Prevention of 7β-hydroxycholesterol-induced cell death by mangafodipir is mediated through lysosomal and mitochondrial pathways

Exacerbated Neuropathy in POLAR A and M Trials Due to Redox Interaction of PledOx-Associated Mn2+ and Oxaliplatin-Associated Pt2+

Disappointing results from the POLAR A and M phase III trials involving colorectal cancer patients on chemotherapy with FOLFOX6 in curative (A) and palliative (M) settings have been reported by the principal investigators and the sponsor (PledPharma AB/Egetis Therapeutics AB). FOLFOX6, oxaliplatin in combination with 5-fluorouracil (5-FU), possesses superior tumoricidal activity in comparison to 5-FU alone, but suffers seriously from dose-limiting platinum-associated Chemotherapy-Induced Peripheral Neuropathy (CIPN). The aim of the POLAR trials was to demonstrate that PledOx [calmangafodipir; Ca4Mn(DPDP)5] reduced the incidence of persistent CIPN from 40% to 20%. However, this assumption was based on “explorative” data in the preceding PLIANT phase II trial, which did not mirror the expected incidence of unwanted toxicity in placebo patients. In POLAR A and M, the assessment of PledOx efficacy was conducted in patients that received at least six cycles of FOLFOX6, enabling analyses of efficacy in 239 A and 88 M patients. Instead of a hypothesized improvement from 40% to 20% incidence of persistent CIPN in the PledOx group, i.e., a 50% improvement, the real outcome was the opposite, i.e., an about 50% worsening in this bothersome toxicity. Mechanisms that may explain the disastrous outcome, with a statistically significant number of patients being seriously injured after having received PledOx, indicate interactions between two redox active metal cations, Pt2+ (oxaliplatin) and Mn2+ (PledOx). A far from surprising causal relationship that escaped prior detection by the study group and the sponsor. Most importantly, recently published data (ref 1) unequivocally indicate that the PLIANT study was not suited to base clinical phase III studies on. In conclusion, the POLAR and PLIANT trials show that PledOx and related manganese-containing compounds are unsuited for co-treatment with platinum-containing compounds. For use as a therapeutic adjunct in rescue treatment, like in ischemia-reperfusion of the heart or other organs, or in acetaminophen (paracetamol)-associated liver failure, there is little or nothing speaking against the use of PledOx or other PLED compounds. However, this must be thoroughly documented in more carefully designed clinical trials.

Attenuation of 7-ketocholesterol- and 7β-hydroxycholesterol-induced oxiapoptophagy by nutrients, synthetic molecules and oils: Potential for the prevention of age-related diseases

Age-related diseases for which there are no effective treatments include cardiovascular diseases; neurodegenerative diseases such as Alzheimer's disease; eye disorders such as cataract and age-related macular degeneration; and, more recently, Severe Acute Respiratory Syndrome (SARS-CoV-2). These diseases are associated with plasma and/or tissue increases in cholesterol derivatives mainly formed by auto-oxidation: 7-ketocholesterol, also known as 7-oxo-cholesterol, and 7β-hydroxycholesterol. The formation of these oxysterols can be considered as a consequence of mitochondrial and peroxisomal dysfunction, leading to increased in oxidative stress, which is accentuated with age. 7-ketocholesterol and 7β-hydroxycholesterol cause a specific form of cytotoxic activity defined as oxiapoptophagy, including oxidative stress and induction of death by apoptosis associated with autophagic criteria. Oxiaptophagy is associated with organelle dysfunction and in particular with mitochondrial and peroxisomal alterations involved in the induction of cell death and in the rupture of redox balance. As the criteria characterizing 7-ketocholesterol- and 7β-hydroxycholesterol-induced cytotoxicity are often simultaneously observed in major age-related diseases (cardiovascular diseases, age-related macular degeneration, Alzheimer's disease) the involvement of these oxysterols in the pathophysiology of the latter seems increasingly likely. It is therefore important to better understand the signalling pathways associated with the toxicity of 7-ketocholesterol and 7β-hydroxycholesterol in order to identify pharmacological targets, nutrients and synthetic molecules attenuating or inhibiting the cytotoxic activities of these oxysterols. Numerous natural cytoprotective compounds have been identified: vitamins, fatty acids, polyphenols, terpenes, vegetal pigments, antioxidants, mixtures of compounds (oils, plant extracts) and bacterial enzymes. However, few synthetic molecules are able to prevent 7-ketocholesterol- and/or 7β-hydroxycholesterol-induced cytotoxicity: dimethyl fumarate, monomethyl fumarate, the tyrosine kinase inhibitor AG126, memantine, simvastatine, Trolox, dimethylsufoxide, mangafodipir and mitochondrial permeability transition pore (MPTP) inhibitors. The effectiveness of these compounds, several of which are already in use in humans, makes it possible to consider using them for the treatment of certain age-related diseases associated with increased plasma and/or tissue levels of 7-ketocholesterol and/or 7β-hydroxycholesterol.

