Pomalidomide: the new immunomodulatory agent for the treatment of multiple myeloma

In this report, we provide a comprehensive review on the preclinical and clinical investigations conducted in development of the next-generation immunomodulatory drug (IMiD) pomalidomide for the treatment of relapsed/refractory multiple myeloma (MM). We consulted PubMed, MEDLINE, ASH, ASCO annual symposium abstracts and http://clinicaltrials.gov/ for the purpose of this literature review. Twenty-six preclinical and 11 clinical studies were examined. These studies delineate the mechanisms of action of pomalidomide and attest to the robust clinical activity in relapsed/refractory MM. MM is the second most common hematological malignancy in the US. Despite availability of several therapeutic agents, MM remains incurable. Thus, the development of new therapies remains a priority. Pomalidomide is the newest member of the IMiDs class of drugs, and in preclinical and clinical investigations, it has demonstrated an improved efficacy and toxicity profile in comparison to its sister compounds, lenalidomide and thalidomide. Importantly, recent clinical studies have demonstrated its activity in relapsed or refractory myeloma, particularly in lenalidomide and bortezomib-refractory patients. Thus, the addition of pomalidomide to the anti-myeloma armamentarium is widely anticipated to have a significant impact on the overall clinical outcome of advanced stage relapsed and refractory MM patients.

Long-term outcome with lenalidomide and dexamethasone therapy for newly diagnosed multiple myeloma

The combination of lenalidomide and dexamethasone (Len-Dex) is a commonly used initial therapy for newly diagnosed multiple myeloma (MM). Although the initial response rates and toxicity are well known, long-term outcome is not well described. We studied 286 consecutive patients with newly diagnosed MM initially treated with Len-Dex. The median (range) age at diagnosis was 63 (28-92) years, 166 (58%) patients ≤ 65 years and 175 (61%) male. The median estimated duration on Len-Dex was 5.3 months with overall response (≥ partial response) of 72%, including 26% with very good partial response or better. The median overall survival (OS) from the diagnosis was not reached (NR) and the estimated 5-year survival was 71%. The median time to first disease progression, irrespective of transplant status, was 30.2 months. Overall, 143 (50%) patients underwent stem cell transplant. The median OS was NR for patients ≤ 70 years and 5.8 years for the older patients (P=0.01). The 5-year OS estimate for patients in International Staging System stage 1, 2 and 3 were 82, 65, and 44% respectively. There were 21 new second malignancies after MM diagnosis (6.6%). The median survival exceeding 7 years reflects the efficacy of novel agents. The risk of second malignancies doesn't appear to be excessive in this population.

Risk of acute leukemia and myelodysplastic syndromes in patients with monoclonal gammopathy of undetermined significance (MGUS): a population-based study of 17 315 patients

The purpose of this study was to determine if there is an increased risk of acute leukemia and myelodysplastic syndromes (MDS) in persons with monoclonal gammopathy of undetermined significance (MGUS). We used a large population-based cohort of individuals systematically screened for the presence or absence of MGUS. MGUS status was then linked to the diagnosis of acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL) and MDS. A total of 17 315 patients age 50 and older (605 MGUS and 16 710 controls) with a cumulative 435 021 person-years of follow-up were studied. MGUS patients had a significantly higher risk of developing MDS compared with controls, hazard ratio 2.4 (95% CI 1.08, 5.32), P=0.031. There was no statistically significant increase in the risk of AML (RR 1.36 P=0.675), and no increased risk of developing ALL.

