Patent Application
20150290029
The present invention pertains generally to the field of ocular treatment, and more specifically to the use of a composition comprising a soothing agent to reduce sensory discomfort. The composition is topically administered to at least a portion of the external surface of the eyelid (preferably the closed eyelid) of the eye to be treated. Preferably, the composition including the soothing agent is carried on or in a swab, wipe, pad, or towelette, for example, an eye swab.
The eye surfaces are exposed to the external environment. These anatomical structures—eyelids, front (anterior) part of the eyeball, conjunctiva, lachrymal system, precorneal film and cornea—are subject to injury by physical, chemical and biological agents. The results of injury to the ocular surface are symptoms of discomfort, defined as blurring of vision, itching, irritation, burning sensations, and pain. The signs of injury in the vascularized portions of the eye are redness, swelling, and increased blood flow. Ophthalmic products such as solutions, ointments, and inserts are used to manage the causes and the symptoms and signs of eye injury.
Ophthalmic solutions, administered onto the eye surface in the form of eyedrops, are the most common form of drug delivery to treat anterior eye disorders. This method is preferred to ointments and inserts because of ease and costs of preparation, patient familiarity with procedures of drug dosing, and the lower frequency of side effects. It is recognized, however, that eyedrops are a relatively inefficient method of delivery because individual eyedrops range from 20 to 50 μl in volume, whereas the precorneal space in normal subjects are about ˜7 μl. The excess volume rolls down the cheek or may be absorbed into the nasolacrimal duct. Eyedrops are also difficult to administer because the patient must be taught to recline their head at a 45 to 55° angle and to manually coordinate delivery while keeping their eyes open. Nevertheless, conventional eyedrops represent approximately 90% of marketed formulations for eye disorders. This can be seen at the pharmacy where eyedrop products for dry eyes (e.g. Systane™) and eye irritation (e.g. Visine™) are on display.
It is known by experience that an ice pack applied to the orbit will relieve the pain and discomfort of eye injury. Systematic studies by Fujishima et al. [Amer. J. Ophthalmol. 119: 301-306, 1195; Cornea 16: 630-634, 1997] showed that cooling will relieve the pain and inflammation in the orbit after cataract surgery. In healthy volunteers, discomfort in the eye induced by pressure on the cornea with a nylon microfilament was much better relieved by artificial tears kept at 4° C. than by tears at 25° C. or 36° C. Thus, cooling is recognized as a potential method for relieving sensory discomfort in the eye. In the patent literature, chemical cooling agents such menthol (in combination with antihistamines) [U.S. Pat. No. 6,147,081], trialkylphosphine oxides [US 20050059639] or p-menthane carboxamides [US 20050137166] have been proposed for use in eyedrops to relieve sensory discomfort. Rohto Pharmaceuticals sells in the United States eyedrops labelled as “Cool”, “Ice”, and “Arctic” to relieve redness and to soothe eye strain. In two of these formulations, the cooling ingredient is most likely menthol, which is listed as an “inactive ingredient.” Menthol is an irritant and, in my experience, the “Ice” and “Arctic” formulations cause an initial stinging sensation in the eye, the intensity of cooling is limited, and the duration of cooling is less than 15 minutes.
An irritated eye surface is a common symptom of many disorders, especially in the condition known as “dry eyes”, which is exacerbated, for example, by a dry climate, an increased use of contact lenses, excessive staring at computer screens, and ageing. The estimated prevalence of dry eyes in the United States is about 10 to 30% of the population over age 40, with about 4.9 million severe cases requiring specific medical treatment. Thus, there is need for innovative technology to improve symptomatic or curative treatment.
In a patent application on new cooling compounds, Wei, US 20080227857, published Sep. 18, 2008, N-Alkylcarbonyl-Amino Acid Ester and N-Alkylcarbonyl-Amino Lactone Compounds and Their Use. described delivery of cooling compounds to the skin using a towelette. The wiping of the towelette across skin results in delivery of dermatologically active ingredient(s), meaning that the skin is substantially medicated.
