114 mg/dL; bone marrow disease decreased from 65% to 10%, and hemoglobin increased from 10.1 to 14.2 g/dL (P < .001). The major and VGPR response rates were 100% and 33%, respectively, with VGPRs observed at lower ulocuplumab dose cohorts. Median times to minor and major responses were 0.9 and 1.2 months, respectively. With a median follow-up of 22.4 months, the estimated 2-year progression-free survival was 90%. The most frequent recurring grade ≥2 adverse events included reversible thrombocytopenia, rash, and skin infections. Ulocuplumab dose-escalation did not impact adverse events. The study demonstrates the feasibility of combining a CXCR4-antagonist with ibrutinib and provides support for the development of CXCR4-antagonists for CXCR4Mut WM. This trial was registered at www.clinicaltrials.gov as #NCT03225716.

Bruton tyrosine kinase inhibitors in the management of Waldenström macroglobulinemia.

Bruton tyrosine kinase (BTK) inhibitors have taken a central role in the management of patients with Waldenström macroglobulinemia and are the only agents approved by the Food and Drug Administration (FDA) to treat these patients. Although associated with high rates of durable responses, unmet needs with BTK inhibitor therapy include indefinite duration therapy, high cost, scarcity of complete responses, and lower rates and shorter duration of response in patients with CXCR4 mutations. Herein, we review the data supporting the use of covalent BTK inhibitors, selected management issues, clinical trials with covalent BTK inhibitor combination regimens, and up-and-coming non-covalent BTK inhibitors.

Safety, tolerability, and response rates of daratumumab in relapsed AL amyloidosis: results of a phase 2 study.

Daratumumab, a monoclonal CD38 antibody, is approved in the treatment of myeloma, but its efficacy and safety in light-chain (AL) amyloidosis has not been formally studied. This prospective phase 2 trial of daratumumab monotherapy for the treatment of AL amyloidosis was designed to determine the safety, tolerability, and hematologic and clinical response. Daratumumab 16 mg/kg was administered by IV infusion once weekly for weeks 1 to 8, every 2 weeks for weeks 9 to 24, and every 4 weeks thereafter until progression or unacceptable toxicity, for up to 24 months. Twenty-two patients with previously treated AL amyloidosis were enrolled. The majority of the patients had received high-dose melphalan and stem cell transplantation and/or treatment with a proteasome inhibitor. The median time between prior therapy and trial enrollment was 9 months (range, 1-180 months). No grade 3-4 infusion-related reactions occurred. The most common grade ≥3 adverse events included respiratory infections (n = 4; 18%) and atrial fibrillation (n = 4, 18%). Hematologic complete and very-good-partial response occurred in 86% of patients. The median time to first and best hematologic response was 4 weeks and 3 months, respectively. Renal response occurred in 10 of 15 patients (67%) with renal involvement and cardiac response occurred in 7 of 14 patients (50%) with cardiac involvement. In summary, daratumumab is well tolerated in patients with relapsed AL amyloidosis and leads to rapid and deep hematologic responses and organ responses. This trial was registered at www.clinicaltrials.gov as #NCT02841033.

Natural history of Waldenström macroglobulinemia following acquired resistance to ibrutinib monotherapy.

Ibrutinib is highly active and produces long-term responses in patients with Waldenström macroglobulinemia (WM), but acquired resistance can occur with prolonged treatment. We therefore evaluated the natural history and treatment outcomes in 51 WM patients with acquired resistance to ibrutinib monotherapy. The median time between ibrutinib initiation and discontinuation was 2 years (range, 0.4-6.5 years). Following discontinuation of ibrutinib, a rapid increase in serum immunoglobulin M level was observed in 60% (29/48) of evaluable patients, of whom ten acutely developed symptomatic hyperviscosity. Forty-eight patients (94%) received salvage therapy after ibrutinib. The median time to salvage therapy after ibrutinib cessation was 18 days (95% confidence interval [CI]: 13-27). The overall and major response rates to salvage therapy were 56% and 44%, respectively, and the median duration of response was 48 months (95% CI: 34-not reached). Quadruple-class (rituximab, alkylator, proteasome inhibitor, ibrutinib) exposed disease (odds ratio [OR] 0.20, 95% CI: 0.05-0.73) and salvage therapy ≤7 days after discontinuing ibrutinib (OR 4.12, 95% CI: 1.07- 18.9) were identified as independent predictors of a response to salvage therapy. The 5-year overall survival (OS) following discontinuation of ibrutinib was 44% (95% CI: 26-75). Response to salvage therapy was associated with better OS after ibrutinib (hazard ratio 0.08, 95% CI: 0.02-0.38). TP53 mutations were associated with shorter OS, while acquired BTK C481S mutations had no impact. Our findings reveal that continuation of ibrutinib until subsequent treatment is associated with improved disease control and clinical outcomes.

