DRAFT for internal Sanofi-Synthelabo use only. Not for distribution. New Concepts for Management of...

DRAFT for internal Sanofi-Synthelabo use only. Not for distribution.

New Concepts for Management of Osteoarthritis in the Knee—An Interactive Forum

Presented by Mark D Hopkins, M.D.Board-certified Orthopedic SurgeonFlagstaff, Arizona


Objectives

• Discuss etiology of osteoarthritis (OA) of the knee

• Explain why hyaluronans are so important for proper knee function

• Go over fundamental differences between the different types of hyaluronans

• Discuss mechanisms of action of hyaluronans

• Provide an opportunity for physician exchange of ideas and clinical experiences


Audience Poll:

• How many have osteoarthritis?

• Which specialties are represented?

• Who uses hyaluronan compounds?


Prevalence of osteoarthritis

• Advertisements from a recent issue of American journal of Orthopedics

• 75% of ads covered some aspect of osteoarthritis

• -8 ads on joint replacement

• -2 on NSAID

• -3 on hyaluronans

• -4 on other osteoarthritis categories


Osteoarthritis

• Osteoarthritis is a degenerative joint disease resulting in cartilage erosion, subchondral bone remodelling, osteophyte formation, and synovial inflammation.

• Osteoarthritis has multiple origins

• Current evidence suggests that both mechanical and biochemical factors play an important role in its progression


Joint injuries leading to osteoarthritis

• Articular cartilage contusions

• Partial or complete meniscectomy

• Ligamentous instability

• Overuse or repetitive trauma

• Secondary weakness in quadriceps, loss of damping effect on knee impact

• Posttraumatic joint deformities from fractures


Joint deformities leading to osteoarthritis

• Varus knee

• Valgus knee

• Ankle and foot problems leading to altered gait

• Hip problems


Genetic predisposition for osteoarthritis

• Cartilage degradation time clock

• Starts early in some people, later in others


Osteoarthritis

• Imbalance of biosynthesis and degradation in cartilage, synovial fluid, bone, muscle and ligaments

• In essence: increased degradation, decreased synthesis

• Leads to decrease in concentration and average molecular weight of hyaluronic acid in synovial fluid


Osteoarthritis

• Hyaluronic acid normal average molecular weight is 7,000,000 daltons

• In knees with osteoarthritis the average molecular weight can drop to 4,800,000 daltons or even as low as 20,000 daltons


ACR 2000 Guidelines— Pharmacologic/Surgical Therapy

American College of Rheumatology Subcommittee on Osteoarthritis Guidelines. Arthritis Rheum. 2000;43:1905-1915.

Mild to Moderate Pain

• Simple analgesics (eg, acetaminophen)

• OTC NSAIDs

• Topical creams

Moderate to Severe Pain

• Rx NSAIDs plus gastroprotective agent,or COX-2–selective inhibitors

AdditionalTherapies

• IA hyaluronans

• IA steroidsSurgical

Intervention

• Total knee replacement


How to treat osteoarthritis

• Imagine a freighter traveling towards the arctic circle directly in to the path of icebergs

• What would you do?

• Some would not alter the course, but would continue directly ahead and repair damages along the way (treat symptoms)

• And if necessary replace the freighter when they returned home. (total knee replacement)


How to treat osteoarthritis

• Others might attempt to alter the course of the freighter to avoid the icebergs. (disease modifying treatments for osteoarthritis, alter the course of the disease)

• Perhaps the treatment for osteoarthritis should be broken down in to disease modifying or simply symptom relieving


Modified ACR 200 guidelines

• Symptom relieving

• Simple analgesics

• OTC NSAID

• Cox 2 inhibitors

• Steroids

• Knee replacement

• Disease modifying

• Hyaluronans

• Glucosamine

• Chondroitin Sulfate

• Unloader braces

• HTO

• Weight loss

• Increase muscular strength

• Improve flexibility


What is your choice?

• What would you want if you were the patient?

• Crash in to icebergs?

• Avoid them?


Product comparisons, hyaluronans

Product Hyalgan Synvisc Supartz

MW (kDa) 500-730 80% 6,000

20% > 6,000

620-1,170

Manufacture Natural Crosslinked Natural

Treatment 3 or 5 inj. X 20 mg/2ml

3 inj. X 16 mg/2ml 5 inj. X 25mg/2.5ml

Repeat series FDA approved Not FDA approved Not FDA approved

Inflammatory reactions

0% 2.2% per injection

0%

Stimulates endogenous hyaluronase production

Yes No Yes


Mechanisms of Action of Hyaluronans

Based on research dating back to the 1980’s• Increases the viscosity and elasticity of OA

synovial fluid• Stimulates endogenous hyaluronic acid

production• Inhibits induction and activity of degradative

enzymes• Reduces inflammatory response• Analgesic effect


Increased viscosity and elasticity of synovial fluid

• This is a temporary effect

• For hyalgan 24 hours

• For supartz 24-72 hours

• For synvisc 3-8 days


How important is this temporary increased viscosity and elasticity?

