Granulocyte Colony-Stimulating Factor: Preclinical and Clinical Studies

Pharmacokinetics and pharmacodynamics of a recombinant human granulocyte colony-stimulating factor

Granulocyte colony-stimulating factor (G-CSF), a hematopoietic growth factor, is a clinically effective drug used to promote neutrophil recovery in patients with chemo- or radiotherapy-induced neutropenia. We have reviewed the pharmacokinetic and pharmacodynamic properties of three kinds of G-CSFs: E. coli derived G-CSF, CHO-derived G-CSF, and mutein G-CSF. The clearances of G-CSFs are saturable and autoinducible in experimental animals and humans. That is, the systemic clearances of G-CSFs decrease as the dose injected increases and approaches a constant value. Both saturable and nonsaturable processes are involved in G-CSF elimination. Also, the systemic clearances of G-CSFs are increased by repeated administration of G-CSF. Although the relative bioavailability of G-CSFs after subcutaneous administration is approximately 60%, the increase in peripheral white blood cells or neutrophils is greater than that after intravenous administration at the same dose. The effects of G-CSFs seem to be time dependent rather than AUC dependent, considering that mean residence time of G-CSFs in the plasma is longer after subcutaneous administration than that after intravenous administration. There is a slight difference in the pharmacokinetics of E-coli- and CHO-G-CSF although they seem to be pharmacologically equivalent. The correlation between G-CSF clearance and peripheral neutrophil counts in the patients suggests that G-CSF receptors contribute to G-CSF clearance. Quantitative pharmacokinetic analysis using mutein G-CSF shows that the G-CSF receptor plays a major role in saturable G-CSF clearance, and that this saturable process accounts for approximately 80% of the total clearance at low doses. That is, the degradation following the receptor-mediated endocytosis in bone marrow might be a major clearance system of G-CSF at a physiological blood level. The G-CSF receptor in bone marrow might work not only as a signal transducer for differentiation and proliferation of granulopoietic precurcer cells but as a regulator of G-CSF levels in blood. In addition, at high doses, glomerular filtration in the kidneys is the major process for nonsaturable G-CSF clearance. At present, polyethylene glycol derivatives of G-CSF are being developed to reduce the frequency of G-CSF administration.

Myeloid and megakaryocytic hypoplasia in related standardbreds

Myeloid and megakaryocytic bone marrow hypoplasia in association with moderate to profound neutropenia was observed in 8 young Standardbred horses sired by the same stallion; 7 horses were intermittently thrombocytopenic. Evaluation of serial neutrophil counts in 2 horses suggested that a cyclic variation in neutrophil numbers was present, that lymphocyte numbers increased when neutrophil counts decreased, and that platelet counts decreased when neutrophil counts decreased. Preliminary bone marrow cultures indicated that myeloid progenitor cells were present and that these cells were able to respond to exogenous growth factors by differentiating. A bone marrow microenvironment or growth factor defect is suspected. Seven of 8 horses died or were euthanized. One horse with moderate neutropenia and a normal platelet count has been racing for 3 years. Necropsies in 4 horses did not reveal a cause for the myeloid hypoplasia. A familial basis for the disease is suspected.

Haematological, bone marrow and clinical chemical changes in neonatal foals given canine recombinant granulocyte-colony stimulating factor

Five Thoroughbred and Quarter Horse cross foals were given 20 micrograms canine recombinant granulocyte-colony stimulating factor (rcG-CSF) per kg bwt intramuscularly (i.m.) on the day of birth and 10 micrograms rcG-CSF/kg for 13 additional days. During this time and for an additional 21 days haematology, bone marrow and clinical chemical analyses were performed. After one day of rcG-CSF administration leucocyte and neutrophil counts increased from 9.16 x 10(9)/l to 23.44 x 10(9)/l and from 6.45 x 10(9)/l to 19.61 x 10(9)/l, respectively. The counts continued to increase for the next 3-4 days and then there was a slight decrease. A second increase followed and the leucocyte and neutrophil counts increased to 52.84 x 10(9)/l and 45.16 x 10(9)/l on the day after the last rcG-CSF administration (Day 15). The counts decreased rapidly immediately after the administration of rcG-CSF was stopped and then at a slower rate. The cell counts were still higher than in the controls at the end of the study period (Day 35). Bone marrow cellularity increased from 10-25% before rcG-CSF was given to 60-80% after 5 days. The increase in cellularity was due to increased myeloid activity because the myeloid to erythroid ratio increased from 2.7 to 8.8. Serum chemistry changes were minimal although foals given rcG-CSF at various times had lower glucose concentrations and increased alkaline phosphatase and gamma glutamyl transferase activities.

Preliminary results of treatment with filgrastim for relapse of leukemia and myelodysplasia after allogeneic bone marrow transplantation

BACKGROUND

Patients whose leukemia relapses after allogeneic bone marrow transplantation have a poor prognosis; few respond to further chemotherapy, and almost none survive over the long term. We present preliminary observations on the use of filgrastim (granulocyte colony-stimulating factor) for relapse after transplantation.