MnDPDP: Contrast Agent for Imaging and Protection of Viable Tissue

The semistable chelate manganese (Mn) dipyridoxyl diphosphate (MnDPDP, mangafodipir), previously used as an intravenous (i.v.) contrast agent (Teslascan™, GE Healthcare) for Mn-ion-enhanced MRI (MEMRI), should be reappraised for clinical use but now as a diagnostic drug with cytoprotective properties. Approved for imaging of the liver and pancreas, MnDPDP enhances contrast also in other targets such as the heart, kidney, glandular tissue, and potentially retina and brain. Transmetallation releases paramagnetic Mn²⁺ for cellular uptake in competition with calcium (Ca²⁺), and intracellular (IC) macromolecular Mn²⁺ adducts lower myocardial T₁ to midway between native values and values obtained with gadolinium (Gd³⁺). What is essential is that T₁ mapping and, to a lesser degree, T₁ weighted imaging enable quantification of viability at a cellular or even molecular level. IC Mn²⁺ retention for hours provides delayed imaging as another advantage. Examples in humans include quantitative imaging of cardiomyocyte remodeling and of Ca²⁺ channel activity, capabilities beyond the scope of Gd³⁺ based or native MRI. In addition, MnDPDP and the metabolite Mn dipyridoxyl diethyl-diamine (MnPLED) act as catalytic antioxidants enabling prevention and treatment of oxidative stress caused by tissue injury and inflammation. Tested applications in humans include protection of normal cells during chemotherapy of cancer and, potentially, of ischemic tissues during reperfusion. Theragnostic use combining therapy with delayed imaging remains to be explored. This review updates MnDPDP and its clinical potential with emphasis on the working mode of an exquisite chelate in the diagnosis of heart disease and in the treatment of oxidative stress.

Mangafodipir as a cardioprotective adjunct to reperfusion therapy: a feasibility study in patients with ST-segment elevation myocardial infarction

AIMS

The aim of the present study was to examine the feasibility of applying the catalytic antioxidant mangafodipir [MnDPDP, manganese (Mn) dipyridoxyl diphosphate] as a cardioprotective adjunct to primary percutaneous coronary intervention (pPCI) in patients with ST-segment elevation (STE) myocardial infarction (STEMI). Both MnDPDP and a metabolite (Mn dipyridoxyl ethyldiamine) possess properties as mitochondrial superoxide dismutase mimetics and iron chelators, and combat oxidative stress in various tissues and conditions.

METHODS AND RESULTS

The study tested MnDPDP (n = 10) vs. saline placebo (n = 10), given as a brief intravenous (i.v.) infusion prior to balloon inflation during pPCI in patients with STEMI. Mangafodipir was well tolerated and did not affect heart rate or blood pressure. Despite longer ischaemic time (205 vs. 144 min, P = 0.019) in the MnDPDP group, plasma biomarker releases were identical for the two groups. With placebo vs. MnDPDP, mean STE resolutions were 69.8 vs. 81.9% (P = 0.224) at 6 h and 73.1 vs. 84.3% (P = 0.077) at 48 h. Cardiac magnetic resonance revealed mean infarct sizes of 32.5 vs. 26.2% (P = 0.406) and mean left ventricular (LV) ejection fractions of 41.8 vs. 47.7% (P = 0.617) with placebo vs. MnDPDP. More LV thrombi were detected in placebo hearts (5 of 8) than MnDPDP-treated hearts (1 of 10; P = 0.011).

CONCLUSIONS

Mangafodipir is a safe drug for use as an adjunct to reperfusion therapy. A tendency to benefit of MnDPDP needs confirmation in a larger population. The study revealed important information for the design of a Phase II trial.

Mangafodipir a Selective Cytoprotectant - with Special Reference to Oxaliplatin and Its Association to Chemotherapy-Induced Peripheral Neuropathy (CIPN)

Oxaliplatin, in combination with 5-fluorouracil plus folinate (or capecitabine), has increased survival substantially in stage III colorectal cancer and prolonged life in stage IV patients, but its use is compromised because of severe toxicity. Chemotherapy-induced peripheral neuropathy (CIPN) is the most problematic dose-limiting toxicity of oxaliplatin. Oncologists included for years calcium and magnesium infusion as part of clinical practice for preventing CIPN. Results from a phase III prospective study published in 2014, however, overturned this practice. No other treatments have been clinically proven to prevent this toxicity. There is a body of evidence that CIPN is caused by cellular oxidative stress. Clinical and preclinical data suggest that the manganese chelate and superoxide dismutase mimetic mangafodipir (MnDPDP) is an efficacious inhibitor of CIPN and other conditions caused by cellular oxidative stress, without interfering negatively with the tumoricidal activity of chemotherapy. MnPLED, the metabolite of MnDPDP, attacks cellular oxidative stress at several critical levels. Firstly, MnPLED catalyzes dismutation of superoxide (O₂^•−), and secondly, having a tremendous high affinity for iron (and copper), PLED binds and disarms redox active iron/copper, which is involved in several detrimental oxidative steps. A case report from 2009 and a recent feasibility study suggest that MnDPDP may prevent or even cure oxaliplatin-induced CIPN. Preliminary results from a phase II study (PLIANT) suggest efficacy also of calmangafodipir, but these results are according to available data obscured by a surprisingly low number of adverse events and a seemingly lower than expected efficacy of FOLFOX.

