Haem arginate as a treatment for myelodysplastic syndromes

Linking Labile Heme with Thrombosis

Thrombosis is one of the leading causes of death worldwide. As such, it also occurs as one of the major complications in hemolytic diseases, like hemolytic uremic syndrome, hemorrhage and sickle cell disease. Under these conditions, red blood cell lysis finally leads to the release of large amounts of labile heme into the vascular compartment. This, in turn, can trigger oxidative stress and proinflammatory reactions. Moreover, the heme-induced activation of the blood coagulation system was suggested as a mechanism for the initiation of thrombotic events under hemolytic conditions. Studies of heme infusion and subsequent thrombotic reactions support this assumption. Furthermore, several direct effects of heme on different cellular and protein components of the blood coagulation system were reported. However, these effects are controversially discussed or not yet fully understood. This review summarizes the existing reports on heme and its interference in coagulation processes, emphasizing the relevance of considering heme in the context of the treatment of thrombosis in patients with hemolytic disorders.

Targeting heme oxygenase-1 in vascular disease

Heme oxygenase-1 (HO-1) metabolizes heme to generate carbon monoxide (CO), biliverdin, and iron. Biliverdin is subsequently metabolized to bilirubin by biliverdin reductase. HO-1 has recently emerged as a promising therapeutic target in the treatment of vascular disease. Pharmacological induction or gene transfer of HO-1 ameliorates vascular dysfunction in animal models of atherosclerosis, post-angioplasty restenosis, vein graft stenosis, thrombosis, myocardial infarction, and hypertension, while inhibition of HO-1 activity or gene deletion exacerbates these disorders. The vasoprotection afforded by HO-1 is largely attributable to its end products: CO and the bile pigments, biliverdin and bilirubin. These end products exert potent anti-inflammatory, antioxidant, anti-apoptotic, and anti-thrombotic actions. In addition, CO and bile pigments act to preserve vascular homeostasis at sites of arterial injury by influencing the proliferation, migration, and adhesion of vascular smooth muscle cells, endothelial cells, endothelial progenitor cells, or leukocytes. Several strategies are currently being developed to target HO-1 in vascular disease. Pharmacological induction of HO-1 by heme derivatives, dietary antioxidants, or currently available drugs, is a promising near-term approach, while HO-1 gene delivery is a long-term therapeutic goal. Direct administration of CO via inhalation or through the use of CO-releasing molecules and/or CO-sensitizing agents provides an attractive alternative approach in targeting HO-1. Furthermore, delivery of bile pigments, either alone or in combination with CO, presents another avenue for protecting against vascular disease. Since HO-1 and its products are potentially toxic, a major challenge will be to devise clinically effective therapeutic modalities that target HO-1 without causing any adverse effects.

Heme oxygenase-1 is induced in peripheral blood mononuclear cells of patients with acute pancreatitis: a potential therapeutic target

Heme oxygenase-1 (HO-1) induction by hemin or Panhematin protects against experimental pancreatitis. As a preclinical first step toward determining whether HO-1 upregulation is a viable target in acute pancreatitis (AP) patients, we tested the hypothesis that HO-1 expression in peripheral blood mononuclear cell (PBMC) subsets of hospitalized patients with mild AP is upregulated then normalizes upon recovery and that cells from AP patients have the potential to upregulate their HO-1 ex vivo if exposed to Panhematin. PBMCs were isolated on days 1 and 3 of hospitalization from the blood of 18 AP patients, and PMBC HO-1 levels were compared with PMBCs of 15 hospitalized controls (HC) and 7 volunteer healthy controls (VC). On day 1 of hospitalization, AP patients compared with VCs had higher HO-1 expression in monocytes and neutrophils. Notably, AP monocyte HO-1 levels decreased significantly upon recovery. Panhematin induced HO-1 in ex vivo cultured AP PBMCs more readily than in HC or VC PBMCs. Furthermore, PBMCs from acutely ill AP patients on day 1 were more responsive to HO-1 induction compared with day 3 upon recovery. Similarly, mouse splenocytes had enhanced HO-1 inducibility as their pancreatitis progressed from mild to severe. In conclusion, AP leads to reversible PBMC HO-1 upregulation that is associated with clinical improvement and involves primarily monocytes. Leukocytes from AP patients or mice with AP are primed for HO-1 induction by Panhematin, which suggests that Panhematin could offer a therapeutic benefit.