Combining fluorescent in situ hybridization data with ISS staging improves risk assessment in myeloma: an International Myeloma Working Group collaborative project

The combination of serum β2-microglobulin and albumin levels has been shown to be highly prognostic in myeloma as the International Staging System (ISS). The aim of this study was to assess the independent contributions of ISS stage and cytogenetic abnormalities in predicting outcomes. A retrospective analysis of international studies looking at both ISS and cytogenetic abnormalities was performed in order to assess the potential role of combining ISS stage and cytogenetics to predict survival. This international effort used the International Myeloma Working Group database of 12 137 patients treated worldwide for myeloma at diagnosis, of whom 2309 had cytogenetic studies and 5387 had analyses by fluorescent in situ hybridization (iFISH). Comprehensive analyses used 2642 patients with sufficient iFISH data available. Using the comprehensive iFISH data, combining both t(4;14) and deletion (17p), along with ISS stage, significantly improved the prognostic assessment in terms of progression-free survival and overall survival. The additional impact of patient age and use of high-dose therapy was also demonstrated. In conclusion, the combination of iFISH data with ISS staging significantly improves risk assessment in myeloma.

High levels of peripheral blood circulating plasma cells as a specific risk factor for progression of smoldering multiple myeloma

Smoldering multiple myeloma (SMM) carries a 50% risk of progression to multiple myeloma (MM) or related malignancy within the first 5 years following diagnosis. The goal of this study was to determine if high levels of circulating plasma cells (PCs) are predictive of SMM transformation within the first 2–3 years from diagnosis. Ninety-one patients diagnosed with SMM at Mayo Clinic from January 1994 through January 2007 who had testing for circulating PCs using an immunofluorescent assay and adequate follow up to ascertain disease progression, were studied. High level of circulating PCs was defined as absolute peripheral blood PCs >5000 ×10⁶/L and/or > 5% cytoplasmic immunoglobulin (Ig) positive PCs per 100 peripheral blood mononuclear cells. Patients with high circulating PCs (14 of 91 patients, 15%) were significantly more likely to progress to active disease within 2 years compared with patients without high circulating PCs, 71% versus 25%, respectively, P=0.001. Corresponding rates for progression within 3 years were 86% versus 35%, respectively, P<0.001. Overall survival (OS) after both SMM diagnosis and MM diagnosis was also significantly different. High levels of circulating PCs identify SMM patients with an elevated risk of progression within the first 2 to 3 years following diagnosis.

A phase III randomized trial of thalidomide plus zoledronic acid versus zoledronic acid alone in patients with asymptomatic multiple myeloma

Patients with asymptomatic (smoldering) multiple myeloma (AMM) have a high risk of transformation to active multiple myeloma (MM). Bisphosphonates such as zoledronic acid (ZLD) reduce skeletal events in MM and the immunomodulatory agent thalidomide (Thal) has proven effectiveness in active MM. We hypothesized that treatment with Thal and ZLD would prolong the time to progression (TTP) to MM over ZLD alone. Eligible patients had asymptomatic MM and all patients received ZLD 4 mg intravenous monthly; the treatment arm also received Thal 200 mg per day. The TTP was superior for Thal/ZLD (n=35) patients compared with ZLD alone (n=33); median TTP of 2.4 years (95% confidence interval (CI): 1.4-3.6) versus 1.2 years (95% CI: 0.7-2.5) (hazard ratio (HR), 2.05; 95% CI: 1.1-3.8; P-value: 0.02). At 1 year, 86% of Thal/ZLD patients were progression free compared with 55% on ZLD alone (P=0.0048). The overall response rate after year 1 was 37% for Thal/ZLD with a median duration of response of 3.3 years (95% CI: 1.1-NA); there were no confirmed responses to ZLD alone (P=0.0004). The addition of Thal to standard ZLD produces anti-tumor responses whereas ZLD alone does not. Thal/ZLD also prolongs TTP from AMM to MM. This study provides the rationale for further studies in patients with AMM to delay chemotherapy.

