Pegfilgrastim, a sustained-duration form of filgrastim, significantly improves neutrophil recovery after autologous marrow transplantation in rhesus macaques

The effects of granulocyte colony-stimulating factor on MR images of bone marrow

Granulocyte colony-stimulating factor (G-CSF) analogs such as filgrastim/pegfilgrastim are increasingly used to enhance neutrophilic recovery after chemotherapy. It is widely known that, physiologically, pegfilgrastim stimulates marrow mitotic activity and induces marrow reconversion from fatty to cellular. However, there is limited literature discussing the effects of pegfilgrastim on musculoskeletal magnetic resonance imaging, with the consensus that marrow reconversion secondary to pegfilgrastim therapy is easily confounded with a malignant process, especially in patients with a history of cancer. We attempt to discuss the expected changes and MRI findings after pegfilgrastim therapy through a summary of current literature. Additionally, we provide images from our own practice to support the previously established findings. G-CSF-stimulated reconversion can appear as patchy expansions of baseline hematopoietic marrow, but can also appear to be diffusely homogeneous, adding to its ambiguity. We conclude that using a baseline MRI, clinical information, and assessing sequential MRI changes in conjunction with pegfilgrastim therapy may aid the differentiation between benign and pathological change. We expand our discussion to include the effects of novel technologies, such as whole-body MRI, chemical shift imaging, and contrast agents in helping the distinction.

Effects of a granulocyte colony stimulating factor, Neulasta, in mini pigs exposed to total body proton irradiation

Astronauts could be exposed to solar particle event (SPE) radiation, which is comprised mostly of proton radiation. Proton radiation is also a treatment option for certain cancers. Both astronauts and clinical patients exposed to ionizing radiation are at risk for loss of white blood cells (WBCs), which are the body's main defense against infection. In this report, the effect of Neulasta treatment, a granulocyte colony stimulating factor, after proton radiation exposure is discussed. Mini pigs exposed to total body proton irradiation at a dose of 2 Gy received 4 treatments of either Neulasta or saline injections. Peripheral blood cell counts and thromboelastography parameters were recorded up to 30 days post-irradiation. Neulasta significantly improved WBC loss, specifically neutrophils, in irradiated animals by approximately 60% three days after the first injection, compared to the saline treated, irradiated animals. Blood cell counts quickly decreased after the last Neulasta injection, suggesting a transient effect on WBC stimulation. Statistically significant changes in hemostasis parameters were observed after proton radiation exposure in both the saline and Neulasta treated irradiated groups, as well as internal organ complications such as pulmonary changes. In conclusion, Neulasta treatment temporarily alleviates proton radiation-induced WBC loss, but has no effect on altered hemostatic responses.

Granulocyte colony-stimulating factor in the treatment of acute radiation syndrome: a concise review

This article concisely summarizes data on the action of one of the principal and best known growth factors, the granulocyte colony-stimulating factor (G-CSF), in a mammalian organism exposed to radiation doses inducing acute radiation syndrome. Highlighted are the topics of its real or anticipated use in radiation accident victims, the timing of its administration, the possibilities of combining G-CSF with other drugs, the ability of other agents to stimulate endogenous G-CSF production, as well as of the capability of this growth factor to ameliorate not only the bone marrow radiation syndrome but also the gastrointestinal radiation syndrome. G-CSF is one of the pivotal drugs in the treatment of radiation accident victims and its employment in this indication can be expected to remain or even grow in the future.

Identification of granulocyte colony-stimulating factor and interleukin-6 as candidate biomarkers of CBLB502 efficacy as a medical radiation countermeasure

Given an ever-increasing risk of nuclear and radiological emergencies, there is a critical need for development of medical radiation countermeasures (MRCs) that are safe, easily administered, and effective in preventing and/or mitigating the potentially lethal tissue damage caused by acute high-dose radiation exposure. Because the efficacy of MRCs for this indication cannot be ethically tested in humans, development of such drugs is guided by the Food and Drug Administration's Animal Efficacy Rule. According to this rule, human efficacious doses can be projected from experimentally established animal efficacious doses based on the equivalence of the drug's effects on efficacy biomarkers in the respective species. Therefore, identification of efficacy biomarkers is critically important for drug development under the Animal Efficacy Rule. CBLB502 is a truncated derivative of the Salmonella flagellin protein that acts by triggering Toll-like receptor 5 (TLR5) signaling and is currently under development as a MRC. Here, we report identification of two cytokines, granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6), as candidate biomarkers of CBLB502's radioprotective/mitigative efficacy. Induction of both G-CSF and IL-6 by CBLB502 1) is strictly TLR5-dependent, 2) occurs in a CBLB502 dose-dependent manner within its efficacious dose range in both nonirradiated and irradiated mammals, including nonhuman primates, and 3) is critically important for the ability of CBLB502 to rescue irradiated animals from death. After evaluation of CBLB502 effects on G-CSF and IL-6 levels in humans, these biomarkers will be useful for accurate prediction of human efficacious CBLB502 doses, a key step in the development of this prospective radiation countermeasure.