Eye drops are also a relatively inefficient method of delivery. The volume of individual eye drops in commercial samples varies and ranged from 25 to 56 μL [German, E. J., Hurst, M. a, & Wood, D. (1999). Reliability of drop size from multi-dose eye drop bottles: is it cause for concern? Eye (London, England), 13 (Pt 1)(June), 93-100.] in one study and 34 to 63 μL in another [Sklubalová, Z., & Zatloukal, Z. (2006). Study of eye drops dispensing and dose variability by using plastic dropper tips. Drug development and industrial pharmacy, 32(2), 197-205]. The volume delivered can be influenced by parameters such as the physicochemical characteristics of the formulation, the aperture of the bottle, and the angle of delivery. The precorneal space in normal subjects is about ˜7 μL per eye. The conjunctival spaces, also called “cul-de-sac” for the extended lower eyelid, is ˜30 μL. The delivered drop impacts the eyeball with a residence time of less than 1 min and the excess volume rolls down the cheek or is shunted to and absorbed into the nasolacrimal duct via the lacrimal puncta.
The surfaces of the eyelids, conjunctiva, and cornea contain sensory nerve endings that respond to stimuli that range from touch and pressure, to cooling, and to warmth, and to noxious stimuli. The sensory receptors are located on the nerve endings of branches of the trigeminal nerve: a) the supraorbital nerve innervates the upper eyelids and the conjunctiva, b) the infraorbital nerve innervates the lower eyelids, and c) the long ciliary nerves innervate the cornea. These sensory afferents then project rostrally to brainstem dorsolateral nucleus where afferent nerve impulses are interpreted as sensations from the ocular surfaces.
The signals that evoke afferent nerve discharge from the cornea have been characterized by studies of single unit recordings from the ciliary nerve [Belmonte, C. et al. (2004) Nerves and sensations from the eye surface, Ocul. Surf., 2, 248-253.] About 15% of corneal fibers, all fast conducting Aδ-type, respond exclusively to mechanical force. About 70% of corneal fibers, mostly slow-conducting C-fibers, respond only to nociceptive stimuli (e.g. heat above 39° C., cold below 29° C., and chemical irritants) and are called polymodal nociceptors. A third category of corneal nerve fibers, about 10-15%, are Aδ and C fibers that discharge spontaneously at rest and increase their firing rate when the normal temperature of the corneal surface (˜33° C.) decreases by ˜0.1° C. These are the cold-sensitive receptors that respond to “innocuous” cooling, that is in the temperature ranges above 29° C. and below 39° C.
The corneal surface is estimated be ⅙ of the total area of the anterior eyeball. It is densely packed with polymodal nociceptors and is exceptionally sensitive to painful stimuli. Eye drops that contain chemical irritants easily evoke discomfort (burning sensations, itch, and pain) from the corneal surface: two examples being Mydriacyl® and Restasis® containing tropicamide and cyclosporine as the active ingredients, respectively. Menthol and ethanol [and other alcohols] are also recognized eye irritants.
The present invention provides a method for topically self-delivering a predetermined dose of a selected drug to an eye via the skin covering the eyeball, the edges of the eyelids and/or the conjunctiva. Using this method of drug delivery that avoids and minimizes contact with the corneal surface, sting and discomfort is reduced. An eye swab or wipe embodiment carrying a preferred drug agent provides a substantial therapeutic improvement over eye drops. Proof of concept with a soothing and cooling agent delivered in this manner is illustrated in the examples.
Broadly, the invention provides a method for topically delivering a predetermined dose of a selected drug to an eye via the skin covering the eyeball, the edges of the eyelids and/or the conjunctiva. An eye swab or wipe embodiment carrying a preferred drug agent provides a substantial therapeutic improvement over eye drops and can be self-delivered.
Description of Preferred Delivery Apparatus
The advantages of the delivery unit and the delivery method over eye drops are several-fold. The risks of contamination of the applied solution are minimized as there is no direct hand contact with the swab tip. The delivery unit is disposable. The intricacies of hand-eye coordination, angulation of the head, and avoiding accidental contact of the eye drops bottle tip to the eye surface, no longer apply with this method of delivery. The method minimizes the bolus effects of eye drops on the corneal surface and, hence, there is less irritation and discomfort. The distribution of the active ingredient over the ocular surface is more uniform by this swab method of delivery.
Prototypes of the delivery unit are available from manufacturers, for example, SwabDose™ from Unicep Corp. [1702 Industrial Drive, Sandpoint, Id.], and Pro-Swabs from American Empire Manufacturing [3828 Hawthorne Court, Waukegan, Illinois]. These units can be produced en masse, for example in lots of 500,000 units. The specifications of the delivery unit are made to order. Traditionally, these units are used for the delivery of dermatological products, e.g. anti-fungal agents for the toenail. A similar, sophisticated device is made by the S & B. Co., Ltd. Masan-Si, Korea. The apparatus, a “Magic Bar” maintains a solution above a cotton tip by capillary action. Twisting the hollow tube containing the solution allows the liquid to descend on the cotton tip and be ready for delivery.
