# Presentation: 283264

## Osteoarthritis (OA): in vitro and animal models

- James Witter MD, PhD
*Division of Analgesic, Anti-inflammatory and Ophthalmic Drug Products (HFD-550) *
*Center for Drug Evaluation (CDER)*
- Food Advisory Committee Meeting
- June 7, 2004

## OA: Are there links?

- Human

- Animal

-  Client
- (companion)

- Experimental model

- Histology

- cell

- enzyme

## There are currently no FDA approved therapies that alter joint structure in OA

*Osteoarthritis Initiative*
*NIH/FDA/Industry/Academia*
*February 28-29, 2000*

## Human OA: Some Estimates

- $76 billion, direct/indirect health care costs
- 68 million lost work days (pain and loss of function)
- clinical OA (MD diagnosis)
- 12.1% of US or 21 million people
- total joint replacements
- 494,000/yr (hip-knee)
- market size
- symptoms- $4.0 billion
- structure- $3.5 billion

## Human OA: Some Questions

- is OA inevitable part of aging?
- certain joints in most people normal in old age
- what is the etiology of OA?
- likely multiple, few examples...
- genetic-developmental
- overuse
- acute and chronic trauma
- underuse
- atrophy
- primary (idiopathic) vs. secondary

## Draft Guidance for OAJuly 1999www.fda.gov/cder/guidance

## Conceptual Model of Human OA

- Biochemical changes

- Structural changes

- Pain* and other signs and symptoms (OA)

- Functional limitation*

- Reduced quality of life*

- Surgical replacement*

- * important to the patient

## “Surrogate” ApprovalSubpart H21 CFR 314.510

- FDA may grant marketing approval for a new drug product on the basis of adequate and well-controlled clinical trials establishing that the drug product has an effect on a _***surrogate endpoint***_* that* is reasonably likely, based on epidemiologic, therapeutic, pathophysiologic, or other evidence, to predict clinical benefit _**or**_ on the basis of an effect on a clinical endpoint other than ***survival or irreversible mortality***.

## Surrogate Endpoint: Definition

- A surrogate endpoint of a clinical trial is a laboratory measurement or a physical sign used as a substitute for a _***clinically meaningful endpoint that measures directly how a  patient feels, functions, or survives***_
- Changes induced by a therapy on a surrogate endpoint are expected to reflect changes in a clinically meaningful endpoint
- Only valid if the effect on the surrogate leads to a clinical benefit

## Surrogates vs. Biomarkers

- Surrogate endpoints are candidates for drug approval
- Biomarkers do not have the same regulatory implication
- Surrogates may be biomarkers, but not all biomarkers are surrogates.

## Clinically Meaningful Outcome

- Biomarker

- Surrogate marker

## Claims and Labels

- Although **label claims** have legal and regulatory uses, their central purpose is to inform health care providers and patients about the _**documented **_benefits and risks associated with a product
- Claims describe clinical benefit
**Promotion allowed on approved claims**
- Accurate product labels allow for effective risk management

## Delay in Structural Progression

- currently JSN (knee/hip) by X-ray accepted as surrogate
- trial length: at least one year
- include endpoints of pain, patient global, and patient reported outcome
- can structure “stand alone”?

## Claim: OA StructureOA draft guidance-1999

- “**Normalize” the X-ray (stand alone)**
**Improve JSN over baseline (stand alone)**
**reflects new or regrown “physiologic” cartilage**
**Slow JSN by “clinically relevant amount”**
**may not need symptom evidence for approval**
**approval contingent on commitment to define the actual symptom benefit in phase 4 studies**
**Slow JSN by < “clinically relevant amount”**
**subpart H approach**
- JSN is surrogate

##  Structure of Hyaline Cartilage

** ****Structure of Hyaline Cartilage**

## Adult Human Cartilage

- chondrocytes in abundant extracellular matrix
- 65-80% water
- 20-35% dry weight is structural macromolecules
- type II collagen ~50%
- aggrecan ~ 25%
- glycosaminoglycans (GAGs)
- chondroitin sulfate (4 vs. 6)
- keratan sulfate
- other types of collagens (IX, XI)
- other proteoglycans
- hyaluronic acid

