Review of what we know about bisphosphonate therapy in horses.

1. BISPHOSPHONATE
THERAPY IN EQUINE
SPORTS MEDICINE
Dane Tatarniuk DVM September 17th,
2014

2. Bisphosphonates
 Developed in the 1800s as industrial
chemicals
 Anti-corrosive
 Soften water for agricultural irrigation
 Medical research began in 1960s
 First licensed medication was ‘alendronate’
 Released by Merck in 1990s

3. Mechanism of Action
 Structural similarity to ‘pyrophosphate’
 Inhibit enzymes that utilized pyrophosphate
 Bisphosphonates = 2 phosphate groups
 Bind to calcium ions
 Therefore, can accumulate in areas of high
calcium deposits
 ie, bone

4. Mechanism of Action
 Bisphosphonates bind to calcium
 Accumulate and persist in bone
 Two classes of bisphosphonates, which each
act against osteoclasts in different ways
1. Non-nitrogenous
2. Nitrogenous

5. Subgroups
 Non-nitrogenous
bisphosphonates
 Metabolized in the cell
 Metabolized product replaces
triphosphate in ATP
 Leads the osteoclast to undergo
apoptosis due to lack of cellular
energy
Tilduronate
Clodronate
Etidronate

6. Subgroups
 Nitrogenous bisphosphonates
 Disrupt enzyme “FDS”
 Farnesyl diphosphate sythase
 FDS enzyme apart of the HMG-CoA
reductase pathway
 Similar to ‘Statin’ family of drugs
 Prevents the formation of two
metabolites essential for connecting
proteins in the cell membrane and
cytoskeleton
Pamidronate
Neridronate
Olpadronate
Alendronate
Ibandronate
Risedronate
Zoledronate

7. Human Medicine
 Used to treat bone resorptive disorders
 Osteoporosis
 Osteitis deformans (Paget’s Disease)
 Bone metastasis
 Multiple myeloma
 Used by astronauts aboard long-duration
space station missions

8. Rationale in Equine
 Navicular bone remodeling
 Enlargement of distal border synovial fossa
 Active osteoblastic & osteoclastic activity
 Thickened flexor compact bone
 Decreased spongiosa
 Ostblom et al., 1989
 Resorption / Formation Ratio
 Degenerative Navicular
 Ratio = 0.51
 Healthy Navicular
 Ratio = 0.10
Østblom, L., Lund, C. and Melsen, F. (1989) Navicular bone disease : a comparative histomorphometric
study. Equine vet. J. 21, 431-433.

9. Rationale in Equine
 Excessive mechanical forces induce bone
remodeling, a component of navicular
degeneration
 Bisphosphonates inhibit osteoclasts, do not
influence osteoblasts
 Prevent ongoing new bone formation
 Minimizes ongoing bone resorption seen in navicular
disease
 Also need to reduce mechanical stimulus for
maximal benefit
 Combine with rest & therapeutic shoeing

10. Rationale in Equine
 Anti-inflammatory effects?
 Decrease amount of nitric oxide and cytokines
released from macrophages
 Monkkonen, 1998
 Inhibits secretion of matrix metalloproteinases
induced by interleukin-1 in chondrocyte/synovial
cells
 Emonds-Alt, 1985 1) Monkkonen, J., Simila, J. and Rogers, M.J. (1998) Effects of tiludronate and ibandronate on the secretion of
proinflammatory cytokines and nitric oxide from macrophages in vitro. Life Sci. 62, PL95-P102.
2) Emonds-Alt, X., Breliere, J.C. and Roncucci, R. (1985) Effects of 1-hydroxyethylidene-1,1 bisphosphonate and
(chloro-4 phenyl) thiomethylene bisphosphonic acid (SR 41319) on the mononuclear cell factor-mediated release of
neutral proteinases by articular chondrocytes and synovial cells. Biochemical. Pharmacol. 34, 4043-4049.

11. Rationale in Equine
 FDA acknowledges in their FAQ that the exact
mechanism of how bisphosphonates improve
navicular syndrome remains unknown

12. Availability
 Licensed in Europe for navicular disease since early
2000s
 Until recently, only available in North American via a
drug import license
 FDA approval, Spring 2014:
 ‘TILDREN’ (Tiludronate)
 Manufacturer: Ceva Sante Animale
 ‘OSPHOS’ (Clodronate)
 Manufacturer: Dechra, LTD.