Pegfilgrastim administered in an abbreviated schedule, significantly improved neutrophil recovery after high-dose radiation-induced myelosuppression in rhesus macaques

Conventional daily administration of filgrastim is effective in reducing the duration of severe neutropenia and enhancing survival following lethal radiation, myelosuppressive cytotoxic therapy or myeloablation and stem cell transplantation. A sustained-duration form of filgrastim, pegfilgrastim has significantly simplified scheduling protocols after chemotherapy-induced neutropenia to a single injection while maintaining the therapeutic effectiveness of daily administration of filgrastim. We examined the ability of a single or double (weekly) administration of pegfilgrastim to significantly improve neutrophil recovery in a rhesus macaque model of severe radiation-induced myelosuppression. Animals were exposed to potentially lethal 6 Gy total-body X radiation. After irradiation all animals received supportive care and were administered either pegfilgrastim at 300 μg/kg on day 1 or day 1 and day 7 post exposure, or filgrastim at 10 μg/kg/day initiated on day 1 post exposure and continued daily through neutrophil recovery. Pharmacokinetic parameters and neutrophil-related values for duration of neutropenia, neutrophil nadir, time to recovery to an absolute neutrophil count ≥500/μL or ≥2000/μL, and days of antibiotic support were determined. Effective plasma concentrations of pegfilgrastim were maintained in neutropenic animals until after the onset of hematopoietic recovery, which is consistent with neutrophil-dependent properties of elimination. Administration of pegfilgrastim at day 1 and day 7 was most effective at improving neutrophil recovery compared to daily administration of filgrastim or a single injection of pegfilgrastim on day 1, after severe, radiation-induced myelosuppression in rhesus macaques.

Pegfilgrastim compared to lenograstim after allogeneic peripheral blood stem-cell transplantation from unrelated donors

We compared a single, subcutaneous fixed dose of 6 mg pegfilgrastim on day +5 with daily lenograstim 263 microg from day +5 and continued until neutrophils were >or=0.5 x 10(9)/L after allogeneic peripheral blood stem-cell transplantation (PBSCT) from unrelated donors for various hematological disorders. Neutrophil engraftment was significantly faster (p = 0.006) in the pegfilgrastim than in the lenograstim group. There was also a tendency towards achieving a faster platelet engraftment (p = 0.06) in the pegfilgrastim group (median 16 vs. 19 days). The duration of thrombocytopenia (<20 x 10(9)/L) was shorter in the pegfilgrastim group (p = 0.05). There were no significant differences in the duration of neutropenia (p = 0.14) and febrile neutropenia (p = 0.25). Differences were not observed in the treatment related mortality, disease free and overall survival between both groups. We conclude that Pegfilgrastim ensured rapid neutrophil engraftment after unrelated allogeneic peripheral SCT, which was at least as effective as daily lenograstim.

Hematologic effects of subcutaneous administration of recombinant human granulocyte colony-stimulating factor (filgrastim) in healthy alpacas

OBJECTIVE

To determine the effects of SC administration of filgrastim on cell counts in venous blood and bone marrow of healthy adult alpacas.

ANIMALS

10 healthy alpacas.

PROCEDURES

Alpacas were randomly assigned to receive treatment with filgrastim (5 microg/kg, SC; n=5) or an equivalent volume of physiologic saline (0.9% NaCl) solution (5) once a day for 3 days. Blood samples were obtained via jugular venipuncture 1 day prior to treatment and once a day for 5 days commencing 24 hours after the first dose was administered. Complete blood counts were performed for each blood sample. Bone marrow aspirates were obtained from the sternum of each alpaca 48 hours before the first treatment was administered and 72 hours after the third treatment was administered. Myeloid-to-erythroid cell (M:E) ratio was determined via cytologic evaluation of bone marrow aspirates.

RESULTS

In filgrastim-treated alpacas, substantial increases in counts of WBCs and neutrophils were detected within 24 hours after the first dose was administered. Band cell count and percentage significantly increased 24 hours after the second dose. Counts of WBCs, neutrophils, and band cells remained high 48 hours after the third dose. Red blood cell counts and PCV were unaffected. The M:E ratio also increased significantly after treatment with filgrastim.

CONCLUSIONS AND CLINICAL RELEVANCE

Filgrastim induced rapid and substantial increases in numbers of circulating neutrophils and M:E ratios of bone marrow in healthy alpacas. Therefore, filgrastim may be useful in the treatment of camelids with impaired bone marrow function.