## The OA Joint as an Organ

- cartilage (hyaline, fibrocartilage)
- aneural        avascular       alymphatic
- menisci (medial, lateral)
- tendons, ligaments,capsule
- bone
- synovial
- membrane
- fluid
- muscles

## Knee Radiography Techniques

- Semi-flexed MTP

- Schuss

- Semi-flexed Fluoroscopy

## X-ray: Standardization issues

- conventional knee X-ray not reproducible
- solution: (Buckland-Wright technique)
- Semi-flexed AP view
- Fluoro-assisted to allow to superimpose  anterior and posterior margins of medial tibial plateau
- To provide alignment of plateau and x-ray beam
- Magnification-corrected JSW using xJSW software
- problem: Not reproducible in clinic for
- Entry criterion
- Monitoring of disease

## In Vitro: Considerations

- maintain matrix equilibrium/environment
- Chrondrocyte highly sensitive to feedback
- anabolic
- proteoglycans and GAGS
- catabolic
- matrix metalloproteinases (MMP)
- biomarkers
- cell-cell and cell-matrix interactions
- loading stresses
- nutrients and waste removal
-  temperature
- core (37°C) vs. ankle joint (29°C)

## Mouse chondrocyteBiochem J. (2003) 376, 511-515

- without glucose, glucosamine  sole source of glycosaminoglycans (GAGs) for cell
- with glucose
- strong competitive inhibitor to utilization of glucosamine to produce GAGs
- with glucosamine
- do not stimulate production of GAGs
- higher concentration produced less GAGs
- what are likely levels of glucose, glucosamine at level of human cell?

## Animal model: Considerations

- pain
- primary clinical symptom
- surgical intervention
- not mimic human situation
- species differences
- 4 vs. 2 legs
- biochemistry
- underuse
- muscle weakness (elderly women)

## PainArthritis Advisory CommitteeJuly 29-30, 2002

## Pain: The Symptom

- studied _*directly*_ (by patient) in _*human*_*** ***OA
- WOMAC for hip and knee
- studied _*indirectly*_ (veterinarians) in _*animal*_* *OA
- chronic
- lameness (function)
- acute
- vocalization
- behavioral changes
- decreased appetite
- increases or decreases in activity
- physiologic changes (pulse, blood glucose)

##  Osteoarthritis: treatment of signs and symptoms claim

- Primary efficacy endpoints:
**Pain**
**Function**
**Patient global**
- Trial length:
**3 months **

## WOMAC pain index

- 1.	Walking on flat surface
- 2.    	Going up or down stairs
- 3.	At night while in bed
- 4.	Sitting or lying
- 5.	Standing upright

## Animal Models of OA: chemically-induced (intra-articular)

- iodoacetate
- chicken
- papain
- guinea pig, mouse
- chymopapain
- dog
- collagenase
- mouse
- TGF-ß
- mouse

## Animal Models of OA:physically induced

- anterior cruciate ligament transection
- unilateral or bilateral
- dog, rabbit
- meniscectomy
- rabbit, guinea pig
- immobilization
- rabbit, dog
- patellar contusion
- rabbit

## Animal Models of OA:spontaneous

- Age/obesity
- Hartley guinea pig
- Genetic
- unidentified
- mouse, primate
- Transgenic mice
- type IX or II collagen mutation
- hip dysplasia
- dog (purebred vs. mixed bred)

## Cruciate-Deficient Dog: Lessons 

- chondrocytes can repair damage
- hypertrophic cartilage
- increased GAGs
- true in humans, rabbits and Rhesus macaques
- neurogenic acceleration
- dorsal route ganglionectomy
- more rapid cartilage damage
- not good model for primary (idiopathic) OA
- homeostatic phase of hypertrophic repair differs
- importance of periarticular muscle
- immobilized joint has atrophic loss of GAGs
- quadriceps weakness in elderly women

