Stanley C. Gill

Preclinical and phase 1A clinical evaluation of an anti-VEGF pegylated aptamer (EYE001) for the treatment of exudative age-related macular degeneration

Background Recent studies have suggested that vascular endothelial growth factor (VEGF) is an important stimulus for the growth of new blood vessels in the eye. Anti-VEGF therapy is thus a potential treatment for exudative macular degeneration and diabetic retinopathy. Methods Previously described animal models of vascular leakage and ocular neovascularization, including the Miles assay, the rat corneal angiogenesis model, and the mouse retinopathy of prematurity (ROP) model, were used to study this drug. After these studies, a phase IA single ascending dose study of intravitreal injections of the drug was performed in 15 patients with subfoveal choroidal neovascularization secondary to exudative age-related macular degeneration (AMD). Results The Miles assay model showed almost complete attenuation of VEGF-mediated vascular leakage following addition of EYE001, and the corneal angiogenesis model also showed a significant reduction in neovascularization with EYE001. The ROP model showed inhibition of 80% of the retinal neovascularization compared with controls (P = 0.0001). The phase IA safety study of patients with exudative AMD showed no significant safety issues related to the drug. Ophthalmic evaluation revealed that 80% of patients showed stable or improved vision 3 months after treatment and that 27% of eyes demonstrated a three-line or greater improvement in vision on the Early Treatment for Diabetic Retinopathy Study chart at this time. Conclusion Anti-VEGF therapy is a promising new avenue for the treatment of neovascular diseases of the eye, including exudative macular degeneration and diabetic retinopathy. Preclinical data from studies with EYE001 support clinical evaluation of its efficacy in such diseases. This report is the first to describe administration of anti-VEGF therapy in humans for exudative macular degeneration and shows the safety of such therapy for single injections. Further clinical studies are necessary to determine the safety of multiple intravitreal injections of EYE001 and larger studies are needed to prove the efficacy of this novel, potentially therapeutic agent for neovascular AMD.

Pharmacokinetics and safety of an anti-vascular endothelial growth factor aptamer (NX1838) following injection into the vitreous humor of rhesus monkeys.

AbstractPurpose. The objective of this study was to determine the pharmacokinetics and safety for NX1838 following injection into the vitreous humor of rhesus monkeys. Methods. Plasma and vitreous humor pharmacokinetics were determined following a single bilateral 0.25, 0.50, 1.0, 1.5, or 2.0 mg/eye dose. In addition, the pharmacokinetics and toxicological properties of NX1838 were determined following six biweekly bilateral injections of 0.25 or 0.50 mg/eye or following four biweekly bilateral injections of 0.10 mg per eye followed by two biweekly bilateral injections of 1.0 mg per eye. Results. Plasma and vitreous humor NX1838 concentrations were linearly related to the dose administered. NX1838 was cleared intact from the vitreous humor into the plasma with a half-life of approximately 94 h, which was in agreement with the plasma terminal half-life. Vascular endothelial growth factor (VEGF)-binding assays demonstrated that the NX1838 remaining in the vitreous humor after 28 days was fully active. No toxicological effects or antibody responses were evident. Conclusions. The no observable effect level was greater than six biweekly bilateral 0.50 mg/eye doses or two biweekly bilateral 1.0 mg/eye doses. These pharmacokinetic and safety data support monthly 1 or 2 mg/eye dose regimens in human clinical trials.

Detection and plasma pharmacokinetics of an anti-vascular endothelial growth factor oligonucleotide-aptamer (NX1838) in rhesus monkeys

Aptamers are oligonucleotide ligands selected, in vitro, to bind a specified target protein. The first aptamer to reach human clinical testing is NX1838, a polyethylene glycol conjugated aptamer that inhibits vascular endothelial growth factor. This paper describes the validation of a high-performance liquid chromatographic anion-exchange method for the determination of NX1838 in plasma. Measurements of intact NX1838 had a coefficient of variation of less than 8% and an accuracy between 107% and 115%. The assay was utilized to determine NX1838 plasma pharmacokinetics in rhesus monkeys following a single 1 mg/kg intravenous or subcutaneous dose. Following intravenous administration, the maximum achieved plasma concentration was 25.5 microg/ml with a terminal half-life of 9.3 h and clearance rate of 6.2 ml/h. After subcutaneous administration, the fraction of the dose absorbed into the plasma compartment was 0.78 with a time to peak concentration (4.9 microg/ml) of 8 to 12 h.