METHODS

Seven female patients with leukemia (one with chronic myelogenous leukemia, five with acute myelogenous leukemia, and one with a myelodysplastic syndrome that transformed into acute myelogenous leukemia) whose disease relapsed within 360 days after allogeneic bone marrow transplantation received filgrastim (5 micrograms per kilogram of body weight per day by subcutaneous injection) to reinduce remission by stimulating residual donor marrow cells. Cytogenetic analysis of bone marrow, fluorescence in situ hybridization, and determination of restriction-fragment--length polymorphisms were used to assess response and chimerism.

RESULTS

Three of the seven patients had a complete hematologic and cytogenetic remission, with reestablishment of hematopoiesis of donor origin. Mild chronic graft-versus-host disease developed in one patient, and acute graft-versus-host disease in none. One patient had a relapse 12 months after treatment, and two others remained in remission after 10 and 11 months. In two of the patients with a response, fluorescence in situ hybridization demonstrated stimulation of donor cells without differentiation of the leukemic clone.

CONCLUSIONS

Filgrastim may be effective in selected cases of leukemic relapse after allogeneic bone marrow transplantation.

Effects of perioperative granulocyte colony-stimulating factor on horses with ascending colonic ischemia

Granulocyte colony-stimulating factor (G-CSF) is a glycoprotein that regulates the proliferation and maturation of hematopoietic progenitor cells and modulates the function of mature neutrophils. The responses to administration of G-CSF alone, and in combination with antimicrobials, were studied in an equine model of ascending colon ischemia. Complete segmental colonic ischemia (3.75 hours) with pelvic flexure enterotomy was created in four treatment groups. Group 1 horses received recombinant canine G-CSF (10 micrograms/kg, every 24 hours, intramuscularly), gentamicin sulfate (2.2 mg/kg, every 8 hours, intravenously), and potassium penicillin G (40,000 IU/kg, every 6 hours, intravenously). Group 2 horses were treated with the G-CSF vehicle and antimicrobials as for group 1. Group 3 horses received G-CSF and the antimicrobial drug vehicles, and group 4 horses served as the untreated control receiving G-CSF vehicle and antimicrobial vehicles. The results for 20 horses, five horses in each group, were compared. Treatment with G-CSF was associated with an increased concentration of white blood cells, band neutrophils, neutrophils, lymphocytes, and monocytes in the peripheral blood after surgery. Antimicrobial administration had no detectable effect on cell concentrations after surgery. Administration of G-CSF was associated with an increased concentration of nucleated cells in the peritoneal fluid including neutrophils, small mononuclear cells and large mononuclear cells. Horses that developed incisional infections had lower neutrophil concentrations in the peripheral blood on postoperative day 2 than horses without infected incisions. These results suggested that the prophylactic administration of G-CSF may be useful in the treatment of patients at risk for developing neutropenia after surgery.

Differential effects of granulocyte- and granulocyte-macrophage colony-stimulating factors (G- and GM-CSF) on neutrophil adhesion in vitro and in vivo

A direct comparison of granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) effects on neutrophil adhesiveness has been carried out. In vitro, GM-CSF and G-CSF upregulate neutrophil CD11b to a similar degree (to 227 +/- 69%, and 232 +/- 70% of control cells, respectively, p < 0.0005), but GM-CSF is more effective in downregulating neutrophil leucocyte adhesion molecule-1 (LAM-1), reducing levels to 33 +/- 4% (p < 0.0005), while G-CSF causes a fall to only 65 +/- 17% (p < 0.005) of control. The concentration of GM-CSF needed to achieve maximal activity is at least one log less than that of G-CSF. In vivo, both GM-CSF and G-CSF upregulate neutrophil CD11b (to 296 +/- 45% and 370 +/- 150%, respectively of baseline), but surface levels of LAM-1 on circulating cells are unchanged. GM-CSF increased neutrophil adhesion to cultured human endothelium in vitro (from 9.3 +/- 0.7% to 15.4 +/- 1.3%, p < 0.0005, n = 10), while G-CSF was without effect. In vivo, both GM-CSF and G-CSF produce a transient leucopenia, but recovery of peripheral counts occurs much earlier (by 60 minutes) with G-CSF, than with GM-CSF (only 50% of cells have demarginated at 120 min). GM-CSF appears to be greater proadhesive agonist for neutrophils than G-CSF.