Calmangafodipir [Ca4Mn(DPDP)5], mangafodipir (MnDPDP) and MnPLED with special reference to their SOD mimetic and therapeutic properties

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) participate in pathological tissue damage. Mitochondrial manganese superoxide dismutase (MnSOD) normally keeps ROS and RNS in check. During development of mangafodipir (MnDPDP) as a magnetic resonance imaging (MRI) contrast agent, it was discovered that MnDPDP and its metabolite manganese pyridoxyl ethyldiamine (MnPLED) possessed SOD mimetic activity. MnDPDP has been tested as a chemotherapy adjunct in cancer patients and as an adjunct to percutaneous coronary intervention in patients with myocardial infarctions, with promising results. Whereas MRI contrast depends on release of Mn(2+), the SOD mimetic activity depends on Mn(2+) that remains bound to DPDP or PLED. Calmangafodipir [Ca4Mn(DPDP)5] is stabilized with respect to Mn(2+) and has superior therapeutic activity. Ca4Mn(DPDP)5 is presently being explored as a chemotherapy adjunct in a clinical multicenter Phase II study in patients with metastatic colorectal cancer.

Fodipir and its dephosphorylated derivative dipyridoxyl ethyldiamine are involved in mangafodipir-mediated cytoprotection against 7β-hydroxycholesterol-induced cell death

OBJECTIVE

Mangafodipir exerts pharmacological effects, including vascular relaxation and protection against oxidative stress and cell death induced by oxysterols. Additionally, mangafodipir has been proposed for cardiovascular imaging. The primary metabolites of mangafodipir, manganese dipyridoxyl ethyldiamine (MnPLED) and its constituent dipyridoxyl diphosphate (Dp-dp) also known as fodipir, are pharmacologically active. However, whether they affect oxysterol-induced cytotoxicity is currently unknown. In this study, we examine whether the mangafodipir metabolite affects 7β-hydroxycholesterol (7β-OH)-induced cell death and identify the underlying mechanisms.

METHODS

U937 cells were pretreated or not with mangafodipir substrate (Ms; 200 µm), MnPLED (100 µmol/l) or Dp-dp (100 µmol/l) for 8 h and then exposed to 7β-OH (28 µmol/l) for 18 h.

RESULTS

Our results revealed that pretreatment with MnPLED or Dp-dp protected against 7β-OH-induced cellular reactive oxygen species (ROS) production, apoptosis, and lysosomal membrane permeabilization (LMP). MnPLED and Dp-dp, in par with Ms, confer protection against 7β-OH-induced cytotoxicity by reducing cellular ROS and stabilization of the lysosomal membrane.

CONCLUSION

These results suggest that fodipir is the pharmacologically active part in the structure of mangafodipir, which prevents 7β-OH-induced cell death by attenuating cellular ROS and by preventing LMP. In addition, MnPLED, which is the dephosphorylated product of fodipir, exerts a similar protective effect against 7β-OH-induced cytotoxicity. This result indicates that dephosphorylation of fodipir does not affect its pharmacological actions. Altogether our result confirms the cytoprotective effect of mangafodipir and justifies its potential use as a cytoprotective adjuvant.

Pretreatment with mangafodipir improves liver graft tolerance to ischemia/reperfusion injury in rat

Ischemia/reperfusion injury occurring during liver transplantation is mainly due to the generation of reactive oxygen species (ROS) upon revascularization. Thus, delivery of antioxidant enzymes might reduce the deleterious effects of ROS and improve liver graft initial function. Mangafodipir trisodium (MnDPDP), a contrast agent currently used in magnetic resonance imaging of the liver, has been shown to be endowed with powerful antioxidant properties. We hypothesized that MnDPDP could have a protective effect against liver ischemia reperfusion injury when administrated to the donor prior to harvesting. Livers from Sprague Dawley rats pretreated or not with MnDPDP were harvested and subsequently preserved for 24 h in Celsior® solution at 4°C. Organs were then perfused ex vivo for 120 min at 37°C with Krebs Henseleit solution. In MnDPDP (5 µmol/kg) group, we observed that ATP content was significantly higher at the end of the cold preservation period relative to untreated group. After reperfusion, livers from MnDPDP-treated rats showed better tissue integrity, less hepatocellular and endothelial cell injury. This was accompanied by larger amounts of bile production and higher ATP recovery as compared to untreated livers. The protective effect of MnDPDP was associated with a significant decrease of lipid peroxidation, mitochondrial damage, and apoptosis. Interestingly, MnDPDP-pretreated livers exhibited activation of Nfr2 and HIF-1α pathways resulting in a higher catalase and HO-1 activities. MnDPDP also increased total nitric oxide (NO) production which derived from higher expression of constitutive NO synthase and lower expression of inducible NO synthase. In conclusion, our results show that donor pretreatment with MnDPDP protects the rat liver graft from cold ischemia/reperfusion injury and demonstrate for the first time the potential interest of this molecule in the field of organ preservation. Since MnDPDP is safely used in liver imaging, this preservation strategy holds great promise for translation to clinical liver transplantation.