Suppression of uninvolved immunoglobulins defined by heavy/light chain pair suppression is a risk factor for progression of MGUS

We hypothesized that the suppression of uninvolved immunoglobulin in monoclonal gammopathy of undetermined significance (MGUS) as detected by suppression of the isotype-specific heavy and light chain (HLC-pair suppression) increases the risk of progression to malignancy. This approach required quantitation of individual heavy/light chains (for example, IgGλ in IgGκ MGUS patients). Of 1384 MGUS patients from Southeastern Minnesota seen at the Mayo Clinic from 1960 to 1994, baseline serum samples obtained within 30 days of diagnosis were available in 999 persons. We identified HLC-pair suppression in 27% of MGUS patient samples compared with 11% of patients with suppression of uninvolved IgG, IgA or IgM. HLC-pair suppression was a significant risk factor for progression (hazard ratio (HR), 2.3; 95% confidence interval (CI) 1.5-3.7; P<0.001). On multivariate analysis, HLC-pair suppression was an independent risk factor for progression to malignancy in combination with serum M-spike size, heavy chain isotype and free light chain ratio (HR, 1.8; 95% CI, 1.1-3.00; P=0.018). The finding that HLC-pair suppression predicts progression in MGUS and occurs several years before malignant transformation has implications for myeloma biology.

Management of treatment-emergent peripheral neuropathy in multiple myeloma

Peripheral neuropathy (PN) is one of the most important complications of multiple myeloma (MM) treatment. PN can be caused by MM itself, either by the effects of the monoclonal protein or in the form of radiculopathy from direct compression, and particularly by certain therapies, including bortezomib, thalidomide, vinca alkaloids and cisplatin. Clinical evaluation has shown that up to 20% of MM patients have PN at diagnosis and as many as 75% may experience treatment-emergent PN during therapy. The incidence, symptoms, reversibility, predisposing factors and etiology of treatment-emergent PN vary among MM therapies, with PN incidence also affected by the dose, schedule and combinations of potentially neurotoxic agents. Effective management of treatment-emergent PN is critical to minimize the incidence and severity of this complication, while maintaining therapeutic efficacy. Herein, the state of knowledge regarding treatment-emergent PN in MM patients and current management practices are outlined, and recommendations regarding optimal strategies for PN management during MM treatment are provided. These strategies include early and regular monitoring with neurological evaluation, with dose modification and treatment discontinuation as indicated. Areas requiring further research include the development of MM-specific, patient-focused assessment tools, pharmacogenomic analysis of patient DNA, and trials to assess the efficacy of pharmacological interventions.

Disparities in the prevalence, pathogenesis and progression of monoclonal gammopathy of undetermined significance and multiple myeloma between blacks and whites

There is marked racial disparity in the incidence of monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma, with a two to threefold increased risk in blacks compared with whites. The increased risk has been seen both in Africans and African Americans. Similarly, an increased risk of monoclonal gammopathies in blacks compared with whites has been noted after adjusting for socioeconomic and other risk factors, suggesting a genetic predisposition. The higher risk of multiple myeloma in blacks is likely a result of the higher prevalence of the premalignant MGUS stage; there are no data to suggest that blacks have a higher progression rate of MGUS to myeloma. Studies are emerging that suggest the baseline cytogenetic characteristics, and progression may differ by race. In contrast, to the increased risk noted in blacks, studies suggest that the risk may be lower in certain racial and ethnic groups, notably persons from Japan and Mexico. We review the literature on racial disparity in the prevalence, pathogenesis and progression of MGUS and multiple myeloma between blacks and whites. We also discuss future directions for research that could inform management of these conditions and positively influence patient outcomes.

Risk of progression and survival in multiple myeloma relapsing after therapy with IMiDs and bortezomib: a multicenter international myeloma working group study

Promising new drugs are being evaluated for treatment of multiple myeloma (MM), but their impact should be measured against the expected outcome in patients failing current therapies. However, the natural history of relapsed disease in the current era remains unclear. We studied 286 patients with relapsed MM, who were refractory to bortezomib and were relapsed following, refractory to or ineligible to receive, an IMiD (immunomodulatory drug), had measurable disease, and ECOG PS of 0, 1 or 2. The date patients satisfied the entry criteria was defined as time zero (T(0)). The median age at diagnosis was 58 years, and time from diagnosis to T(0) was 3.3 years. Following T(0), 213 (74%) patients had a treatment recorded with one or more regimens (median=1; range 0-8). The first regimen contained bortezomib in 55 (26%) patients and an IMiD in 70 (33%). A minor response or better was seen to at least one therapy after T(0) in 94 patients (44%) including ≥ partial response in 69 (32%). The median overall survival and event-free survival from T(0) were 9 and 5 months, respectively. This study confirms the poor outcome, once patients become refractory to current treatments. The results provide context for interpreting ongoing trials of new drugs.

