FlexileRx is sold exclusively through licensed veterinarians.

OSTEOARTHRITIS (OA) is a Metabolic Deficiency Disease Metabolic processes contribute to the progression of OA in both dogs and people. After initial joint damage from trauma, overuse or genetic factors, an inflammatory cascade, triggered by the release of cytokines, initiates OA development. Cytokines, such as TNF?, IL-?, IL-6 as well as other factors, up-regulate the expression of COX-2 (cyclooxygenase-2) and 5-LOX (5-lipoxygenase) enzymes which metabolize fatty acids in the joint. Enzymatic and oxidative processes occur at the cellular level where the essential fatty acid, arachidonic acid (AA), is converted into various inflammatory products such as prostaglandin-2 (PGE₂) and leukotriene-B4 (LTB₄) which sustain and cause progression of the disease. Increased intake of dietary sources of omega-6 fatty acids, commonly found in pet food, are converted to AA in the body, contribute to the increased conversion of AA to PGE₂ and LTB₄ and then produce further damage in the joint.

FlexileRx benefits OA patients by managing AA metabolism: It decreases damaging metabolic inflammatory processes in the joint to improve functional mobility, reduce stiffness and decrease joint discomfort. When joint damage occurs, phospholipids released from damaged cell membranes are converted to AA. COX-1 enzymatic breakdown of AA then generates fatty acid metabolites that are involved in platelet aggregation and blood flow (thromboxanes) as well as maintenance of stomach mucosa (prostaglandins). COX-2 enzymatic breakdown of AA generates fatty acid metabolites that are involved in organ function, proper blood flow, urine production, blood pressure, viral immunity, bone turnover and tissue repair (prostaglandins and prostacyclins). 5-LOX enzymatic breakdown of AA then generates fatty acid metabolites that are involved in blood flow, lung function and tissue repair (leukotrienes).

Balanced AA metabolism by COX-1 and COX-2 is essential to sustain proper levels of critical regulators for renal and cardiovascular function maintained by thromboxanes (vasoconstrictors) and prostacyclins (vasodilators). An imbalance of these metabolites due to selective inhibition of COX-2 can result in high blood pressure, peripheral edema and, in severe cases, myocardial infarction as vasoconstrictive thromboxanes reduce blood flow in the kidney and urine perfusion due to depleted vasodilatory prostacyclins as a counter balance. AA, metabolized by 5-LOX, produces leukotrienes (particularly LTB4) that are strong chemo-attractant molecules responsible for the migration of white blood cells (WBCs) to the site of injury. WBCs attracted to the joint by leukotrienes release histamines and produce reactive oxygen species (ROS) and cytokines, triggering additional inflammatory processes not treated by traditional non-steroidal anti-inflammatory drugs (NSAIDs) or selective COX-2 inhibitors. Inhibition of either or both COX-1 and COX-2 has been shown to shunt AA metabolism down the 5-LOX pathway, thereby increasing, rather than reducing, inflammation in cartilage, the stomach, the kidneys and the cardiovascular system. In addition, AA is converted via an oxidative mechanism mediated by reactive oxygen species (ROS) to the oxidized lipids F2-isoprostanes, malondialdehyde, and 4-hydroxynonenal that directly degrade cartilage and induce production of other inflammatory proteins.

DESCRIPTION

Primary Ingredients FlexileRx consists of a proprietary blend of two types of flavonoids, Free-B-Ring flavonoids from Scutellaria baicalensis and flavans, from Acacia catechu. The ingredients in FlexileRx are GRAS ingredients, which require technical demonstration of non-toxicity and safety, general recognition of safety through widespread usage and agreement of safety by experts in the field. Many ingredients have been determined by the FDA to be GRAS and are listed as such by regulation, in Code of Federal Regulations 21 (CFR) Sections 182, 184 and 186. Other ingredients may achieve “self-affirmed” GRAS status via a panel of experts in the pertinent field who co-author a GRAS Report. Finally, the FDA has specifically permitted a few ingredients as safe medical foods ingredients in CFR 21Section 172.345(f).