First-in-human study demonstrating pharmacological activation of heme oxygenase-1 in humans

Heme oxygenase (HO)-1 degrades heme and protects against oxidative stress, but it has not been pharmacologically induced in humans. In this randomized study of 10 healthy volunteers, hemin (3 mg/kg intravenously in 25% albumin) was shown to increase plasma HO-1 protein concentration four- to fivefold and HO-1 activity ~15-fold relative to baseline at 24 and 48 h (placebo -56.41 +/- 6.31 (baseline), 69.79 +/- 13.00 (24 h), 77.44 +/- 10.62 (48 h) vs. hemin -71.70 +/- 9.20 (baseline), 1,126.20 +/- 293.30 (24 h), 1,192.20 +/- 333.30 (48 h)) in four of five subjects as compared with albumin alone (P </= 0.03). This represents the overcoming of a fundamental hurdle to HO-1 research in humans.

Physicochemical properties, pharmacokinetics, and pharmacodynamics of intravenous hematin: a literature review

INTRODUCTION

Intravenous (i.v.) hematin has been used in the treatment of acute intermittent porphyria (AIP) since the early 1970s and commercially available as Panhematin (hemin for injection; Ovation Pharmaceuticals, Inc., USA) since 1983, yet no publication to date has attempted to summarize the known pharmacodynamics and toxicological actions of hematin and the implications on treatment. It is the objective of this literature review to identify, consolidate, and summarize the available scientific literature regarding the physicochemical properties, pharmacokinetics, toxicology, and hemostatic effects of i.v. hematin injections.

METHODS

A comprehensive search of the available literature was performed and resulting data were summarized. Furthermore, previously unpublished toxicology data extracted from the original New Drug Application were included.

RESULTS

Hematin, reconstituted with sterile water, rapidly degrades and it is hypothesized that the degradation products lead to morbidities such as thrombophlebitis, thrombocytopenia, and transient anticoagulation. Reconstitution with human serum albumin produces a well-tolerated hematin preparation and improves its stability significantly. The clearance of i.v. hematin infusions are shown to fit a two-compartment model consisting of a rapid initial rate followed by a slower and prolonged second phase. This model is supported by the evidence demonstrating that hematin is first bound by hemopexin and, upon saturation, second by albumin. The highest i.v. human hematin dose reported in the literature was 12.2 mg/kg (1000 mg) and resulted in acute gastrointestinal pain, paresthesia, and acute tubercular necrosis. The patient's renal function returned to normal over the following 15 hours.

CONCLUSION

Hematin, at doses approved by the US Food and Drug Administration, is generally well tolerated. Reconstitution with albumin produces a significantly more stable preparation than reconstitution with sterile water and may lead to a more tolerable administration with less hemostatic interference. Hematin, once administered, is cleared hepatically and is best represented pharmacokinetically by a two-compartment model comprised of a rapid initial phase followed by a slower second phase.

