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Chapter VI.A.Pharmacologic Vitreolysis

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Chapter VI.A.Pharmacologic Vitreolysis Pharmacologic Vitreolysis VI.A. J. Sebag Outline Keywords I. Introduction Vitreous • Vitreoretinal interface • Hyaluronan • Collagen II. Classifi cation of Approaches to Pharmacologic Vitreolysis Extracellular matrix • Pharmacologic vitreolysis A. Chemical Action of Pharmacologic Vitreolysis Agents B. Biological Action of Pharmacologic Vitreolysis Agents Posterior vitreous detachment (PVD) • Anomalous PVD Liquefactant • Interfactant III. Pharmacologic Vitreolysis Agents A. Agents with Failed or Discontinued Development 1. Hyaluronidase (Vitrase®) 2. Chondroitinase 3. Nattokinase Key Concepts ® 4. Vitreosolve 1. Vitreous and the vitreoretinal interface are com- 5. RGD Peptides B. Agents Under Development prised of molecules that dictate structure and func- 1. Dispase (Vitreolysin™) tion as well as underlie the changes that result in C. Agents Approved for Pharmacologic Vitreolysis posterior vitreous detachment (PVD) in most cases 1. Ocriplasmin and anomalous PVD in some individuals. a. Case Study b. Case Selection 2. Pharmacologic vitreolysis, which is the molecular IV. Future Considerations manipulation of vitreous to induce liquefaction via A. Enhancing Drug Delivery liquefactant agents and dehiscence at the vitreoreti- B. Improving Vision Outcome Measures nal interface via interfactant activity, is destined to C. Combination Therapy D. Prevention replace the surgical cure of various pathologies of 1. Prophylactic Posterior Vitreous Detachment anomalous PVD. 2. Anomalous PVD Prevention 3. The failures and success of different pharmacologic References vitreolysis agents under development hold impor- tant lessons for future progress that may include combination therapy but should also emphasize improved drug delivery to the target tissues. Electronic supplementary material Supplementary material is available in the online version of this chapter at 10.1007/978-1-4939-1086-1_47 . Videos can also be accessed at http://www.springerimages.com/ videos/978-1-4939-1085-4 . I. Introduction J. Sebag is a past or present consultant to Advanced Corneal Systems/ ISTA Pharmaceuticals, Storz/B & L, ThromboGenics, ALCON Vitreous constitutes about 80 % of the volume of the human eye. It is an extended extracellular matrix that is composed of J. Sebag , MD, FACS, FRCOphth, FARVO collagen, hyaluronan, and other extracellular matrix mole- VMR Institute for Vitreous Macula Retina , 7677 Center Avenue, suite 400 , cules but is 98 % water. In both health as well as disease, the Huntington Beach , CA 92647 , USA molecular composition and organization of vitreous dictate Doheny Eye Institute , Los Angeles , CA, USA the structure and function of the vitreous body as well as the e-mail: [email protected] status of the vitreoretinal interface. During aging, there is J. Sebag (ed.), Vitreous: in Health and Disease, 799 DOI 10.1007/978-1-4939-1086-1_47, © Springer Science+Business Media New York 2014 800 J. Sebag reorganization of vitreous macromolecules resulting in gel cause or worsen pathology. Furthermore, a variety of liquefaction and structural changes that destabilize the vitre- physiologic effects are introduced, which are, in some set- ous body. Molecular changes at the vitreoretinal interface, tings, very benefi cial. whose components are the retinal inner limiting membrane The foregoing chapters of this book are witness to the (ILM), the posterior vitreous cortex, and the intervening expansion of our knowledge about vitreous and its role in extracellular matrix (ECM), usually weaken vitreoretinal disease. Various predisposing genetic factors and congenital adhesion and allow the collapsing destabilized vitreous to anomalies, contributing systemic diseases, anomalous aging separate from the retina, a condition called posterior vitreous effects, and ocular conditions have been described. A few good detachment (PVD) [see chapter II.C . Vitreous Aging and examples are chapters I.C . [Hereditary Vitreo-Retinopathies], Posterior Vitreous Detachment]. When there is insuffi cient III.A . [Congenital Vascular Vitreo-Retinopathies], I.E . weakening of vitreoretinal adherence, anomalous PVD [Diabetic Vitreopathy], III.K . [Vitreous in Retino-Vascular occurs with various pathologic effects on both vitreous and Diseases and Diabetic Macular Edema], III.B . [Anomalous retina [see chapter III.B . Anomalous PVD and Vitreoschisis]. PVD and Vitreoschisis], III.G . [Vitreous in AMD], III.I . [Role To date, these pathologies have been treated with surgery. of Vitreous in the Pathogenesis of Retinal Detachment], and Throughout the history of medicine, therapeutics have II.B . [Myopic Vitreopathy]. The surgical management of these evolved as a direct result of advances in our basic under- conditions