Efficacy of Daratumumab-Based Regimens for the Treatment of Plasma Cell Leukemia

Changing lanes: extending CAR T-cell therapy to high-risk plasma cell dyscrasias

Chimeric antigen receptor (CAR) cellular therapies have advanced outcomes in challenging hematologic malignancies like leukemia, lymphoma, and multiple myeloma. Plasma cell-directed CAR T-cell therapies have been particularly beneficial in multiple myeloma, suggesting that these agents may have a role in other challenging plasma cell disorders such as systemic AL amyloidosis and plasma cell leukemia. AL amyloidosis is a monoclonal plasma cell disorder resulting in the deposition of protein fibrils that compromise end-organ function. Delays in diagnosis can result in end-organ dysfunction and organ failure, making designing and completing treatment difficult. Plasma cell leukemia (PCL) is a rare and highly challenging malignancy with dismal survival outcomes despite aggressive therapy. Both diagnoses are currently treated with regimens borrowed from myeloma: a combination of novel agents and chemotherapy induction, then autologous stem cell transplantation (ASCT), with the current practice trending towards consolidation and maintenance. Unfortunately, only 20% of AL amyloidosis patients are transplant-eligible at diagnosis. Those transplant-ineligible (TIE) patients are treated with combination induction chemotherapy, which may be limited by worsening disease-related end-organ dysfunction. Plasma cell leukemia patients are still very likely to relapse after this intensive and prolonged therapy. Despite the promise of a shorter course of therapy, CAR T-cell therapies directed against plasma cells have not been rigorously investigated in patients with AL amyloidosis or PCL; most trials of MM have excluded these patients. Herein, we describe current treatment paradigms for AL amyloidosis and PCL and review the evidence for CAR T-cell therapies in these challenging plasma cell disorders. Further investigation into CAR T-cell therapies for plasma cell disorders other than multiple myeloma is warranted.

European Myeloma Network Group review and consensus statement on primary plasma cell leukemia

BACKGROUND

Primary plasma cell leukemia (PPCL) is the most aggressive disorder among plasma cell malignancies, with new diagnostic criteria recently established by the International Myeloma Working Group. Studies have shown that PPCL patients receiving a combination of novel agents, but not eligible for transplantation, may have a median survival up to 2 years, extended to 3 years or more in those undergoing transplant procedures. These findings remain unsatisfactory, particularly if compared with progresses obtained in multiple myeloma.

DESIGN

A European Myeloma Network (EMN) expert panel reviewed the most recent literature and selected the areas of major concern in the management of PPCL by generating and rank ordering key questions using the criterion of clinical relevance. Multistep procedures were utilized to achieve a consensus on recommendations. The Delphi questionnaire method was used and a consensus of at least 80% was reached for all final statements.

RESULTS

An extended overview of current biological, clinical, prognostic, and therapeutic aspects of PPCL, including ongoing and close to start clinical trials, is presented. Furthermore, updated guidelines for the management of PPCL and practical recommendations are provided, in the context of current knowledge about this disease, also looking at possible future perspectives to ameliorate the outcome of these patients.

CONCLUSIONS

PPCL still remains an unmet clinical need. Notwithstanding, some not negligible progresses have been recently achieved. The European Myeloma Network panel strongly support ongoing and planned clinical trials, as well as biological studies based on novel technologies, strategies, and treatment options that could represent breakthroughs we have been waiting for too long.

Clinical Characteristics and Survival Outcomes of Patients With Primary and Secondary Plasma Cell Leukemia According to the 2021 Definition: A Single Center Retrospective Study

INTRODUCTION

Plasma cell leukemia (PCL) is a rare malignancy with poor overall survival (OS). Recently, its diagnostic criteria were revised by lowering the threshold of circulating plasma cells from ≥ 20% to ≥ 5%.

METHODS

Between 2010 and 2024, patients with primary PCL (pPCL) and secondary PCL (sPCL) were identified at a tertiary center. We retrospectively analyzed baseline characteristics, treatment, and survival in months (m).

RESULTS

We identified 30 patients with pPCL and 29 patients with sPCL. The median time to sPCL in patients who received Daratumumab (Dara)-containing regimens for multiple myeloma was 46.8m compared with 12.3m in patients who did not (P=0.007). Of the whole cohort, 51.9% received an induction regimen with novel agents without chemotherapy. Of the evaluable patients with pPCL and sPCL, 82.1% (23/28) and 64.7% (11/17) achieved partial response or better respectively. Median progression free survival was significantly worse in patients with sPCL than pPCL (2.2 vs. 38.3 months; HR 0.16; 95% CI (0.07-0.35), P < .001). Median OS was also worse in patients with sPCL compared with pPCL (3.1 months vs. NR [not reached]; HR 0.09; 95%CI 0.04-0.23, P < .001). The median post-SCT survival for patients with pPCL was NR compared with 6.7m for patients with sPCL (HR 0.17; 95% CI (0.03-0.83), P = .03). Dara-refractory status was associated with worse OS (HR 5.63; 95% CI (2.75-11.51), P < .0001).

