CLINICAL PHARMACOLOGY
Mechanism of Action
LIMBREL (flavocoxid) acts on COX-1, COX-2 and 5-LOX pathways. LIMBREL (flavocoxid) is NOT selective for
either COX-1 or COX-2 enzymes. LIMBREL (flavocoxid) acts by restoring and maintaining the
balance of fatty acids in OA. LIMBREL (flavocoxid) 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.
This balanced inhibition of metabolism in the COX pathway yields relatively
equal levels of thromboxanes, prostaglandins, and prostacyclins that are key
mediators of systemic organ 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.
LIMBREL (flavocoxid) 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. LIMBREL (flavocoxid) has demonstrated an
oxygen radical absorbance capacity (ORAC) of 5,517 μmolTE/g, as compared
to Vitamin E (1,100 μmolTE/g) and Vitamin C (5,000 μmolTE/g).
Through these enzyme inhibition and antioxidant mechanisms, LIMBREL (flavocoxid) is beneficial
for the clinical dietary 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
the progression of OA. Thus, successful dietary management of the metabolic
processes ofOA, results in a reduction of its characteristic inflammation
by correcting OA's distinctive imbalance in AA metabolism.
Hepatic, Renal, and Gastrointestinal Histology
LIMBREL (flavocoxid) 's effect on hepatic, renal, gastric, and duodenal tissue histology
was tested in four animal toxicity studies; two for acute use and two for sub-
chronic use.
In the acute use studies, healthy juvenile male and female mice received a
2,000 mg/kg oral dose (10,000 mg per day human equivalent, or at least 10 times
the recommended human use of 500 - 1,000 mg per day) or placebo daily for 14
days. In two different sub-chronic use studies, three groups of healthy adult
male and female mice consumed either 50 mg, 250 mg or 500 mg/kg doses (250 mg,
1,250 mg and 2,500 mg per day human equivalent) 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 no 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
LIMBREL (flavocoxid) is safe taken with or without other foods. Taking LIMBREL (flavocoxid) one hour
before or after meals may help to increase the absorption of LIMBREL (flavocoxid) 's key ingredients.
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 LIMBREL (flavocoxid) and may buffer effects of slight
indigestion.
Metabolism
LIMBREL (flavocoxid) 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 occurs intra-hepatically.
In vitro CYP assays using a microsomal enzyme system demonstrated minimal
CYP inhibition (see below).
Drug Interactions
In vitro studies indicated that LIMBREL (flavocoxid) is not a significant inhibitor
of cytochrome P450 1A2, 2C9, 2C19, 2D6, or 3A4. 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, LIMBREL (flavocoxid) does not appear to have a pronounced effect on drug metabolizing
enzymes.
LIMBREL (flavocoxid) was tested at a 10 μM 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 μM, CYP inhibition is considered to be insignificant and no further
development of titration curves is deemed necessary. Inhibition by LIMBREL (flavocoxid) ranged
from 11% inhibition to 23% inhibition of selected isozymes when studied at a
10 μM concentration.
LIMBREL (flavocoxid) , therefore, does not appear to have a pronounced effect on the inhibition
of hepatic drug metabolizing enzymes based on this 10 μM concentration. The
data for CYP inhibition is shown below:
Table 1. Cytochrome P450 Assay
CYP Isoenzyme |
% Inhibition by LIMBREL |
1A2 |
23% |
2C9 |
11% |
2C19 |
16% |
2D6 |
15% |
3A4 |
11% |
Clinical Experience
LIMBREL (flavocoxid) has demonstrated significant functional improvements when used for
the clinical dietary management of the metabolic processes of OA.
Double-blind, Randomized Clinical Study vs. Naproxen
LIMBREL (flavocoxid) was evaluated in a double-blind, randomized, active comparator (naproxen)
controlled clinical study that enrolled 103 subjects with moderate or moderate-severe
OA of the knee. Subjects were randomly assigned to receive either LIMBREL (flavocoxid) (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), investigator VAS for global response, 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 gastroprotective 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 thisstudy, both LIMBREL (flavocoxid) 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 LIMBREL (flavocoxid) and naproxen
arms performed nearly identically, and the between group differences were not
statistically significant for any efficacy endpoint. See Figures 1-4 below for
efficacy results of LIMBREL (flavocoxid) vs. naproxen in this study.
Figure 1. Improvement in WOMAC*
Figure 2. Improvement in Physician VAS (Global Disease Assessment)**
Figure 3. Improvement in Subject VAS (Global Disease Assessment)†
Figure 4. Improvement in Subject VAS (Discomfort Assessment)
††
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 physician global
disease assessment VAS in the LIMBREL (flavocoxid) arm and WOMAC in the naproxen arm.
Table 2. Percent of OA Patients with Improvement
|
LIMBREL (flavocoxid)
500 mg BID
(N=52) |
Naproxen
500 mg BID
(N=51) |
p-value |
WOMAC |
79% |
88% |
< 0.001 |
Physician VAS (global disease assessment) |
83% |
75% |
< 0.001 |
Subject VAS (global disease assessment) |
87% |
88% |
< 0.001 |
Subject VAS (discomfort assessment) |
87% |
88% |
≤ 0.001 |
Double-blind, Randomized Clinical Study vs. Placebo
LIMBREL (flavocoxid) was evaluated in a 90-day randomized, double blind, placebo-controlled
clinical trial of 60 subjects. 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 LIMBREL (flavocoxid) at 125 mg and 250 mg BID resulted in significant
improvements in WOMAC functional endpoints of stiffness and mobility over those
scores of placebo users. In this study, patients using LIMBREL (flavocoxid) 250 mg twice
daily experienced greater improvements in functional stiffness and functional
mobility at 90 days than did patients using 125 mg twice daily. See Tables 3
and 4 below for a comparison of LIMBREL (flavocoxid) results to placebo for each noted measure.
Table 3. 90-day Functional Stiffness WOMAC Scores
|
Mean % Change* |
p-value |
Conclusion |
LIMBREL 250 mg/day |
-27.2% |
p=0.005 |
Significant improvement |
LIMBREL 500 mg/day |
-38.0% |
p=0.002 |
Significant improvement |
Placebo |
+3.1% |
p=0.324 |
No significant improvement |
* Negative values indicated improvement
in functional stiffness. |
Table 4. 90-day Functional Mobility WOMAC Scores
|
Mean % Change* |
p-value |
Conclusion |
LIMBREL 250 mg/day |
+19.2% |
p=0.018 |
Significant improvement |
LIMBREL 500 mg/day |
+28.4% |
p=0.001 |
Significant improvement |
Placebo |
+2.3% |
p=0.895 |
No significant improvement |
* Positive values indicated improvement
in functional mobility. |
Open Label Study
LIMBREL (flavocoxid) has been 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 LIMBREL (flavocoxid) .