Mechanisms of tissue uptake and retention in zotarolimus-coated balloon therapy.

BACKGROUND: Drug-coated balloons are increasingly used for peripheral vascular disease, and, yet, mechanisms of tissue uptake and retention remain poorly characterized. Most systems to date have used paclitaxel, touting its propensity to associate with various excipients that can optimize its transfer and retention. We examined zotarolimus pharmacokinetics. METHODS AND RESULTS: Animal studies, bench-top experiments, and computational modeling were integrated to quantify arterial distribution after zotarolimus-coated balloon use. Drug diffusivity and binding parameters for use in computational modeling were estimated from the kinetics of zotarolimus uptake into excised porcine femoral artery specimens immersed in radiolabeled drug solutions. Like paclitaxel, zotarolimus exhibited high partitioning into the arterial wall. Exposure of intimal tissue to drug revealed differential distribution patterns, with zotarolimus concentration decreasing with transmural depth as opposed to the multiple peaks displayed by paclitaxel. Drug release kinetics was measured by inflating zotarolimus-coated balloons in whole blood. In vivo drug uptake in swine arteries increased with inflation time but not with balloon size. Simulations coupling transmural diffusion and reversible binding to tissue proteins predicted arterial distribution that correlated with in vivo uptake. Diffusion governed drug distribution soon after balloon expansion, but binding determined drug retention. CONCLUSIONS: A large bolus of zotarolimus releases during balloon inflation, some of which pervades the tissue, and a fraction of the remaining drug adheres to the tissue-lumen interface. As a result, the duration of delivery modulates tissue uptake where diffusion and reversible binding to tissue proteins determine drug transport and retention, respectively.

Development of three-dimensionally printed vascular stents of bioresorbable poly(l-lactide-co-caprolactone).

With the ripening of 3D printing technology and the discovery of a variety of printable materials, 3D-printed vascular stents provide new treatment options for patients with angiocardiopathy. Bioresorbable stent not only combines the advantages of metallic stent and drug-coated balloon, but also avoids the disadvantages of them. 3D printing is also an economical and efficient way to produce stents and makes it possible to construct complex structures. In this study, stents made from poly(l-lactic acid) (PLLA), poly(ε-caprolactone) (PCL) and poly(l-lactide-co-caprolactone) (PLCL) were manufactured by 3D printing and evaluated for radial strength, crystallinity and molecular weight. PLCL copolymerized by different proportions of lactic acid and caprolactone showed different mechanical and degradation properties. This demonstrated the potential of 3D printing as a low-cost and high throughput method for stent manufacturing. The PLLA and PLCL 95/5 stents had similar mechanical properties, whereas PLCL 85/15 and PCL stents both had relatively low radial strength. In general, PLCL 95/5 had a faster degradation rate than PLLA. These two materials were made into peripheral vascular bioresorbable scaffolds (BRS) and further studied by additional bench testing. PLCL 95/5 peripheral BRS had superior mechanical properties in terms of flexural/bending fatigue and compression resistance.

Inhibition of experimental neointimal hyperplasia and neoatherosclerosis by local, stent-mediated delivery of everolimus.

