Preclinical Safety Assessment of Topical Drugs and Associated Pathology Flandre T IATP and STP-I Webinar January 2020 Agenda
TM – PCS
Preclinical safety assessment of topical drugs and associated pathology Flandre T IATP and STP-I Webinar January 2020 Agenda
. Topical/wound healing drug safety assessment . Formulation . Pathology associated with topical drug . Pathology associated with wound healing drug
Important Reminder: Please send any questions you may have to Satish Panchal: [email protected]
Questions will be addressed at the end of the presentation
2 IATP and STP-I Webinar – preclinical safety of topical drugs Why safety assessment of topical/wound healing drug ?
. Hazard identification: Characterize hazard . Risk assessment . Fulfilling regulatory expectations
3 Hazard identification
. Characterize hazard/safety findings – Qualitative and quantitative assessment effects (latency; reversibility) – Species specificity – translatability to humans? – Clinical monitorability (at EARLY stage) – Threshold value – Molecular mechanism – target-related?
4 Hazards
. Genetic toxicity – Proliferative changes are expected, but is it uncontrolled or mutagenic? . Local toxicity – Is it tolerated by skin and exposed tissue? – Is the vehicle tolerated? . Is the toxicity identified relevant for humans? – Is it species-specific? – Related to mechanism of action? – Monitorable? Reversible? . Phototoxicity is a special consideration given skin is the target organ
5 Risk assessment
. Risk assessment – Determine and describe exposure – Quantify possible exposure in man and estimate likelihood for hazard to occur . Assess risk – Human relevance of hazard Translatability to human – Safety factors (consider populations particularly sensitive to the toxicity) – Differs depending on the indication, dose, treatment route and duration
6 Risk management
. Is there a therapeutic window? – What should the therapeutic index (TI) be? 10, 30, or some other number? – What is being used to estimate the TI? – The longer you treat, the more toxicity you expect to see which reduces the TI . Is the hazard species-specific or translatable to humans? . Is there extensive systemic exposure? – Evaluate absorption from skin (intact or wounded), compare this to a systemically available dose (iv or po administration) – If topical delivery yields high systemic exposure, your risk is much greater for target organ toxicity and DDIs . Is there phototoxicity? – Phototoxicity guidances give special consideration for dermal treatments; both UVA and UVB must be considered in the safety testing – Threshold will be different (lower) with topical drug as skin is the target organ
7 Regulatory requirements/expectations
. No dedicated guidance for preclinical safety assessment for topical/wound healing products – Principles and procedures for evaluating toxicity of household substances, NAS, 1977 (acute dermal toxicity) – OECD 410, Repeat dose dermal toxicity study, 1981 (21 or 28-day repeat dose dermal toxicity) – EPA health effects test guidelines OPPTS 870.3200, 1998, (21 or 28-day repeat dose dermal toxicity) – Guidance for Industry Chronic Cutaneous Ulcer and Burn Wounds — Developing Products for Treatment, 2006
8 Regulatory requirements/expectations
. General guidelines for small molecules/biologics apply – ICH M3R2: guidance on non-clinical safety studies for FIH and marketing – ICH S2: Genotoxocity testing – ICH S3: Toxicokinetic – ICH S4: Chronic toxicity testing – ICH S6: Biotechnology derived pharmaceuticals – ICH S5: Reprotox testing – ICH S7: Safety pharmacology – ICH S10: Phototoxicity testing
9 Regulatory expectations – general considerations
. Route of administration – Intended clinical route needs to be used – Topical application yields low systemic exposure, limiting systemic tox assessment – Systemic dosing will provide target organ toxicity . Species selection – Small molecules are evaluated in two (or more) species: rodent + non-rodent – If for oral programs, rat and dog are default species unless scientific reason for an alternative, for topical programs, minipig is well accepted as pig and human skin are similar – For biologics, nonhuman primate is typically the appropriate species if antibody specificity is limited . Duration and frequency of treatment in general toxicology studies – Day-for-day coverage up to chronic (>6 months) treatment – Treatment frequency also needs to cover or exceed clinical plan (qod would be covered with qod, but given the high chance for misdose, qd would be added)