Incidence of extramedullary disease in patients with multiple myeloma in the era of novel therapy, and the activity of pomalidomide on extramedullary myeloma

We studied 174 consecutive patients with relapsed refractory multiple myeloma (MM) enrolled on a phase II clinical trial of pomalidomide plus low-dose dexamethasone at Mayo Clinic. Extramedullary disease (EMD) was present at the time of trial entry in 7.5% (13 of 174 patients). The rate of EMD in the first 3 years following diagnosis of MM was 3%. The response of EMD to pomalidomide plus low-dose dexamethasone included two complete and two partial responses among the 13 patients (response rate, 31%). Overall survival measured from trial entry was significantly shorter for patients with treatment-emergent EMD compared with those who did not have EMD, (median 16 months versus not reached, P=0.002).

Melphalan and prednisone versus melphalan, prednisone and thalidomide for elderly and/or transplant ineligible patients with multiple myeloma: a meta-analysis

Trials comparing efficacy of melphalan prednisone (MP) with MP plus thalidomide in transplant ineligible, elderly patients with multiple myeloma have provided conflicting evidence. Although there is agreement regarding improved response rates (RRs) and higher toxicity with the addition of thalidomide to MP, the impact on progression free survival (PFS) and overall survival (OS) is less clear. We performed a meta-analysis comparing efficacy of melphalan, prednisone and thalidomide (MPT) and MP by pooling results on RR, PFS and OS reported in all the identified randomized controlled trials (RCTs) under a random effects model. Overall, six prospective RCTs, with data extractable from five published trials (n=1571) [corrected] were identified. The pooled odds ratio of responding to therapy with MPT vs MP was 3.39 (P<0.001, 95% CI: 2.24-5.12). The pooled hazard ratios for PFS and OS were and 0.68 (P<0.001; 95% CI: 0.55-0.82) and 0.80 (P=0.07; 95% CI: 0.63-1.02), respectively, in favor of MPT. The odds ratios for high grade peripheral neuropathy and deep venous thrombosis were 6.6 and 2.4, respectively, in favour of MP. There was significant heterogeneity among the RCTs. Our meta-analysis demonstrates that in previously untreated, transplant ineligible, elderly myeloma patients, the addition of T to MP results in significantly improved RR and PFS with a trend towards improvement in OS compared with MP alone, but at a cost of significantly greater toxicity.

IgM multiple myeloma: disease definition, prognosis, and differentiation from Waldenstrom's macroglobulinemia

IgM multiple myeloma (MM) and Waldenstrom's macroglobulinemia (WM) are two distinct hematologic entities with the common finding of an IgM monoclonal gammopathy. Distinguishing these two diagnoses is critical as the approach to therapy is different. A priori, we defined IgM MM as a symptomatic clonal plasma cell proliferative disorder characterized by an IgM monoclonal protein (regardless of size), 10% or more plasma cells on bone marrow biopsy, plus the presence of lytic bone lesions and/or translocation t(11;14). Twenty-one patients met this definition of IgM MM. All 21 patients had lytic bone lesions. Of the 16 evaluated with FISH, 6 (38%) demonstrated t(11;14). Median overall survival was 30 months, which is similar to non-IgM myeloma patients treated during this period and shorter than what would be expected for WM. In this, the largest series of patients with IgM MM, we describe the clinical features and prognosis of patient with IgM MM using a strict definition for the disease. The subset of patients without lytic lesions or t(11;14) but with immunophenotypic features suggestive of MM need further study.

