Noriyuki Kuno

Serum concentrations of bevacizumab (avastin) and vascular endothelial growth factor in infants with retinopathy of prematurity.

PURPOSE To determine the serum concentrations of bevacizumab and vascular endothelial growth factor (VEGF) in infants with retinopathy of prematurity (ROP) who received intravitreal bevacizumab; and to determine whether the changes in the serum concentration of bevacizumab were significantly correlated with the serum concentration of VEGF after intravitreal bevacizumab. DESIGN Case series. METHODS Eleven infants (4 girls and 7 boys) with ROP were studied. They received 0.25 mg or 0.5 mg of intravitreal bevacizumab to either 1 eye (unilateral cases) or both eyes (bilateral cases) with vascularly active ROP. Serum samples were collected before and 1 day, 1 week, and 2 weeks after the intravitreal bevacizumab. The serum concentrations of bevacizumab and VEGF were measured by enzyme-linked immunosorbent assay, and the correlation in the serum levels between the 2 was determined. RESULTS The serum concentration of bevacizumab before and 1 day, 1week, and 2 weeks after a total of 0.5 mg of intravitreal bevacizumab was 0 ng/mL, 195 ± 324 ng/mL, 946 ± 680 ng/mL, and 1214 ± 351 ng/mL, respectively. The serum bevacizumab level before and 1 day and 1 week after a total 1.0 mg of intravitreal bevacizumab was 0 ng/mL, 248 ± 174 ng/mL, and 548 ± 89 ng/mL, respectively. The serum concentration of VEGF before and 1 day, 1 week, and 2 weeks after a total of 0.5 mg intravitreal bevacizumab was 1628 ± 929 pg/mL, 427 ± 140 pg/mL, 246 ± 110 pg/mL, and 269 ± 157 pg/mL, respectively. There was a significant negative correlation (r = -0.575, P = .0125) between the serum concentration of bevacizumab and VEGF when a total of 0.25 mg or 0.5 mg of bevacizumab was injected. CONCLUSIONS These results indicate that bevacizumab can escape from the eye into the systemic circulation and reduce the serum level of VEGF in infants with ROP. Continued extensive evaluations of infants are warranted for possible effects after intravitreal bevacizumab in ROP patients.

Pharmacokinetics of Bevacizumab after Topical, Subconjunctival, and Intravitreal Administration in Rabbits

PURPOSE To investigate the pharmacokinetics of bevacizumab in rabbits for three different routes of administrations: intravitreal injection, subconjunctival injection, and eye drops. METHODS Pigmented rabbits received bevacizumab in one eye by topical eye drops (1.25 mg/0.05 mL six times daily for the first 7 days), single subconjunctival injection (1.25 mg/0.05 mL), or single intravitreal injection (1.25 mg/0.05 mL). Bevacizumab concentrations in plasma and ocular tissues in the treated and fellow eyes were determined by sandwich enzyme-linked immunosorbent assay at 1, 2, 4, and 12 weeks after administration. RESULTS After intravitreal injection in the treated eye, the mean maximum concentrations (C(max)) of bevacizumab in the iris/ciliary body and retina/choroid were 109,192.6, and 93,990.0 ng/g, respectively, whereas after subconjunctival injection, the C(max) was 1418.7 and 295.8 ng/g, respectively. In the fellow eyes, when the drug was administered by intravitreal injection, the C(max) was 753.6 ng/g in the iris/ciliary body and 224.2 ng/g in the retina/choroid and by subconjunctival injection was 1192.9 and 187.0 ng/g, respectively. With eye drops, only a small level of bevacizumab was detected in the iris/ciliary body and retina/choroid. Systemic exposure to bevacizumab was at the same level when administered by intravitreal or subconjunctival injection. CONCLUSIONS Intravitreal injection of bevacizumab was the most effective route of administration for intraocular tissue. Also, bevacizumab injected subconjunctivally was transported into the intraocular tissues of the treated eyes at an effective level. Both intravitreal and subconjunctival injections of bevacizumab resulted in high plasma concentrations. Bevacizumab was distributed into the intraocular tissues in fellow eyes via the systemic circulation. This treatment may be effective for blocking vascular endothelial growth factor activity.