Flavonoids Flavonoids are a group of phytochemical compounds found in all vascular plants, including fruits and vegetables. They are a part of a larger class of compounds known as polyphenols. Many of the therapeutic or health benefits of colored fruits and vegetables, red wine, and green tea are directly related to their flavonoid content.

The specially formulated flavonoids found in FlexileRx, or their related compounds, i.e., other flavonoids, anthocyanins, cannot be obtained from conventional canine diets at the same level as found in FlexileRx. OA may not be managed simply by a change to the normal diet due to the high volume of vegetable and fruit matter that would need to be consumed.

Baicalin Baicalin (5, 6, 7-trihydroxyflavone, 7-O-?-D-glucuronopyranoside) is a Free-B-Ring flavonoid derived from the phytochemical food source material Scutellaria baicalensis.

Catechin Catechin (3,3’,4’,5,7-pentahydroxyflavan (2R,3S form)), and its stereo-isomer, epicatechin (3,3’,4’,5,7-pentahydroxy- flavan (2R,3R form)), are flavans from the phytochemical food source material Acacia .

Classification FlexileRx is classified as a supplement according to rules and regulations of the USDA and FDA.

Physical Description FlexileRx is yellow to light brown in color. It is partially soluble in water and glycerol and soluble in ethanol, methanol and acetonitrile. It is practically insoluble in hexane. Each chewable tablet of FlexileRx contains 250 mg of flavox, as noted in the Primary Ingredients Section, above.

CLINICAL PHARMACOLOGY

Mechanism of Action FlexileRx acts on COX-1, COX-2 and 5-LOX pathways. FlexileRx is NOT selective for either COX-1 or COX-2 enzymes, but acts by restoring and maintaining the balance of fatty acids in OA. FlexileRx dampens AA metabolism at relatively equal levels in the COX pathway (mediated by conversion of AA via the COX-1 & COX-2 enzymes), as well as inhibiting the metabolism of AA by the 5-LOX enzyme at a comparable level.²

This unique, balanced inhibition of metabolism in the COX pathway yields relatively equal levels of thromboxanes, prostaglandins and prostacyclins that are key mediators of systemic organ and cardiovascular function. Inhibition of these mediators in the COX pathway, in conjunction with inhibition of leukotrienes in the LOX pathway, results in a “dual inhibition” mechanism that manages inflammation with minimal effects on organ function.

Inhibition of 5-LOX has been shown in cell-based assays to reduce the production of LTB₄, an agent that fosters WBC chemotaxis and the subsequent release of histamines, ROS and pro-inflammatory cytokines. In addition, direct inhibition of the 5-LOX enzyme has been observed in enzymatic assays. This balanced down-regulation of these enzymatic pathways is relatively weak when compared to the effects of traditional NSAIDs and selective COX-2 inhibitors, thus allowing the body to produce AA metabolites at relatively equal levels to maintain physiologic function.

FlexileRx also acts as a strong antioxidant to limit the oxidative conversion of AA by ROS to other damaging fatty acid products, including hydroxyl radicals, superoxide anion radicals and hydrogen peroxide. FlexileRx has demonstrated an oxygen radical absorbance capacity (ORAC) of 5,517 ?molTE/g, as compared to Vitamin E (1,100 ?molTE/g) and Vitamin C (5,000 ?molTE/g).

Through these enzyme inhibition and antioxidant mechanisms, FlexileRx is beneficial for the management of the metabolic aspects of osteoarthritis. Inflammation, joint discomfort and reduced flexibility are shown in published studies to be clinical manifestations of OA. At a biochemical and metabolic level, inflammation is not simply a marker of the disease process but also plays an important role in OA progression.

Chronic inflammation, with elevated metabolic production of inflammatory metabolites, has an etiological role in OA progression. Thus, successful management of the metabolic processes of OA with FlexileRx results in a reduction of its characteristic inflammation by correcting OA’s distinctive imbalance in AA metabolism.

