Proteasome inhibition in multiple myeloma

Carfilzomib: a second-generation proteasome inhibitor for the treatment of multiple myeloma

PURPOSE

The pharmacology, clinical efficacy, safety, cost, dosage and administration, and place in therapy of carfilzomib for the treatment of multiple myeloma (MM) are reviewed.

SUMMARY

Proteasome inhibition in MM has become a cornerstone in treatment regimens. Carfilzomib, a second-generation proteasome inhibitor, has demonstrated efficacy in patients with relapsed or refractory disease who have received at least two prior therapies including bortezomib and an immunomodulatory agent. Carfilzomib is an irreversible inhibitor and binds to a different site than bortezomib on the proteasome. A Phase II study evaluated 266 heavily pretreated patients with relapsed or refractory MM who had received at least two prior therapies, including bortezomib and either thalidomide or lenalidomide. The overall response rate was 23.7%, with a median duration of response of 7.8 months. The median overall survival time was 15.6 months. Carfilzomib has a similar adverse-effect profile to bortezomib, including anemia, thrombocytopenia, fatigue, dyspnea, and nausea; however, it does not result in the development or worsening of peripheral neuropathy. Carfilzomib is infused intravenously over 2-10 minutes for 2 consecutive days every week for three out of four weeks, with a 12-day rest period. Dosing is based on the patient's actual body surface area. Carfilzomib is available in 60-mg vials for single infusion. The total cost for a year of therapy is approximately $155,852.

CONCLUSION

Carfilzomib, a second-generation proteasome inhibitor that irreversibly inhibits the 26S proteasome, has shown efficacy in clinical studies of patients with relapsed or refractory MM, though the drug's role in the management of MM is not yet clear.

Threonine peptidases as drug targets against malaria

INTRODUCTION

Malaria is caused by the intracellular parasite Plasmodium falciparum. Although numerous therapies are available to fight the disease, the number of pharmacophores is small, and constant development of novel therapies, especially with new targets, is desirable to fight developing resistance against presently prescribed drugs.

AREAS COVERED

This review discusses research on plasmodial threonine peptidases along with recent advances in proteasome inhibitor development.

EXPERT OPINION

While PfHslV is an attractive drug target in malaria, more investigation is required to clarify its functional role in the parasite. More efforts should also be invested in assessing the plasmodial proteasome as a drug target. The few papers investigating the effect of proteasome inhibitors on different stages of the life cycle point towards important roles not only during asexual, but also in hepatic and sexual stages, in humans and the mosquito. If this holds true, this is a key argument to further develop proteasome inhibitors for use against malaria.

Pathogenesis of myeloma bone disease

Multiple myeloma (MM) is the most common cancer to involve bone with up to 90% of patients developing bone lesions. The bone lesions are purely osteolytic in nature and do not heal in the vast majority of patients. Up to 60% of patients develop pathologic fractures over the course of their disease. Bone disease is a hallmark of MM, and myeloma bone disease differs from bone metastasis caused by other tumors. Although myeloma and other osteolytic metastases induce increased osteoclastic bone destruction, in contrast to other tumors, once myeloma tumor burden exceeds 50% in a local area, osteoblast activity is either severely depressed or absent. The basis for this severe imbalance between increased osteoclastic bone resorption and decreased bone formation has been the topic of intensive investigation over the last several years. These studies have helped to identify novel targets for treating myeloma bone disease and will be discussed in this chapter.

Treatment of multicentric Castleman's Disease accompanying multiple myeloma with bortezomib: a case report

Multicentric Castleman's disease (MCD) is a rare lymphoproliferative disorder of unknown etiology and characterized by various clinical manifestations and multiple organ involvement. It has been reported in association with POEMS syndrome and can progress to Kaposi's sarcoma or malignant lymphoma. The disease runs a more aggressive course and a poor prognosis. Optimal therapies have not been well established up to now. We here reported a case of rare MCD complicated with multiple myeloma who received bortezomib and achieved very good remission. To our knowledge, this is the first report on MCD in the setting of multiple myeloma with good response to bortezomib.