Bone marrow involvement and subclonal diversity impairs detection of mutated CXCR4 by diagnostic next-generation sequencing in Waldenström macroglobulinaemia.

CXCR4 mutations impact disease presentation and treatment outcomes in Waldenström macroglobulinaemia (WM). Non-uniform testing for CXCR4 mutations may account for discordant findings in WM clinical trials. We compared two approaches used in these trials for detection of the most common CXCR4 (S338X) variant: targeted next-generation sequencing (NGS) using unselected bone marrow (BM) samples, and combined allele-specific polymerase chain reaction (AS-PCR) and Sanger sequencing with unselected and CD19-selected BM samples. Our findings showed that targeted NGS frequently yielded false-negative results. Both CD19 selection and AS-PCR markedly improved detection of CXCR4S338X mutations. Sensitivity was adversely impacted by low BM involvement and CXCR4 mutation clonality.

How to Sequence Therapies in Waldenström Macroglobulinemia.

OPINION STATEMENT: There are multiple treatment options in patients with Waldenström macroglobulinemia, including chemotherapy, monoclonal antibodies, proteasome inhibitors, and covalent Bruton tyrosine kinase (BTK) inhibitors. The choice of therapy should take into account the patient's clinical presentation, comorbidities, and preferences. A thorough discussion should take place to outline the administration, safety, and efficacy of the regimens under consideration. The patient's genomic profile can provide insightful information for the treatment selection. In the frontline and relapsed settings, we favor ibrutinib monotherapy over chemoimmunotherapy or proteasome inhibitor-based regimens in patients with MYD88 and without CXCR4 mutations. For patients with MYD88 and CXCR4 mutations or without MYD88 or CXCR4 mutations, chemoimmunotherapy or proteasome inhibitor-based regimens are favored, but efficacy data with ibrutinib in combination with rituximab and with novel covalent BTK inhibitors are emerging. Autologous stem cell transplant should be considered in special cases in the relapsed setting. Participation in clinical trials is positively encouraged in WM patients in frontline and relapsed settings. Agents of interest include the BCL2 antagonist venetoclax, the CXCR4 inhibitor mavorixafor, and the non-covalent BTK inhibitors pirtobrutinib and ARQ-531.

Risk Factors for Development of Hypocalcemia in Patients With Cancer Treated With Bone-Modifying Agents.

BACKGROUND: This retrospective analysis describes the prevalence of and risk factors associated with the development of hypocalcemia in patients with cancer receiving bone-modifying agents (BMAs) as supportive care. PATIENTS AND METHODS: Patients with cancer treated with an intravenous or subcutaneous BMA, including pamidronate, zoledronic acid, or denosumab, at a tertiary care/safety net hospital in 2005 through 2015 were included in this retrospective review. We reviewed the medical records for predictive clinical and laboratory parameters and for patient outcomes. RESULTS: A total of 835 patients with cancer received at least one dose of a BMA during the specified time frame; 205 patients (25%) developed hypocalcemia of CTCAE grade ≥1 within 8 weeks of BMA initiation, 18 of whom (8.8%) had grade ≥3, and 3 patients died as a result. Multivariate analysis showed that patients with hematologic malignancy (odds ratio [OR], 1.956; P=.025), bone metastases (OR, 2.443; P=.017), inpatient status (OR, 2.592; P<.001), and deficient baseline vitamin D levels (OR, 2.546; P<.023) were more likely to develop hypocalcemia. Hypercalcemia before BMA administration (OR, 0.474; P=.032) was protective. CONCLUSIONS: Certain patient populations, including those with hematologic malignancies and/or bone metastases, warrant closer monitoring of calcium levels while receiving BMAs because of the high rate of hypocalcemia. Low pretreatment vitamin D levels are associated with the development of hypocalcemia. These data support close monitoring of calcium levels in patients with cancer receiving BMAs, in addition to adequate repletion of vitamin D before initiation of BMAs when possible.

Long-term outcome of kidney transplantation in AL amyloidosis.

