Erythropoiesis equivalence, pharmacokinetics and immune response following repeat hematide administration in cynomolgus monkeys.

Hematide is a synthetic PEGylated peptidic erythropoiesis stimulating agent (ESA) that is presently being developed for the correction of anemia in patients with chronic renal failure. Unlike currently marketed ESAs, Hematide does not possess any sequence homology to erythropoietin (EPO) and has not elicited moribund immune responses in animal safety studies thereby allowing the generation of a robust safety package. Animals administered marketed ESAs develop anti-EPO antibodies that null the effect of the administered ESA and neutralize endogenous EPO, resulting in severe anemia that precludes the interpretation of chronic safety studies. The primary objective of this study is to determine whether Hematide-specific antibodies are generated when male monkeys are exposed to high Hematide doses (10 mg/kg, intravenous [IV] and subcutaneous [SC]) administered at frequent dosing intervals (every two weeks) for a total of 9 doses; secondary objectives are to evaluate whether developed antibodies impact pharmacokinetics (PK) and pharmacology. In this study, no Hematide-specific antibodies were detected. Hematide exhibits a prolonged plasma half-life and slow clearance by either IV or SC administration. Hematide induced significant erythropoiesis with reticulocytosis and subsequent increases in red blood cells, hematocrit and hemoglobin (Hgb) levels. No erythropoietic differences were noted between the IV and the SC dosed groups with mean +/- SD Hgb levels of 20.9 +/- 2.5 and 20.3 +/- 2.1 g/dL, respectively, occurring on Day 48, corresponding to Hgb increases of 6.5 and 6.7 g/dL, respectively, over pre-dose levels. In conclusion, Hematide is a potent erythropoiesis stimulating agent that exhibits plasma persistence in monkeys. Similar erythropoietic responses were produced following IV and SC administration. The absence of antibody development suggests that Hematide, at the doses and regimen described, has a low immunogenic potential in cynomolgus monkeys.

Motexafin gadolinium: a redox active drug that enhances the efficacy of bleomycin and doxorubicin.

The effect of motexafin gadolinium (MGd), a redox mediator, on tumor response to doxorubicin (Dox) and bleomycin (Bleo) was investigated in vitro and in vivo. MES-SA human uterine sarcoma cells were studied in vitro using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide viability assay. Rif-1, a murine fibrosarcoma cell line, was studied using a clonogenic survival assay. Tumor growth delay assays were performed using the EMT-6 murine mammary sarcoma cell line in BALB/c mice. MGd (25-100 microM) produced dose-dependent enhancement of Bleo cytotoxicity to MES-SA cells. The IC(50) for Bleo was reduced by approximately 10-fold using 100 microM MGd. In clonogenic assays using Rif-1 cells, MGd enhanced the activity of Bleo approximately 1000-fold. This effect was shown to be mediated, in part, by MGd inhibition of potentially lethal damage repair. MGd enhanced the tumor response to bleomycin and Dox in vivo. MGd had no significant effect on the systemic exposure to Dox (expressed in terms of the plasma area under the curve, 0-24 h) and did not increase Dox myelosuppression. MGd enhanced the effectiveness of the redox active drugs, Bleo and Dox.

Photodynamic therapy with motexafin lutetium (Lu-Tex) reduces experimental graft coronary artery disease.

BACKGROUND: Motexafin lutetium (Lu-Tex) is a photodynamic therapy (PDT) agent that localizes in atheromatous plaque in which it can be activated by far-red light. Lu-Tex biolocalization was examined in graft coronary artery disease (GCAD) with a rodent allograft model. After photoactivation, the effect on intimal proliferation was assessed. METHODS: A PVG to ACI rat heterotopic heart transplantation model was used. Lu-Tex (10 mg/kg) was intravenously administered 90 days after transplantation. Photoactivation was performed 24 hr after Lu-Tex administration. A light-emitting diode, central wavelength of 742 nm, was used to illuminate the intraperitoneally placed allografts via a laparotomy (light fluence of 75 J/cm2 at a power density of 75 mW/cm2). Animals were divided into four groups according to postoperative treatments: PDT with Lu-Tex injection and light illumination (n=21), Lu-Tex injection and laparotomy (n=14), laparotomy with light only (n=14), and laparotomy only (n=16). GCAD was quantitatively assessed 14 days after treatments. RESULTS: Lu-Tex localized in atherosclerotic plaque in vessels with GCAD. PDT significantly reduced both the percent of affected vessels and intimal proliferation compared to all other control study groups. alpha-Smooth muscle cell actin and anti-rat macrophage antibody-positive areas were significantly reduced within the neointima in allografts treated with PDT compared to all other study groups. CONCLUSIONS: PDT significantly reduced atherosclerotic lesions of GCAD. Lu-Tex-mediated PDT may, therefore, be a potential method for treating accelerated atherosclerosis associated with transplantation.