Pomalidomide (CC4047) plus low dose dexamethasone (Pom/dex) is active and well tolerated in lenalidomide refractory multiple myeloma (MM)

Patients with multiple myeloma progressing on current therapies have limited treatment options. Pomalidomide (CC4047), an immunomodulatory drug, has significant activity in relapsed myeloma and previous studies suggest activity in lenalidomide refractory disease. To better define its efficacy in this group, we treated a cohort of lenalidomide refractory patients. Pomalidomide was given orally (2 mg) daily, continuously in 28-day cycles along with dexamethasone (40 mg) given weekly. Responses were assessed by the International Myeloma Working Group Criteria. Thirty-four patients were enrolled. The best response was very good partial response in 3 (9%), partial response (PR) in 8 (23%), best responses (MR) in 5 (15%), stable disease in 12 (35%) and progressive disease in 6 (18%), for an overall response rate of 47%. Of the 14 patients that were considered high risk, 8 (57%) had responses including 4 PR and 4 MR. The median time to response was 2 months and response duration was 9.1 months, respectively. The median overall survival was 13.9 months. Toxicity was primarily hematologic, with grade 3 or 4 toxicity seen in 18 patients (53%) consisting of anemia (12%), thrombocytopenia (9%) and neutropenia (26%). The combination of pomalidomide and dexamethasone (Pom/dex) is highly active and well tolerated in patients with lenalidomide-refractory myeloma.

Bortezomib, dexamethasone, cyclophosphamide and lenalidomide combination for newly diagnosed multiple myeloma: phase 1 results from the multicenter EVOLUTION study

This phase 1 study (Clinicaltrials.gov: NCT00507442) was conducted to determine the maximum tolerated dose (MTD) of cyclophosphamide in combination with bortezomib, dexamethasone and lenalidomide (VDCR) and to assess the safety and efficacy of this combination in untreated multiple myeloma patients. Cohorts of three to six patients received a cyclophosphamide dosage of 100, 200, 300, 400 or 500 mg/m(2) (on days 1 and 8) plus bortezomib 1.3 mg/m(2) (on days 1, 4, 8 and 11), dexamethasone 40 mg (on days 1, 8 and 15) and lenalidomide 15 mg (on days 1-14), for eight 21-day induction cycles, followed by four 42-day maintenance cycles (bortezomib 1.3 mg/m(2), on days 1, 8, 15 and 22). The MTD was the cyclophosphamide dose below which more than one of six patients experienced a dose-limiting toxicity (DLT). Twenty-five patients were treated. Two DLTs were seen, of grade 4 febrile neutropenia (cyclophosphamide 400 mg/m(2)) and grade 4 herpes zoster despite anti-viral prophylaxis (cyclophosphamide 500 mg/m(2)). No cumulative hematological toxicity or thromboembolic episodes were reported. The overall response rate was 96%, including 20% stringent complete response (CR), 40% CR/near-complete response and 68% >or=very good partial response. VDCR is well tolerated and highly active in this population. No MTD was reached; the recommended phase 2 cyclophosphamide dose in VDCR is 500 mg/m(2), which was the highest dose tested.

Sorafenib, a dual Raf kinase/vascular endothelial growth factor receptor inhibitor has significant anti-myeloma activity and synergizes with common anti-myeloma drugs

Multiple myeloma is characterized by increased bone marrow neovascularization driven in part by vascular endothelial growth factor (VEGF). In addition, the Ras/Raf/MEK/ERK pathway is critical for the proliferation of myeloma cells and is often upregulated. Sorafenib (Nexavar) is a novel multi-kinase inhibitor that acts predominantly through inhibition of Raf-kinase and VEGF receptor 2, offering the potential for targeting two important aspects of disease biology. In in vitro studies, sorafenib-induced cytotoxicity in MM cell lines as well as freshly isolated patient myeloma cells. It retained its activity against MM cells in co-culture with stromal cells or with interleukin-6, VEGF or IGF; conditions mimicking tumor microenvironment. Examination of cellular signaling pathways showed downregulation of Mcl1 as well as decreased phosphorylation of the STAT3 and MEK/ERK, as potential mechanisms of its anti-tumor effect. Sorafenib induces reciprocal upregulation of Akt phosphorylation; and simultaneous inhibition of downstream mTOR with rapamycin leads to synergistic effects. Sorafenib also synergizes with drugs such as proteasome inhibitors and steroids. In a human in vitro angiogenesis assay, sorafenib showed potent anti-angiogenic activity. Sorafenib, through multiple mechanisms exerts potent anti-myeloma activity and these results favor further clinical evaluation and development of novel sorafenib combinations.