INTRODUCTION: A novel self-expanding, drug-eluting stent (DES) was designed to slowly release everolimus in order to prevent restenosis after percutaneous peripheral intervention. The purpose of this experimental animal study was to test the hypothesis that long-term local, stent-mediated delivery of everolimus would reduce neointimal hyperplasia in porcine iliac arteries. METHODS: The iliac arteries of 24 Yucatan mini-swine were percutaneously treated with overlapping 8- × 28-mm self-expanding nitinol stents loaded with everolimus (225 µg/cm2 stent surface area) formulated in a poly(ethylene-co-vinyl alcohol) copolymer intended to deliver the drug in a sustained fashion over about 6 months (DES). Bare nitinol self-expanding stents (bare metal stent [BMS]) were implanted in an identical fashion on the contralateral side to serve as controls. After 3, 6, or 12 months, the animals were sacrificed and the stented arteries perfusion-fixed for histomorphometric analysis. RESULTS: The chronic presence of everolimus in arterial tissue reduced stent-induced inflammation after 3 months (inflammation score: BMS 2.29±0.44 vs DES 0.17±0.17; P=.001) and 6 months (BMS 2.06±0.43 vs DES 0.50±0.5; P=.007), although some late inflammation was observed after drug exhaustion (BMS 1.00±0.25 vs DES 2.56±0.62 after 12 months; P=not significant [NS]). Treatment with locally delivered everolimus significantly reduced neointimal hyperplasia after 3 months (neointimal thickness: BMS 0.79±0.20 vs DES 0.37±0.04 mm; P=.03) and 6 months (BMS 0.73±0.14 vs DES 0.41±0.08 mm; P=.05), although the effect had dissipated after 12 months (BMS 0.68±0.11 vs DES 0.67±0.11 mm; P=NS). Remarkably, stent-induced neoatherosclerosis, characterized by the histologic presence of foamy macrophages and cholesterol clefts, was significantly attenuated by treatment with everolimus (atherogenic change scores at 3 months: BMS 0.56±0.15 vs DES 0.04±0.04; P=.003; 6 months: BMS 0.84±0.23 vs DES 0.00±0.00; P=.004; and 12 months: BMS 0.09±0.10 vs DES 0.19±0.19; P=NS). CONCLUSIONS: In this experimental animal model, local arterial stent-mediated delivery of everolimus inhibited the formation of neointimal hyperplasia and neoatherosclerosis during the first 6 months. The effect was transient, however, as arterial morphology and histology appeared similar to control stented arteries after 12 months.

A review on biodegradable biliary stents: materials and future trends.

Biliary stricture is defined as the reduction and narrowing of the bile duct lumen, which can be caused by many factors such as cancer and inflammation. Biliary stent placement can effectively alleviate benign and malignant biliary strictures. However, the commonly used plastic or metallic biliary stents are far from ideal and do not satisfy all clinical requirements，although several types of biodegradable biliary stents have been developed and used clinically. In this review, we summarized current development status of biodegradable stents with the emphasis on the stent materials. We also presented the future development trends based on the published literature.

Transmural communication at a subcellular level may play a critical role in the fallout based-endothelialization of dacron vascular prostheses in canine.

A microporous and permeable wall is important for the healing of vascular prostheses, however, the significance of its permeability to soluble substances at subcellular level has not been demonstrated. Polyester arterial prostheses were prepared in such a way that each of them contained three segments, of which at least one segment was impervious and another segment was permeable to water but impermeable to cells. Twenty graft segments were implanted in 7 dogs as a thoraco-abdominal bypass for 2 months. The prostheses were then harvested, photographed, and treated for histological and morphological studies. The low porosity graft capped by two thrombogenic segments was fully endothelialized, proving the fallout mechanism. The striking contrast with its impermeable counterpart demonstrated that a wall permeable to small substances of subcellular level was critical for the endothelial healing. A wide range of water permeabilities did not reveal advantages of high water permeable segments over low water permeable ones. Endothelial ingrowth from anastomoses was also jeopardized in the absence of wall permeability. In conclusion, transmural communication at a subcellular level may have played a critical role in the fallout based-endothelialization of arterial prostheses in canine. This highlights the potential function of perigraft cytokines and growth factors in endothelial healing.

The effects of the oral, pan-VEGF-R kinase inhibitor CEP-7055 and chemotherapy in orthotopic models of glioblastoma and colon carcinoma in mice.