Enhancement of host defense by Y-25510, (+-)-3-[4-(2-dimethylamino-1-methylethoxy)phenyl]-1H-pyrazolo[3,4 -b] pyridine-1-acetic acid, a novel synthetic compound. A comparison with recombinant human granulocyte colony-stimulating factor in 5-fluorouracil-treated mice

The effect of a novel synthetic compound, Y-25510, (+-)-3-[4-(2-dimethylamino-1-methylethoxy)phenyl]-1H-pyrazolo[3,4 -b] pyridine-1-acetic acid, on recovery from long-lasting leukopenia induced by 5-fluorouracil was compared with that of recombinant human granulocyte colony-stimulating factor (rhG-CSF). When mice were administered i.p. with 5-FU (200 mg/kg) on days 0 and 7, intravenous administration of Y-25510 (100 and 1000 micrograms/kg) prevented the decrease in the peripheral leukocyte and neutrophil number and accelerated the recovery from leukopenia. Subcutaneous administration of rhG-CSF (50 micrograms/kg) did not prevent leukopenia but accelerated the recovery from leukopenia. In particular, peripheral neutrophil number increased over a normal level. The administration of Y-25510 (10, 100 and 1000 micrograms/kg) restored the decrease in the number of bone marrow cells, spleen cells, lymphocytes, neutrophils and monocytes. The administration of rhG-CSF (50 micrograms/kg) restored the decrease in the number of bone marrow cells, spleen cells, and neutrophils but not that of lymphocytes and monocytes. In fractions of bone marrow cells on day 21, the administration of Y-25510 (1000 micrograms/kg) showed a tendency of restoring the decrease in neutrophil number. In conclusion, the administration of Y-25510 prevented leukopenia and accelerated the recovery from leukopenia in the 5-FU-treated mice. It is suggested that the mechanism of the restorative action of Y-25510 is different from that of rhG-CSF. In a number of immature bone marrow cells Y-25510 has a potent stimulatory effect on the recovery from the decrease in number of hematopoietic cells, keeping a balance in number of each blood cell.

Hematopoietic colony-stimulating factors

In summary, hematopoietic growth factors have been discovered, biochemically characterized, cloned, produced by recombinant DNA technology, and put into clinical use in a period of 25 years. We are approaching a greater understanding of the cellular anatomy and molecular mechanisms that regulate production of the CSFs, the ways in which the CSFs interact with their cell surface receptors and trigger their biological effects, the nature of these receptors themselves and their mechanisms of signal transduction, and the effects of the CSFs in vitro and in vivo on hematopoietic progenitor cells and mature leukocytes. However, many questions remain. What is the mechanism that couples growth-factor binding to the triggering of cellular proliferation? How do multi-CSF and GM-CSF cross-compete at the level of the cell-surface receptor, and yet show no primary amino acid sequence homology? What are the mechanisms that regulate the tissue expression profile of multi-CSF compared to the genetically similar growth factor GM-CSF? And, what are the optimal dosages, schedules of administration, and combinations of CSFs optimal for each of several conditions of marrow failure? These are but a few of the questions that continue to occupy much current research interest.

Subcutaneous administration of recombinant human granulocyte colony-stimulating factor (KRN8601) in intensive chemotherapy for patients with advanced lung cancer

The efficacy and toxicity of recombinant human granulocyte colony-stimulating factor (rh G-CSF, KRN8601) given subcutaneously was evaluated in patients with advanced lung cancer undergoing intensive chemotherapy. Twenty-nine and 30 patients with or without prior therapy were enrolled in this study. At dose levels of 50, 90 and 130 micrograms/m2 of rh G-CSF for 14 consecutive days after chemotherapy, the mean neutrophil nadir counts, the mean neutrophil nadir ratios and the duration of neutropenia (days of less than 1000/mm3) were significantly improved. No significant differences were seen in frequency and duration of febrile episodes (greater than 38 degrees C). When rh G-CSF is given subcutaneously, the dose required for an equal effect in alleviating neutropenia is 50% of that required when it is given intravenously. The monocyte counts in the peripheral blood were also significantly increased after chemotherapy cycles with rh G-CSF. The cumulative plasma concentration of rh G-CSF showed a decrement after 7-9 days despite maintenance of the same dose of rh G-CSF for the entire 14 days. In conclusion, 50-130 micrograms/m2 of sc rh G-CSF increased the neutrophil nadir count and shortened the duration of neutropenia in patients undergoing intensive chemotherapy for lung cancer without intolerable side effects.

The use of myeloid hematopoietic growth factors in patients with HIV infection

Hematologic abnormalities are frequent occurrences in patients with HIV infection. Myelosuppression in AIDS may be due to multiple factors and has significant impact on the treatment of HIV-infected individuals, as it is the major dose-limiting toxicity of a number of antimicrobial compounds and chemotherapy. Both granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) are hematopoietic hormones which effect myeloid progenitor cells and enhance the function of mature neutrophils. Clinical studies of the effects of these agents in patients with AIDS indicate that GM-CSF and G-CSF can increase the production of leukocytes in a dose-dependent fashion. This increase in leukocyte production may allow the continued administration of full doses of antiviral or other myelosuppressive medications in previously hematologically intolerant patients with AIDS. Investigations of the hematopoietic, virologic, and immunologic effects of these agents alone and in combination with other hematopoietins, cytokines, and chemotherapeutic agents will ultimately define their clinical utility in patients with HIV infection.