Regular ArticlesNovel Approach to Specific Growth Factor Inhibition in Vivo: Antagonism of Platelet-Derived Growth Factor in Glomerulonephritis by Aptamers

Mesangial cell proliferation and matrix accumulation, driven by platelet-derived growth factor (PDGF), contribute to many progressive renal diseases. In a novel approach to antagonize PDGF, we investigated the effects of a nuclease-resistant high-affinity oligonucleotide aptamer in vitro and in vivo. In cultured mesangial cells, the aptamer markedly suppressed PDGF-BB but not epidermal- or fibroblast-growth-factor-2-induced proliferation. In vivo effects of the aptamer were evaluated in a rat mesangioproliferative glomerulonephritis model. Twice-daily intravenous (i.v.) injections from days 3 to 8 after disease induction of 2.2 mg/kg PDGF-B aptamer, coupled to 40-kd polyethylene glycol (PEG), led to 1) a reduction of glomerular mitoses by 64% on day 6 and by 78% on day 9, 2) a reduction of proliferating mesangial cells by 95% on day 9, 3) markedly reduced glomerular expression of endogenous PDGF B-chain, 4) reduced glomerular monocyte/macrophage influx on day 6 after disease induction, and 5) a marked reduction of glomerular extracellular matrix overproduction (as assessed by analysis of fibronectin and type IV collagen) both on the protein and mRNA level. The administration of equivalent amounts of a PEG-coupled aptamer with a scrambled sequence or PEG alone had no beneficial effect on the natural course of the disease. These data show that specific inhibition of growth factors using custom-designed, high-affinity aptamers is feasible and effective.

Pharmacokinetic-pharmacodynamic assessment of faropenem in a lethal murine Bacillus anthracis inhalation postexposure prophylaxis model.

ABSTRACT There are few options for prophylaxis after exposure to Bacillus anthracis, especially in children and women of childbearing potential. Faropenem is a β-lactam in the penem subclass that is being developed as an oral prodrug, faropenem medoxomil, for the treatment of respiratory tract infections. Faropenem was shown to have in vitro activity against B. anthracis strains that variably express the bla1 β-lactamase (MIC range, ≤0.06 to 1 μg/ml). In this study we evaluated the pharmacokinetic-pharmacodynamic (PK-PD) relationships between the plasma faropenem free-drug (f) concentrations and efficacy against B. anthracis in a murine postexposure prophylaxis inhalation model. The plasma PKs and PKs-PDs of faropenem were evaluated in BALB/c mice following the intraperitoneal (i.p.) administration of doses ranging from 2.5 to 160 mg/kg of body weight. For the evaluation of efficacy, mice received by inhalation aerosol doses of B. anthracis (Ames strain; faropenem MIC, 0.06 μg/ml) at 100 times the 50% lethal dose. The faropenem dosing regimens (10, 20, 40, and 80 mg/kg/day) were administered i.p. at 24 h postchallenge at 4-, 6-, and 12-h intervals for 14 days. The sigmoid maximum-threshold-of-efficacy (Emax) model fit the survival data, in which the free-drug area under the concentration-time curve (fAUC)/MIC ratio, the maximum concentration of free drug in plasma (fCmax)/MIC ratio, and the cumulative percentage of a 24-h period that the free-drug concentration exceeds the MIC under steady-state pharmacokinetic conditions (f %TMIC) were each evaluated. Assessment of f %TMIC demonstrated the strongest correlation with survival (R2 = 0.967) compared to the correlations achieved by assessment of fAUC/MIC or fCmax/MIC, for which minimal correlations were observed. The 50% effective dose (ED50), ED90, and ED99 corresponded to f %TMIC values of 10.6, 13.4, and 16.4%, respectively, and Emax was 89.3%. Overall, faropenem demonstrated a high level of activity against B. anthracis in the murine postexposure prophylaxis inhalation model.

EFFECT OF INTERMITTENT DOSING REGIMENS OF ERLOTINIB ON METHYLNITROSOUREA-INDUCED MAMMARY CARCINOGENESIS

EGF receptor (EGFR) inhibitors are used in the therapy of lung and pancreatic cancers and effectively prevent cancers in multiple animal models. Although daily dosing with erlotinib is effective, weekly dosing may reduce toxicity and have advantages, particularly for prevention. We tested alternative dosing regimens for preventive/therapeutic efficacy in a rat mammary cancer model. For prevention, erlotinib was administered by gavage beginning 5 days after methylnitrosourea (MNU). For therapy and biomarker studies, rats with palpable mammary cancers were treated for six weeks or for six days, respectively. Experiment A, erlotinib (6 mg/kg body weight/day, intragastric): daily (7 times/week); one day on/one day off; and two days on/two days off. All regimens decreased tumor incidence, increased tumor latency, and decreased cancer multiplicity versus controls (P < 0.01). However, intermittent dosing was less effective than daily dosing (P < 0.05). Experiment B, erlotinib (6 mg/kg body weight/day) daily or two days on/two days off or one time per week at 42 mg/kg body weight. All regimens reduced cancer incidence and multiplicity versus controls (P < 0.01). Interestingly, daily and weekly dosing were equally effective (P > 0.5). Experiment C, erlotinib administered at 42 or 21 mg/kg body weight 1 time per week, decreased tumor incidence and multiplicity (P < 0.01). Erlotinib had a serum half-life of ≤8 hours and weekly treatment yielded effective serum levels for ≤48 hours. Daily or weekly treatment of cancer bearing rats reduced mammary tumor size 25% to 35%, whereas control cancers increased >250%. Levels of phosphorylated extracellular signal-regulated kinase (ERK) were strongly decreased in rats treated daily/weekly with erlotinib. Thus, altering the dose of erlotinib retained most of its preventive and therapeutic efficacy, and based on prior clinical studies, is likely to reduce its toxicity. Cancer Prev Res; 6(5); 448–54. ©2013 AACR.