CEP-7055, a fully synthetic, orally active N,N-dimethylglycine ester of CEP-5214, a C3-(isopropylmethoxy)-fused pyrrolocarbazole with potent pan-vascular endothelial growth factor receptor (VEGFR) kinase inhibitory activity, has recently completed phase I clinical trials in cancer patients. These studies evaluated the antitumor efficacy of CEP-7055 using orthotopic models of glioblastoma and colon carcinoma in combination with temozolomide, and irinotecan and oxaliplatin, respectively, for their effects on primary and metastatic tumor burden and median survival. Chronic administration of CEP-7055 (23.8 mg/kg/dose) and temozolomide resulted in improvement of median survival of nude mice bearing orthotopic human glioblastoma xenografts compared with temozolomide alone (261 versus 192 days, respectively; P < or = 0.02). Reductions in neurologic dysfunction, brain edema, hemorrhage, and intratumoral microvessel density (CD34 staining) were observed in glioma-bearing mice receiving CEP-7055 alone, temozolomide alone, and the combination of CEP-7055 and temozolomide relative to vehicle and to temozolomide monotherapy. The administration of CEP-7055 in combination with irinotecan (20 mg/kg/dose i.p. x 5 days), and to a lesser degree with oxaliplatin (10 mg/kg/dose i.v.), showed reductions on primary colon carcinoma and hepatic metastatic burden in the CT-26 tumor model relative to that achieved by irinotecan and oxaliplatin monotherapy. These data show the significant efficacy and tolerability of optimal efficacious doses of CEP-7055 when given in combination with temozolomide and irinotecan relative to monotherapy with these cytotoxic agents in preclinical orthotopic glioma and colon carcinoma models and lend support for the use of these treatment regimens in a clinical setting in patients with glioblastoma and colon carcinoma.

Antiangiogenic and antitumor efficacy of EphA2 receptor antagonist.

Tumor-associated angiogenesis is critical for tumor growth and metastasis and is controlled by various pro- and antiangiogenic factors. The Eph family of receptor tyrosine kinases has emerged as one of the pivotal regulators of angiogenesis. Here we report that interfering with EphA signaling resulted in a pronounced inhibition of angiogenesis in ex vivo and in vivo model systems. Administration of EphA2/Fc soluble receptors inhibited, in a dose-dependent manner, microvessel formation in rat aortic ring assay, with inhibition reaching 76% at the highest dose of 5000 ng/ml. These results were further confirmed in vivo in a porcine aortic endothelial cell-vascular endothelial growth factor (VEGF)/basic fibroblast growth factor Matrigel plug assay, in which administration of EphA2/Fc soluble receptors resulted in 81% inhibition of neovascularization. The additive effects of simultaneous inhibition of VEGF receptor 2 and EphA signaling pathways in aortic ring assay and antiangiogenic efficacy of EphA2/Fc soluble receptors against VEGF/basic fibroblast growth factor-mediated neovascularization in vivo indicated a critical and nonredundant role for EphA signaling in angiogenesis. Furthermore, in two independent experiments, we demonstrated that EphA2/Fc soluble receptors strongly (by approximately 50% versus controls) suppressed growth of ASPC-1 human pancreatic tumor s.c. xenografts. Inhibition of tumor growth was due to decreased proliferation of tumor cells. In an orthotopic pancreatic ductal adenocarcinoma model in mice, suppression of EphA signaling by i.p. administration of EphA2/Fc (30 micro g/dose, three times a week for 56 days) profoundly inhibited the growth of primary tumors and the development of peritoneal, lymphatic, and hepatic metastases. These data demonstrate a critical role of EphA signaling in tumor growth and metastasis and provide a strong rationale for targeting EphA2 receptors for anticancer therapies.

Chemopotentiation of temozolomide, irinotecan, and cisplatin activity by CEP-6800, a poly(ADP-ribose) polymerase inhibitor.

