An old drug with a new future: bendamustine in multiple myeloma

Optimizing high dose melphalan

Melphalan, has been a major component of myeloma therapy since the 1950s. In the context of hematopoietic cell transplantation (HCT), high dose melphalan (HDM) is the most common conditioning regimen used due to its potent anti-myeloma effects and manageable toxicities. Common toxicities associated with HDM include myelosuppression, gastrointestinal issues, and mucositis. Established approaches to reduce these toxicities encompass dose modification, nausea prophylaxis with 5HT3 receptor antagonists, cryotherapy, amifostine use, and growth factors. Optimization of melphalan exposure through personalized dosing and its combination with other agents like busulfan, or bendamustine show promise. Propylene glycol-free melphalan (Evomela) represents a novel formulation aiming to enhance drug stability and reduce adverse effects. This review explores strategies to enhance the efficacy and mitigate the toxicity of HDM in multiple myeloma. Future directions involve exploring these strategies in clinical trials to improve the safety and efficacy of HDM, thereby enhancing outcomes for multiple myeloma patients undergoing autologous HCT.

Adding bendamustine to melphalan before ASCT improves CR rate in myeloma vs. melphalan alone: A randomized phase-2 trial

Definite cure remains exceptional in myeloma patients even after high-dose chemotherapy (HDCT) with melphalan (Mel) and autologous stem cell transplantation (ASCT). Thus, improving efficacy of HDCT in MM remains an unresolved issue. This randomized phase II trial compared standard 200 mg/m² Mel HDCT to experimental HDCT with 200 mg/m² bendamustine, given both at days −4 and −3, combined with 100 mg/m² melphalan at days −2 and −1 (BenMel) before ASCT as first-line consolidation in myeloma patients. The primary endpoint aimed to identify at least a 15% improvement in the complete remission rate (stringent CR + CR) after HDCT with BenMel compared with Mel alone. A total of 120 MM patients were 1:1 randomized. The rate of sCR/CR after ASCT was higher in BenMel than in Mel treated patients (70.0% vs. 51.7%; p = 0.039). Three patients in the BenMel group (5.0%) had reversible acute renal insufficiency compared with none in Mel patients. Minimal residual disease negativity (<10-5) by flow cytometry was observed in 26 (45.6%) BenMel patients and 22 (37.9%) in the Mel group (p = 0.375). Our data suggest that BenMel HDCT is safe and improves the sCR/CR rate compared with standard Mel alone.

Spotlight on Melphalan Flufenamide: An Up-and-Coming Therapy for the Treatment of Myeloma

Despite recent therapeutic advances, multiple myeloma (MM) patients experience relapses as they become resistant to various classes and combinations of treatment. Melphalan (L-PAM) is an ageless drug. However, its use in the autologous stem cell transplantation (ASCT) setting and the innovative quadruplet regimen as well as daratumumab, bortezomib, and prednisone make this old drug current yet. Melflufen is a peptide-conjugated alkylator belonging to a novel class of compounds, representing an overcoming of L-PAM in terms of mechanism of action and effectiveness. The improved melflufen cytotoxicity is related to aminopeptidase activity, notably present in normal and neoplastic cells and remarkably heavily overexpressed in MM cells. Upon entering a cell, melflufen is cleaved by aminopeptidases, ultimately releasing the L-PAM payload and eliciting further the inflow and cleavage of the conjugated peptide. This virtuous loop persists until all extracellular melflufen has been utilized. The aminopeptidase-driven accumulation results in a 50-fold increase in L-PAM cell enrichment as compared with free alkylator. This condition produces selective cytotoxicity, increased on-target cell potency, and decreased off-target cell toxicity, ultimately overcoming resistance pathways triggered by previous treatments, including alkylators. Due to its distinct mechanism of action, melflufen plus dexamethasone as a doublet, and in combination with other novel drugs, has the potential to be beneficial for a broad range of patients with relapsed/refractory (RR) MM in third- or even in second-line therapy. The safety profile of melflufen has been consistent across studies, and no new safety concerns have been identified when melflufen was administered in doublet and triplet combinations. Based on growing clinical evidence, melflufen could be not only a good addition in the fight against RRMM but also a drug with a very favorable tolerability profile.