Clinical value of minor responses after 4 doses of rituximab in Waldenström macroglobulinaemia: a follow-up of the Eastern Cooperative Oncology Group E3A98 trial

Waldenström macroglobulinaemia is a low-grade, lymphoplasmacytic lymphoma that is responsive to rituximab. We report the role of a minor response in predicting overall outcomes. We extended follow-up of a previously described cohort (n = 69) treated with 4 weekly doses of rituximab and observed durable responses (median time to progression, 30 months; 5-year survival rate, 66%). Patients achieving a minor response [25-50% immunoglobulin M (IgM) reduction] appeared to do as well as those achieving an objective response (>50% IgM reduction), which suggests that more aggressive or intensive therapy for minor responders is not required. Future studies of Waldenström macroglobulinaemia should report minor responses because they are associated with clinically meaningful benefits. This trial was registered at http://www.clinicaltrials.gov as #NCT00005609.

International myeloma working group (IMWG) consensus statement and guidelines regarding the current status of stem cell collection and high-dose therapy for multiple myeloma and the role of plerixafor (AMD 3100)

Multiple myeloma is the most common indication for high-dose chemotherapy with autologous stem cell support (ASCT) in North America today. Stem cell procurement for ASCT has most commonly been performed with stem cell mobilization using colony-stimulating factors with or without prior chemotherapy. The target CD34+ cell dose to be collected as well as the number of apheresis performed varies throughout the country, but a minimum of 2 million CD34+ cells/kg has been traditionally used for the support of one cycle of high-dose therapy. With the advent of plerixafor (AMD3100) (a novel stem cell mobilization agent), it is pertinent to review the current status of stem cell mobilization for myeloma as well as the role of autologous stem cell transplantation in this disease. On June 1, 2008, a panel of experts was convened by the International Myeloma Foundation to address issues regarding stem cell mobilization and autologous transplantation in myeloma in the context of new therapies. The panel was asked to discuss a variety of issues regarding stem cell collection and transplantation in myeloma especially with the arrival of plerixafor. Herein, is a summary of their deliberations and conclusions.

International myeloma working group consensus statement and guidelines regarding the current role of imaging techniques in the diagnosis and monitoring of multiple Myeloma

Several imaging technologies are used for the diagnosis and management of patients with multiple myeloma (MM). Conventional radiography, computed tomography (CT), magnetic resonance imaging (MRI) and nuclear medicine imaging are all used in an attempt to better clarify the extent of bone disease and soft tissue disease in MM. This review summarizes all available data in the literature and provides recommendations for the use of each of the technologies. Conventional radiography still remains the 'gold standard' of the staging procedure of newly diagnosed and relapsed myeloma patients. MRI gives information complementary to skeletal survey and is recommended in MM patients with normal conventional radiography and in all patients with an apparently solitary plasmacytoma of bone. Urgent MRI or CT (if MRI is not available) is the diagnostic procedure of choice to assess suspected cord compression. Bone scintigraphy has no place in the routine staging of myeloma, whereas sequential dual-energy X-ray absorptiometry scans are not recommended. Positron emission tomography/CT or MIBI imaging are also not recommended for routine use in the management of myeloma patients, although both techniques may be useful in selected cases that warrant clarification of previous imaging findings, but such an approach should ideally be made within the context of a clinical trial.