Intracellular localization of the radiation enhancer motexafin gadolinium using interferometric Fourier fluorescence microscopy.

Motexafin gadolinium (MGd) is a unique therapeutic agent that localizes in cancer cells and increases tumor response to ionizing radiation and certain chemotherapeutics. The in vitro intracellular localization, accumulation, and retention of MGd in murine EMT6 mammary sarcoma and Rif-1 fibrosarcoma cell lines were studied using interferometric Fourier fluorescence microscopy. MGd cellular uptake was semiquantified using its characteristic fluorescence emission band centered at 758 nm. Colocalization studies were performed using mitochondrial, endoplasmic reticulum, Golgi apparatus, nuclear, and lysosomal fluorescent organelle probes, and verified using interferometric Fourier spectroscopy. Cellular uptake was gradual and increased significantly with incubation time. MGd localized primarily within the lysosomes and endoplasmic reticulum, and to a lesser extent within the Golgi apparatus and mitochondria. Mitochondrial staining was increased in media without serum. No nuclear uptake was detected in the Rif-1 cells, but after 48 h nuclear uptake was observed in 15% of EMT6 cells. These results indicated that MGd accumulates within cytoplasmic compartments. The sustained intracellular localization of MGd may, in part, account for its unique radiation and chemotherapy enhancement properties. Interferometric Fourier fluorescence microscopy is a potentially powerful tool in delineating and verifying localization sites of therapeutic agents.

Photodynamic therapy with motexafin lutetium induces redox-sensitive apoptosis of vascular cells.

Motexafin lutetium is a photosensitizer that accumulates in atherosclerotic plaque and, after activation by far-red light, produces cytotoxic singlet oxygen. The combination of photosensitizer and illumination, known as photodynamic therapy (PDT), has been shown to reduce atheroma formation in animal models and is under clinical investigation. However, the effects of PDT with motexafin lutetium on isolated vascular cells are unknown. This study was designed to characterize the effects of PDT on vascular cell viability and to define the cell-death pathway for this agent. Fluorescence microscopy of RAW macrophages and human vascular smooth muscle cells revealed time-dependent uptake of motexafin lutetium. Illumination of motexafin lutetium-loaded cells with 732-nm light (2 J/cm(2)) impaired cellular viability and growth (IC(50) 5 to 20 micromol/L). Depletion of intracellular glutathione potentiated (P=0.035) and the addition of antioxidant N-acetylcysteine attenuated (P=0.002) cell death, suggesting that the intracellular redox state influences motexafin lutetium action. PDT was associated with the loss of mitochondrial membrane potential, mitochondrial release of cytochrome c, and caspase activation. PDT promoted phosphatidylserine externalization and induced apoptotic DNA fragmentation, with the number of apoptotic cells increasing from 7+/-2% to 34+/-3% of total cells. Reducing plaque cellularity by the induction of apoptosis may be one mechanism by which PDT reduces plaque burden, possibly modulates plaque vulnerability, and inhibits restenosis in vivo.

Reduction of vein graft disease using photodynamic therapy with motexafin lutetium in a rodent isograft model.