Chemotherapy-based regimens in multiple myeloma in 2020

Multiple myeloma (MM) represents the second-most common hematologic malignancy. In the 1980s, induction therapy with alkylating agents, such as anthracyclines and steroids, as well as high-dose chemotherapy followed by autologous stem cell transplantation were the main therapeutic approaches for MM. Since the introduction of more effective drugs, such as proteasome inhibitors, immunomodulatory drugs, monoclonal antibodies and histone deacetylase inhibitor, the new therapeutic algorithm allows of achieving a significantly improvement of prognosis. Numerous regimens, which differently combine these new agents, have been developed and tested in clinical trials. The results of these new regimens are reported each year. In this variegated new contest, old chemotherapeutic drugs still maintain an overriding weight, especially when beneficially combined with new drugs. Also, this is particular true in specific situations, such as extramedullary manifestations, in which tumor mass reduction becomes an urgent clinical need, or in case of chemotherapy-induced stem-cell mobilization. Moreover, melphalan represents the gold standard conditioning regimen since 2002, either alone or, possibly in the next future, in combination with busulfan. Finally, new chemotherapeutic agents with new mechanisms of action, such as melflufen, are in early experimental phase.

Nitrogen Mustards as Anticancer Chemotherapies: Historic Perspective, Current Developments and Future Trends

Nitrogen mustards, a family of DNA alkylating agents, marked the start of cancer pharmacotherapy. While traditionally characterized by their dose-limiting toxic effects, nitrogen mustards have been the subject of intense research efforts, which have led to safer and more effective agents. Even though the alkylating prodrug mustards were first developed decades ago, active research on ways to improve their selectivity and cytotoxic efficacy is a currently active topic of research. This review addresses the historical development of the nitrogen mustards, outlining their mechanism of action, and discussing the improvements on their therapeutic profile made through rational structure modifications. A special emphasis is made on discussing the nitrogen mustard prodrug category, with Cyclophosphamide (CPA) serving as the main highlight. Selected insights on the latest developments on nitrogen mustards are then provided, limiting such information to agents that preserve the original nitrogen mustard mechanism as their primary mode of action. Additionally, future trends that might follow in the quest to optimize these invaluable chemotherapeutic medications are succinctly suggested.

Dose-intensified bendamustine and melphalan (BenMel) conditioning before second autologous transplantation in myeloma patients

Consolidation in myeloma patients with high-dose melphalan chemotherapy (Mel HDCT) and autologous transplantation (ASCT) is standard of care since more than 2 decades. However, definite cure remains exceptional despite intensive treatment, and improving effectiveness of HDCT remains an unmet clinical need. Combining intensified bendamustine with melphalan may represent an option. We analyzed safety and efficacy of combining dose-intensified bendamustine (200 mg/m² on days -4/-3) with high-dose melphalan (100 mg/m² on days -2/-1) before a second (tandem) ASCT in adverse risk myeloma patients after Mel HDCT/ASCT1. Twelve patients received BenMel conditioning before ASCT2 because of high-risk cytogenetics and/or failure to achieve complete remission (CR) after Mel HDCT/ASCT1. Comparing Mel HDCT/ASCT1 and BenMel HDCT/ASCT2, we observed no differences in hematologic recovery and tolerance. Acute renal injury after BenMel conditioning occurred in 3 (25%) patients, but was reversible in all patients, and there were no treatment related deaths. Complete remission rates were increasing from 42% after Mel/ASCT1 to 75% after BenMel/ASCT2. PFS 1 year after ASCT2 was 67%, and OS was 83%. These data suggest that dose-intensified bendamustine with melphalan conditioning is safe and warrants a prospective randomized comparison to standard melphalan HDCT in myeloma patients.

The Multiple Myeloma Drug Pipeline-2018: A Review of Small Molecules and Their Therapeutic Targets

Treatment of multiple myeloma (MM), a neoplasm of plasma cells, formerly dependent on alkylating drugs, corticosteroids, and autologous stem cell transplantation, has changed dramatically in the past 20 years because 3 new classes of small molecule drugs (arbitrarily defined as having a molecular weight of < 900 kDa)-immunomodulators, proteasome inhibitors, and histone deacetylase blockers-have been introduced for the disease. Therapeutic options for MM expanded further in 2015 when 2 new monoclonal antibodies (daratumumab and elotuzumab) were approved by the Food and Drug Administration for MM. Although MM remains incurable, the cumulative effect of these advances has resulted in a near-doubling of the 5-year survival rate since the late 1980s. Despite these advances, therapy for MM continues to pose substantial challenges because resistance to therapy frequently develops, and relapse and recurrence are all too common. The present review focused on the pipeline for new small molecules in various stages of development and their associated cellular targets. In addition to newer versions of alkylators, immunomodulators, proteasome inhibitors, and histone deacetylase inhibitors, the present review considered the prospects for adding new classes of small molecules to the MM armamentarium, which offer the potential for oral efficacy, relative simplicity of preparation, and prospects for improvement in the cost-to-benefit ratio. Included are agents that affect myeloma epigenetics and the ubiquitination-proteasome system and the unfolded protein response, apoptotic mechanisms, chromosomal abnormalities, nuclear protein transport, and various kinases involved in cellular signaling pathways.