• When the original patents were being developed, it was thought that the viscosity increase was the primary effect by which these substances worked.

• They were thought of as a lubricant for the knee joint.

• Synvisc was thought to be superior because of its larger molecular weight. It would stay in the knee longer and lubricate it better. This is why during the development process for synvisc , it was crosslinked.


Possible sequelae of crosslinking

• Some have pointed to the cause of synvisc’s inflammatory reactions being linked to its larger size.

• Possible foreign body reaction

• Possible autoimmune response


Stimulates endogenous hyaluronase production

• How could injecting hyaluronase stimulate hyaluronase production?

• One would logically think that the body would sense the substance was increased and limit its production.


Hyaluronase

• Is present as a polydisperse species with an average MW of up to 10,000,000 Daltons.

• The concentration in normal synovial fluid is 3mg/ml.

• Is responsible for the normal viscosity of synovial fluid.

• Also lubricates the joints.

• A knee with low quantities of hyaluronase or the wrong molecular weight is like an engine with not enough oil or the wrong type.


Hyaluronase

• Type B fibroblasts in synovium are responsible for hyaluronase production.

• The response of fibroblasts to different molecular weights of hyaluronase was studied.

• High MW fractions (4,000,000) were less effective in stimulating hyaluronase synthesis than lower MW (500,000-4,000,000)


Stimulation of endogenous hyaluronase production

• Synovial fibroblasts do not increase the biosynthesis of hyaluronase when the hyaluronase in their environment is of a MW within a range which could be functionally acceptable.

• The stimulus for increased biosynthesis of hyaluronase only becomes operational when the hydrodynamic size distribution of extrinsic hyaluronase falls within a particular mean range.


Stimulation of endogenous hyaluronase production

• Receptor binding as a function of molecular weight.

MW < 500,000, weak binding no HA synthesis

MW 500,000-4,000,000, strong binding because # of receptors stimulated increases HA biosynthesis

MW > 4,000,000 maximal receptor binding, large domains limit # of sites, decrease HA production


Mechanism of action of hyaluronans

• Inhibit induction and activity of degradative enzymes

• Hyaluronase suppresses

• MMP-3 (matrix metalloproteinase-3) MMP-3 degrades

• cartilage proteoglycan and type 2 collagen

•

• IL-1Beta (interleukin-1 Beta) IL-1Beta is responsible for

• cartilage catabolism



• Hyaluronase reduces inflammatory response

• Hyaluronase inhibits leukocyte and mononuclear cell phagocytosis, adherence and mitogen-induced proliferation

• Hyaluronase protects tissues and synovial proteins from free radicals

• Hyaluronase decreases levels of prostaglandin E2 and cyclic AMP. HA impairs migration of AA (arachidonic acid) away from cells. Since extracellular AA is rapidly taken up by activated leukocytes within joints and may be converted to inflammatory prostanoids, the observed inhibitory effects of HA on AA release could be considered antiinflammatory.



• Analgesic activities of hyaluronase

• By modulating inflammatory cell activities, including their release of pro-inflammatory mediators, cytokines and free radicals, HA could indirectly influence the sensitization of pain receptors in arthritic joints.


Summary

• All of the effects are centered around hyaluronase

• The most important effect of administering hyaluronase in to a joint is its effect on stimulating endogenous hyaluronase production because it is the hyaluronase that mediates all of the other effects.


Summary, continued

• Only two of the substances on the market stimulate endogenous hyaluronase production, hyalgan and supartz.

• We have to understand that the treatment of osteoarthritis is a long term problem. The only substance FDA approved for repeat series is hyalgan. It makes no sense to treat a long term problem for six months, then stop.

• Hyalgan, then, by deduction is currently the most logical choice for the long term treatment of osteoarthritis. Remember, we’re not treating the symptoms, we are trying to alter the course of the disease. Avoid the icebergs.


Focus Questions

• Use of hyaluronans in other joints?

• What do we do when a patient does not respond to hyaluronan treatment?

• What is the reason that some patients don’t respond and some do with the same type and degree of osteoarthritis?

• Which grades of osteoarthritis respond best to hyaluronan therapy?


Focus Questions, continued

• Does obesity play a role in response to hyaluronase treatment?

• When a patient has a total knee on one side, do you try hyaluronase on the other side or just go to a TKA?

• What do you do with a patient with a meniscus tear that may be degenerative and osteoarthritis on the same side? TKA? Scope? Hyaluronase? Therapy? Other?


The End

DRAFT for internal Sanofi-Synthelabo use only. Not for distribution. New Concepts for Management of...

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