Hepatic, Renal and Gastrointestinal Histology FlexileRx’s effect on hepatic, renal, gastric and duodenal tissue histology was tested in four animal toxicity studies, two for acute and two for subchronic use.

In the acute use studies, healthy juvenile male and female mice received a 2,000 mg/kg oral dose (25 to 75 times the recommended canine use of 125-375 mg per day) or placebo daily for 14 days.

In the two subchronic use studies, three groups of healthy adult male and female mice consumed 50 mg, 250 mg or 500 mg/kg doses for 28 and 91 days, respectively.

In all studies, the test subjects were evaluated relative to placebo control groups of healthy subjects with similar ages and sexes. Observations across all groups revealed neither organ or behavioral abnormalities nor differences in weight gain. Neither study showed changes in hepatic, renal, gastric or duodenal histology. Blood electrolytes were unchanged, and liver enzyme levels and markers of renal function were all within normal limits.

Food Effects FlexileRx is safe taken with or without other foods. Taking FlexileRx one hour before or after meals may help to increase the absorption of FlexileRx’s key ingredients by approximately 10% (Data on file). This observation is based upon a pharmacokinetic study in humans, as well as in-market clinical experience in analyzing physician and patient product reports. Food does not affect the metabolism of FlexileRx and may buffer effects of slight indigestion.

Metabolism FlexileRx is primarily carried bound to albumin in the blood and only a minor amount (<10%) is metabolized via glucuronidation and sulfation by hepatic metabolism involving cytochrome P450 isoenzymes (CYP). A primary ingredient constituent, baicalin, undergoes hydrolysis of the glucuronide moiety in the upper intestine via the action of intestinal flora and is absorbed as the aglycone, baicalein. Glucuronidation and sulfation of baicalein then also occurs across the lumen of the intestine and intra-hepatically. In vitro CYP450 assays using a microsomal enzyme system demonstrated minimal CYP inhibition (see below).

Drug Interactions In vitro studies indicated that FlexileRx is not a significant inhibitor of cytochrome P450, 1A2, 2C9, 2C19, 2D6 or 3A4 isoenzymes.³ These isoenzymes are principally responsible for 95% of all detoxification of drugs, with CYP3A4 being responsible for detoxification of approximately 50% of drugs. Based on the results of this assay, FlexileRx does not appear to have a pronounced effect on drug metabolizing enzymes.

FlexileRx was tested at a 10?M concentration in human recombinant (sf9 cells) using spectrophotometric quantization of 7-benzyloxy-4- (trifluoromethyl) -coumarin as substrate. In this test model, if inhibition does not reach at least 50% at 10?M, CYP inhibition is considered to be insignificant and no further development of titration curves is deemed necessary. Inhibition by FlexileRx ranged from 11% inhibition to 23% inhibition of selected isozymes when studied at a 10 ?M concentration.³

FlexileRx, therefore, does not appear to have a pronounced effect on the inhibition of hepatic drug metabolizing enzymes based on this 10 ?M concentration.³

CLINICAL EXPERIENCE

The ingredients in FlexileRx have demonstrated significant functional improvements when used for the clinical management of the metabolic processes of OA in both canine and human patients.

Double-blind, Randomized Clinical Study vs. Naproxen The ingredients in FlexileRx were evaluated in a double-blind, randomized, active comparator (naproxen), controlled clinical study that enrolled 103 human subjects with moderate or moderate-severe OA of the knee.⁴ Subjects were randomly assigned to receive
either FlexileRx (500 mg BID) or naproxen (500 mg BID) for 4 weeks. Primary endpoints were the short WOMAC composite index (Western Ontario and McMaster Universities Osteoarthritis Index) as well as investigator VAS and subject VAS scales for global response and discomfort. Subjects were sex-matched and recruited from ages 35 to 85 years, with an average age of 57-60 years per arm. There were no differences in demographic characteristics or in baseline WOMAC or VAS scores between the two arms. Subjects taking NSAIDs and/or gastro-protective medication underwent a 2-week washout period before beginning the trial. Subject activity was not restricted, and subjects were free to withdraw from the trial at any time, for any reason. Dropouts were minimal in both arms. Two subjects, one from each arm, failed to complete the trial for personal reasons unrelated to the study.