Bendamustine-PAMAM Conjugates for Improved Apoptosis, Efficacy, and in Vivo Pharmacokinetics: A Sustainable Delivery Tactic

Successful delivery of a chemotherapeutic agent like bendamustine still remains a challenge in clinical conditions like chronic lymphatic leukemia (CLL), non-Hodgkin lymphoma (NHL), and multiple myeloma. We have conjugated bendamustine to polyamidoamine (PAMAM) dendrimers after conjugating with N-(hydroxyethyl)maleimide (spacer) via an ester bond. The particle size of PAMAM-bendamustine conjugate was 49.8 ± 2.5 nm. In vitro drug release resulted in sustained release with improved solution stability of drug up to 72 h. In a 24 h cytotoxicity study by MTT assay against human monoblastic leukemia cells (THP-1), the IC50 value for PAMAM-bendamustine was 32.1 ± 4.8 μM compared to 50.42 ± 3.4 μM and 2303 ± 106.5 μM for bendamustine and PAMAM dendrimer, respectively. Significantly higher cell uptake and apoptosis were observed in THP-1 cells by PAMAM-bendamustine conjugate which was confirmed by flow cytometry and confocal laser scanning microscopy. Preliminary in vivo studies undertaken included pharmacokinetics studies, organ distribution studies, and tumor inhibition studies. In healthy Wistar rat model (1CBM IV push model), the pharmacokinetic studies revealed that bioavailability and t_1/2 increased significantly, i.e., almost 8.5-fold (193.8 ± 1.116 vs 22.8 ± 0.158 μg mL^-1/h) and 5.1-fold (0.75 ± 0.005 vs 3.85 ± 0.015 h), respectively, for PAMAM-bendamustine conjugate compared to pure bendamustine ( p < 0.05), however, clearance and volume of distribution were found to be decreased compared to those of free drug. The study suggests that PAMAM-bendamustine conjugate was not only stable for the longer period but also least toxic and highly taken up by THP-1 cells to exert an anticancer effect at the reduced dose. Tumor inhibition and biodistribution studies in tumor-bearing BALB/c mice revealed that PAMAM-bendamustine conjugate was more effective than the pure drug and showed higher accumulation in the tumor.

Clinical Outcomes Related to the Use of Bendamustine Therapy for Multiple Myeloma Patients Relapsed/Refractory to Immunomodulatory Drugs and Proteasome Inhibitors

Objective:

Multiple myeloma patients who are relapsed or refractory to both proteasome inhibitors (PIs) and immunomodulatory drugs (IMiDs) have been reported to have poor outcomes. Bendamustine has been reported to have an antitumor effect in newly diagnosed as well as relapsed/refractory multiple myeloma (RRMM). The aim of this retrospective study was to evaluate the efficacy of bendamustine therapy in heavily pretreated MM patients who were refractory to PIs and IMiDs.

Materials and Methods:

Nineteen RRMM patients treated either with bendamustine and steroids (n=13) or a combination of bendamustine with novel drugs (n=6) were included. The median number of previous treatment lines was 5 (minimum-maximum: 3-8) and median time from diagnosis was 6 years (minimum-maximum: 1-16). All of the patients were resistant to at least one of the IMiDs and one of the PIs. Bendamustine was given at doses ranging from 90 mg/m² to 120 mg/m² on days 1 and 2 of 28-day cycles.

Results:

A median of 2 (minimum-maximum: 1-8) treatment cycles was administered per patient. The toxicity of bendamustine was mild and mostly of hematological origin. No complete remission was achieved. There was partial remission and stable disease in 21% and 11% of the patients, respectively. Sixty-eight percent of patients had progressive disease. The median progression-free survival and overall survival was 2 and 4 months, respectively.

Conclusion:

Bendamustine therapy was well tolerated but showed limited anti-myeloma activity in heavily pretreated patients who were refractory to IMiDs and PIs.

Combination of bendamustine and rituximab as front-line therapy for patients with chronic lymphocytic leukaemia: multicenter, retrospective clinical practice experience with 279 cases outside of controlled clinical trials