13. Potency?
 Equine formulations
are lower potency
compared to newer
formulations used now
in human medicine
Etidronate 1
Clodronate 10
Tiludronate 10
Pamdronate 100
Neridronate 100
Olpadronate 500
Alendronate 500
Ibandronate 1000
Risedronate 2000
Zoledronate 10000

14. Efficacy?
 Monitor response
 Radiographs
 Difficult to appreciate small changes in bone mineral
density
 Scintigraphy
 Likely not sensitive enough to detect changes
 Long-term treatment for osteoporosis in
humans
 Only 1 to 7% increase in bone mineral density
 Subtle changes

15. Complications
 Colic
 Altered motility
 35% incidence during FDA field study
 Transient, last ~90 minutes
 Occur during or shortly after administration (4hr)
 Rationale for slow dosing, dilute in IV fluids
 Nephrotoxicity

16. Complications
 Alters electrolyte homeostasis
 Bone fragility disorder
 Influences normal remodeling, cannot easily
repair microfractures
 Chronic pain
 Documented with long-term use in humans

17. Complications
 FDA recommendations:
 Do not use in horses with renal compromise
 Increased risk if previously using other nephrotoxic
drugs
 Ie, phenylbutazone, Banamine
 No concurrent NSAID use (+/- 48 hours)
 Baseline creatinine & BUN profile
 Do not use in horses with electrolyte disruptions
 Hypocalcaemia
 Hyperkalemia

18. Complications
 FDA disclaimers:
 Have not been studied in horses < 4 years old
 What is the effect on skeleton of growing & maturing
animals?
 Have not been used on breeding animals
 What is the effect on the reproductive tract?
 Safe to use in pregnant mares?
 May have greater bisphosphonate uptake in fetus
 Influence embryogenesis of the skeleton?
 Safe to use in lactating mares?
 Growing foal

19. FDA Freedom of Information

20. Tiludronate
 Most common bisphosphonate in equine
 “TILDREN”

21. Tildren Field Study

22. Tildren Field Study
 204 horses completed the study
 835 screened
 136 treated with Tiludronate
 68 treated with placebo control (mannitol)
 Age: 4 to 20
 Variety of breeds, gender, weight
 Bilateral in 78% of cases
 Most cases diagnosed within last 6 months of
treatment

23. Tildren Field Study
 Inclusion
 >4 years old
 Lameness in forelimb
 Grade 2 or 3
 Alleviated by palmar digital nerve block
 Navicular disease noted on standing MRI exam
 No major soft tissue involvement
 Exclude renal disease horses

24. Tildren Field Study
 Dosage
 Tiludronate diluted in 1 liter of 0.9% saline
 Administered IV over 60 minutes
 All horses had corrective shoeing concurrently
 Observers masked to treatment group
 Observations
 2 weeks
 1 month
 2 months
 Last time point

25. Tildren Field Study
 Efficacy
 Improvement of 1 grade of lameness or more
 No worsening of lameness
 Results
 P-value suspiciously close to 0.05

26. Tildren Field Study
 Complications
 Colic noted in 41% of Tiludronate treated horses
 Colic noted in 10% of placebos
 Mean duration of colic symptoms was 81 minutes
 Expanded dose-pharmacokinetic study

27. Tildren Safety Study
 Sallisaw Equine Clinic, OK
 30 horses, 6 horses per group
 Group 1 – 1.0mg/kg IV once
 Group 2 – 1.0mg/kg, IV, 3 doses 1 month apart
 Group 3 – 3.0mg/kg, IV, 3 doses 1 month apart
 Group 4 – 5.0mg/kg, IV, 3 doses 1 month apart
 Group 5 – Control

28. Tildren Safety Study

29. Tildren Safety Study

30. Tildren Safety Study

31. Tildren-HYPP Safety Study
 Heterozygous HYPP positive
 12 quarter horses
 2 doses of 1.0mg/kg, IV, given 30 days apart
 Results
 No abnormalities in potassium concentration
 1 horse with non-descript abnormal clinical signs
 Muscle fasciculations, agitation
 Colic or HYPP?
 Determined to be safe in HYPP horses