BACKGROUND: Motexafin lutetium (Lu-Tex) is a photosensitizer that targets atheromatous plaque. Subsequent photoactivation (photodynamic therapy [PDT]) induces local cytotoxic effects. The aim of the present study was to investigate whether Lu-Tex targets vein graft intimal hyperplasia and whether subsequent photoactivation attenuates the disease process. METHODS AND RESULTS: The subcellular localization of Lu-Tex and postillumination viability were studied in cultured human vein graft smooth muscle cells. Inferior vena cava-grafted rats were injected with Lu-Tex (10 mg/kg) 4 or 12 weeks after grafting. Biodistribution was assessed in a subgroup 24 hours after administration. Light therapy (742 nm) was performed 24 hours after Lu-Tex injection by illuminating intraperitoneally placed isografts using a laparotomy. Animals were divided into the following 4 groups: PDT (n=15), Lu-Tex injection and laparotomy (n=13), light treatment (n=14), and laparotomy only (n=13). Grafts were harvested 14 days after treatment for histochemical analysis. Lu-Tex localized within subcellular organelles of smooth muscle cells, and subsequent photoactivation induced cell death via apoptosis. The Lu-Tex concentrations present in the vein grafts were 9.3 times higher than those in the normal inferior vena cava. Postoperative PDT at 4 weeks after surgery significantly reduced the intima/media ratio, whereas treatment at 12 weeks did not reduce the intima/media ratio. Activated macrophages were observed 4 weeks after grafting; however, a significant reduction occurred in these cells by 12 weeks. The mechanism by which PDT works may be related to the presence of activated macrophages. CONCLUSIONS: PDT significantly reduces the intima/media ratio in the early phase of vein graft disease. Lu-Tex-mediated PDT may be a viable method for the attenuation of atherosclerotic disease in vein grafts.

Photoangioplasty: An emerging clinical cardiovascular role for photodynamic therapy.

Photodynamic therapy (PDT) has been studied and applied to various disease processes. The potential of PDT for selective destruction of target tissues is especially appealing in cardiovascular disease, in which other existing interventional tools are somewhat nonselective and carry substantial risk of damage to the normal arterial wall. Enthusiasm for photoangioplasty (PDT of vascular de novo atherosclerotic and, potentially, restenotic lesions) is fueled by more effective second-generation photosensitizers and technological advances in endovascular light delivery. This excitement revolves around at least 4 significant attributes of light-activated therapy: the putative selectivity and safety of photoangioplasty, the potential for atraumatic and effective debulking of atheromatous plaque through a biological mechanism, the postulated capability to reduce or inhibit restenosis, and the potential to treat long segments of abnormal vessel by simply using fibers with longer light-emitting regions. The available nonclinical data, coupled with the observations of a new phase I trial in human peripheral atherosclerosis, suggest a promising future for photoangioplasty in the treatment of primary atherosclerosis and prevention of restenosis.

Lutetium texaphyrin (Lu-Tex): a potential new agent for ocular fundus angiography and photodynamic therapy.

PURPOSE: To investigate the suitability of lutetium texaphyrin (lu-tex) as a fluorescence imaging agent in the delineation of retinal vascular and choroidal vascular diseases. The utilization of an efficient fluorescent molecule that is also a photosensitizer represents a unique opportunity to couple diagnosis and therapy. METHODS: Fundus fluorescence angiography comparing lu-tex (motexafin lutetium, Optrin, Pharmacyclics Inc, Sunnyvale, California) with the conventional angiographic dyes, sodium fluorescein, and indocynanine green (ICG), was performed on the eyes of normal and laser-injured New Zealand white rabbits. Plasma pharmacokinetic data and plasma protein binding were assessed in addition to light microscopy of the retina in both imaged and laser-injured eyes. RESULTS: Normal retinal and choroidal vasculature was well delineated by lu-tex angiography. Experimentally induced choroidal and retinal vascular lesions were enhanced by lu-tex and demonstrated different staining patterns than fluorescein or ICG, particularly at the margins of the lesions. Lu-tex cleared rapidly from the plasma, with 39.7% bound to the high-density lipoprotein (HDL) fraction while 15.8% was bound to the low-density lipoprotein (LDL) fraction. No evidence of retinal toxicity after dye administration was observed by either ophthalmoscopy and fundus photography or by light microscopy. CONCLUSION: Lu-tex angiography is a potentially valuable method for retinal vascular and choroidal vascular evaluation, and it has advantages over fluorescein and ICG angiography. The same agent could conceivably be used for both the identification of abnormal vasculature and subsequent photodynamic treatment.

Photodynamic therapy of B16F10 murine melanoma with lutetium texaphyrin.