Poly(ADP-ribose) polymerase 1 (PARP-1) is a nuclear zinc finger DNA-binding protein that is implicated in the repair of DNA damage. Inhibition of PARP-1 through genetic knockouts causes cells to become hypersensitive to various chemotherapeutic agents. We tested the chemopotentiating ability of the PARP-1 inhibitor, CEP-6800, when used in combination with temozolomide (TMZ), irinotecan (camptothecin or SN38), and cisplatin against U251MG glioblastoma, HT29 colon carcinoma, and Calu-6 non-small cell lung carcinoma xenografts and cell lines, respectively. Exposure of tumor cells to TMZ, camptothecin (or SN38), and cisplatin before, or in the presence of, CEP-6800 significantly increased the onset and the magnitude of DNA damage, the duration for cells to effect repair, and the onset, duration, or fraction of cells arrested at the G(2)/M boundary. In addition, in vivo biochemical efficacy studies with CEP-6800 showed that it was able to attenuate irinotecan- and TMZ-induced poly(ADP-ribose) accumulation in LoVo and HT29 xenografts, respectively. Treatment of CEP 6800 (30 mg/kg) with TMZ (17 and 34 mg/kg) resulted in 100% complete regression of U251MG tumors by day 28 versus 60% complete regression caused by TMZ alone. CEP-6800 (30 mg/kg) in combination with irinotecan (10 mg/kg) resulted in a 60% inhibition of HT29 tumor growth versus irinotecan alone by day 33. The combination therapy of cisplatin (5 mg/kg) with CEP-6800 (30 mg/kg) caused a 35% reduction in Calu-6 tumor growth versus cisplatin alone by day 28. These data suggest that CEP-6800 could be used as a chemopotentiating agent with a variety of clinically effective chemotherapeutic agents.

Assessment of self-expanding nitinol stent deformation after chronic implantation into the femoropopliteal arteries.

AIMS: The purpose of this prospective clinical investigation was to quantify the degree and range of compressive and bending deformations sustained by self-expanding nitinol stents when implanted into the femoropopliteal arteries of patients with symptomatic peripheral vascular disease (PVD). METHODS AND RESULTS: Twenty-three nitinol self-expanding stents (Absolute; Abbott Vascular, Santa Clara, CA, USA) with diameters ranging from 5-10 mm and lengths ranging from 40-100 mm were implanted in 19 lesions in 18 extremities of 17 patients. Two days following implantation, in vivo stent compression and bending were assessed by measurement of stent length and deflection angle via lateral view radiographs. The results showed that leg flexion was associated with significant stent bending; popliteal stents bent almost 90° while SFA stents bent only minimally. Leg flexion was also associated with stent shortening (compression), the greatest amount being observed for stents implanted into the popliteal artery (popliteal 8.5% ± 3.2%; SFA/prox pop 5.3% ± 0.5%; SFA 3.1% ± 1.8%). After a mean follow-up of 7.1 ± 1.3 months, the degree of stent deformation during leg flexion was essentially unchanged as compared to immediate post-procedure levels. CONCLUSIONS: Indwelling nitinol stents are routinely bent and compressed during leg flexion, with most bending observed in stents implanted near the popliteal artery. The degree of deformation observed immediately after implantation appears to be predictive of the chronic state, as repeat measurements obtained after a mean of seven months were essentially unchanged from baseline.

A theoretical model to characterize the drug release behavior of drug-eluting stents with durable polymer matrix coating.

The time-dependent local drug delivery from drug-eluting stents (DES) plays a critical role in reducing restenosis in intravascular stenting. To better understand the basic mechanism of drug release for certain polymer-drug-coated DES platforms, a cylindrical diffusion model was applied successfully to quantitatively describe the experimental drug release data of Dynalink-E in vitro and in vivo. The results showed that the profiles of Dynalink-E everolimus release could be controlled by such characteristic parameters as coating thickness and diffusion coefficient. The model could be used to quantitatively characterize the drug release profiles and IVIV correlations.

Synthesis and biological profile of the pan-vascular endothelial growth factor receptor/tyrosine kinase with immunoglobulin and epidermal growth factor-like homology domains 2 (VEGF-R/TIE-2) inhibitor 11-(2-methylpropyl)-12,13-dihydro-2-methyl-8-(pyrimidin-2-ylamino)-4H-indazolo[5,4-a]pyrrolo[3,4-c]carbazol-4-one (CEP-11981): a novel oncology therapeutic agent.