As shown in the Examples, the substrate on the tip of the applicator must have a certain liquid absorptive capacity to deliver the correct volume, upon wiping of the substrate onto the ocular skin and eyelashes. This was determined by experiment and, surprisingly, approximated the same volume as a small eye drop: namely, ˜30 μL. But the dispersion of the liquid on the target site was quite different from an eye drop.
By creating a method of delivery of an agent to the ocular surface by wiping, the delivery procedure is made more convenient than eye drops. Also, by wiping a liquid composition, contact with the cornea is minimized, and the active ingredient is delivered to the ocular surface with less irritation and discomfort.
Drug Delivery Considerations:
Ophthalmic solutions, administered onto the eye surface in the form of eye drops, represent at least 90% of formulations marketed for treatment of anterior eye disorders. The eye drops method is preferred to ointments and inserts because of ease and costs of preparation, patient familiarity with procedures of drug dosing, and the lower frequency of side effects. It is recognized, however, that eye drops are a relatively inefficient method of delivery. Thus, the pulsatile delivery of an eye drop bolus impacts the curved surface of the eye but there is little time for the active ingredient to reach target receptors. The excess volume splashes on the eye surface, rolls down the cheek, or may be absorbed into the nasolacrimal duct. The contact time of the eyedrop with the ocular surface is less than 1 min and washout is further accelerated by the blink reflex and tear turnover.
Fluid Mechanics of the Ocular Surface:
There are several key surfaces on the orbit. The skin, with a contact angle with water of 100 degrees, is mildly hydrophobic, and, like polyethylene, is not easily “wettable” by water. The eyelashes, like skin, are also hydrophobic, and the cylindrical hair shaft increases the surface area for deposition of liquid. Wettability of the eye is achieved using the eye lashes, the mucocutaneous junction, and the eye surface which has a precorneal tear film that is ˜98% water.
When an aqueous solution is delivered onto the ocular surface, several scenarios can be described.
Logic of Delivery by Swabbing or Wiping:
The eye has its own natural wiping mechanisms. Tears, secreted from the lacrimal gland into the upper lateral corner of the eye, are composed ˜98% of water, but also contain biologically active ingredients such as mucins, lipids, proteins such as immunoglobulins and lysozyme, some peptide hormones, and salts. Blinking, the alternate contraction and relaxation of the orbicularis oculi and the levator palpebral superior muscles, close and open the eyelids, respectively. The margins of the eyelids distribute the tears evenly over the ocular surface, and gently push the tear film towards the puncta at the medial canthus for drainage. At the inner lid border, the marginal conjunctiva forms a thickened epithelial cushion that is in closest contact with the bulbar surface, and facilitates distribution of the tears as a thin precorneal film. This thickened cushion has been termed a “lid wiper” [Knop, E., Korb, D. R., Blackie, C. a, & Knop, N. (2010). The lid margin is an underestimated structure for preservation of ocular surface health and development of dry eye disease. Developments in ophthalmology, 45, 108-22.] and is analogous to the edges of a wiper blade on the windshield of the car. By analogy, the added ingredients in tears may be viewed as supplements in the windshield wiper fluids.
The delivery method described here utilizes the eyelashes, the lid wiper, and the blink to distribute the applied solution into the precorneal film. The chosen active ingredient is present in aqueous solution or as a suspension in the substrate of the applicator. Intuitively, one can see wiping is a more physiological method of delivery by contrast to eye drops, which are delivered as a sudden bolus onto the bulbar surface or the conjunctival sac.
By wiping the applicator from the lateral to medial direction, one is taking advantage of the natural direction of tear secretion, distribution, and flow. The eyelid skin and eyelashes serve as a platform and reservoir for the delivered fluid to mimick the properties of secreted tears. By wiping from the lateral to medial direction, one is also taking advantage of the fact that the eyelashes on the lateral half of the eye are slightly longer on average than the medial half, and is therefore a more efficient reservoir.
The solution may also be applied by touching the wet applicator to the lateral canthus with the eyes closed, followed by opening the eyes and blinking. But in this method there is a greater chance of formation of a bolus, and this enlarged drop will then affect the corneal surface and produce irritation.