10 Regulatory expectations – considerations for topical drugs
. In general, the preclinical safety program is targeted for the type of compound, application route, and duration of treatment . FDA and ICH Guidances for preclinical studies supporting human pharmaceutical development (general guidances) – Content and Format of INDs (11/95) – Exploratory INDs (1/06) – M3-Nonclinical safety studies to perform clinical trials (7/97, updated 1/10) – S6-Preclinical testing of biologics (7/97) . Topical administration (cutaneous ulcers and burn applications, FDA June 2006) – Guidance includes toxicology guidance proposing vehicle and sham control groups, treatment multiples over intended clinical dose, and administration to reflect the clinical route – Immunogenicity evaluation to be included for biologic agents – Carcinogenicity studies for “chronic wound” indication for small molecules. For others, tumor promotion models and scientific assessment of tumor risk (including scar carcinomas) given the compounds are typically growth factors . Aerosol products require pulmonary toxicity testing
11 Preclinical safety program – Key considerations for topical drugs
. Preclinical assessment to be performed in two species: a rodent and a non- rodent . Topical as well as systemic exposure and toxicity are measured . Studies typically run in minipig (topical and systemic) and rat (systemic) . Systemic rat studies in support of wound healing projects are accepted by the regulatory agencies . Testing the clinical concentrations in the topical arm (intact skin) will be sufficient
12 Preclinical safety program – Key consideration for wound healing drugs
. Study designs can be inspired from topical programs, and modified as appropriate for wound healing, as there is no dedicated guidance for preclinical safety assessment for wound healing products . Lack of translatable chronic animal model . Preclinical assessment to be performed in two species: – Rodent for systemic exposure and toxicity – Non-rodent (minipig) for: – Systemic exposure and toxicity – Topical exposure and toxicity (Intact + wounded skin) at same concentration as clinic
13 Pig as preferred non-rodent species for topical/wound healing drug – why ?
Human NHP Pig Dog Rodent Epidermal pattern Epidermal Epidermal Epidermal Infundibular Infundibular Epidermal 86.2 ± 6.8 26.9 ± 3.1 51.9 ± 1.5 21.2 ± 2.5 Rat 13.3 ± 2.2 thickness (µm) Mouse 21.7 ± 1.2 Sweat gland Eccrine glands Eccrine glands Eccrine glands in Eccrine glands in Eccrine glands in over entire body; over entire body; carpal glands; footpad, nose; footpads; no apocrine in apocrine in apocrine glands apocrine glands apocrine glands genitals, genitals, associated with all associated with all underarms underarms follicles follicles (and perianal region Sebaceous Associated with Associated with Associated with Associated with Associated with glands all follicles all follicles all follicles all follicles all follicles Superficial Yes Yes Yes Yes Yes (no in mouse) vascular plexus Also metabolism and physiology (i.e. skin permeability) of the skin minipig is closer to human compared to dog or NHP
14 Pig as preferred non-rodent species for topical/wound healing drug – why ?
Mouse Cyno Minipig Human
15 Minipig wound healing toxicity study
Wound from punch biopsy in rat Wound
Topical
16 Typical preclinical toxicity package for IND/CTA (GLP studies)
. 2- (or 4-)week rodent and nonrodent studies with 4-week recovery by the intended clinical route of administration . Safety pharmacology studies (rat CNS/respiratory, in vitro hERG, and non-rodent telemetry) for small molecules (LMW) . Genotoxicity (Ames and in vitro chromosome aberration) (for LMW) . Photosafety (in vitro 3T3 NRU or in vivo study, based on UV/VIS spectra) (for LMW) . Tissue cross-reactivity for biologics Notes: . Additional studies could be needed (eg to identify target organ toxicity in the absence of significant exposure by the intended route). . Shorter duration general tox studies may be employed under special circumstances.
17 Preclinical safety program
2-wk minipig* 4/13-wk topical minipig 39-wk topical minipig 3T3 screen topical UV-LLNA topical LLNA 3T3
4-d screening rat 4/13-wk oral/iv minipig 2-wk oral/iv minipig 4/13-wk oral/iv rat 26-wk oral/iv rat 2-wk oral/iv rat systemic
Ames screen Ames Test Chromosomal Aberr.