In this study, both the FlexileRx ingredients and naproxen arms noted significant reduction in the signs and symptoms of knee OA. All within-arm improvements in efficacy endpoints were statistically significant (p?0.001). The FlexileRx ingredient and naproxen arms performed almost identically, and the between-group differences were not statistically significant for any efficacy endpoint.

Fisher’s exact test was computed for improved vs. not improved (sum of unchanged and worsened) for all parameters (see Table 2). Both arms had a large percentage of subjects with significant improvement (75% to 88%). Differences were not significant between arms for percent of patients with improvement. There was a slight, non-significant trend toward greater improvement in subject global disease assessment VAS in the FlexileRx ingredient arm and WOMAC in the naproxen arm.

Double-blind, Randomized Clinical Study vs. Placebo The ingredients in FlexileRx were evaluated in a 90-day randomized, double-blind, placebo-controlled clinical trial of 60 human subjects (Data on file). Subjects were sex-matched and recruited from ages 40 to 75 years, with an average age of 55-57 years per arm. Subjects taking NSAIDs engaged in a two-week washout period before beginning the trial. Subject activity was not restricted, and subjects were free to withdraw from the trial at any time, for any reason. Three subjects withdrew from the study for personal reasons unrelated to study procedures or products.

In patients with OA, use of the FlexileRx ingredients at 125 mg and 250 mg BID resulted in significant improvements in WOMAC functional endpoints of discomfort, stiffness and mobility over those scores of placebo users. In this study, patients using FlexileRx ingredients 250 mg twice daily experienced greater improvements in discomfort, functional stiffness and functional mobility at 90 days than did patients using 125 mg twice daily.

FlexileRx vs. Glucosamine/Chondroitin (Cosequin DS®) This study shows that FlexileRx could be provided as an “ethical” supplement for support of joint health in dogs with OA (Data on file).

Materials and Methods Enzyme inhibition studies COX-1, COX-2 and 5-LOX were done according to Burnett et al. (2007) comparing the ingredients of FlexileRx to rofecoxib, valdecoxib, celecoxib, meloxicam, diclofenac, naproxen, ibuprofen, rimadyl and aspirin. In order to test the safety and efficacy of this formulation, a multi-site, double-blind, randomized, direct-comparator trial in dogs weighing at least 15 lbs. each was performed comparing FlexileRx (n=33) to a combination chondroitin sulfate, glucosamine hydrochloride and manganese ascorbate formulation (n=36) over a two month period. An interim analysis was performed at 27 days and final analysis at 57 days using owner and veterinary visual analog scale (VAS) assessments. Outcomes data were calculated as the percent change from pre-to-interim and from pre-to-final. Change was calculated for weight, veterinarian VAS rating of dog’s pain, owner VAS rating of dog’s pain and a mean VAS rating using both owner and vet values. Distributions of all variables were analyzed for normality and homogeneity of variance. Following the elimination of the two outliers, no variables were found to have significant departures from normality. Thus, all analyses were performed on untransformed variables. Unscheduled visits to the veterinarian, adverse events and/or compliance issues were recorded by the veterinarian at interim and final visits.

Results IC50 enzyme analysis showed that FlexileRx had equivalent inhibition of COX-1 and COX-2 with 3-fold less inhibition of 5-LOX enzyme in vitro. No other tested NSAID or COX-2 inhibitor showed balanced inhibition of the COX enzymes or any 5-LOX inhibitory activity. In the clinical trial, adverse events were generally mild and equivalent in both groups. Only one dog in each study arm was removed from the study due to increasing pain. All other animals were removed from the final analysis due to compliance issues, with n=30 remaining in the FlexileRx and n=29 in the chondroitin/glucosamine arms at 57 days. At 27 days, the veterinary and average scores for FlexileRx showed statistically significant improvement over the chondroitin + glucosamine formulation by Anova analysis:

At 57 days, all VAS scores for FlexileRx showed statistically significant improvement over the comparator:

p-value < .05, ** p-value < .01, *** p-value < .0001

Discussion/Conclusion The results of this study demonstrate the balanced “dual inhibitor” nature of FlexileRx, exhibiting good safety and efficacy in dogs with OA compared to a chondroitin/glucosamine formulation. It can be recommended in dogs as an “ethical” supplement.