Peg-filgrastim versus filgrastim after autologous stem cell tranplantation: Case-control study in patients with multiple myeloma and review of the literature

We investigated the effects of a single s.c. injection of peg-filgrastim in 32 patients with multiple myeloma who underwent autologous stem cell transplantation (AuSCT) as first line treatment. For comparison, 32 myeloma patients with similar characteristics and receiving standard daily administration of filgrastim were matched. Overall, there were no statistically significant differences between peg-filgrastim and filgrastim in terms of tolerability, marrow recovery, severity of neutropenia, incidence and duration of febrile neutropenia, documented infections and transfusions. However, some favourable trends or effects in favour of peg-filgrastim were observed. This was confirmed by a review of the published papers about this topic.

Antiapoptotic cytokines in combination with pegfilgrastim soon after irradiation mitigates myelosuppression in nonhuman primates exposed to high irradiation dose

OBJECTIVE

Preservation of hematopoietic stem and progenitor cells from early radiation-induced apoptosis is the rationale for emergency antiapoptotic cytokine therapy (EACK) after radiation accidents. This strategy is based on the combination of stem cell factor + Flt3-ligand + thrombopoietin + interleukin 3 (SFT3). The long-term safety and efficacy of EACK in managing severe radiation exposure were evaluated.

MATERIAL AND METHODS

Early administration of SFT3 + pegfilgrastim was assessed in 7-Gy gamma total body-irradiated (TBI) monkeys. Efficiency of delayed administration was also addressed after 5-Gy TBI.

RESULTS

Here we showed that a single, intravenous injection of SFT3 2 hours after 7-Gy TBI reduced the period of thrombocytopenia (platelet count <20 x 10(9)/L: 0.8 +/- 1.5 day vs 23.8 +/- 15.9 days in controls; p < 0.05) and blood transfusion needs. Moreover, addition of pegfilgrastim to SFT3 treatment shortened the period of neutropenia compared with SFT3 and control groups (neutrophil count <0.5 x 10(9)/L: 7 +/- 1.4 days vs 13 +/- 3.2 days and 15.2 +/- 1.5 days; p < 0.05). In both SFT3 groups, bone marrow activity recovered earlier and, in contrast with controls, platelet count returned to baseline values from 250 days after irradiation. Furthermore, delayed (48 hours) single SFT3 administration in 5-Gy irradiated monkeys significantly reduced thrombocytopenia compared to controls. Finally, SFT3 did not increase frequency of total chromosome translocations observed in the blood lymphocytes of controls 1 year after 5 Gy TBI.

CONCLUSION

These results suggest the safety and efficacy of EACK in managing severe radiation exposure.

Pegfilgrastim compared with filgrastim after high-dose melphalan and autologous hematopoietic peripheral blood stem cell transplantation in multiple myeloma patients

We undertook a comparative study of Pegfilgrastim vs. Filgrastim after high-dose melphalan and autologous peripheral blood stem cell transplantation (APBSCT) in multiple myeloma (MM) patients. Thirty-seven consecutive patients were randomly assigned to receive a single 6 mg dose of Pegfilgrastim on day 1 post-transplant (n = 18 patients) vs. daily subcutaneous injections of Filgrastim 5 microg/kg (n = 19 patients) starting on day 5 post-transplant. The median duration of grade 4 neutropenia in the Pegfilgrastim and Filgrastim groups was 5 and 6 d, respectively (P = ns). The results for the two groups were also not significantly different for time to neutrophil and platelet recovery, but incidence of febrile neutropenia (61.1% vs. 100%, P = 0.003) and duration of febrile neutropenia (1.5 d vs. 4 d, P = 0.005), were lower in the Pegfilgrastim arm. After initial haematopoietic reconstitution, we observed significantly higher value of leukocytes x 10(9) L on day 15 (6.0 vs. 2.7, P = 0.004), in the Pegfilgrastim group compared with the Filgrastim group. This study shows that a single injection Pegfilgrastim can be used with safety and efficacy similar to those provided by daily injections of Filgrastim and it is associated with a decrease incidence of infectious events after APBSCT in MM patients.

Sustained G-CSF plasma levels following administration of pegfilgrastim fasten neutrophil reconstitution after high-dose chemotherapy and autologous blood stem cell transplantation in patients with multiple myeloma

OBJECTIVE

Pegfilgrastim has shown to decrease the duration of severe neutropenia after conventional chemotherapy, but its use after high-dose chemotherapy and autologous blood stem cell transplantation has not been established yet. Therefore we studied the efficacy and the pharmacokinetic profile of pegfilgrastim in patients with multiple myeloma undergoing high-dose chemotherapy.