A substantial body of evidence supports the utility of antiangiogenesis inhibitors as a strategy to block or attenuate tumor-induced angiogenesis and inhibition of primary and metastatic tumor growth in a variety of solid and hematopoietic tumors. Given the requirement of tumors for different cytokine and growth factors at distinct stages of their growth and dissemination, optimal antiangiogenic therapy necessitates inhibition of multiple, complementary, and nonredundant angiogenic targets. 11-(2-Methylpropyl)-12,13-dihydro-2-methyl-8-(pyrimidin-2-ylamino)-4H-indazolo[5,4-a]pyrrolo[3,4-c]carbazol-4-one (11b, CEP-11981) is a potent orally active inhibitor of multiple targets (TIE-2, VEGF-R1, 2, and 3, and FGF-R1) having essential and nonredundant roles in tumor angiogenesis and vascular maintenance. Outlined in this article are the design strategy, synthesis, and biochemical and pharmacological profile for 11b, which completed Phase I clinical assessing safety and pharmacokinetics allowing for the initiation of proof of concept studies.

CEP-32496: a novel orally active BRAF(V600E) inhibitor with selective cellular and in vivo antitumor activity.

Mutations in the BRAF gene have been identified in approximately 7% of cancers, including 60% to 70% of melanomas, 29% to 83% of papillary thyroid carcinomas, 4% to 16% colorectal cancers, and a lesser extent in serous ovarian and non-small cell lung cancers. The V600E mutation is found in the vast majority of cases and is an activating mutation, conferring transforming and immortalization potential to cells. CEP-32496 is a potent BRAF inhibitor in an in vitro binding assay for mutated BRAF(V600E) (K(d) BRAF(V600E) = 14 nmol/L) and in a mitogen-activated protein (MAP)/extracellular signal-regulated (ER) kinase (MEK) phosphorylation (pMEK) inhibition assay in human melanoma (A375) and colorectal cancer (Colo-205) cell lines (IC(50) = 78 and 60 nmol/L). In vitro, CEP-32496 has multikinase binding activity at other cancer targets of interest; however, it exhibits selective cellular cytotoxicity for BRAF(V600E) versus wild-type cells. CEP-32496 is orally bioavailable in multiple preclinical species (>95% in rats, dogs, and monkeys) and has single oral dose pharmacodynamic inhibition (10-55 mg/kg) of both pMEK and pERK in BRAF(V600E) colon carcinoma xenografts in nude mice. Sustained tumor stasis and regressions are observed with oral administration (30-100 mg/kg twice daily) against BRAF(V600E) melanoma and colon carcinoma xenografts, with no adverse effects. Little or no epithelial hyperplasia was observed in rodents and primates with prolonged oral administration and sustained exposure. CEP-32496 benchmarks favorably with respect to other kinase inhibitors, including RAF-265 (phase I), sorafenib, (approved), and vemurafenib (PLX4032/RG7204, approved). CEP-32496 represents a novel and pharmacologically active BRAF inhibitor with a favorable side effect profile currently in clinical development.

Vascular response to zotarolimus-coated balloons in injured superficial femoral arteries of the familial hypercholesterolemic Swine.