Therapies for AL amyloidosis have dramatically improved, leading to longer patient survival; however, more AL amyloidosis patients are reaching end-stage renal disease (ESRD). There are no clear guidelines regarding eligibility for kidney transplantation in patients with AL amyloidosis, and data on outcomes are limited. We evaluated the clinical and laboratory data of 49 patients who were followed in the Amyloidosis Center at Boston University and underwent kidney transplantation at a center in the United States between 1987-2017. During a median follow-up of 7.2 years (range 0-19), the median patient survival from diagnosis was 15.4 years, and from kidney transplantation was 10.5 years. One, three, and five-year graft survival were 94%, 89%, and 81%, respectively. Patients with hematologic complete response or very good partial response prior to kidney transplantation had significantly better patient survival than patients with partial response or no response, and the median time to graft loss was 10.4 years versus 5.5 years, respectively. This is the largest published series of kidney transplantation in patients with AL amyloidosis, suggesting that kidney transplantation can have a good outcome in carefully selected patients, particularly in those who have achieved a complete response or very good partial response at the time of kidney transplantation.

Induction Therapy with Bortezomib and Dexamethasone and Conditioning with High-Dose Melphalan and Bortezomib Followed by Autologous Stem Cell Transplantation for Immunoglobulin Light Chain Amyloidosis: Long-Term Follow-Up Analysis.

In immunoglobulin light-chain (AL) amyloidosis, the depth of hematologic response to treatment is associated with improved survival and organ responses. We conducted a clinical trial using bortezomib in induction and in conditioning with melphalan before stem cell transplantation (SCT) for AL amyloidosis. The results of this clinical trial with a median follow-up of 36 months have been reported previously. Here we report the long-term results of this clinical trial with a median follow-up of 77 months. We describe survival, durability of hematologic and organ responses, and relapse rates. Thirty-five patients were enrolled between 2010 and 2013. Hematologic complete response and very good partial response (VGPR) were noted in 100% (27 of 27) of the evaluable patients at 6 months post-SCT. Four patients (15%) had hematologic relapse at a median of 42 months, and 1 patient (3.7%) had organ progression despite maintaining a VGPR at 37 months. The median overall survival and progression-free survival have not yet been reached at the time of this report. Renal and cardiac responses occurred in 65% and 88%, respectively, at 5 years post-SCT. The median time to renal and cardiac response was 12 months and 6 months, respectively. In conclusion, incorporating bortezomib into induction and conditioning yielded durable hematologic responses of AL amyloidosis, with corresponding organ responses and prolonged survival.

Prevalence and prognostic value of D-dimer elevation in patients with AL amyloidosis.

Light chain (AL) amyloidosis is a protein folding disorder that can affect many different organ systems, in addition to the coagulation pathway. D-dimer, a measurement of fibrin degradation, is commonly elevated in hematologic malignancies, but the prevalence and significance of D-dimer elevation in AL amyloidosis is unknown. We conducted an analysis of 921 patients with AL amyloidosis that presented to the Boston University Amyloidosis Center. Baseline characteristics and laboratory data of the 897 patients included in the final cohort were analyzed. Four hundred twenty three patients (47%) had an elevated D-dimer (>0.5 µg/mL). Multivariate analysis demonstrated that a normal D-dimer level of ≤0.5 µg/mL, and a level of >0.5 µg/mL but <1 µg/mL, conferred a lower risk of mortality (HR 0.49 and 0.59, respectively) when compared to a D-dimer level ≥ 1 µg/mL. The increased risk of mortality in patients with a D-dimer level ≥ 1 µg/mL was present in all cardiac stages. The median overall survival based on D-dimer range of ≤0.5, >0.5 but <1, and ≥ 1 µg/mL was 5.86, 4.04, and 2.08 years, respectively (P < .001). This retrospective analysis demonstrates the high prevalence of D-dimer elevation in AL amyloidosis and confirms that this laboratory finding is independently associated with decreased survival.

High-Dose Melphalan and Stem Cell Transplantation in Patients on Dialysis Due to Immunoglobulin Light-Chain Amyloidosis and Monoclonal Immunoglobulin Deposition Disease.