Biodegradable intraocular therapies for retinal disorders: progress to date.

In general, it is difficult to achieve effective levels of drugs in the vitreous and the retina via topical and/or systemic administration. Intraocular drug delivery systems that achieve longer duration of pharmacological effect with lower administration frequency are urgently needed. Intraocular sustained drug release via implantable devices or injectable particles has been investigated for the treatment of various vitreoretinal disorders. Several non-biodegradable implants are available in clinical practice or in the late developmental phase: Vitrasert® (ganciclovir intravitreal implant) for cytomegalovirus retinitis, Retisert™ (fluocinolone acetonide intravitreal implant) for non-infectious uveitis, Iluvien™ (fluocinolone acetonide intravitreal implant) for diabetic macular oedema, and NT-501 (a polymer implant containing human retinal epithelial cells genetically modified to secrete ciliary neurotrophic factor) for non-neovascular (dry) age-related macular degeneration and/or retinitis pigmentosa. Many biodegradable formulations, including different shapes of rods, nail-like plugs, discs, or micro- or nano-particles, have also been investigated, but are not available as yet for the treatment of vitreoretinal disorders. The most developed biodegradable device, Ozurdex™ (dexamethasone intravitreal implant), is approved as first-line therapy for the treatment of macular oedema following branch retinal vein occlusion or central retinal vein occlusion.In this article, we review the progress of major biodegradable drug delivery systems currently in clinical trials or in experimental stages for the treatment of vitreoretinal disorders.

Degeneration of Retinal ON Bipolar Cells Induced by Serum Including Autoantibody against TRPM1 in Mouse Model of Paraneoplastic Retinopathy

The paraneoplastic retinopathies (PRs) are a group of eye diseases characterized by a sudden and progressive dysfunction of the retina caused by an antibody against a protein in a neoplasm. Evidence has been obtained that the transient receptor potential melastatin 1 (TRPM1) protein was one of the antigens for the autoantibody against the ON bipolar cells in PR patients. However, it has not been determined how the autoantibody causes the dysfunction of the ON bipolar cells. We hypothesized that the antibody against TRPM1 in the serum of patients with PR causes a degeneration of retinal ON bipolar cells. To test this hypothesis, we injected the serum from the PR patient, previously shown to contain anti-TRPM1 antibodies by westerblot, intravitreally into mice and examined the effects on the retina. We found that the electroretinograms (ERGs) of the mice were altered acutely after the injection, and the shape of the ERGs resembled that of the patient with PR. Immunohistochemical analysis of the eyes injected with the serum showed immunoreactivity against bipolar cells only in wild-type animals and not in TRPM1 knockout mice,consistent with the serum containing anti-TRPM1 antibodies. Histology also showed that some of the bipolar cells were apoptotic by 5 hours after the injection in wild type mice, but no bipolar cell death was found in TRPM1 knockout mice, . At 3 months, the inner nuclear layer was thinner and the amplitudes of the ERGs were still reduced. These results indicate that the serum of a patient with PR contained an antibody against TRPM1 caused an acute death of retinal ON bipolar cells of mice.

Clinical Application of Drug Delivery Systems for Treating AMD

Due to transparent ocular media, it is relatively easy to observe intraocular tissues such as the vitreous and retina without invasion, and various administration approaches including intravitreal and subretinal injection, or implantation can be applicable. Since the eye-ball is a closed organ, novel therapeutic molecules such as an antisense oligonucleotide for cytomegalovirus retinitis (Fomivirsen; Vitraven®, Isis Pharmaceuticals, Inc., Carlsbad, CA U.S. and Novartis, Basel, Switzerland), an aptamer (e.g. Pegaptanib sodium; Macugen®, Pfizer, Inc., New York, NY, U.S.) or a small interfering RNA for neovascular (wet) agerelated macular degeneration (AMD), have been investigated in human eyes before their applications for systemic diseases. In addition, many injectable or implantable drug delivery systems for chronic vitreoretinal diseases including AMD, diabetic macular edema, retinal vein occlusion, uveitis, and retinitis pigmentosa (RP), using polymer technology and/or mechanical engineering, have been developing (Figure 1).