Bone-targeting radiopharmaceuticals for the treatment of bone-metastatic castration-resistant prostate cancer: exploring the implications of new data.

BACKGROUND: Clinical features of patients with castration-resistant prostate cancer (CRPC) are characterized by a high incidence of bone metastases, which are associated with impairment of quality of life, pain, skeletal-related events (SREs), and a negative impact on prognosis. Advances in the understanding of cancer cell-bone stroma interactions and molecular mechanisms have recently permitted the development of new agents. PURPOSE: We review the merits, applications, and limitations of emerging data sets on bone-metastatic CRPC with a focus on radium-223, an α-emitting radiopharmaceutical, and its use in therapy for this disease. METHODS: References for this review were identified through searches of PubMed and Medline databases, and only papers published in English were considered. Related links in the databases were reviewed, along with relevant published guidelines, recently published abstracts from major medical meetings, and transcripts from a recent round table of clinical investigators. RESULTS: Prior to radium-223, available bone-targeted therapies demonstrated the ability to delay SREs and palliate bone pain in patients with metastatic CRPC but without evidence of improvement in overall survival (OS). In a randomized controlled phase III trial, radium-223 demonstrated the ability to improve OS and delay SREs in docetaxel-pretreated or docetaxel-unfit men with symptomatic bone-metastatic CRPC and was not associated with significantly more grade 3 or 4 adverse events than placebo. CONCLUSION: Radium-223 has a targeted effect on bone metastases in CRPC and has an important role in docetaxel-pretreated or docetaxel-unfit men with symptomatic bone-metastatic CRPC.

Proteasome inhibition for antibody-mediated rejection.

PURPOSE OF REVIEW: The purpose of this review is to describe the biochemistry and physiology of proteasome inhibition and to discuss recent studies with proteasome inhibitor therapy in organ transplantation. RECENT FINDINGS: Traditional antihumoral therapies do not deplete plasma cells, the source of antibody production. Proteasome inhibition depletes both transformed and nontransformed plasma cells in animal models and human transplant recipients. Bortezomib is a first in a class proteasome inhibitor that has been shown to effectively treat antibody-mediated rejection in kidney transplant recipients. In this experience, bortezomib provided reversal of histologic changes and also induced a reduction in donor-specific anti-HLA antibody levels. Recent experiences have also shown that bortezomib reduces donor-specific anti-human leukocyte antigen antibody in the absence of rejection. Finally, evidence has been presented that bortezomib therapy depletes human leukocyte antigen-specific antibody producing plasma cells. SUMMARY: Proteasome inhibition induces a complex series of biochemical events that results in pleiotropic effects on multiple cell populations, and plasma cells in particular. Initial clinical results have provided evidence that bortezomib effectively treats antibody-mediated rejection and acute cellular rejection and reduces or eliminates donor-specific anti-human leukocyte antigen antibody. Carefully designed clinical trials are needed to accurately define the role of proteasome inhibition in transplant recipients.

Role of proteasome inhibition in sensitized transplant candidates.

OBJECTIVE: To review this efficacy and safety of bortezomib, a proteasome inhibitor, in the setting of the sensitized transplant candidate. DATA SOURCES: The data used in this review were from articles published (PubMed) between 2000 to 2010. Additionally abstracts from medical meetings related to transplant were also used. STUDY SELECTION: Articles were selected if they were trial results or case studies for the use of bortezomib in the sensitized patient population. RESULTS: The early data using bortezomib as a part of desensitization regimens has shown success. Although one cycle (4 doses) of bortezomib seems to have affect on many patients, it also seems likely that to provide complete desensitization multiple cycles will be required. Regarding safety, bortezomib has been shown to have minimal side effects. The most common side effects reported are those of thrombocytopenia and anemia. These side effects are dose related and self limiting upon discontinuation of the treatment. CONCLUSIONS: Bortezomib with plasmapheresis is a promising new alternative to desensitization protocols that use either high dose intravenous immune globulin (IVIG) or low dose IVIG and plasmapheresis. The efficacy on antibody reduction looks to be batter that that of the IVIG based regimens without significant addition toxicity. The results of ongoing prospective trials are positive and their complete results are greatly anticipated.

Proteasome inhibitor-based primary therapy for antibody-mediated renal allograft rejection.

BACKGROUND: Rapid and complete elimination of donor-specific anti-human leukocyte antigen antibodies (DSA) during antibody-mediated rejection (AMR) is rarely achieved with traditional antihumoral therapies. Proteasome inhibitor-based therapy has been shown to effectively treat refractory AMR, but its use as a primary therapy for AMR has not been presented. Our initial experience with proteasome inhibition as a first-line therapy for AMR is presented. METHODS: Adult kidney transplant recipients with AMR, diagnosed by Banff criteria, received a bortezomib-based regimen as the primary therapy. Bortezomib therapy was administered per package insert with plasmapheresis performed immediately before each bortezomib dose, and a single rituximab dose (375 mg/m2) given with the first bortezomib dose. DSA were quantitated using single-antigen beads on a Luminex platform. RESULTS: Two patients underwent bortezomib-based therapy for acute AMR occurring within the first 2 weeks after transplantation. High DSA levels and positive C4d staining of peritubular or glomerular capillaries were present at the time of diagnosis. Both patients experienced prompt AMR reversal and elimination of detectable DSA within 14 days of bortezomib-based therapy. Renal function remains excellent with normal urinary protein excretion at 5 and 6 months after AMR diagnosis. One patient experienced a repeated elevation of DSA (including two new human leukocyte antigen specificities) 2 months after initial bortezomib therapy, but without C4d deposition or histologic evidence of AMR. Retreatment with bortezomib provided prompt, complete, and durable DSA elimination. CONCLUSIONS: Proteasome inhibitor-based combination therapy provides a potential means for rapid DSA elimination in early acute AMR in renal transplant recipients.