Photodynamic therapy (PDT) of pigmented melanoma has generally been unsuccessful because of insufficient light penetration in such tissues. In this study, the responsiveness of the heavily pigmented B16F10 murine melanoma to lutetium texaphyrin (PCI-0123), a water-soluble sensitizer with strong absorbance in the near infrared (700-760 nm), was examined. These studies were carried out in both normal and ApoE deficient C57BL/6 mice. The latter strain exhibits a lipoprotein profile more like humans (low density lipoprotein > high density lipoprotein) than rodents (high density lipoprotein >> low density lipoprotein). Under optimal conditions of drug dose, light dose, and interval between drug administration and irradiation--the median survival time of C57BL/6 tumor bearing mice was approximately doubled (29 d) compared with tumor bearing control animals (13 d). The life-span of the ApoE knockout mice was greater (33 d) than the C57BL/6 animals (23 d) when irradiation occurred 3 h after administration of a 10 micromol per kg drug dose. The greater efficacy of PDT in the ApoE deficient mice was associated with more rapid clearance of drug from the blood, greater accumulation of sensitizer in tumor tissue, and substantially greater drug binding to the very low density lipoprotein/low density lipoprotein plasma fraction. Confocal laser scanning microscopy showed that the predominant subcellular site of photosensitizer binding was to melanosomes; costaining was performed with Mel-5. Melanosomes are susceptible to oxidative stress. Photo-oxidation, mediated by PCI-0123 PDT, could potentially overload an already highly oxidized stressed state leading to cell death. The good tissue penetration depth achieved by PCI-0213 mediated PDT and the activation of melanosomes makes PDT of pigmented melanoma, for the first time, clinically relevant.

Localization and efficacy analysis of the phototherapeutic lutetium texaphyrin (PCI-0123) in the murine EMT6 sarcoma model.

Lutetium texaphyrin (PCI-0123) is a pure, water-soluble photodynamic therapy (PDT) agent that is activated by tissue-penetrating far red light. The sensitizer is highly fluorescent and exhibits a strong, broad emission signal at 750 nm. In vitro cellular uptake studies revealed an increase in sensitizer retention with incubation time. Confocal laser scanning microscopy demonstrated that the intracellular localization site of PCI-0123 is the lysosomes. Ensuing illumination of the EMT6 cells led to lysosomal breakup, extensive cytoplasmic blebbing and subsequent cell death. Noninvasive spectral imaging analysis of PCI-0123 fluorescence depicted selective drug uptake, compared to surrounding normal tissue, in EMT6 mammary sarcomas syngeneic to BALB/c mice. The PCI-0123 PDT was shown to effectively treat the EMT6 murine sarcoma. Irradiation (732 nm light) 3 h postintravenous injection of 10 mumol PCI-0123 per kg gave 100% cures (no evidence of cancer), whereas light exposure at 5 h resulted in 75% cures. Hematoxylin and eosin histologic examination of photoirradiated tumors indicated apoptosis of the EMT6 neoplasms at early times post-PDT progressing, with time, to extensive necrotic areas. Gel electrophoresis of extracted photoirradiated tumors showed the typical apoptotic DNA ladder pattern that increased in intensity following PDT treatment.

Phototherapy of cancer and atheromatous plaque with texaphyrins.

Cancer and cardiovascular disease are the leading causes of death in the western world. Photodynamic therapy (PDT) has demonstrated activity in the treatment of superficial cancerous lesions and as an intraoperative adjunct during surgical debulking. Texaphyrins are pure, synthetic water-soluble macrocycles that localize in both cancerous lesions and atheromatous plaque. Lutetium texaphyrin (PCI-0123) is activated by tissue-penetrating far red light (720-760 nm). Patient diagnosis and treatment planning is possible via magnetic resonance imaging (MRI) with the paramagnetic gadolinium texaphyrin (PCI-0120) or via fluorescence imaging using the diamagnetic PCI-0123. In this study it is shown that texaphyrins localize selectively in cancer and atheromatous plaque. PDT with PCI-0123 is found to cause selective photodamage to the diseased tissue. Specifically, PCI-0123 acts to eradicate the SMT-F murine mammary tumors and diet-induced atheromatous plaque in rabbits.

Lutetium texaphyrin (PCI-0123): a near-infrared, water-soluble photosensitizer.

Lutetium texaphyrin, PCI-0123, is a pure, water-soluble photosensitizer with a large broad absorption band centered at 732 nm. The compound was tested for photodynamic therapy (PDT) effectiveness in a murine mammary cancer model. The texaphyrin macrocycle as illustrated by magnetic resonance imaging and 14C-radiolabeled texaphyrin studies was shown to be tumor selective; a tumor-to-muscle ratio of 10.55 was seen after 5 h. Lutetium texaphyrin, at a drug dose of 20 mumol/kg with irradiation 5 h postinjection at 150 J/cm2 and 150 mW/cm2, had significant efficacy (P < 0.0001) in treating neoplasms of moderate size (40 +/- 14 mm3) and also had significant efficacy (P < 0.0001) in treating larger neoplasms (147 +/- 68 mm3). The PDT efficacy was correlated with the time interval between PCI-0123 administration and light exposure. A 100% cure rate was achieved when photoirradiation took place 3 h postinjection compared to 50% for 5 h using 10 mumol/kg and 150 J/cm2 at 150 mW/cm2. The PDT efficacy was attributable to the selective uptake/retention of the texaphyrin photosensitizer in addition to the depth of light penetration achievable at the 732 nm laser irradiation.