The myelodysplastic syndrome(s): a perspective and review highlighting current controversies

The myelodysplastic syndrome (MDS) includes a diverse group of clonal and potentially malignant bone marrow disorders characterized by ineffective and inadequate hematopoiesis. The presumed source of MDS is a genetically injured early marrow progenitor cell or pluripotential hematopoietic stem cell. The blood dyscrasias that fall under the broad diagnostic rubric of MDS appear to be quite heterogeneous, which has made it very difficult to construct a coherent, universally applicable MDS classification scheme. A recent re-classification proposal sponsored by the World Health Organization (WHO) has engendered considerable controversy. Although the precise incidence of MDS is uncertain, it has become clear that MDS is at least as common as acute myelogenous leukemia (AML). There is considerable overlap between these two conditions, and the former often segues into the latter; indeed, the distinction between AML and MDS can be murky, and some have argued that the current definitions are arbitrary. Despite the discovery of several tantalizing pathophysiological clues, the basic biology of MDS is incompletely understood. Treatment at present is generally frustrating and ineffective, and except for the small subset of patients who exhibit mild marrow dysfunction and low-risk cytogenetic lesions, the overall prognosis remains rather grim. In this narrative review, we highlight recent developments and controversies within the context of current knowledge about this mysterious and fascinating cluster of bone marrow failure states.

The prognostic value of in vitro cultures of erythroid and megakaryocyte progenitors in myelodysplastic syndromes

The prognostic value of colony formation by granulocyte-macrophage progenitors (CFU-GM) in myelodysplastic syndromes (MDS) has been investigated in several studies. We studied the in vitro growth patterns of hematopoietic progenitors of 83 patients with an MDS to find out whether erythroid (BFU-E) and megakaryocyte (CFU-Meg) cultures yield additional prognostic information to that obtained with CFU-GM cultures. Thirty-nine of 82 patients showed normal CFU-GM colony formation; the others had either excessive growth of colonies/clusters or reduced growth. Five of 74 patients had normal BFU-E and nine of 39 patients normal CFU-Meg growth; the others showed reduced or absent colony formation. The cultures of each cell lineage had a similar prognostic impact: the patients with a normal growth pattern had a lower risk of developing leukemia and a longer survival than those with an abnormal growth pattern (significant difference or trend). All patients with normal BFU-E or CFU-Meg colony growth also had normal CFU-GM colony formation, and all patients with normal BFU-E growth also had normal CFU-Meg growth. Among the patients with normal CFU-GM cultures, those with normal erythroid or megakaryocyte colony formation had a trend towards a better outcome compared to those with an abnormal growth pattern in the same cell lineage. In conclusion, erythroid and megakaryocyte cultures did not significantly contribute to the prognostic information obtained with CFU-GM cultures in MDS.

Lineage involvement and karyotype in a patient with myelodysplasia and blood basophilia

We report a 63-year-old woman with myelodysplastic syndrome (MDS), refractory anaemia with ring sideroblasts (RARS), and blood basophilia with pathological forms. Karyotype analysis revealed a complex rearrangement: 46,XX,del(3)(p13p25),del(5)(q13q33),der(16)t(1;16) (p13;q12)/47,idem,add(20)(?p11)/49,idem, + add(1)(q32),add(20)(?p11), + mar/46,XX. Karyotype, immunophenotype and in situ hybridization studies by the MAC (morphology antibody chromosomes) combination technique revealed the chromosomal abnormality in granulocytic/monocytic and erythrocytic metaphase cells. Also mature basophils and other granulocytes were involved with the abnormality. We suggest that our patient with the MDS has a stem cell disorder affecting all myeloid cell lineages and that basophilia constitutes a part of the malignant process.

Synergistic effect of heme and IL-1 on hematopoietic stromal regeneration after radiation