Transgenic inhibition of astroglial NF-kappa B improves functional outcome in experimental autoimmune encephalomyelitis by suppressing chronic central nervous system inflammation

In the CNS, the transcription factor NF-kappaB is a key regulator of inflammation and secondary injury processes. Following trauma or disease, the expression of NF-kappaB-dependent genes is activated, leading to both protective and detrimental effects. In this study, we show that transgenic inactivation of astroglial NF-kappaB (glial fibrillary acidic protein-IkappaB alpha-dominant-negative mice) resulted in reduced disease severity and improved functional recovery following experimental autoimmune encephalomyelitis. At the chronic stage of the disease, transgenic mice exhibited an overall higher presence of leukocytes in spinal cord and brain, and a markedly higher percentage of CD8(+)CD122(+) T regulatory cells compared with wild type, which correlated with the timing of clinical recovery. We also observed that expression of proinflammatory genes in both spinal cord and cerebellum was delayed and reduced, whereas the loss of neuronal-specific molecules essential for synaptic transmission was limited compared with wild-type mice. Furthermore, death of retinal ganglion cells in affected retinas was almost abolished, suggesting the activation of neuroprotective mechanisms. Our data indicate that inhibiting NF-kappaB in astrocytes results in neuroprotective effects following experimental autoimmune encephalomyelitis, directly implicating astrocytes in the pathophysiology of this disease.

Novel targets for myeloma bone disease

BACKGROUND

Multiple myeloma (MM) is a plasma cell malignancy in which osteolytic bone lesions develop in over 80% of patients. The increased bone destruction results from increased osteoclast formation and activity, which occurs adjacent to marrow sites involved with MM cells. This is accompanied by suppressed or absent osteoblast differentiation and activity, resulting in severely impaired bone formation and development of purely osteolytic lesions.

OBJECTIVE

The pathophysiology underlying this bone remodeling is reviewed, and potential new strategies to treat MM bone disease are discussed.

RESULTS

Recent advances in our understanding of factors involved in pathogenesis of MM bone disease have identified novel therapeutic targets. Several of these are or will be in clinical trials soon.

CONCLUSION

Agents which target the tumor and bone-destructive process, such as the immunomodulatory drugs (IMiDs) or bortezomib, in combination with novel anti-resorptives should be effective. These combinations should be in clinical trials in the next few years. It is unclear if these treatments will be able to 'heal' bone lesions in MM patients.

Pathogenesis of myeloma bone disease

Bone disease in multiple myeloma (MM) is characterized by lytic bone lesions, which can cause severe bone pain, pathologic fractures and hypercalcemia. However, the lytic bone disease in MM differs from that in other cancer patients who have lytic bone metastases. Although increased osteoclastic bone destruction is involved in MM and other tumors involving bone, in contrast to other tumors, once the MM tumor burden exceeds 50% in a local area, osteoblast activity is either suppressed or absent. The basis for this severe imbalance between increased osteoclastic bone resorption and decreased bone formation has been a topic of intensive investigation over the last several years and will be reviewed in this article.

Myeloma cells and bone marrow osteoblast interactions: role in the development of osteolytic lesions in multiple myeloma

Bone destruction is the hallmark of multiple myeloma (MM) due to the high capacity of malignant plasma cells to induce a severe imbalance of bone remodeling. Growing evidences suggest that MM cell interactions with bone marrow (BM) osteoblast have a critical role in the pathophysiology of osteolytic lesions. Indeed histomorphometric studies have demonstrated that MM patients with osteolytic bone lesions have lower numbers of osteoblasts and decreased bone formation together with osteoclast activation. Recently, the biological mechanisms involved in the osteoblast inhibition induced by MM cells have begun to be elucidated, underlying the main role of the block of osteoblast differentiation in the development of bone lesions. In this article, we summarize the main mechanisms regulating MM cell and osteoblast interactions.