In summary, delivery of the active ingredient by the swab method is analogous to adding the active ingredient to the windshield wiper fluid and utilizing the blink as the blade to wipe the active ingredient across the eye surface. By contrast, an eye drop delivery method is like putting an active ingredient into a bucket of water and splashing the bucket's contents over the eye surface.
In principle, any ocular drug used as eye drops can be adapted to swabs because of convenience of use. Examples of such ocular drugs include: antihistamines, muscarinic receptor agonists and antagonists, adrenergic receptor agonists and antagonists, anti-inflammatory steroids, antibiotics, non-steroidal anti-inflammatory drugs, analgesics, demulcents [“lubricants”], local anesthetics, medications for glaucoma, and immunosuppressants, etc. A second reason for selecting an ingredient is to relieve ocular discomfort by a soothing and cooling action.
The active pharmaceutical ingredient (API) should be evenly dispersible in a liquid composition so that during manufacture the wipe can be moistened with a constant and uniform solution when produced under clean or sterile conditions. For purposes of formulation, the API should preferably be miscible or soluble in aqueous solutions at neutral pH and/or isotonicity and not adherent as a particle to the absorbent substrate. The aqueous solubility of an API will facilitate meeting requirements of sterility, a unit dose dispenser, uniform dose delivery, and formulations free of preservatives.
Examples of ocular drugs that may be incoproated into swabs include: cyclosporine, antihistamines such as olopatadine, α-adrenergic agonist vasoconstrictors such as phenylephrine, napthazoline, or tetrahydrozoline, anti-inflammatory drugs such as diclofenac, anti-viral agents, antibiotics, and demulcents such as polymer “lubricants” such as carboxymethylcellulose, hypromellose, polyethylene glycol 400, hyaluronan, and propanediol(s). The lubricants increase the elastoviscous properties of the ocular fluids [usually this can be achieved with ophthalmic solutions in the range of 25 to 50 centipoises] and are especially useful for the dry eyes syndrome.
A surprising discovery made here is that an eye wipe, for example a 2″×2″ sterile pad, which carries a cooling agent, can be used as a substrate to deliver the cooling agent to the eyes for long-lasting relief of eye irritation, without side-effects. A second surprise was that certain cooling agents evoked a sense of wetness, accompanied by an improvement in visual acuity. Thus, an eye swab or wipe embodiment carrying a preferred cooling or soothing agent provides a substantial therapeutic improvement over eyedrops. Particularly preferred cooling or soothing agents include those designated CPS-148 and 2-5, further described hereinafter.
Neural Mechanisms of Drug Action:
The surfaces of the eyelids, cornea, and conjunctiva contain sensory nerve endings that respond to thermal stimuli that range from cooling to warmth and to pain. Rostral projections of these nerve endings are to the brainstem dorsolateral nucleus via various branches of the trigeminal nerve. By delivering a cooling agent to the upper and lower eyelids, and to the conjunctiva, it is assumed that activation of nerve endings will then create signals that rostrally in the brainstem interdict signals of irritation and discomfort from other sensory nerves. This “gating” or sensory over-ride of nociceptive inputs provides the basis of antinociceptive or analgesic relief.
Effects Evoked from Eye Surface with Cooling and Soothing Agents:
I have found that an unusual effect obtained with application of CPS-148 to the eye surface was an increased sensation of “wetness”. This effect was seen without increased tear production or irritation and may have special benefit for relieving a sense of dryness on the eye surface.
Design of Eye Wipes:
Pre-moistened towelettes are used in personal care products, for example, to wipe one's hands, to wipe a baby's skin after a diaper change, or to remove make-up on the face and around the eyes (e.g Pond's 6″×8″ Clean Sweep Cleansing and Make-up Remover Towelettes). The design of towelettes is well known to the art and generally each is packaged as a single-use sealed unit. Suitable wrapper materials are those which are relatively vapor impermeable, to prevent drying out of the towelette, and able to form a “peelable” seal. Examples of suitable towelette materials for practicing this invention by using as eye wipes include a polypropylene nonwoven, a rayon-polyester formed fabric, polyethylene terephthalate (PET), or polyester polypropylene blends. An example of a towelette packaging is Walgreens Lens Cleaning Wipe which can be purchased at 120 units per box. A suitable size for an eye wipe is exemplified by Walgreens Sterile Pad, 2″×2″, which can be used to deliver the active ingredient to the eye surface. Using these pads, and based on two wipes per eye, the liquid solution delivered per eye is estimated to be ˜16 μl.
