Relevance and Challenges of Juvenile Toxicity Studies Can we? Should we? Will we?

1. Relevance and Challenges of Juvenile Toxicity Studies Can we? Should we? Will we? Diane Stannard Senior Study Manager Huntingdon Life Sciences 25 February 2013

2. Contents • Background • Challenges – can we? • Relevance – should we? • The future – will we? • Summary/Conclusion • References

3. Background • Until ~10 years ago, lack of targeted paediatric drug development – extensive “off-label” use. • Assumed children exhibit similar disease progression and respond similarly to the intended therapeutic intervention. • Estimated 50% - 90% of drugs never specifically evaluated for paediatric use. • How can we be sure that adult/paediatric toxicity profiles are the same? • Inherent differences of mature/immature systems » risk of: • Unique tox profile in children • Poor efficacy • Exaggerated pharmacology • Unexpected adverse effects (even death)

4. Background • 2002 – EU consultation paper “Better Medicines for Children” – proposed new legislation. • FDA issued formal guidance in 2006: “Guidance for Industry – Nonclinical Safety Evaluation of Pediatric Drug Products”. • EMA guideline issued in 2008: “Guideline on the need for non-clinical testing in juvenile animals of pharmaceuticals for paediatric indications” • Oct 2012: Japanese MHLW guideline issued:“Guideline on the Nonclinical Safety Study in Juvenile Animals for Pediatric Drugs” • Now, drug dvlpt programs for a paediatric population must take into consideration possible effects on developmental processes specific to the relevant age groups.

5. Why are they needed? • To obtain information on potentially different safety profiles from those seen in adults – bridging the gap between reprotox and repeat dose tox studies. General tox study – direct dosing from ~6 weeks of age in rats Pre and post-natal study – no direct dosing

6. When are they needed? • Situations that would justify toxicity studies in juvenile animals include, but are not limited to: • When the indication is specifically targeted for children • Findings in non-clinical studies that indicate target organ or systemic toxicity relevant for developing systems. • Possible effects on growth and development in the intended age group. • If a pharmacological effect of the test compound could/would affect developing organs. • Unique chemical class or unique combination product.

7. Regulatory involvement • The original proposal was that the conduct of juvenile toxicity studies should be considered on a case-by-case basis. • The emphasis has changed though. Rather than questioning whether studies need to be conducted, there is now an assumption that these are required unless you can justify why they are not! • Study design/content must be discussed with, and approved by, the Regulatory Agencies (FDA/EMA). • In the EU, as part of regulation a Paediatric Investigation Plan must be submitted and agreed by the Paediatric Committee (PDCO)

8. Paediatric Investigation Plan (PIP) • The PIP facilitates the development, accessibility and safe use of new drugs in the paediatric population through clinical studies to provide justification for a waiver/deferral from such studies. Exemptions include: • Generics • Biosimilars • Well-established medicinal use • Homeopathics • Herbals • As well as any proposed paediatric studies, the PIP must include proposals for juvenile toxicity studies. Needs to: • Highlight what juvenile animal work is planned • What the specific endpoints will be (eg. neurotox assessment) • Outline the study design • Provide timelines for work … be warned, this must be accurate!

9. Challenges – Can we??? • There are many!!! • Children are not “miniature adults” • Predicting responses in children based on adult data is hard. • Known cases of different sensitivity between children and adults exist.

10. Reasons for sensitivity differences • Post-natal growth and development can affect drug disposition and action: • Metabolism (maturation rate of Phase I/II enzyme activities) • Body composition (water and lipid partitions) • Receptor expression and function • Growth rate • Organ functional capacity • These are all susceptible to modification or disruption by drugs.

11. Comparative age categories

12. Structural & functional development Human Rat Brain:by ~ 35 days. Pulmonary system: by 28-35 days. Reproductive system: ~35/45 days (F/M). Renal system (anatomical): 4-6 weeks. Renal system (functional): ~ 21 days. Immune system: by ~ 60 days. Liver:adult structure reached by ~28 days. Enzyme/transporter activity still not clearly understood, but P450 considered to be ~ 45 days. Nervous system: up to adulthood. Pulmonary system: up to 2 yrs. Reproductive system: up to adulthood. Renal system (anatomical): GW35. Renal system (functional): up to 1 year. Immune system: up to adulthood. Liver:depending on the endpoint:differences in functioning of drug-metabolising enzymes, transporters, etc. during the first months ca 3years US FDA CDER Guidance 2006

13. Dose route/volume • Stage of physical development determines feasibility of dose route: • SC/IP/Oral (buccal cavity): Day 1. • Oral gavage: Day 14-18. • IV: single dose from ~Day 14; repeat dose from Day 21. • IM: Day 21. • Inhalation: depends on who you ask!

14. Oral dosing at PND4

15. Inhalation administration • Poses some unique challenges whencompared to other routes: • Size of animals • Much smaller than mice (handling issues?) • No fur to ~Day 11 of age (maintenance of body temp during exposure?) • Age of start of treatment? • Is there time for and/or is it practical to acclimatise to the restraint tubes? • Duration of removal from dam? • Dose determined by length of exposure due to max. prac. conc. • Maternal rejection?