32. Clodronate
 Brand new product on market
 “OSPHOS”

33. OSPHOS Field Study

34. OSPHOS Field Study
 Dosage
 1.8mg/kg, not to exceed 900mg total dose
 Intramuscular
 Volume divided into 3 separate injection sites
 Pilot – Dose Characterization
 29 horses
 Placebo, 300mg, 900mg, 1500mg
 900mg was the lowest effective dose for improving
lameness scores
 No injection site reactions

35. OSPHOS Field Study
 146 horses in study
 86 treated with OSPHOS
 28 treated with saline
 Various genders, weights
 Age: 4 – 22 years old
 Breed
 49% Quarter Horses

36. OSPHOS Field Study
 Inclusion
 Clinical diagnosis of navicular disease
 Grade 2/5 or higher
 Palmer digital nerve block
 Radiographic evidence of navicular disease
 No MRI
 Exclusion
 Hindlimb lameness
 Horses <4 years old
 Neurectomy
 Change in shoeing within 2 weeks of enrollment
 No changes allowed through study
 Any indication that pain originated from soft tissue
structures

37. OSPHOS Field Study
 Evaluated lameness subjectively at day 0, 28,
56, 180
 Treatment failures at day 56 administered a
second dose of OSPHOS & evaluated at day 180
 Considered treatment success if improved by
1 grade by day 56

38. OSPHOS Field Study
 Day 180

39. OSPHOS Field Study
 Adverse Effects

40. OSPHOS Safety Study
 Administered IM, every 28 days, for 6 months
 Groups:
 1.8 mg/kg (1x)
 3.6 mg/kg (2x)
 5.4 mg/kg (3x)
 Saline

41. OSPHOS Safety Study
 Injection Site
 Inflamed and swollen in 7 of 32 cases
 Recommend not to give more than 10ml of
OSPHOS per injection site, to reduce this risk.

42. Clinical Studies

43.  Criteria:
 Flexion test
 Palmar digital nerve block
 Radiographs
 Osteophytes, enthesophytes, sclerosis, osteolysis
 Lameness exam
 Graded blindly by 1 observer
 Excluded:
 <2 year olds, surgically treated, fractures, NSAIDs in last
15 days, corticosteroids last 30 days
 Same shoeing & trim, no NSAIDs, no joint
supplements

44.  Treatment
 Tiludronate & placebo – same vials, appearance
GROUP Dose/Day Tiludronate Placebo Total Dose
1 0.1mg/kg
Tiludronate
10 days - 1.0mg/kg
2 0.1mg/kg
Tiludronate
5 days 5 days 0.5mg/kg
3 Placebo - 10 days 0mg/kg

45. Inclusion
Baseline
Day 1 – 9:
Therapy
Radiographs,
Lameness
Day 38:
1 month
Lameness
Day 10:
Lameness
Exam Post-
Therapy
Exam
Day 66:
2 month
Lameness
Exam
Day 192:
6 month
Lameness Exam
Study
End

46.  Cases
 Split into 2 groups for analysis
 Acute
 Clinical signs appeared within 6 months of treatment
 Chronic
 Clinical signs persisted for 6 months of treatment or longer

47.  Recent Cases
 No change in extension test
 No change in radiographic scores
 Improvement in lameness scores in 1.0mg/kg
group
 Trend, not statistically significant

48.  Chronic Cases
 No significant differences between treatment groups
at any time point
 Ancillary Information
 6 horses treated with 1.0mg/kg, considered failures at 2
months
 2 horses = second treatment
 1 horse = second & third treatment
 Other 3 horses did not receive additional doses
 All 3 horses that were repeat treated deemed successful
improvement after 2 months following last dose

49.  Advantages of the study
 Placebo control
 Randomized into groups
 Administered therapy blind
 Lameness evaluation ‘blind’ video interpretation
 Cons
 Lameness exams subjective
 No force plate
 No statistically significant data
 Just trends of improvement