The ocular surface is highly sensitive to soothing and cooling agents. Thus, CPS-148 is clinically effective at ˜8 μg/eye delivered via a 0.5 mg/ml solution.
Therapeutic Indications:
Disorders of the ocular structures in which discomfort is a major symptom can be contemplated for treatment by the compositions and methods of the present discovery, these include, but are not limited to:
The eye swab, spray, or wipe with an agent effective to reduce sensory discomfort of the eye as the single active ingredient may be used as a stand alone analgesic. Alternatively, the liquid composition in the wipe may be combined with other ocular drugs, for example, to reduce irritancy and to imrpove therapy. Examples of such adjunctive ocular drugs are cyclosporine, antihistamines such as olopatadine, α-adrnergic agonist vasoconstrictors such as phenylephrine, napthazoline, or tetrahydrozoline, anti-inflammatory drugs such as diclofenac, anti-viral agents, antibiotics, and polymer “lubricants” such as hypromellose, polyethylene glycol 400, hyaluronan, and propanediol(s). The lubricants increase the elastoviscous properties of the ocular fluids and are especially useful for the dry eyes syndrome.
Novelty: Why are Eye Wipes Better than Eyedrops for the Delivery of Active Agents?
The new observation made here is that, for equivalent concentrations of soothing and cooling agents, eye wipes are effective but eyedrops are not effective because of adverse sensations such as stinging, irritation and pain. I deduce the reasons for this phenomenon as follows:
Ethanol, in sufficient concentration, is an irritant on the human ocular surface. Subjects received different ethanol-water concentrations either in eye drops or via the delivery unit. Subjects were asked to report irritation, stinging, burning sensations, or pain in the 2 to 5 min after application. The intensity of the subjective eye sensation was rated as 0, 1, 2 or 3 with: 0 as no effect; 1 as slight; 2 as a clear-cut effect; and 3 as severe. The results are shown in the Table, with several trials in the same individual. The solutions were coded so the subject did not know the nature of the applied substance.
The results are shown in Table 1. The 5% ethanol solution was clearly aversive as an eye drop, producing stinging and pain upon delivery. When 20% was applied to the eye with a wipe, there were mild burning sensations in two subjects, when the solution entered the eye: but it was considered tolerable and acceptable. None of the sensations were present 5 min after exposure. This experiment shows that the swab method of ethanol delivery is less likely than eye drops to cause eye irritation. For ethanol/water, there is ˜4-fold change in decreased sensitivity to irritation when the swab method is used.
1-(Di-sec-butyl-phosphinoyl)-heptane, coded as CPS-148 (also known as WS-148), is representative of a class of cooling agents called trialkylphosphine oxides [Rowsell and Spring U.S. Pat. No. 4,070,496, Jan. 24, 1978] and was synthesized and tested. Briefly, in the method of synthesis, di-sec-butylphosphinoyl chloride was prepared (as described by R. H. Williams, L. A. Hamilton J. Am. Chem. Soc. (1952), 74, 5418), by addition of sec-butyl magnesium bromide to diethyl phosphite in dry tetrahydrofuran (THF), followed by chlorination in carbon tetrachoride solution at 0-10° C., to yield the di-sec-butylphosphinoyl chloride, which was purified by distillation. A solution of di-sec-butylphosphinoyl chloride (3.9 gm) in dry tetrahydrofuran (50 ml.) was added drop-wise under dry nitrogen to a refluxing solution of n-heptylmagnesium bromide (prepared from magnesium turnings (1.2 gm), n-heptyl bromide (9.0 gm) and dry THF (100 ml.). The mixture was heated under reflux for 18 hours. After cooling to room temperature, the reaction mixture was poured onto ice and 2N HCl (300 ml.), and extracted with methylene dichloride. The combined extracts were washed with lithium hypochlorite solution to oxidize any phosphorus (III) compounds to phosphorus(V) compounds or phosphorus-containing acids, 2N NaOH solution and finally with water, then dried (MgSO4). The solvent was removed by distillation and the residual yellow oil (8 gm) was eluted with chloroform down a silica gel column. The product (Rf=0.1 to 0.2 on silica t.l.c. (CHCl3)) was finally distilled to yield 1-(Di-sec-butyl-phosphinoyl)-heptane (coded as CPS-148) as a colorless liquid, bp. 120° C.