genotox MNT in vitro Micronucleus in vivo Reprotox battery rat hERG screen hERG in vitro Sec. safety pharm ECG telem. minipig Carcinogenicity dermal rat
others CNS + Resp in rat Carcinogenicity mouse
18 Therapeutic window
. Therapeutic Index (also called safety margin or exposure multiple) is calculated for AUC and Cmax: – Animal AUC0-24h/Predicted human AUC0-24h and/or – Animal Cmax/predicted human Cmax . Calculated for each route of exposure and each species . Calculating human predictions are made based on the proposed clinical dosing concentration and projected average treated area to be covered . Safety margin generally shrinks the longer the animals are dosed
19 Therapeutic window - consideration for wound healing drugs
. Wound size would impact exposure, limited size for preclinical studies relying on TI for extrapolation to clinical studies: – Ratio of systemic exposure in the most sensitive animal species and the projected human systemic exposure – Calculated human predictions are made based on the proposed highest clinical dosing concentration and projected average wound area to be covered
20 Formulation – general consideration
. Topical formulation (cream, ointment, solution, gel, ...) – drives pharmacokinetic properties – might be the reason for clinical failure – might be the cause of species-specific dermal reactions . Systemic formulation – Exposure and safety – Identify target organs and reversibility – Used for establishing safety margin . Safety of the clinical formulation (CSF) should be tested in the GLP studies. . Programs typically require a bridging study between DRF and GLP studies if the former are run with an experimental formulation
21 Formulation – tolerability of topical CSF
. Choice of CSF for topical formulation – Aims on human use (cream, ointment, solution, gel, ...): – Will drive pharmacokinetic properties of compound – Might have neutral effects on wound healing for clinical trial (PoC) . Translation of local tolerability to human vs tox species not easy as sometimes tox species is/are oversensitive to a certain vehicle requesting a contingency plan
22 Formulation tolerability
. Here is an example of assessment of formulation tolerability in wound healing model for which re-epithelialization, granulation tissue and inflammation are benchmarked again control hydrogel formulation.
150 5 5
4 4 100 3 3
2 2 50 1 1
0 0 0 l t l l l l D e n m m s m s m C a a CD e nt a e nt a b opol G mes e b m e am m e am HPMC b s o r HPMC re re HPMC tm re re HP s C so C C so C C + o +HP o x +HPbCD o x C Car drou le C Carbopo Ointm C Carbopo Oin M y Lip Lip e Lip e imp mplex Cre HP Anh S o HPM Anhydrous Ge Simpleomple HPM Anhydrous Ge siv Simpleomple C C lu C Occlusive Ointme Occlusiv Occ
23 Pathology associated with formulation
Hydrogel (control)
Re-epithelialization
Granulation tissue
24 Pathology associated with formulation
Carbopol Formulation Poor re-epithelialization visible
Poor granulation tissue
25 Pathology associated with formulation
Liposome
Poor re-epithelialization
Inflammatory cells
26 Pathology associated with topical drug
. Potential microscopic findings associated with topical drug should be compared with untreated and formulation treated control skin. . Different mechanisms involved in skin damage: – direct toxicity (e.g., chemical burns from strong acids or alkalis) – immune-mediated reactions (i.e., allergic reactions) – phototoxic or photoallergic reactions – genotoxicity . In the following slides, few pictures of most common findings associated with topical drug administration.
Further description of microscopic finding terminology could be found on – goReni: https://www.goreni.org/ – NTP: https://ntp.niehs.nih.gov/nnl/
27 Single cell necrosis, epidermal (and vacuolation, epidermal)
28 Hyperplasia, epidermal
29 Hyperkeratosis (orthokeratotic)
30 Infiltration, inflammatory cells, dermal to epidermal
31 Vagina (topical): erosion/ulceration with inflammation Formulation 1 + drug Formulation 2 + drug Vehicle control
Mucosa
Erosion/Ulceration
32 Prepuce (topical): erosion/ulceration with inflammation Formulation 1 + drug Formulation 2 + drug Vehicle control
Mucosa
Erosion/Ulceration
33 Pathology associated with wound healing drug
34 Re-epithelialization Anti-Keratin 5 (purple staining) Epidermis expressing K5 in basal layer
Wound border Wound bed with no expressing K5 K5 expression
35 Delay in wound healing (decreased re-epithelialization, granulation tissue progression and collagen deposition) Treated
Control
Granulation tissue
Re-epithelialization
36 Inflammation (and bacterial colony )
37 Granulomatous inflammation
38 Pathology associated with UV-LLNA phototoxicity model . Few examples of ear skin findings associated with phototoxicity model.
39 Hyperplasia, epidermal (and edema)
40 Infiltration, mononuclear cell, dermal (with hyperplasia and hyperkeratosis (crust))
41 Acknowledgement
Boisclair J. Saravan C. Sukhdeep S.
Important Reminder
Please send any questions you may have to Satish Panchal [email protected]
Questions will be addressed at the end of the presentation.
42