# Presentation: 522106

## Preclinical and Clinical Safety Assessments for PPAR Agonists

- Jeri El-Hage, Ph.D.
-  Metabolic and Endocrine Drug Products
- Center for Drug Evaluation and Research  FDA

##  Peroxisome Proliferator – Activated Receptor (PPAR) Agonists and their Potential Therapeutic Indications

- PPAR alpha agonists – dyslipidemia
- PPAR gamma agonists  – type 2 diabetes
- PPAR alpha/gamma (dual, co-agonists) - diabetes
- PPAR alpha/gamma/delta (pan agonists) - diabetes
- PPAR delta – obesity , prevention of fluid retention?

## Preclinical Considerations for PPAR Agonists

- Divisional Guidance available – at preIND meeting or upon request.
- Animal models – excellent concordance for rat, monkey, and humans for  edema, cardiac, skeletal muscle, bone marrow, and renal toxicity.
- 	Exposures (AUC) at animal NOAEL = AUC for safe clinical doses (chronic)
- 	Dogs more sensitive to PPAR-induced toxicities ( liver, bone marrow)
- 	Duration of chronic non-rodent study – one year study recommended  to define NOAELs for heart failure, urothelial hyperplasia

## Recommended monitoring for potential cardiac toxicities

	Multiple dose ECG data in non-rodents – for QT  effects 

	Echocardiograms in chronic non-rodent studies

	Evaluations for plasma volume expansion (gamma agonists)

	Troponin measurements for PPAR alpha or delta agonists due to potential for drug-induced cardiac degeneration/necrosis

	Monitoring for heart failure – edema, pericardial/ thoracic fluid,  BNP ( ?)  
	CHF observed with gamma and dual agonists in rats, dogs, monkeys and humans.  

- 	Multiple dose ECG data in non-rodents – for QT  effects
- 	Echocardiograms in chronic non-rodent studies
- 	Evaluations for plasma volume expansion (gamma agonists)
- 	Troponin measurements for PPAR alpha or delta agonists due to potential for drug-induced cardiac degeneration/necrosis
- 	Monitoring for heart failure – edema, pericardial/ thoracic fluid,  BNP ( ?)
- 	CHF observed with gamma and dual agonists in rats, dogs, monkeys and humans.

- Preclinical Considerations for PPAR Agonists

## Preclinical Considerations for PPAR Agonists

-  Monitoring for hepatic effects
- Peroxisome proliferation in rats and non-rodents – biochemical markers (e.g. acyl coA oxidase,  CYP 4A, carnitine palmitoyl transferase, etc) and assessment via histology or EM .
- Mitochondrial proliferation or swelling – via electron microscopy
- Fatty changes – Sudan IV or Oil Red-O
- 	 Monitoring for bone marrow effects
- Smears for cellularity, reticulocyte counts
- Fatty infiltration – NOAELs, progression, reversibility

## Target Organs for PPAR Agonists

- Agonists with PPAR alpha activity (alpha, dual, pan)
- Monitoring for skeletal muscle toxicity (rat, dog, monkey,  humans)
- Perform routine evaluations of CPK
- Evaluate multiple sites – diaphragm, gastrocnemius, soleus
- For agonists with alpha activity seeking indications in combination with statin drugs,  a 3 –month combination toxicity study in rats is recommended

## Target Organs for PPAR Agonists

- Agonists with PPAR alpha activity (cont)
- Renal proximal tubular toxicity (rat, monkey, human)
- In addition to creatinine and BUN, markers of early tubular injury ( e.g.,  alpha GST, N acetyl-glucosamine and/or B2 microglobulin) should be considered when renal tubular pathology is observed.
- Assess reversibility
- Cardiac degeneration/necrosis (alpha and delta ?)
- Observations in animals trigger clinical troponin evaluations

## Target Organs for PPAR Agonists

- Other common target organs
- Reproductive organs – impaired ovarian follicular development, testicular atrophy
- Liver- peroxisome proliferation, hypertrophy, necrosis
- Adipose  – brown and white fat proliferation, vesiculation
- Gastrointestinal lesions – stomach erosions/ulcers, fatty infiltration of the caecum
- Immune system – thymic atrophy, sepsis
- lacking good assessments of immune effects

## Preclinical Recommendations for PPAR Agonists

- Two year carcinogenicity studies in mice and rats are recommended for PPAR agonists.
- Due the prevalence of positive tumor findings with this class, alternative assays not accepted in lieu of the 2-year mouse study.
-     Doses producing heart weight increases of 25% or greater at 3 months have been associated with excess cardiac mortality with chronic dosing in 2-yr rat studies.  Therefore, heart weight increases of approximately 25% at 13-weeks can be used to establish the maximum tolerated dose for 2-year oncogenicity studies.

## Carcinogenicity Findings for PPAR Agonists

- Accumulating data for 11 compounds (mouse and rat data)  demonstrate that PPAR agonists are multi-species, multi-strain, multi-sex, multi-site carcinogens.
-  CDER Executive Carcinogenicity Assessment Committee has reviewed the available rodent carcinogenicity data for this class of compounds and assisted the Division in policy development to insure patient safety.
- Mechanistic data to explain MOA for tumor formation is not available .
- Tumors sites are consistent with the known distribution of PPAR receptors.
- Oncogenic potency correlates with PPAR agonist potency.
- A receptor-mediated mechanism cannot be ruled out.