Results from this study show that a combination of heme and interleukin-1 (IL-1) treatment resulted in the most improved recovery of hematopoietic-stromal regeneration after sublethal irradiation. Less pronounced effects were obtained when heme or IL-1 were given singly. Sublethal irradiation of mice produced an initial (as early as day 1) intense depression of the hematopoietic system as evidenced by leukopenia. In vivo treatment of animals with heme in combination with IL-1, accelerated hematopoietic and stromal regeneration as determined by hematopoietic spleen colony forming unit assay (CFU-S), erythroid (BFU-E), myeloid (CFU-GM) clonal cultures, long-term bone marrow cultures (LTBMC), and the ability to regenerate hematopoiesis by ectopic (renal) stromal hemopoietic transplantation. Sixteen days after irradiation, leukocyte levels in heme and IL-1 treatment groups were higher than non-treated animals and were near normal values by 27 days. One day after irradiation, the capacity of stromal progenitors to form new bone and hematopoietic cells (ectopic foci) was severely impaired, but recovered after 2-4 weeks. This recovery process was accelerated in heme and IL-1-treated animals. BFU-E, CFU-GM, and CFU-S capacity was also severely impaired in all animals 1-27 days after irradiation. CFU-S was only 0.15% of control by day 1 and 5% of control by day 16. Treatment with heme or IL-1 improved recovery by as much as 70% after 27 days of irradiation. A similar but enhanced recovery was seen for BFU-E and CFU-GM, with erythroid recovery the best. Total cellularity, adherent cell layer (ACL) formation, and clonogenic capacity by LTBMCs (10 weeks) derived from irradiated animals was severely reduced, whereas the hematopoietic capacity by LTBMCs derived from heme- and IL-1-treated animals had recovery values similar to non-irradiated controls. These results suggest therapeutic use of heme and IL-1 after chemotherapy or bone marrow depression may be beneficial.

Pharmaceutics and drug delivery aspects of heme and porphyrin therapy

The importance of porphyrins and metalloporphyrins as therapeutic drugs has increased significantly over the last decade. This review highlights some of the challenges faced by pharmaceutical scientists in formulating these drugs into stable, effective, and safe dosage forms. Most activity in the clinic has focused on three areas: photodynamic therapy of cancer (e.g., hematoporphyrin derivatives), porphyrias and hematological diseases (e.g., heme), and various forms of jaundice (e.g., tin porphyrins). The biodistribution, stability, aggregation, toxicology, and analytical methodology of porphyrin drugs are all important considerations in the pharmaceutical development of porphyrin drugs. The utility of delivery systems such as liposomes hold promise of increasing the therapeutic potential of these drugs. Future prospects for therapeutic applications of porphyrin drugs are also discussed.

Therapeutic effect of heme arginate in myelodysplastic syndromes

In order to investigate, whether heme would induce a response in myelodysplastic syndromes (MDS), 14 symptomatic patients (4 RA, 3 RARS and 7 RAEB) were treated with infusions of heme arginate 3 mg/kg body weight on 4 consecutive days, mostly for six cycles at 2-week intervals. Three of 14 patients (21%) showed an improvement in anemia (97-152, 79-120 and 92-114 g/l) within a few weeks, and 1 showed a milder increase in hemoglobin level (102-118 g/l). Of the 2 responders with marked thrombocytopenia, 1 showed an improvement in the platelet count (7-37 x 10(9)/l) and her regular need for red cell and platelet transfusions ceased. Some regression in bone marrow (BM) cytology was seen in all 3 responders. One of the responders is still in remission 41 months after cessation of the treatment, while in the other 2 the response lasted for 26 and 5 months. Four patients progressed during the treatment: 1 RA to RAEB, 1 RAEB to RAEBt and 2 RAEB, both with very complex chromosomal abnormalities at the beginning of the therapy, to acute erythroleukemia (AML-M6). Pretreatment delta-aminolevulinic acid synthase and heme synthase activities were generally low. Five patients had mild thrombophlebitis, but not after the infusion procedure was changed. No other side-effects common to growth factors occurred. In conclusion, it is likely that heme arginate has a therapeutic effect on some MDS patients, obviously by stimulating erythropoiesis. The response may be long-lasting.