Open Label Study The ingredients in FlexileRx were shown to be effective in an open label human trial with a mean duration of use of 6.5 months. This trial consisted of 24 subjects: 13 males and 11 females, ranging from 26 to 60 years of age. The primary endpoints were WOMAC functional mobility (65% improvement; p=0.002) and functional stiffness (62% improvement; p=.001) scores before-vs.-after taking the FlexileRx ingredients.

ADVERSE REACTIONS

In a randomized, double-blind, placebo-controlled safety study of 60 days, subjects ingested either 250 mg of FlexileRx ingredients or placebo.³ Rates of symptomatic adverse events were low and did not differ between the FlexileRx ingredients and placebo arms. There were also no usage-related changes in routine hematological or biochemical safety parameters.

In a controlled clinical trial of 90 days duration, the incidence of clinical side effects and changes in routine hematological and biochemical parameters and incidence of fecal occult blood positivity were identical for the FlexileRx and placebo groups (Data on file). Reported adverse events included 1 incidence of the following out 45 patients (15 per arm): varicose veins; hypertension; fluid accumulation in the knee; psoriasis in the FlexileRx ingredient 125 mg BID arm and psoriasis in the FlexileRx ingredient 250 mg BID arm; and reduced flexibility in the placebo arm.

Adverse reactions were also collected in a double-blind, randomized clinical trial of 30 days, although this study was not designed to specifically assess usage-related differences in adverse events.⁴ Overall, no serious adverse events were reported for the FlexileRx ingredients. There was a non-significant trend toward more frequent edema and nonspecific musculoskeletal events in the naproxen arm. No significant changes were observed within or between arms for weight, systolic blood pressure or diastolic blood pressure. As expected in a trial of this duration, no fecal occult blood was detected in study subjects, including those taking naproxen.

SPECIAL STUDIES

Gastrointestinal In a retrospective study, 8 healthy, adult subjects ranging in age from 41 to 60 years ingested FlexileRx ingredients daily for periods ranging from 5 to 11 months (mean=7 months)[Data on file]. Daily amount ranged from 300 mg to 1,500 mg (mean=825 mg). Six subjects were male, and two were female. No subjects reported a prior history of gastrointestinal ulceration. Analysis for fecal occult blood was conducted on three consecutive days. No subjects in this trial were positive for fecal occult blood.

In a second retrospective study, 13 healthy, adult subjects ranging in age from 38 to 58 ingested FlexileRx ingredients daily for periods ranging from 5 to 15 months (mean=8 months)[Data on file]. Daily administration ranged from 150 mg to 600 mg (mean=375 mg). Seven subjects were male, and six were female. No subjects reported a prior history of gastrointestinal illness. Analysis for fecal occult blood was conducted on three consecutive days.

No subjects in this trial were positive for fecal occult blood. One subject had an event of occult bleeding prior to the measurement date, withdrew from the product and was unavailable for retrospective analysis. This subject was found to have an unreported prior history of gastrointestinal ulceration. The most commonly reported FlexileRx ingredient adverse events in all clinical trials were diarrhea and flatulence, occurring in 5-8% of subjects. No subject discontinued participation in a trial because of these symptoms. Endoscopic examinations have not been conducted in FlexileRx ingredient users.