CONCLUSION

Outcomes of pPCL are improving but remain dismal for sPCL. We explored the role of novel agents, especially Dara, in the treatment of PCL. More prospective trials are needed to improve its outcomes.

Current Status on Management of Primary Plasma Cell Leukemia

PURPOSEOF REVIEW

Plasma Cell Leukemia (PCL) is a very rare and highly aggressive form of plasma cell dyscrasia. This review seeks to evaluate the outcomes of PCL in the context of combination novel agent therapy and stem cell transplant (SCT) protocols.

RECENT FINDINGS

The diagnostic criteria for PCL have now evolved to include patients with 5% circulating PC. While management remains challenging, the incorporation of novel agent-based induction regimen has significantly improved early mortality and reduced attrition of patients proceeding to SCT. In recent prospective clinical trials, patients with PCL demonstrated an overall response rates of 69% to 86%, with progression-free and overall survival ranging from 13.8 to 15.5 months and 24.8 to 36.3 months, respectively. B-cell lymphoma 2 (BCL2) inhibitors, such as venetoclax present a targeted intervention opportunity for patients with PCL with t(11;14). Dedicated clinical trials tailored to PCL are crucial, integrating newer therapies in the frontline setting to further optimize responses and enhance overall outcomes.

Single-Center Experience of Patients with Plasma Cell Leukemia in the Era of New Therapeutics

INTRODUCTION

Plasma cell leukemia (PCL) can occur de novo as primary PCL (pPCL), or in patients with prior diagnosis of multiple myeloma (MM) as secondary PCL (sPCL). In 2021, the diagnostic criteria have been revised, establishing a new cut-off of ≥5% plasma cells in the peripheral blood. Lacking specific clinical trials, PCL is treated similarly to MM; however, outcome for patients with PCL remains poor. Here, we report outcomes for patients with pPCL and sPCL in the era of novel agents.

METHODS

We performed a retrospective analysis and identified 19 patients (11 pPCL, 8 sPCL) who have been treated for PCL between 2010 and 2022 at University Hospital Essen.

RESULTS

Patients with pPCL had a median overall survival (OS) of 37.8 months (95% CI: [15.4; 52.3] months) from diagnosis, with a median time to next treatment (TTNT) of 18.4 (2.0; 22.9) months. All patients were treated with a proteasome-inhibitor (PI)-based induction therapy, and the majority was consolidated with an autologous stem cell transplantation (SCT). Five of these patients received a tandem transplantation. Patients with sPCL had a median OS of only 1.5 months after diagnosis of PCL. Only 1 patient achieved a remission with daratumumab and subsequent allogenic SCT.

CONCLUSION

With our study, we add evidence for a PI-based induction therapy followed by a consolidating autologous SCT for patients with pPCL and give further evidence that a tandem transplant concept might be beneficial. The diagnosis of sPCL remains devastating and needs new therapeutic approaches.

The Current State of Knowledge About Evolution of Multiple Myeloma to Plasma Cell Leukemia

Plasma cell leukemia is a rare form of multiple myeloma (MM). In contrast to de novo primary plasma cell leukemia (pPCL), which is very uncommon presentation of MM, there is increasing frequency of transformation to secondary plasma cell leukemia (sPCL) with increasing survival of patients (MM). The molecular basis of sPCL remains poorly understood sPCL is particularly aggressive and is associated with an extremely poor prognosis, constituting a major unmet medical need. High-quality data in sPCL regarding presentation, treatment and outcomes is limited. Herein we review the current state of knowledge on sPCL diagnostics, molecular biology, clinical characteristics, prognosis and reported treatment outcomes and the emergence of the new therapeutic strategies.

Case report: Plasma cell leukemia secondary to multiple myeloma successfully treated with anti-BCMA CAR-T cell therapy

Chimeric antigen receptor (CAR)-T cell therapy provides an effective salvage treatment for relapsed/refractory multiple myeloma (RRMM) patients. End-stage RRMM with plasma cell leukemia (PCL) transformation is highly aggressive and resistant to conventional therapy. There is an urgent need for new therapeutics and CAR-T therapy may play an important role. We report a case of PCL secondary to RRMM successfully treated with CAR-T cell therapy targeting B-cell maturation antigen (BCMA). A woman was diagnosed as having MM 4 years ago and progressed to secondary PCL (sPCL) of five prior lines of treatment including proteasome inhibitors, an immunomodulatory agent, cytotoxic drugs, and an anti-CD38 monoclonal antibody. After receiving a BCMA CAR-T therapy, she achieved a stringent complete response that lasted 9 months. Then, the patient irregularly took venetoclax 10 mg per day due to a slightly higher λ FLC concentration, which did not meet the criteria for progression. She maintained a complete response for the following 7 months. In conclusion, BCMA CAR-T therapy may be a promising therapeutic approach in PCL patients. More studies are needed to evaluate the benefit of anti-BCMA CAR-T therapy in PCL patients.

Clinical Trial Registration:www.chictr.org.cn, ChiCTR1900024388, Registered 9 July 2019.