Biodistribution of haematoporphyrin analogues in a lung carcinoma model.

In an attempt to identify novel compounds useful for the optimization of Photodynamic Therapy (PDT), the tissue localization of new synthetic porphyrins was compared with Photofrin II in nude mice xenografted with a human small cell lung cancer (POVD). Three haematoporphyrin analogues were selected for this study based on prior in vitro photosensitivity screening of a series of 15 such derivatives, as well as on the basis of improved localization in C6 gliomas in mice. Two of the porphyrins yielded better tumour:normal lung ratios than Photofrin II and, of these two, one (P13) is known to exhibit good photosensitization properties both in vitro and in vivo, and is therefore a good candidate as a lead compound for the development of porphyrins suitable for the photodynamic treatment of lung tumours.

Evaluation of a morpholinothiolporphyrin for use in photodynamic therapy.

The photonecrotic effectiveness of a morpholinothiolporphyrin derived from haematoporphyrin was measured in an animal model of cerebral glioma. The dose administered was 20 mg kg-1 and the laser dose varied from 0 to 200 J cm-2. The tumour necrosis was at least as good as that of HpD, and this therapeutic response may be attributed to the targeting of specific 'photopotent' subcellular sites.

Evaluation of porphyrin characteristics required for photodynamic therapy.

The cytotoxicity (in the dark), phototoxicity (red light) and subcellular localization (using confocal laser scanning microscopy) were determined for 15 porphyrins (1-15) in C6 glioma cells. The partition coefficient in 2-octanol was also determined for each porphyrin at pH 7.4. The cytotoxicity increased with pi (log of partition coefficient) up to pi values of +2. The 7 porphyrins with cationic side chains exhibited a classical parabolic correlation between phototoxicity and pi, with maximal activity at a pi value of approximately 1.0. There was also a significant correlation between subcellular localization and degree of phototoxicity, with the three most photosensitive porphyrins all possessing cationic side chains, and all three localizing in mitochondria.

Evaluation of tumour and tissue distribution of porphyrins for use in photodynamic therapy.

A range of pure, monomeric porphyrins were synthesised and their localising capacities compared to HpD and Hp at 6 h and 24 h post injection in the mouse C6 intracerebral glioma model as well as in normal brain, skin, muscle, kidney, spleen, liver, lung and whole blood. The partition coefficients were examined between PBS and 2-octanol over the pH range 7.4-6.6 and pH profiles were established. A parabolic relationship was observed between log (porphyrin tumour concentration) at pH 7.4, with maximal tumour localisation at log (partition coefficient), pi, of approximately zero. Porphyrins with side chains with nett cationic character also exhibited up upward (parabolic) dependence on pi for most tissues studied, with maximal porphyrin localisation at pi of 0-0.5. In contrast, those porphyrins with nett anionic character exhibited a downward (negative) parabolic trend for all eight tissues studied, with minimal porphyrin localisation at pi of approximately zero. Four porphyrins (4, 11, 12, 13) exhibited similar or better tumour localisation than HpD, and two (11 and 12) offer promise as lead compounds for the design of improved porphyrins for use in PDT.

Subcellular localization of porphyrins using confocal laser scanning microscopy.

The in vitro subcellular distribution patterns of 10 porphyrins, varying in hydrophobicity and charge, were studied using confocal laser scanning microscopy on two cell lines (V79 and C6 glioma cells) for incubation times up to 24 h. All of the porphyrins were taken up rapidly by both cell lines and distinct classes of subcellular distribution patterns were observed: general cytoplasmic staining; localization in lysosomes (usually associated with general cytoplasmic staining); localization in mitochondria (and general cytoplasmic staining); localization in mitochondria with subsequent uptake into lysosomes. Structure-localization relationships which have emerged are that porphyrins with dominantly cationic side chains localize in mitochondria, whereas those with a more anionic character tend to localize in lysosomes.