16. Inhalation administration (cont’d) • Method of exposure • Snout only a challenge due to size (pivot ability → turn around in tubes?; tubes small enough?) • Whole body → risk of maternal exposure through grooming → possible “double-hit” exposure through milk? • Stage of respiratory system maturation

17. Practicality of procedures • Ophthalmoscopy: • Not possible prior to Day 15, so pre-treatmentassessment often not feasible; can confound datainterpretation. • Urine collection: • Not practicable prior to weaning; probably not meaningful. • Early post-weaning: individual volumes low – pooled samples? limited list of parameters? • Behaviour assessments: • Essential to tailor to age at testing. • During treatment - conducted prior to dosing. • Ensuring correct identification of pups pre-weaning • Robust toe marking (or alternative) required.

18. Practicality of procedures(cont’d) • Blood sample collection: • Currently subject to many changes!!

19. Study design considerations There is no such thing as a “standard” study design – each study is uniquely tailored according to the test material, target population, organ system of interest & duration of use. • Age of animals at start of dosing • To match lowest age of target patient group. • Pre-weaning: relatively easy for rats, may be possible for minipigs, but tricky for other species, as difficult to obtain dams with litters or gestating females. • Post weaning: equivalent to 2yr old, all species can be used. • Duration of dosing period • To cover developing organ system(s) of interest. • Link with age that general tox studies started. • Will treatment be life-span? • Will recovery period be necessary?

20. Study design considerations • Route of administration • As intended clinical route, where possible. • … but not always practical (eg. repeat IV in the rat from Day 4 of age) • Selection of species • Must be appropriate for evaluating tox endpoints relevant for intended pediatric popn • Rats and dogs are traditionally the species of first choice. • Testing in one appropriate species using both sexes will normally be sufficient (but not always!).

21. Study design considerations • Dose selection • Exaggerated toxicity not desirable, aim is to detect any possible increase in sensitivity of young vs adults. • Preliminary study essential • To assess tolerability/dose-range • Inclusion of TK essential • Endpoints • Numerous and flexible • Each study has tailor-made design • Numbers per sex per group not standard • Depends on endpoints • Practical issues!!!

22. Relevance – Should we? • So we’ve established that whilst challenging, these studies are practically and logistically possible, but … should we be conducting them? • Are the study results relevant? • Are we seeing clear new toxicities that would affect dosing in a paediatric population or just findings related to exposure/maturation differences? • In 2011, a survey (on behalf of ILSI/HESI DART technical committee) was conducted to clarify what has been learned for the safety assessment of paediatrics. • 24 pharma companies contributed, with a combined total of 241 juvenile studies (range-finding, mechanistic and definitive) revealed the following:

23. 2011 Survey (Bailey & Marien) • 84% of studies conducted in rats, 14% in dogs and remaining 2% in other species • 15% of programs – existing adult pre-clinical & clinical data considered sufficient to support paediatric trials. • Majority of studies showed findings comparable to adults, yielding no new information. • Quantitatively, a general trend for increased sensitivity in terms of general toxicity was observed in rats but not dogs • Novel toxicity (finding in an organ system not previously seen in adult animals) was only seen in 14 rat studies and 2 dog studies, and in many cases these could have been predicted from either known pharmacology or adult data • Concluded that a targeted study design on a case-by-case basis rather than a prescriptive “standard” toxicology study design should be the norm.

24. Are the studies assisting labelling? • Strattera (atomoxetine): treatment for ADHD (www.rxlist.com) • Growth, neurobehaviour, sexual dvlpt assessed in rats from Day 10 of age to adulthood at doses ~8-fold higher than max. human dose • Slight delays on sexual maturation, ↓ epididymal weight and sperm numbers, ↓ corpora lutea, ↑ locomotor activity • But, no effects on fertility, reproductive performance or learning and memory • Product label states that significance of these findings to humans is unknown & safety/efficacy/PK in paediatric patients under 6yrs has not been established (Day 10 = 1 month old child!) • So did this juvenile animal work really add to the risk assessment process???

25. Are the studies assisting labelling? • Tamiflu (oseltamivir): treatment for influenza infection (www.rxlist.com) • A single dose of 1000 mg/kg to 7-day old rats resulted in death, although no deaths occurred at 2000 mg/kg in 14-day old rats • Found that drug concentration in brain was ~1500-fold higher in 7-day old versus adult (plasma levels ~10-fold higher) • Brain levels of drug decrease with increasing age – due to maturation of blood-brain-barrier • No adverse effects at 500 mg/kg/day from Day 7-21 of age – exposure ~800-fold higher that expected in 1yr old child • Product label states drug is not indicated for paediatric patients under 1 year old. • Important finding for human infant safety but all due to kinetics, not toxicology, so was juvenile work useful???