De novo cancers arising in organ transplant recipients are associated with adverse outcomes compared with the general population.

BACKGROUND: Transplant recipients are at increased risk of malignancy; however, the influence of transplantation on cancer outcomes has not been rigorously defined. The purpose of this study was to examine the influence of transplantation on the outcomes of individual cancers. METHODS: De novo nonsmall cell lung cancer, colon cancer, breast cancer, prostate cancer, bladder cancer, renal cell cancer (RCC), and malignant melanoma data in 635 adult (>18 years of age) transplant recipients (from the Israel Penn International Transplant Tumor Registry) were compared with data from 1,282,984 adults in the general population (from the Surveillance, Epidemiology, and End Results database). RESULTS: Compared with the general population, transplant patients were more likely to have early stage (AJCC stage 0-II) RCC, but more advanced (AJCC stage >II) colon cancer, breast cancer, bladder cancer, and malignant melanoma. Compared with the general population, disease-specific survival was worse in the transplant population for colon cancer (all stages), nonsmall cell lung cancer (stage II), breast cancer (stage III), prostate cancer (stage II, III, and IV), bladder cancer (stage III), and RCC (stage IV). Multivariate analyses demonstrated transplantation to be a negative risk factor for survival for each cancer studied, and transplantation and cancer stage at diagnosis to be the most profound negative survival predictors. CONCLUSIONS: These analyses indicate that, for several common cancers, transplant patients experience worse outcomes than the general population. The data also suggest that cancers in transplant recipients are more aggressive biologically at the time of diagnosis.

Bortezomib provides effective therapy for antibody- and cell-mediated acute rejection.

BACKGROUND: Current antihumoral therapies in transplantation and autoimmune disease do not target the mature antibody-producing plasma cell. Bortezomib is a first in class proteosomal inhibitor, that is Food and Drug Administration approved, for the treatment of plasma cell-derived tumors that is multiple myeloma. We report the first clinical experience with plasma cell-targeted therapy (bortezomib) as an antirejection strategy. METHODS: Eight episodes of mixed antibody-mediated rejection (AMR) and acute cellular rejection (ACR) in six transplant recipients were treated with bortezomib at labeled dosing. Monitoring included serial donor-specific antihuman leukocyte antigen antibody (DSA) levels and repeated allograft biopsies. RESULTS: Six kidney transplant patients received bortezomib for AMR and concomitant ACR. In each case, bortezomib therapy provided (1) prompt rejection reversal, (2) marked and prolonged reductions in DSA levels, (3) improved renal allograft function, and (4) suppression of recurrent rejection for at least 5 months. Moreover, immunodominant DSA (iDSA) (i.e., the antidonor human leukocyte antigen antibody with the highest levels) levels were decreased by more than 50% within 14 days and remained substantially suppressed for up to 5 months. One or more additional DSA were present at lower concentrations (non-iDSA) in each patient and were also reduced to nondetectable levels. Bortezomib-related toxicities (gastrointestinal toxicity, thrombocytopenia, and paresthesias) were all transient. CONCLUSIONS: Bortezomib therapy: (1) provides effective treatment of AMR and ACR with minimal toxicity and (2) provides sustained reduction in iDSA and non-iDSA levels. Bortezomib represents the first effective antihumoral therapy with activity in humans that targets plasma cells.

Immunomodulatory effects of human recombinant granulocyte-macrophage colony-stimulating factor (rhuGM-CSF): evidence of antitumour activity.

Human recombinant granulocyte-macrophage colony-stimulating factor (rhuGM-CSF) is traditionally used as supportive care for patients undergoing cytotoxic chemotherapy or haematopoietic cell progenitor mobilisation. Emerging evidence suggests rhuGM-CSF, through activity on monocytes and dendritic cells, acts as a potent modulator of immune responses and has the ability to recruit inflammatory cells and cytokines to local and systemic sites of infection. The immunomodulatory effects of rhuGM-CSF suggest the potential to enhance innate and acquired immune responses against tumour-related antigens. Enhancement of innate antitumour immunity, especially in the context of minimal residual disease, is of central importance and presents the potential for meaningful contributions to long-term disease survival. This article discusses the immunomodulatory effects of rhuGM-CSF in the context of single-agent therapy in solid tumours, as well as combination therapy in lymphoma. In addition, dendritic cell modulation with rhuGM-CSF in haematopoietic progenitor grafts and rhuGM-CSF-transduced tumour vaccines will be discussed.