Post-Marketing Surveillance In post-marketing surveillance of over 69,000 human patients, only 63 adverse events were reported. The most serious adverse events were: edema (2 cases), upper gastrointestinal bleeding (1) and elevation of liver tests [ALT, AST and Alkaline phosphatase] (3). All cases resolved without residual effects after discontinuing the product. Notably, no serious or acute cardiovascular events have been reported. A first trimester miscarriage has been reported in a patient taking 7 prescription drugs concomitantly (including 2 drugs with warnings against use during pregnancy). The relevance of this case to the product is unknown. No other serious events have been reported (Data on file).

References

¹Burnett BP, Levy RM, Cole BJ. 2006. Metabolic Pathogenesis of Osteoarthritis. J Knee Surg. 19(3):191-7

²Burnett BP, Jia Q, Zhou Y, Levy RM. 2007. A Medicinal Extract of Scutellaria baicalensis and Acacia catechu acts as a Dual Inhibitor of Cyclooxygenase and 5-lipoxygenase to Reduce Inflammation J Med Food. 10(3):442-51.

Recommended Use FlexileRx is intended for the clinical dietary management of the metabolic processes of canine osteoarthritis (OA).

Disclaimed Use FlexileRx has not been investigated for use in the clinical management of acute pain, and concurrent use with NSAIDs has not been evaluated.

PRECAUTIONS AND CONTRAINDICATIONS

General FlexileRx is contraindicated in an extremely small number of patients with hypersensitivity to any component of flavox or to flavonoids. Foods rich in flavonoid contents include: colored fruits and vegetables, dark chocolate, tea (especially green tea), red wine and Brazil nuts.

Gastrointestinal (GI) Effects FlexileRx is expected to produce low toxicity in the upper GI because of its mechanism of action, particularly its inhibition of 5-LOX and modest inhibition of COX-1. COX-1 inhibition causes the up-regulation of 5-LOX in the stomach, which converts AA to leukotrienes (particularly LTB₄). LTB₄ attracts WBCs to the stomach mucosa, which cause and expand ulcerations. Data from an interim analysis of a preliminary study showed that the number of upper GI adverse events of FlexileRx to be about the same as placebo and less than half that of naproxen (Data on file). Clinical experience by physicians has shown FlexileRx ingredients to be well-tolerated in patients with a history of mild ulceration.

Pediatric, Pregnancy and Lactation There are no formal studies with FlexileRx in puppies or pregnant or lactating patients. For this reason, FlexileRx is not recommended for pediatric, pregnant or lactating patients.

Over Usage There are no known cases of FlexileRx over usage. Animal studies have shown that consuming the equivalent of at least 20 times the recommended human usage of 500 -1000 mg/day did not produce adverse effects.³ However, as in most over usage situations, symptoms following an over usage of FlexileRx could vary according to the patient. If an over usage were to occur, patients should be managed by systematic and supportive care as soon as possible following product consumption.

Veterinary Supervision FlexileRx is sold exclusively through licensed veterinarians.

PRODUCT ADMINISTRATION

Recommended Administration For the clinical management of the metabolic processes of OA, depending on weight, offer ½ to 1 ½ chewable tablets daily as directed by a veterinarian. FlexileRx is safe taken with or without other foods.

How Supplied FlexileRx is supplied in chewable tablets containing the equivalent of 250mg flavox. FlexileRx chewable tablets are two-part scored with a smooth surface, supplied as:

Bottle of 60 chewable tablets (250 mg)

Bottle of 180 chewable tablets

Sample bottle of 30 chewable tablets (Not for Resale)

Store at room temperature, 59-86?F (15-30?C) [see USP Controlled Room Temperature]. Protect from light and moisture. FlexileRx is supplied to veterinarians in a plastic bottle with a child-resistant cap. Dispense in a light-resistant container, as defined in the USP/NF, with a child-resistant closure.

Manufactured for: ProLabs, Ltd. - PO Box 3103 - St. Joseph, MO 64503 - 1-800-367-6359

U.S. Patents No. 7,108,868, 7,192,611 Other patents pending

Copyright © 2008 ProLabs, Ltd. All rights reserved.

CANI-0010 Rev. 0508 www.flexilerx.com