BACKGROUND: Drug-coated balloons are rapidly emerging as a therapeutic alternative for the interventional treatment of peripheral vascular disease. The purpose of this study was to test the hypothesis that an angioplasty balloon coated with the mTOR inhibitor zotarolimus (ZCB) would inhibit neointimal hyperplasia in a novel injury-based superficial femoral artery model in the familial hypercholesterolemic swine. METHODS AND RESULTS: A total of 44 familial hypercholesterolemic swine were included (12 designated to study tissue pharmacokinetics and 32 to study safety and efficacy). Fogarty balloon denudation was performed in all superficial femoral artery segments, followed by balloon angioplasty. In the pharmacokinetic study, a total of 24 ZCBs (300 µg/cm(2)) were used. Zotarolimus was detected in arterial tissue at 5 minutes (162 ng/mg of tissue), 24 hours (5.9 ng/mg of tissue), and 28 days (0.007 ng/mg of tissue) after ZCB inflation. In the safety and efficacy study, superficial femoral artery segments were randomized to either high-dose (600 µg/cm(2), n=16), low-dose (300 µg/cm(2), n=16), or paired uncoated balloons (high-dose ZCB control, n=16; low-dose ZCB control, n=16). At 28 days, the percentage of angiographic stenosis was similar among all tested groups. Histological analysis demonstrated a reduction in neointimal formation in both ZCB groups compared with controls (high-dose ZCB 44% reduction, P=0.007; low-dose ZCB 22% reduction, P=0.08). There was no evidence of delayed arterial healing or vascular toxicity in any of the ZCB groups. CONCLUSIONS: The single delivery of zotarolimus via coated balloon is feasible, and therapeutic levels are maintained up to 28 days. The ZCB technology appears to be effective in the reduction of neointimal proliferation in the superficial femoral artery of the familial hypercholesterolemic swine.

Late stent expansion and neointimal proliferation of oversized Nitinol stents in peripheral arteries.

For peripheral endovascular intervention, self-expanding (SE) stents are commonly oversized in relation to target arteries to assure optimal wall apposition and prevent migration. However, the consequences of oversizing have not been well studied. The purpose of this study was to examine the effects of SE stent oversizing (OS) with respect to the kinetics of late stent expansion and the long-term histological effects of OS. Pairs of overlapped 8 x 28-mm Nitinol SE stents were implanted into the iliofemoral arteries of 14 Yucatan swine. Due to variations in target artery size, the stent-to-artery ratio ranged from 1.2:1 to 1.9:1. Lumen and stent diameters were assessed by quantitative angiography at the time of implantation. Following angiographic assessment at 6 months, stented arteries were perfusion-fixed, sectioned, and stained for histological analysis. Immediately following implantation, the stents were found to be expanded to a range of 4.7-7.1 mm, largely conforming to the diameter of the recipient target artery. The stents continued to expand over time, however, and all stents had enlarged to nearly their 8-mm nominal diameter by 6 months. The histological effects of OS were profound, with marked increases in injury and luminal area stenosis, including a statistically significant linear correlation between stent-to-artery ratio and area stenosis. In this experimental model of peripheral endovascular intervention, oversized Nitinol SE stents are constrained by their target artery diameter upon implantation but expand to their nominal diameter within 6 months. Severe OS (stent-to-artery ratio >1.4:1) results in a profound long-term histological response including exuberant neointimal proliferation and luminal stenosis.

CEP-18770: A novel, orally active proteasome inhibitor with a tumor-selective pharmacologic profile competitive with bortezomib.

Modulating protein ubiquitination via proteasome inhibition represents a promising target for cancer therapy, because of the higher sensitivity of cancer cells to the cytotoxic effects of proteasome inhibition. Here we show that CEP-18770 is a novel orally-active inhibitor of the chymotrypsin-like activity of the proteasome that down-modulates the nuclear factor-kappaB (NF-kappaB) activity and the expression of several NF-kappaB downstream effectors. CEP-18770 induces apoptotic cell death in multiple myeloma (MM) cell lines and in primary purified CD138-positive explant cultures from untreated and bortezomib-treated MM patients. In vitro, CEP-18770 has a strong antiangiogenic activity and potently represses RANKL-induced osteoclastogenesis. Importantly, CEP-18770 exhibits a favorable cytotoxicity profile toward normal human epithelial cells, bone marrow progenitors, and bone marrow-derived stromal cells. Intravenous and oral administration of CEP-18770 resulted in a more sustained pharmacodynamic inhibition of proteasome activity in tumors relative to normal tissues, complete tumor regression of MM xenografts and improved overall median survival in a systemic model of human MM. Collectively, these findings provide evidence for the utility of CEP-18770 as a novel orally active proteasome inhibitor with a favorable tumor selectivity profile for the treatment of MM and other malignancies responsive to proteasome inhibition.