In a previous study [Wei, Ophthalmic compositions and method for treating eye discomfort and pain. US 2005/0059639A1, Mar. 17, 2005], I had reported the testing of CPS-148 in an eye drop formulation. These procedures were used: A 0.05% (0.5 mg/ml) di-sec-butyl-n-heptyl-phosphine oxide or di-sec-butyl-n-hexyl-phosphine oxide eye drop solution was prepared by adding the compound to an isotonic solution of sodium chloride, 0.65% in deionized water, monobasic potassium phosphate/sodium hydroxide buffer, preserved with disodium EDTA and benzalkonium chloride. The liquid was individually aliquoted into a ¼ oz. bottle with a Yorker spout (E.D. Luce Packaging) suitable for droplet delivery. This solution was applied to the opened eyes of three volunteers, with two to three drops of the solution applied to each eye. The subjects complained of stinging and burning sensations on the eye surface, lasting for about 2 min and requiring the subjects to shut their eyes. Afterwards, the stinging sensations disappeared and were replaced by cooling sensations on the eyelids and eye surfaces lasting for about 1.5 to 2 hours.
The above experiment was repeated at the various concentration of CPS-148, only this time the solution was wiped onto the eyes, using procedures described in Example A. Surprisingly, and to my amazement, there was no irritation and refreshing cooling sensations were obtained from this method of application, although if the residue of the agent was washed onto the eye surface, for example, when taking a shower or wiping the face with a wet towel, irritation was observed. The dose-response data for CPS-148 on cooling sensations in the eye after wipes are shown in
Thus, the use of an indirect method of drug delivery such an eye wipe is a key factor in obtaining the desired pharmacological result: namely, soothing and coolness, without sting and discomfort.
A 75-year old male had a diagnosis of “dry eyes syndrome” of 3 years duration. His principal complaints were of dryness, itch, and discomfort at the corner of his eyes and blurred vision. These symptoms were present on a daily basis at various levels of intensity. He used Systane™ eyedrops but said they were minimally effective. It was not clear if he adhered to a strict regimen of self-administration, but he complained of the eye drops running down his cheeks and the expense of the OTC medication. When the symptoms were severe, the subject found some relief by wetting his eyes with cold tap water, but the relief was only temporary. He volunteered to test an eye wipe containing 0.8 ml of a 0.5 mg/ml solution of CPS-148. Within two minutes the subject reported cooling and soothing sensations on his eyes that were maintained for 1.5 hours. The subject remarked on the sensation of “wetness”, and a feeling of comfort. The subject continues to use the eye wipes for symptomatic relief on an “as-needed basis.”
Sensory discomfort of the eye is a conspicuous symptom in patients diagnosed with “dry eyes disease.” The study described below was conducted by Prof. K. C. Yoon of the Department of Ophthalmology, Chonnam National University Medical School, Gwangju, South Korea. Prof. Yoon is an acknowledged expert on the investigation of dry eyes disease and has published extensively on this subject [e.g. Yoon, K.-C. et al. Application of umbilical cord serum eyedrops for the treatment of dry eye syndrome. Cornea 25, 268-72 (2006). Yoon, K.-C. et al. Comparison of autologous serum and umbilical cord serum eye drops for dry eye syndrome. Am. J. Ophthalmol. 144, 86-92 (2007).] The methods used in these two publications were also used in the experiments described below. This report was presented as an Oral Communication entitled “Effect of a periocular spray of a TRPM8 agonist on the ocular surface” at the 110th Meeting of the Korean Ophthalmological Society, Bexco, Busan, Korea on Apr. 13, 2014.