has also been discussed at length (see chapters standing of disease pathogenesis. This has led to less inva- V.A.1. to V.A.6. and V.B.1. to V.B.9. ). However, owing to the sive yet increasingly effective therapeutics. At fi rst, when signifi cantly expanded fund of knowledge related to vitreous little is known, little, if anything, is done. As recognition and and its role in retinal disorders, nonsurgical therapies are being understanding of anatomic pathology increases, surgery is developed, initially to augment but eventually to replace sur- employed. With increasing knowledge about the cause(s) of gery. The following reviews these approaches to the future. Of disease, surgery is supplemented with and eventually note is the fact that of the seven major pharmacologic vitreoly- replaced by pharmacotherapy. When we fully understand a sis modalities that have been undertaken to date, one has been disease, we develop ways to prevent it, obviating the need for approved for clinical use, one is currently under development, both surgery and pharmacotherapy. Consider, for example, and fi ve have either failed or been disbanded. All seven that the treatment of severe infections by surgical drainage of research and development programs will be critically reviewed an abscess has been to a great extent replaced by the use of below and presented in greater detail in the remaining chapters antibiotics. Peptic ulcers, for many years a surgical disease of this section. believed to be caused by stress, had high mortality. Antacids, antihistamines, and proton pump inhibitors as well as good gastroscopies made huge improvements. The breakthrough II. Classifi cation of Approaches came with the discovery of Helicobacter pylori as the under- to Pharmacologic Vitreolysis lying cause in the vast majority, and now, antibiotic therapy has largely eliminated surgery in many settings. Cervical The fi rst retrievable publication on pharmacologic vitreoly- cancer, once treated with hysterectomy, was increasingly sis appeared 65 years ago in the British Journal of recognized to arise from subtle dysplastic changes in the epi- Ophthalmology [17 ]. Since this and other initial approaches thelium. A population level screening program and develop- all used enzymes as adjuncts to surgery, the term “ enzymatic ment of less invasive biopsies and surgical procedures made vitreolysis ” was prevalent in the early literature [see chapter a huge difference in survival. Recognition of a papilloma VI.B . History of pharmacologic vitreolysis]. However, in virus as the underlying cause has led to widespread vaccina- 1998, the term “pharmacologic vitreolysis ” replaced the tion programs, which may prevent the vast majority of cases older term, so that vitreolytic agents could be grouped with this disease. according to more than just an enzymatic mechanism of This type of evolution is now occurring in the discipline action [ 23 ]. The following presents two different classifi ca- of vitreoretinal diseases and surgery. Laser surgery for tions based upon the actions of the various pharmacologic exudative maculopathies due to diabetic retinopathy, vein vitreolysis agents. occlusions, and age-related macular degeneration (AMD) has been largely replaced by intravitreal anti-VEGF pharma- cotherapy. Another recent development is “ pharmacologic A. Chemical Action of Pharmacologic vitreolysis ,” a term that was coined in 1998 to refer to the use Vitreolysis Agents of drugs to alter the molecular structure of vitreous and the vitreoretinal interface [ 23 ]. The objective of this therapy is to In 1998, pharmacologic vitreolysis was viewed in terms of pharmacologically induce an innocuous PVD and thus the chemical activity of the various agents under develop- mitigate any untoward effects of vitreous on the retina that ment [ 23 ]. Thus, the two broad classes of drugs were VI.A. Pharmacologic Vitreolysis 801 Table VI.A-1 Classifi cation of pharmacologic vitreolysis agents by however, the chemical and biological classifi cation systems chemical activity are not mutually exclusive, since there can be further subdi- Enzymatic Nonenzymatic visions based upon chemical activity (enzymatic vs. nonen- Substrate specifi c zymatic) and substrate specifi city. Of further note is that Chondroitinase Urea/vitreosolve several agents are considered to have both liquefactant and Hyaluronidase RGD peptides interfactant effects. Dispase The following will consider the various agents that are Nonspecifi c being developed or already approved for use in clinical tPA pharmacologic vitreolysis. Of considerable interest are Plasmin those agents whose development has been discontinued, as Ocriplasmin there are lessons to be learned from their failure or Nattokinase discontinuation. Table VI.A-2 Pharmacologic vitreolysis classifi cation based on bio- logic
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