## Tumor Findings with PPAR Gamma Agonists

| Drug | Hemangio
Sarcoma | Bladder/
Renal | Lipoma/
Sarcoma | Liver | Other 
Tumors |
| --- | --- | --- | --- | --- | --- |
| A | Mice
M, F |  | Rat
M, F | Mice, F |  |
| B |  |  | Rat
M, F |  |  |
| C |  | Rats
M, F |  |  |  |
| D | Mice 
M, F |  | Rat 
M |  | Mice  M, F
Gallbladder adenoma |
| E | Mice 
M, F |  |  | Rats, F | Rat, M - stomach
leiomyosarcoma |

## Tumor Findings with PPAR Dual Agonists

| Drug | Hemangio
Sarcoma | Bladder/
Renal | Fibro-
Sarcoma | Lipoma/
Sarcoma | Liver | Other 
Tumors |
| --- | --- | --- | --- | --- | --- | --- |
|  |  |  |  |  |  |  |
| F |  | Rat
M,F |  |  | Rat
 F | Rat - testicular |
| G | Mice 
M,F | Rat
M,F | Rat,  F |  | Mice
M, F | Rat, F - mammary |
| H | Mice 
M,F | Rat
M,F |  | Rat  M, F
Mice M, F |  | Mice – mammary
Mice , M- stomach |
| I | Hamster
M |  | Rat
M, F |  | Rat
M, F | Rat, F - thyroid |
| J | Mouse
F | Rat
M |  | Rat
M, F |  | 
Rat- uterus |
| K | Mice 
M,F | Rat
M,F |  |  |  | Rat – leukemia M, F
Rat -Uterine |

## Common Tumor Findings  for PPAR Agonists

- Hemangioma/ hemangiosarcoma – 8/11 studies,
- 	3 gamma, 5 dual agonist.  Observed in CD-1, B6C3F1 mice of both sexes and hamsters. (liver, spleen, skin, adipose).
- Urinary bladder/ renal pelvic transitional cell carcinomas –
- 	5/6 dual agonists, 1 gamma agonist.  SD, Wistar, Fischer rats of both sexes.
- Renal proximal tubular carcinoma was also observed with 2 dual agonists (undifferentiated sarcomatous tumors)

## Other  Tumor Findings  with PPAR Agonists

- Lipoma/liposarcoma (3 γ, 2 dual)- rats (5) , mice (1)
- Fibrosarcoma in skin (3 dual) - rats
- Mammary adenocarcinoma (2 dual) – mice, rats
- Gallbladder adenoma (1 γ, 1 dual)) – mice
- Leiomyosarcoma (2 γ, 1 dual) – mice – cervix, stomach;
- 	 rats - stomach
- Liver ( 2 γ, 3 dual) – mice, rats

## Clinical Implications of Carcinogenicity Results

- High prevalence of positive carcinogenicity findings with this class of compounds raises  significant safety concerns.
- Sponsors have voluntarily discontinued development when tumors were observed at all doses and the lowest dose evaluated produced clinically relevant exposures.
- Sponsors with ongoing Phase 3 programs have completed carcinogenicity studies and have demonstrated safety margins between exposures associated with tumors and therapeutic exposures.

##  Implications for Phase 3  Product Development

- Clinical studies longer than 6 months in duration are not permissible until the two-year rodent carcinogenicity studies are
- 	completed and draft reports are submitted for agency review.
- The Division is in the process of generating general statements for inclusion in the Investigator Brochures and Informed Consent forms regarding the carcinogenicity findings for PPAR agonist drug products.

## Interpretation of Carcinogenicity Study Results

- PPAR agonists submitted to date are not genotoxic in the standard ICH testing battery.  Since threshold doses for tumors can be established:
- 	If  tumors  are observed at  doses producing AUC in animals ≥ 10-fold therapeutic exposures with the MRHD, then Phase 3 studies longer than 6 months may proceed.
- 	If tumors are observed at doses producing AUC in animals that are 1 to 9-fold clinical exposures OR all doses tested are associated with AUC exposures in animals < 10X the clinical exposure, carcinogenicity study results will be reviewed on a case by case basis.

##  Recommendations for Clinical Monitoring

- Agonists with Gamma Activity
- Plasma volume expansion – weight gain, edema, initiation of diuretics use or diuretic dose increases
- Cardiomegaly/Congestive heart failure
- Echocardiograms
- Enrollment of NYHA class  I and II only
- Exposures at NOAELs from  rat carcinogenicity study (heart failure) and chronic non-rodent study (edema) predict  safe clinical doses
- Urinalysis/bladder monitoring – written guidance available.

## Recommendations for Non-Routine Clinical Monitoring

- Agonists with Alpha Activity
- Skeletal muscle  - CPK, no dose escalation beyond animal NOAELs
- Renal proximal tubule injury – BUN, creatinine, microalbuminuria
-     early tubular injury markers  (?)– alpha GST, N-acetyl glucosamine
- Cardiac degeneration/necrosis – troponins
- Gastrointestinal hemorrhage/ ulcer
- Urinalysis for bladder safety

## Conclusions

- Excellent cross species concordance for PPAR-induced toxicities.  Therapeutic exposures should be selected based on NOAEL exposures in  animals ( e.g., rats and monkeys).  In general, toxicity signals in animals should raise clinical concerns.
- The prevalence of PPAR agonist -induced tumor findings raise  safety concerns  for long-term clinical studies.  	Preliminary results from completed 2- year rodent carcinogenicity studies should be submitted for agency review prior to conducting trials > 6 months in duration .
-     The Division of Metabolic and Endocrine Drug Products  has an extensive database and knowledge of the nonclinical and clinical safety issues associated with the PPAR agonist drug products.
-      Consultation with the Division to discuss development programs is encouraged.