Chemical Synthesis:
The test compound, designated as 2-5 in the figures [1-di(sec-butyl) phosphinoyl-pentane also known as Dapa-8, CAS Registry No. 52911-13-4] was prepared by custom synthesis at Phoenix Pharmaceuticals, Burlingame, Calif., USA. The method of synthesis was: 100 mL (23.7 g, ˜200 mmol) of sec-butylmagnesium bromide, obtained from Acros, as a 25% solution in tetrahydrofuran (THF)), was placed under nitrogen in a 500 mL flask (with a stir bar). Diethylphosphite solution in THF (from Aldrich, D99234; 8.25 g, 60.6 mmol in 50 mL) was added drop-wise. After approximately 30 minutes, the reaction mixture warmed up to boiling. The reaction mixture was stirred for an extra 30 minutes, followed by a drop-wise addition of n-pentane iodide solution in THF (from TCI; 60 mmol in 20 mL). The reactive mixture was then stirred overnight at room temperature. The reaction mixture was diluted with water, transferred to a separatory funnel, acidified with acetic acid (˜10 mL), and extracted twice with ether. The ether layer was washed with water and evaporated (RotaVap Buchi, bath temperature 40° C.). The light brown oil was distilled under high vacuum. The final product, verified by mass as determined by mass spectrometry, was a clear, colorless liquid.
2-5 was prepared as a 2 mg/mL solution in distilled water and administered as a spray [sprayed volume of ˜0.1 mL] over the closed right eye of test subjects. There were 20 subjects in the normal group [9 males/11 females] and 17 subjects in the group with defined “dry eyes syndrome” [7 males/10 females]. Exclusion criteria for patient selection was age of <18 years, systemic medication that may affect tear secretion, previous punctal plug insertion, history of contact lenses use, previous ocular surgery or trauma, pregnancy or lactation, and ocular or systemic disease. The average age of the subjects was 29 years, and both groups had normal values for visual acuity, intraocular pressure, and corneal sensitivity [Cochet-Bonnet esthesiometry, measured with a microfilament]. In the “dry eyes syndrome” group, however, the Breakup Time of tears [BUT, sec], Schirmer I test [mm] were significantly impaired: BUT 11.1±2.1 vs 5.5±1.5 [sec] and Schirmer I of 14.1±3.5 vs 5.1±1.1 [mm]. The score for keratoepitheliopathy [National Eye Institute system] was 0.1±0.3 and 2.5±1.7, in the normal vs the “dry eyes syndrome” group.
Subjective symptoms were graded on a numerical score. A visual analog scale score [0 to 10 units] was used for grading the degree of soothing and cooling sensation on the ocular surface. For symptoms of the dry eyes syndrome, a scale of zero to four was used, with zero representing no symptoms and four representing very severe symptoms that caused discomfort and interfered with normal activities. These methods have been described in detail elsewhere and are incorporated by reference [Yoon, K.-C. et al. Application of umbilical cord serum eyedrops for the treatment of dry eye syndrome. Cornea 25, 268-72 (2006). Yoon, K.-C. et al. Comparison of autologous serum and umbilical cord serum eye drops for dry eye syndrome. Am. J. Ophthalmol. 144, 86-92 (2007)].
After delivery of 2-5 to the ocular surface by spraying the closed eye, all subjects felt soothing and cooling sensations on the ocular surface after blinking. The onset was less than 3 min and reached maximal effect in the first 10 min. The mean duration of cooling was 42±8 min and all cooling sensations disappeared by 1 hr. For patients previously diagnosed with “dry eyes” disease there was a reduction of symptom score from 1.8 to 0.5, a highly significant event [P<0.001]. The Tear Film BUT and tear secretion rates were not significantly affected in the normal group, and slightly elevated in the first 30 min in the dry eyes group. However, the magnitude of the effect was not considered clinically significant and may have been due to increased sensitivity of the dry eyes patients to foreign solutions applied to the ocular surface. The keratoepitheliopathy score was not affected by treatment.
The mechanical sensitivity of the cornea, measured with the Cochet-Bonnet esthesiometer, was not affected in all patients, in the 1.5 hr test period with 5 points of measurement, spaced 30 min apart. This is an important observation from the viewpoint of safety in use, because numbness of the corneal surface will increase risks of eye injury from foreign materials.
These experiments provide the first direct human evidence that the sensory discomfort experienced by patients diagnosed with “dry eyes syndrome” can be relieved by topical applications of a trialkyl phosphine oxide cooling agent. The indirect method of drug delivery to the ocular surface is a key factor for a successful demonstration of this drug action.
This application is a continuation-in-part of a National Stage application filed Feb. 9, 2012 as application Ser. No. 13/261,061, which has an International Filing date of Jun. 4, 2010 (International App. No. PCT/GB2010/001094) and has priority from U.S. provisional application 61/217,834 (filed Jun. 5, 2009) and 61/270,214 (filed Jul. 6, 2009), the contents of both of which are incorporated herein by reference in their entirety.