## Domain Structure of Matrix Metalloproteinase (MMP) Family

**Pre**

**Pro            Catalytic                      Hemopexin-like**

**Fibronectin   ********1(V)    Transmembrane**

**     **_**MMP**_**                       **_**Pre **_**     **_**Pro **_**     **_**Cat **_**     **_**Fn**_**    **_****__**1(V**_**)     **_**Tm**_**     **_**Hpx**_** **

**Matrilysin                                                                                                       **
**Collagenase-1,-2,-3      **
**Stromelysin-1,-2,-3    **
**Macro elastase            **
**MT MMP-1 to -4         **
**Gelatinase A         **
**Gelatinase B**

## Evidence for MMPs in Pathophysiology of Osteoarthritis

- hydrolyze relevant matrix substrates in vitro
- upregulated by disease mediators (IL-1, TNF)
- in situ hybridization and immunofluorescence at sites of tissue degeneration
- signature cleavage fragments in vivo
- Collagen neoepitopes
- blockage by natural compounds and selective MMP inhibitors in vitro models

## Collagenases Present in Different Species

_**Collagenase**_**    **_**Human**_**    **_**Rat**_**   **_**Mouse**_**    **_**Rabbit**_**    **_**Dog**_
**        ****1                 Yes         No       No         Yes      Yes**
**        ****2                 Yes          ?        Yes        Yes        ?**
**        ****3                 Yes         Yes     Yes        Yes     Yes**

## Protection of Cartilage by Therapy X in Rabbit Meniscectomy Model

**Therapy X (mg/kg/d)**

_**Parameter**_

_**Normal**_

_**Sham**_

_**Vehicle**_

**1**

**3**

**10**

**Fibrillation**

**0.1**

**0.1**

**3.6**

**4.1**

**2.7**

_***2.1***_

**Fissures**

**0.1**

**0.1**

**3.5**

**4.5**

**2.1**

_***0.7***_

**Erosions**

**0.0**

**0.0**

**2.9**

**2.9**

**1.0**

_***0.9***_

**Global**

**0.3**

**0.5**

**13.1**

**15.9**

**8.8**

_***5.5***_

**          ****p < 0.01**

## Protection of Cartilage by Therapy X in Dog Cruciotomy Model (8 months)

**                                      **
**Treatment              Area                Composite**
**Vehicle                 ****	****32 ********  10          1.7 ******** 0.6**
**Low Dose X****	****	****22 ********  7.7         1.4 ******** 0.8**
**High Dose X           19 ********  8.4         1.0 ******** 0.8**

## OA and Structure Modifiers

- Hypothesis
- Limit joint destruction
- Results (clinical trials)
- MMP inhibitors
- No effect in RA or OA
- Some stopped due to safety data in oncology trials
- Stiffness/pain particularly in shoulders and hands
- Bisphosphonates
- Suggestion of efficacy in phase 2 trial, not confirmed in phase 3 trials (ACR-Orlando, 2003)

## Timing of Approval and: 

- Time

- Drug approval

- RA

- OA

- Clinical Benefit

- Structural Benefit

**Timing of Approval and: **

- OA: structural modifier

## OA: JSN progression

- Time

- JSN

- Rapid

- Slow

- No change

- a

- a

- b

- c

## “Virtual” TJR endpoint in OA

- to facilitate and standardize development of disease-modifying agents
- consists of the following key elements:
- pain
- function
- radiographic endpoints
- idea that agreed upon endpoint of joint failure reached (and surgery may occur)

## Osteoarthritis: The “Joint Organ”   

- Function

- Bone

- Cartilage

- Tendon/Ligament

- Total Joint Replacement

*Clinical*

*Surrogate*

- 1

- 2

- 3 or 4

- Drug development
-            phase

**Osteoarthritis: The “Joint Organ”   **

- Synovium

- Biomarkers

## Human OA

**Human OA**

**animal**

**In vitro**

*...**validation of a molecular target in human disease can be obtained only*
*after positive results are obtained in Phase III clinical trials in humans.*
*	**	**	**	**Ken Brandt, Biorheology 39 (2002) 221-235 *