Recently, encouraging results in terms of safety and efficacy have been obtained using bendamustine-rituximab (BR) in untreated chronic lymphocytic leukaemia (CLL) patients enrolled in a phase II study. Here, we report a retrospective international multicenter study of CLL patients treated with BR as front-line therapy. The cohort included 279 patients with progressive CLL from 33 centers (29 Italian, 3 Israeli and 1 German) who received at least 1 cycle of BR as first-line treatment during the 2008-2014 period. The primary objective of this study was to evaluate the efficacy and safety of BR administered as front-line therapy, outside of controlled clinical trials. Median age was 70 years (range, 43-86 years); 62.4% were males and 35.8% had Binet stage C. Forty-two patients (15.2%) were unfit (cumulative illness rating scale [CIRS] score ≥7), and 140 (50.2%) had creatinine clearance ≤70 ml/min. Fluorescent in situ hybridisation analysis, available for 192 cases, showed that 21 (10.9%) had del11q and 18 (9.4%) del17p. The overall response rate (ORR) was 86.4%, with a complete remission rate of 28%. Patients with del17p had an ORR of 66.7%. After median follow-up of 24 months, the 2-year progression-free survival (PFS) was 69.9%; CIRS ≥7, immunoglobulin heavy-chain variable-region (IGHV) unmutated status, del17p and BR dose intensity <80% were independently associated with shorter PFS. Grade III or IV neutropenia, thrombocytopenia, and anaemia were observed in 25.9%, 15.4%, and 15.1% of patients, respectively. Twenty-four patients (8.6%) had severe infections. BR is also an effective and safe regimen for untreated CLL patients, outside of controlled clinical trials.

Bendamustine, bortezomib and prednisone for the treatment of patients with newly diagnosed multiple myeloma: results of a prospective phase 2 Spanish/PETHEMA trial

Bendamustine is a bifunctional alkylating agent with proven activity in myeloma. In this study 60 newly diagnosed myeloma patients were given bendamustine plus bortezomib and prednisone in a regimen consisting of one cycle of bortezomib twice weekly for 6 weeks (1.3 mg/m(2) on days 1, 4, 8, 11, 22, 25, 29, and 32), plus bendamustine (90 mg/m(2) on days 1 and 4) and prednisone. The following cycles included bortezomib once weekly. Patients who were transplant candidates proceeded to stem cell collection after four cycles and the transplant was performed after six cycles. Patients who were not candidates for transplantation received up to nine cycles. Forty-two patients were transplant candidates and after six cycles, 50% achieved at least a very good partial response, with 24% having complete responses; 35 proceeded to a transplant, and the complete response rate was 54%. Seventeen patients continued up to nine cycles, and 57% achieved at least a very good partial response, including 26% with complete responses. The 2-year progression-free survival and overall survival rates were 62% and 86%, respectively. The safety profile was manageable, but stem cell mobilization was compromised in 35% of patients. In summary, this combination is effective in untreated patients, with an acceptable toxicity profile, but given the introduction of second-generation novel agents and monoclonal antibodies, the combination will probably be better reserved for relapsing patients, in whom stem cell collection is not needed, while cost-effective combinations with non-cross-resistant drugs continue to represent a medical need. This trial was registered with ClinicalTrials.gov, number NCT01376401.

[Chronic lymphocytic leukemia accompanied by renal failure]

AIM

To evaluate the efficiency and safety of monotherapy with bendamustine (B) and therapy with B in combination with rituximab (B + R) in patients with chronic lymphocytic leukemia (CLL) accompanied by renal failure (RF).

SUBJECTS AND METHODS

The prospective pilot study included 8 patients (6 men, 2 women) with CLL concurrent with RF. The patients' median age was 63 years (51-77 years). The Binet classification stage of CLL corresponded to B in 2 cases and C in 6. The mean (± standard error) pretreatment concentration of creatinine was 218 ± 92 μmol/l and the glomerular filtration rate (GFR) was 33 ± 20 ml/min. The efficiency of monotherapy with B (n=5) and combination therapy with B + R (n=3) was evaluated. In progressive CLL, therapy was performed in specific treatment-naïve patients (n = 5) and in pretreated patients refractory to alkylating agents (cyclophosphan, chlorambucil) (n = 3). A total of cycles of B and B + R were carried out.

RESULTS

After B monotherapy, one of the 5 cases achieved a complete remission, 3 a partial remission, and 1 a nodular partial remission. Three patients developed recurrence. In the B monotherapy group, the cumulative risk of recurrence was 70% at a median follow-up of 22 months and at a maximum follow-up of 27 months. In the B + R therapy group, all the 3 patients achieved a complete remission. The median follow-up was 7 months; the maximum follow-up was 1 year. There were no deaths or recurrences. During B monotherapy and B + R combination therapy, there was improved kidney function: the mean concentration of creatinine decreased from 218 ± 92 to 140 ± 57 μmol/l (p < 0.05); GFR increased from 33 ± 20.0 to 54 ± 25 ml/min; the mean increment was 20 ml/min (p < 0.01). Mild and moderate anemia and thrombocytopenia were most common during B and B + R therapies. Neutropenia with mild infection complications, as well as nonhematologic complications were detected in some cases. The drugs were observed to have no nephrotoxic effects.

CONCLUSION

The performed pilot prospective indicated that the B + R combination therapy was effective in patients with RF-associated CLL. No toxic effect of B on kidney function was seen. During B therapy, there was better kidney function manifesting itself as a statistically and clinically important decrease in creatinine concentrations and a statistically and clinically important increase in GFR as compared to the baseline values.