50.  Osteoarthritis of the DIT and TMT joints
 Remodeling involves osteoclast and osteoblast
activity
 Influence bone metabolism
 Randomized, double blinded, placebo control
field study
 Both attending veterinarian and owner blinded to
treatment vs. placebo
 At day 60, horses with no improvement could be
treated with dose of tiludronate

51.  Inclusion:
 Intra-articular localization of lameness to DIT & TMT
joints
 Grade 3/10 or higher (Europe scale)
 Radiographic signs of osteoarthritis
 Lameness of >6 weeks to 1 year duration
 Excluded
 NSAID or joint supplements in last 14 days
 Intra-articular corticosteroid administration in last 60
days or more than 2 injections in the last year
 Change in shoeing in last 4 weeks

53.  Blocked the least-lame hind-limb, performed
exam, and graded unblocked limb lameness
 Eliminate influence of bilateral disease
 Assessment at day 0, 60, and 120
 Re-blocked least-lame limb prior to assessment
 If horse increased in lameness, re-blocked
afflicted limb to confirm hocks remains the site of
lameness

54.  Enrolled 108 horses
 Similar population
statistics for
treatment and control
group
 In-study exclusion
 Final group size
 42 Tiludronate
 45 placebo

56.  Anecdotal reports of equine vets administering
Tiludronate intra-articularly for osteoarthritis
 Reportedly 50mg injected
 In a 25 to 30ml joint, results in a concentration of
1666 to 2000mg/L
 Label IV dose is 1mg/kg
 Peak plasma concentration is 9mg/L
 Large discrepancy

57.  Used standard in-vitro cartilage explant model
 Incubated with recombinant IL-1
 Exposed to 6 concentrations of Tiludronate
 0, 0.19, 1.9, 19, 190, 1900 (mg/L)
 Measured:
 Prostaglandin E2
 Glucosaminoglycan
 MMP-1, MMP-3, MMP-13
 IL-6, IL-8

58.  Prostaglandin E2
 No effect in any of the Tiludronate groups
 Glucosaminoglycan
 Lower concentrations (0, 0.19, 1.9, 190mg/L)
significantly reduced release of GAGs
 Highest concentration (1900mg/L) significant
increased release of GAGs

59.  Chondrocyte apoptosis
 Higher concentrations of Tiludronate (19, 190,
1900 mg/L) significantly increased chondrocyte
apoptosis
 Cytokines/MMPs
 All concentrations of Tiludronate significantly
increased matrix metalloproteinase (-1, -3, -13)
and IL-8 concentrations
 IL-6 concentration was up-regulated with the
0.19mg/L Tiludronate group

60.  Conclusion
 Intra-articular concentrations of Tiludronate
greater than 19mg/L appear to be detrimental to
articular cartilage
 Intra-articular concentrations of Tiludronate less
than 1.9mg/L do not appear to have any negative
effect on articular cartilage
 Avoid administering intra-articular or regional limb
 Concentration is high – damages cartilage

61.  Immobilized limbs in casts for 8 weeks to induce
osteopenia
 2 groups (n=8), placebo or Tiludronate (1.0mg/kg IV, 2
doses 28 days apart)
 Measured:
 C-telopeptides of type 1 collagen crosslink (CTX-1)
 Indicate bone resorption
 Alkaline phosphatase
 Indicate bone formation
 Results:
 Significant decrease in CTX-1 in Tiludronate treated group
 No difference in bone ALP concentration
 Conclusion:
 Tiludronate works in horses to prevent disuse osteopenia
induced by a cast

62.  Evaluated Tiludronate therapy in 28 horses
with osteoarthritis of the thoracolumbar joints
 Treatment (14) & control (14) groups
 1.0mg/kg IV slow infusion
 Evaluated on day 60 and 120
 Measured dorsal flexibility, subjective
interpretation of improvement

64. Other Bisphosphonates
 Pamidronate:
 Zoledronate:

65. QUESTIONS?
 Take Home
 Notable complications can occur with therapy
 FDA approval does not equal efficacy. Questionable
science.
 Pathogenesis of navicular disease and influence of
bisphosphonates on said pathogenesis remain unknown
 With advent of OSPHOS, bisphosphonate therapy will
likely become more commonly utilized in general equine
practice to treat navicular disease