The kidney is the most common organ affected by immunoglobulin light-chain (AL) amyloidosis and monoclonal immunoglobulin deposition disease (MIDD), often leading to end-stage renal disease (ESRD). High-dose melphalan and stem cell transplantation (HDM/SCT) is effective for selected patients with AL amyloidosis, with high rates of complete hematologic response and potential for improved organ dysfunction. Data on tolerability and response to HDM/SCT in patients with ESRD due to AL amyloidosis and MIDD are limited. We analyzed data on toxicity, efficacy, and hematologic and renal response of HDM/SCT in 32 patients with AL amyloidosis and 4 patients with MIDD who were dialysis-dependent for ESRD treated at Boston Medical Center between 1994 and 2016. The most common grade 3/4 nonhematologic toxicities were infections (75%), metabolic abnormalities (56%), mucositis (42%), constitutional symptoms (39%), pulmonary complications (39%), and diarrhea (28%). Treatment related mortality (defined as death within 100 days of SCT) occurred in 8% (3 of 36). A complete hematologic response was achieved in 70% of evaluable patients (19 of 27) at 1 year after HDM/SCT. In the entire cohort, median overall survival (OS) after HDM/SCT was 5.8 years; median OS was 1 year for those who did not achieve a complete hematologic response and 8 years for those who did achieve a complete hematologic response. Twelve patients (33%) underwent kidney transplantation after successful treatment with HDM/SCT at a median of 2.4 years after SCT. HDM/SCT is safe and effective in inducing hematologic complete responses and prolonging survival in patients with ESRD from AL amyloidosis and MIDD. Achievement of a durable hematologic response can make these patients possible candidates for renal transplantation.

Modified High-Dose Melphalan and Autologous Stem Cell Transplantation for Immunoglobulin Light Chain Amyloidosis.

High-dose melphalan and autologous stem cell transplantation (HDM/SCT) have been used in patients with immunoglobulin light chain (AL) amyloidosis for over 2 decades now with durable responses, prolonged survival, and decreasing treatment-related mortality. Historically, patients with poorer baseline functional status, advanced age, renal compromise, and cardiac involvement have been treated with a risk-adapted modified conditioning dose of melphalan (mHDM) of 100 to 140 mg/m2 before SCT. In part because of these baseline characteristics, patients receiving mHDM/SCT have had poorer outcomes compared with patients receiving full-dose melphalan at 200 mg/m2. With the advent of novel therapeutic agents such as proteasome inhibitors, immunomodulatory agents, and monoclonal antibodies for the treatment of AL amyloidosis, it is imperative to understand the long-term effects of mHDM/SCT. Here we report the long-term outcomes of 334 patients with AL amyloidosis treated with mHDM/SCT. Median overall survival was 6.1 years and median event-free survival 4.3 years, with median overall survival reaching 13.4 years for patients who had achieved a hematologic complete response (CR). Overall hematologic response rate was 69%, and treatment-related mortality was 3% after 2010. Thus, mHDM/SCT leads to prolonged survival and favorable outcomes, especially if a hematologic CR is achieved.

Evaluation of a new continuous mononuclear cell collection procedure in a single transplant center cohort enriched for AL amyloidosis patients.

BACKGROUND: The Spectra Optia continuous mononuclear cell (CMNC) program is newly available, and herein validated in a single-center cohort enriched with AL amyloidosis patients to collect a target CD34+ yield of 2.5 × 106 cells/kg within 2 days. METHODS: Consecutive autologous transplant patients in 2016 are included. Patients undergo leukapheresis with Optia CMNC and Spectra v4.7 over a 2-day cycle. Data collection includes collection efficiency, adverse events and engraftment kinetics. RESULTS: 36 leukapheresis procedures on 18 patients are included. The diagnoses are AL amyloidosis (9), myeloma (7), lymphoma (2), and scleroderma (1). Median age is 60; 12 are men. Plerixafor was employed pre-emptively in 6 cycles. Median blood CD34+ on Day 1 of leukapheresis was 46 cells/uL. Median number of blood volumes processed on Day 1 was 3.1. All collection cycles were completed within 2 days; only one in a heavily pretreated lymphoma patient did not reach the target requiring a second mobilization attempt. Mean collection efficiencies were comparable between the two devices. There were 2 adverse events: tubing rupture on the Optia; and one case of hypotension. All 18 patients underwent high-dose chemotherapy: median cell dose infused was 7.7 × 106 CD34+ cells/kg. Median days to neutrophil and platelet engraftment were 10 and 13 respectively. CONCLUSION: The Optia CMNC collection protocol is safe and effective in a small single-center autologous stem cell transplant cohort enriched for high-risk patients with AL amyloidosis and cardiac involvement. Caution is needed for tubing setup because there is less cumulative experience with Optia.