Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Having -c- – wherein x is chalcogen – bonded directly to...
Reexamination Certificate
1999-09-24
2002-09-10
Fay, Zohreh (Department: 1614)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Having -c-, wherein x is chalcogen, bonded directly to...
Reexamination Certificate
active
06448283
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention provides methods for preventing and/or treating hearing loss and loss of the sense of balance. More specifically, the present invention provides methods for preserving sensory hair cells and cochlear neurons in a subject by administering an effective amount of compounds of Formula I and/or Formula II.
BACKGROUND OF THE INVENTION
The mammalian ear functions by transforming sound waves, or airborne vibrations, into electrical impulses. The brain then recognizes these electrical impulses as sound. The ear has three major parts, the outer, middle, and inner ear. Sound waves enter the outer ear and cause the eardrum to vibrate. The vibrations of the eardrum are transmitted serially through the three ossicles in the middle ear- the malleus, incus and stapes, also called the hammer, anvil and stirrup, respectively. The stirrup transmits the vibrations to the inner ear. The inner ear comprises the cochlea and is connected to the middle ear via the oval and round windows. The inner ear is filled with fluid and vibrations transmitted to the inner ear cause fluid movement in the cochlea of the inner ear. Fluid movement in the cochlea causes movement of sensory hair cells which initiates nerve impulses. These nerve impulses are interpreted in the brain as sound.
The sensory hair cells are contained in the organ of Corti, which coils around the inside of the cochlea. Within the organ of Corti there are inner and outer sensory hair cells. The outer sensory hair cells are present in three rows, designated OHC1, OHC2 and OHC3; inner sensory hair cells are present in one row. The sensory hair cells are attached to the basilar membrane and contact the tectorial membrane. Movement of fluids within the inner ear causes a movement of the basilar membrane relative to the tectorial membrane. This relative movement causes the cilia on the sensory hair cells to bend and leads to electrical activity. Cochlear ganglion neurons below the sensory hair cells transmit this electrical activity to auditory regions of the brain via the auditory nerve.
The fluid filled inner ear, also called the membranous labyrinth, further contains the two mammalian organs of equilibrium which make up the vestibular system. The first organ of equilibrium is composed of the saccule and utricle which detect and convey information on body position relative to gravitational force. Both the saccule and utricle also contain sensory hair cells. Tiny particles of calcium carbonate lie on the sensory hair cells in the saccule and utricle and bend the cilia to stimulate the sensory hair cells to send appropriate signals to the brain, including “up”, “down”, “tilt” and “acceleration” in a particular direction. Sensory hair cells in the utricle detect linear movement in the horizontal plane while sensory hair cells in the saccule detect movement in the vertical plane.
The second organ of equilibrium is composed of three semicircular canals which detect and convey information on movement, detected as fluid acceleration, to the brain. The semicircular canals are also lined with sensory hair cells, and are arranged at near 90 degree angles with respect to one another and can detect movement in three dimensions. As the head is accelerated in one of these planes, fluid movement in the canal corresponding to the plane of movement stimulates movement of the cilia of the sensory hair cells.
The vestibular organs—the saccule, the utricle and the semicircular canals —stimulate nerve endings of vestibular ganglion neurons which then transmit information to a number of sites for different purposes. For example, information is transmitted from the vestibular system to the eyes to keep the eyes focused on a target while the body is moving. Neurons also interconnect the vestibular system and the cerebellum for producing smooth and coordinated bodily movements. Vestibular information also travels down the spinal cord to muscles in order to maintain proper posture and balance.
Significant hearing loss causing communication problems occurs in about ten percent of the population and more than one third of us will have substantial hearing loss by old age. Noise-induced hearing loss is estimated to be the cause of hearing loss in about one-third of the 28 million Americans with hearing loss (NIH Publication No. 97-4233, April 1997). In most cases, the auditory impairment results from the death of sensory hair cells in the organ of Corti. Sensory hair cells are delicate cells and thus are susceptible to damage from several sources, including, but not limited to, noise, infection, drugs, vascular insufficiency and idiopathic effects. Idiopathic effects are those effects which arise spontaneously or from an unknown or obscure cause.
Presbycusis is age-related hearing loss. Four distinct types of presbycusis have been described which are based upon audiograms and pathological analyses: 1) sensory—loss of sensory hair cells and secondary degeneration of cochlear neuronal structures, 2) neural—loss of cochlear ganglion cells and/or nerve, 3) metabolic—atrophy of the
stria vascularis
, and 4) mechanical—stiffening of the basilar membrane (Schuknecht, Arch. Otol., 80:369-382, 1964). The neural and metabolic causes of presbycusis may also result in the ultimate loss of hair cells.
While no frequency data is associated with the descriptions of the types of presbycusis, sensory presbycusis is the most common (Working Group on Speech Understanding and Aging, Speech understanding and aging, J. Acoust. Soc. Am. 83:859-895, 1988). Johnsson et al. have described both degeneration of the
stria vascularis
and hair cell loss in 150 patients ranging in age from newborn to 97 years of age. Both are progressive and most pronounced in elderly subjects. An age-related loss of hair cells of the vestibular apparatus—saccule and utricle—was also noted that may account for vestibular disturbances in the elderly (Johnsson et al., Ann. Otol. Rhinol. Laryngol. 81:179-193, 1972; Johnsson et al., Ann. Otol. Rhinol. Laryngol. 81:364-376, 1972).
We are born with a complement of about 16,000 sensory hair cells and 30,000 auditory neurons in each ear. These cells do not regenerate during postnatal life. Therefore, loss of each cell, due to, for example, noise, infection, toxic drugs (such as platinum-based cytotoxic agents and aminoglycosides) or idiopathic effects is irreversible and cumulative. If enough sensory cells are lost, the end result can be total deafness.
Noise trauma is a widespread cause of hearing loss. Sound overexposure has been demonstrated to lead to sensory hair cell apoptosis in the avian inner ear (Nakagawa et al., ORL, 59:303-310, 1997). There is increasing evidence that the death of sensory hair cells caused by drugs such as platinum-based cytotoxic agents and aminoglycosides is partially, if not mainly, apoptotic. Noise-induced sensory hair cell loss in the cochlea apparently has a similar mechanism.
Aminoglycosides are widely used antibiotics used in patients with Gram-negative bacterial infections (Paparella et al, Otolaryngology, 1817, Saunders-Philadelphia, 1980). Aminoglycosides are known to cause damage to sensory hair cells and thereby affect hearing. Aminoglycosides include, but are not limited to, neomycin, kanamycin, amikacin, streptomycin and gentamicin. Amikacin causes apoptosis of sensory hair cells in rat cochleas (Vago et al., NeuroReport 9:431-436, 1998). Gentamicin treatment results in degeneration of sensory hair cells in guinea pigs (Li et al., J. Comparative Neur., 355:405-417, 1995; Lang et al., Hearing Res., 111:177-184, 1997).
The loss of sensory hair cells in the cochlea has been attributed to aminoglycoside ototoxicity. Apoptosis of sensory hair cells of guinea pigs was observed following chronic treatment with aminoglycoside (Nakagawa et al., Eur. Arch. Otor., 254:9-14, 1997; Nakagawa et al., Acta Otol., 255(3):127-131, 1998). Studies have assessed the protective effect of various polypeptides on sensory hair cells in the cochlea. (See, for example, Malgrange et al., Abstr. Assoc. Res.
Hudkins Robert L.
Pirvola Ulla
Saarma Mart
Walton Kevin M.
Ylikoski Jukka
Cephalon Inc.
Fay Zohreh
Woodcock & Washburn LLP
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