METHOD

In total, 21 patients received a single subcutaneous injection of 6 mg pegfilgrastim on day +1 after transplantation and pegfilgrastim plasma levels were measured daily by enzyme-linked immunosorbent assay. Clinical outcome was compared with pegfilgrastim levels of 282 plasma samples and data of a historical control group of patients without granulocyte colony-stimulating factor (G-CSF) support.

RESULTS

Pegfilgrastim levels showed an inverse correlation (r = -0.68, p < 0.01) with neutrophil counts. Peak levels were reached at day +4 (94 ng/mL; range: 37-205) and were maintained until day +7 (85 ng/mL; range: 35-186). Comparison with the control group without G-CSF support showed that time to neutrophil reconstitution was significantly shorter in the pegfilgrastim group with 10 vs 15 days, respectively (p < 0.001). There was no correlation of pegfilgrastim levels and the duration of neutropenia, although patients with a fivefold increase in neutrophil counts the day after pegfilgrastim administration had a significantly shorter median duration of neutropenia in comparison to patients who were less susceptible to G-CSF stimulation (5 vs 7 days, p < 0.01).

CONCLUSION

Neutrophil reconstitution after high-dose chemotherapy could be accelerated by the use of pegfilgrastim in patients with myeloma. Responsiveness of neutrophils to pegfilgrastim before neutropenia was correlated with faster neutrophil reconstitution, whereas G-CSF levels had no impact on neutrophil recovery.

Pegfilgrastim compared with Filgrastim after autologous hematopoietic peripheral blood stem cell transplantation

In order to assess the effect of Pegfilgrastim on the duration of neutropenia and clinical outcome of patients after autologous peripheral blood stem cell (PBSC) transplantation, we compared 20 consecutive patients with lymphoma or multiple myeloma receiving a single 6-mg dose of Pegfilgrastim on day 1 posttransplant to an historical control group of 60 patients receiving daily Filgrastim 5 microg/kg starting on day 1 posttransplant. The duration of neutropenia was similar in the Pegfilgrastim group compared with the control group. There were no differences in time to neutrophil, erythroid, or platelet engraftment nor in the incidence of fever and infections. The duration of antibiotic therapy, transfusion support, and time to hospital discharge were similar in the two groups. However, after initial hematopoietic reconstitution, we observed significantly higher values of lymphocytes (e.g., 1,660+/-1,000 versus 970+/-460 on day 80, p=0.0002), neutrophils (e.g., 3,880+/-2,030 versus 2,420+/-1,500 on day 25, p=0.0004), reticulocytes (e.g., 148,160+/-90,590 versus 87,140+/-65,920 on day 25, p<0.0001), and platelets (e.g., 210,700+/-116,090 versus 150,240+/-58,230 on day 55, p=0.0052) up to day 100 in the Pegfilgrastim group compared with the Filgrastim group. These observations had no impact on clinical outcome of the patients after day 30 due to the low incidence of infectious events after engraftment in autologous PBSC transplantation. We conclude that the effect of Pegfilgrastim administrated on day 1 posttransplant is comparable to that of daily Filgrastim on initial hematopoietic reconstitution. The possibly superior effect of Pegfilgrastim on cell counts we observed after initial engraftment should be further tested in a prospective randomized trial.

Cytokine-based treatment of accidentally irradiated victims and new approaches

A major goal of medical management of acute radiation syndrome following accidental exposures to ionizing radiation (IR) is to mitigate the risks of infection and hemorrhage related to the period of bone marrow aplasia. This can be achieved by stimulating the proliferation and differentiation of residual hematopoietic stem and progenitor cells (HSPC) related to either their intrinsic radioresistance or the heterogeneity of dose distribution. This is the rationale for treatment with hematopoietic growth factors. In fact, apoptosis has recently been shown to play a major role in the death of the continuum of more or less radiosensitive HSPC, soon after irradiation. Therefore, administration of antiapoptotic cytokine combinations such as stem cell factor, Flt-3 ligand, thrombopoietin, and interleukin-3 (4F), may be important for multilineage recovery, particularly when these factors are administered early. Moreover, acute exposure to high doses of IR induces sequential, deleterious effects responsible for a delayed multiple organ dysfunction syndrome. These considerations strongly suggest that therapeutics could include tissue-specific cytokines, such as keratinocyte growth factor, and pleiotropic agents, such as erythropoietin, in addition to hematopoietic growth factors to ensure tissue damage repair and mitigate the inflammatory processes. Noncytokine drugs have also been proposed as an alternative to treat hematopoietic or nonhematopoietic radiation effects. To develop more effective treatments for radiation injuries, basic research is required, particularly to improve understanding of stem cell needs within their environment. In the context of radiological terrorism and radiation accidents, new growth promoting molecules need to be approved and available cytokines stockpiled.