Myeloma bone disease and proteasome inhibition therapies

Bone disease is one of the most debilitating manifestations of multiple myeloma. A complex interdependence exists between myeloma bone disease and tumor growth, creating a vicious circle of extensive bone destruction and myeloma progression. Proteasome inhibitors have recently been shown to promote bone formation in vitro and in vivo. Preclinical studies have demonstrated that proteasome inhibitors, including bortezomib, which is the first-in-class such agent, stimulate osteoblast differentiation while inhibiting osteoclast formation and bone resorption. Clinical studies are confirming these observations. Bortezomib counteracts the abnormal balance of osteoclast regulators (receptor activator of nuclear factor-κB ligand and osteoprotegerin), leading to osteoclast inhibition and decreased bone destruction, as measured by a reduction in markers of bone resorption. In addition, bortezomib stimulates osteoblast function, possibly through the reduction of dickkopf-1, leading to increased bone formation, as indicated by the elevation in bone-specific alkaline phosphatase and osteocalcin. The effect of bortezomib on bone disease is thought to be direct and not only a consequence of the agent's antimyeloma properties, making it an attractive agent for further investigation, as it may combine potent antimyeloma activity with beneficial effects on bone. However, the clinical implication of these effects requires prospective studies with specific clinical end points.

Bortezomib in combination with intermediate-dose dexamethasone and continuous low-dose oral cyclophosphamide for relapsed multiple myeloma

A phase 2 trial was performed to study the combination of bortezomib (VELCADE) with intermediate-dose dexamethasone (DEX), and continuous low-dose oral cyclophosphamide (CY) in patients with relapsed multiple myeloma (MM). Fifty-four patients with advanced MM were enroled to receive eight 3-week treatment cycles with bortezomib 1.3 mg/m(2) on days 1, 4, 8, and 11, followed by three 5-week cycles with bortezomib 1.3 mg/m(2) on days 1, 8, 15, and 22. Within all cycles, DEX 20 mg/d was given orally on the day of bortezomib injection and the day thereafter. In addition, patients received CY continuous oral treatment at a dose of 50 mg/d p.o. once daily. Fifty patients completing at least one treatment cycle were evaluable for response. Complete, partial, and minor responses occurred in 16%, 66% and 8% of patients, respectively; overall response rate 90% (efficacy analysis). Median event-free survival was 12 months, with a median overall survival of 22 months. Adverse events (AE) of grades 3 or 4 occurring in at least 10% of patients comprised leucopenia, infection, herpes zoster, thrombocytopenia, neuropathy and fatigue. Bortezomib combined with DEX and CY is a highly effective treatment for relapsed MM at an acceptable rate of grade 3/4 AE. Antiviral prophylaxis appears to be mandatory.

The proteasome inhibitor bortezomib affects osteoblast differentiation in vitro and in vivo in multiple myeloma patients

The proteasome inhibitor bortezomib may increase osteoblast-related markers in multiple myeloma (MM) patients; however, its potential osteoblastic stimulatory effect is not known. In this study, we show that bortezomib significantly induced a stimulatory effect on osteoblast markers in human mesenchymal cells without affecting the number of osteoblast progenitors in bone marrow cultures or the viability of mature osteoblasts. Consistently we found that bortezomib significantly increased the transcription factor Runx2/Cbfa1 activity in human osteoblast progenitors and osteoblasts without affecting nuclear and cytoplasmatic active beta-catenin levels. Consequently a stimulatory effect of bortezomib on bone nodule formation was also demonstrated in osteoblast progenitors. These in vitro observations were confirmed in vivo by the finding of a significant increase in the number of osteoblastic cells x mm(2) of bone tissue and in the number of Runx2/Cbfa1-positive osteoblastic cells that was observed in MM patients who responded to bortezomib. Our in vitro and in vivo observations support the hypothesis that a direct stimulatory effect on bone formation process could occur during bortezomib treatment.

Multiple myeloma bone disease: Pathophysiology of osteoblast inhibition

Multiple myeloma (MM) is a plasma cell malignancy characterized by a high capacity to induce osteolytic bone lesions. Bone destruction in MM results from increased osteoclast formation and activity that occur in close proximity to myeloma cells. However, histomorphometric studies have demonstrated that MM patients with osteolytic bone lesions have lower numbers of osteoblasts and decreased bone formation. This impaired bone formation plays a critical role in the bone-destructive process. Recently, the biologic mechanisms involved in the osteoblast inhibition induced by MM cells have begun to be elucidated. In this article, the pathophysiology underlying osteoblast inhibition in MM is reviewed.