26. Regulatory thinking (Carleer & Karres) • EU (EMA/PDCO) view on juvenile animal studies given in paper of 97 approved/ongoing PIPs (Nov ‘08-May ‘10): • Studies proposed by Applicant company for 32/97 (33%) drugs • For these drugs, PDCO requested revisions/further justification on design for 14 of them (endpoints; duration; timing versus clinical studies; species; route of admin) • Stressed that scientifically based justifications must be provided when no juvenile animals studies are proposed. • Studies were required for a further 26/97 (26%) drugs due to: • Change in clinical plan (lower paediatric age); lack of knowledge of maturation of pharmacological target; toxicity signals; lack of sufficient nonclinical information • Concluded it is too early to ascertain the actual value of juvenile studies in these PIPs but should be able to establish if new or unexpected (developmental) toxicities and different sensitivities are seen and if they are reversible.

27. Regulatory thinking (Tassinari et al) • FDA publication on use of juvenile animal data for labeling purposes. • Data in label for 39 marketed products (1998-2009) reported as: • Contributing to overall safety assessment • Giving better characterisation of possible risks • Aiding dosing considerations especially in cases where the developing animal is more sensitive than adults • Detecting unique toxicities not seen in fully grown adult animals • BUT … pointed out that the value of design specifics and endpoints used in these juvenile animal studies remains unanswered

28. Regulatory differences (Cappon) • Evidence of a trend towards FDA requesting 2 juvenile studies per drug in some divisions: • Neurology division wants rat for behaviour assessment but dog for CNS maturation • To support paediatric programme for anidulafungin (to treat invasive fungal infection) • FDA did not require a juvenile animal study; PDCO did! • FDA seem to have little need for juvenile animal studies to support use of drugs in adolescent patients, but EU PDCO have requested studies to support adolescent indications.

29. Concerns • The questions remain: • Do juvenile animal studies investigate findings that cannot be adequately/ethically/safely assessed in paediatric clinical trials? • Do juvenile animal studies examine development not covered in adult tox studies (CNS; sexual maturation; bone growth)? • Do juvenile animal studies result in added parameters for safety evaluation in paediatric work? • Do juvenile animal studies really help with product labelling/prescribing?

30. And what do the results mean? • CNS effects (eg ↓ motor activity) at small margin of clinical dose • Real potential for neurological effect in children? • Effect on long bone growth (not likely to be seen in adults as growth complete) • Concern for children? • Altered/delayed sexual maturation in rats (not likely to be seen in adults as sexually mature) • Concern for children?

31. The future – Will we? • Ultimately, yes we will!! • We know we can conduct these studies, although limited information database • Regulators are asking for more and more studies based on a scientific need rationale • Juvenile animal data are included in product labels to assist informed decisions for drug use • But we must be clear that if juvenile studies are conducted that they are actually useful in supporting paediatric clinical trials and/or identify a specific safety concern for the paediatric population and NOT just a “box ticking” exercise.

32. The future – Will we? • It could be that the majority of different toxicities between adults and juveniles are purely due to an immature state and/or kinetics • Currently there is a lack of substantive proof of cases where juvenile animals have predicted novel human toxicities • How do we really interpret the study findings (especially if different from adult data) • Therefore, the challenge for the future is to convince fellow scientists/regulators that toxicology studies in juvenile animals should only be performed if strictly needed.

33. References • Bailey G, Mariën D, The value of juvenile animal studies “What have we learned from preclinical juvenile toxicity studies? II” Birth Defects Research, Developmental and Reproductive Toxicology 2011; 92;273-291 • Baldrick P, Juvenile animal testing in drug development – Is it useful? Regulatory Toxicology and Pharmacology 57 (2010) 291-299 • Baldrick P, Developing drugs for pediatric use: a role for juvenile animal studies? Regulatory Toxicology and Pharmacology 39 (2004) 381-380 • Cappon et al. Juvenile animal toxicity study designs to support paediatric drug development. Birth Defects Research, Developmental and Reproductive Toxicology 2011; 92;269-272. • Carleer J, Karres J, Juvenile animal studies and pediatric drug development: a European regulatory perspective Birth Defects Research, Developmental and Reproductive Toxicology 2011; 92;254-260 • Clark JB, Bates TE, Cullingford T, Land JM. Development of enzymes of energy metabolism in the neonatal mammalian brain. Dev Neurosci 1993;15:174-180. • Costa LG, Aschner M, Vitalone A, Syversen T, and Soldin OP. Developmental neuropathology of environmental agents. Ann Rev PharmacolToxicol. 2004;44:87-110. • Myers DP, Bottomley AM, Willoughby CR et al. Juvenile toxicity studies : key issues in study design. Reproductive Toxicology. 2005;20:475-6. • Tassinari MS et al, Juvenile animal studies and pediatric drug development retrospective review: use in regulatory decisions and labelling Birth Defects Research, Developmental and Reproductive Toxicology 2011; 92;261-5 • CDER pediatric. In CDER website : http://www.fda.gov/cder/foi/label/2006/021087s033lbl.pdf • EMEA/CHMP/SWP/169215/2005 in EMA website: http://www.ema.europa.eu/ema/index

34. Thank you for listening 