Haem arginate treatment for hereditary sideroblastic anaemia

It has been shown that haem arginate treatment increases blood cell counts, improves the sideroblast status of the bone marrow and normalises decreased activities of haem synthesising enzymes in some patients with acquired sideroblastic anaemia, or with other types of myelodysplastic syndromes. 4 patients with hereditary sideroblastic anaemia (HSA), belonging to two families, were therefore treated with haem arginate infusions, 3 mg/kg, on 4 consecutive days, and thereafter weekly for 10 wk. No effect was observed on the mildly anaemic haemoglobin levels or on the red cell counts. However, the initially low or low-normal myeloid to erythroid ratio in the marrow increased in all patients. A consistent decrease in the percentage of ring sideroblasts and other abnormal sideroblasts was seen in 1 patient (Family A), and a temporary decrease of abnormal sideroblasts took place during the most intensive treatment period in 2 other patients (Family B). Two of three initially abnormal haem synthesising enzyme activities became normal in Family A, whereas no clearly consistent effects on the haem synthesising enzymes were observed in Family B. The present study shows that haem arginate infusions can normalise the activities of haem synthesising enzymes in some patients with HSA. Further studies are needed to evaluate the impact of haem infusions on the iron balance of these patients.

Haem arginate improves hepatic oxidative metabolism in variegate porphyria

1. The elimination of antipyrine was investigated before and after intravenous administration of haem arginate (3 mg haem kg-1 day-1 on three or four successive days) to six patients with variegate porphyria in remission. 2. Haem arginate decreased the faecal content of protoporphyrin from 557 +/- 91 to 118 +/- 32 (mean +/- s.e. mean) and of coproporphyrin from 144 +/- 19 to 19 +/- 3 nmol g-1 dry weight. 3. Before haem treatment antipyrine elimination half-life was long (30.5 +/- 5.6 h), but the treatment decreased it to 6.3 +/- 0.8 h. Antipyrine clearance increased from 0.25 +/- 0.05 to 1.03 +/- 0.11 ml min-1 kg-1 (P less than 0.001), being 4.6 times higher after haem arginate infusions. 4. The volume of distribution of antipyrine did not change. 5. The severe impairment of hepatic mixed function oxidase activity even in the symptomless stage of porphyria indicates cautious dosage of drugs primarily eliminated by hepatic oxidative reactions.

Heme arginate treatment for myelodysplastic syndromes

Heme arginate was given to 26 patients with a myelodysplastic syndrome (MDS) as infusions of 2-3 mg/kg body weight weekly for 8-12 weeks. Most of the patients first received a loading dose on four consecutive days. Six of the patients showed improvement in cytopenias during the therapy. In three of the responders severely depressed blood cell counts recovered to normal or close to normal. So far the maximum duration of a response after the cessation of the treatment is 25 months, and the two ongoing responses have lasted for 11 and 12 months, respectively. In two responders of the eight patients with more than 15% ring sideroblasts the number of ring sideroblasts decreased during the treatment but remained unchanged in six non-responders. The responders were characterized by a low or low normal heme synthase activity which increased during the treatment, whereas the non-responders showed a higher mean heme synthase activity which decreased during the treatment. In general, the responders had significantly fewer defects in heme synthetic enzyme activities than the non-responders. FAB type, karyotype or growth pattern in in vitro cultures of hematopoietic progenitors did not predict the response. Apart from one case of mild venous irritation, no other adverse effects were seen. The present study shows that heme arginate induces beneficial effects on cytopenia in some MDS patients and has very few side-effects.

Optical and EPR spectroscopy studies on haem arginate, a new compound used for treatment of porphyria

A protohaem compound, used for treatment of porphyrias, has been studied to elucidate its state of aggregation. EPR and absorption spectroscopy measurements reveal that 38.3 mM protohaem, dissolved in 40% 1,2-propanediol/10% ethanol/water solution, also containing 153 mM arginine, is partly EPR silent. It exists as high molecular weight aggregates and probably also as mu-oxo-dimers. Dilution in the aqueous alcohol solution dissolves the aggregates first to oligomers and dimers, and finally to monomers (Kdiss = 24 X 10(-6)M). When haem is diluted in 0.9% sodium chloride, a fully monomeric state is not reached even at 1 microM concentration. At 3.5 microM concentration, that used for infusion in patients, the haem is still totally aggregated.