Accelerated Stability Assessment Program (ASAP) Using Science to Set Shelf Life Ken Waterman, Ph.D. Research Fellow Pfizer Global R&D, Groton, CT USA
Outline Background and Scope Heterogeneous Kinetics and Isoconversion Moisture Sensitivity ASAP Experimental Design Packaging Regulatory Considerations Conclusions 2
Accelerated Stability Assessment Program (ASAP) Modeling tool that improves product understanding Credible predictions for product expiration dating Reduces uncertainty Has the potential to change the way industry meets its stability commitments Clinical investigations Registration Annual review Post-Approval Changes Scope Solid drug products Solid API s Small molecules 3
Heterogeneous Kinetics for Solids API Overall product excipient API/excipient interface Inside crystal molecules 4
Excipient/API Interactions lo og k -0.6-0.8-1 -1.2-1.4-1.6 Power Law relation for API + excipients: more surface interactions---more reactivity 0 0.5 1 1.5 2 2.5 log (100/%API) Aspirin tablets at 40ºC/75%RH 5
Stability at Different Temperatures %Degra adant 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 100 200 300 400 500 600 Low Temperature High Temperature 0 10 20 30 40 50 60 Relative Time Same curvature independent of T 6
Stability at Different Temperatures: Historical Approach 60 Days at low or high T 60 0 100 200 300 400 500 600 Low T High T k<<k to specification limit k k to specification limit 60 Historical approach: Time axis fixed independent of actual % degradant or T 7
Stability at Different Temperatures: ASAP (Isoconversion) Approach 0 100 200 300 400 500 600 Low T High T ASAP approach: % degradant fixed at specification limit, time adjusted as needed 8
80 C Arrhenius Plot: Two Approaches 70 C 60 C 50 C 30 C isoconversion CP-456,773/60%RH Historical method: high T deviations give nonlinear behavior Real time data Predicted Shelf Life (historical method) Predicted Shelf Life (ASAP/isoconversion) Experimental Shelf Life 0.5 yrs 1.2 yrs 1.2 yrs 9
Humidity Corrected Arrhenius Equation collision frequency humidity sensitivity factor 1.986 cal/deg ln k = ln A - E a /(RT) + B(ERH) 1/(isoconversion time) equilibrium relative humidity activation energy 10
Aspirin Tablet Degradation 70 C 50 C 40 C 30 C 20 C 75% RH 10%RH Parallel Arrhenius curves seen at each RH 11
Typical E a and B values (n=60) 29.8 0.043 RH sensitivity does not indicate hydrolysis! 12
Effect of B Values on Shelf Life (Constant T) B 0.00 low moisture sensitivity 0.04 average moisture sensitivity 0.09 high moisture sensitivity 60%RH in PVC Blister 65%RH in PVC Blister 75%RH in PVC Blister 60%RH in Bottle + Desiccant 5.0 yrs 5.0 yrs 5.0 yrs 5.0 yrs 5.0 yrs 3.8 yrs 2.6 yrs 7.1 yrs 5.0 yrs 3.0 yrs 1.2 yrs 8.8 yrs 13
Effect of Activation Energies on Shelf Life (Constant RH) Shelf-Life (years) E a (kcal/mol) 25 C 30 C 40 C 12 Low activation energy 5.0 3.6 1.9 29 Average activation energy 5.0 2.2 0.5 39 High activation energy 5.0 1.7 0.2 14
ASAP Screening-Protocol: Set to Generate Specification Levels Generically Protocol T ( C) %RH Days 50 75 14 60 40 14 Drug Product 70 5 14 Stability Screen 70 75 1 80 40 2 Actual protocol is product-specific! 15
ASAP Design Space (DOE) ln k = ln A - E a /R(1/T) + B(%RH) ln k %RH 70/75 80/40 60/40 50/75 40/75 30/75 Ln A 70/ 5 30/65 25/60 B E a /R 1/T 16
Error Bars for Predicted Shelf-Life ln k Shelf-life error bars depend on: Extrapolation distance Errors in k s Design/degrees of freedom 70/75 %RH 80/40 60/40 50/75 Ln A 70/ 5 25ºC/60%RH B 1/T E a /R 17
Error Bars for Predicted Shelf-Life Example: Confidence Interval For 2 year shelf life (25ºC/60%RH) = 95% For 3 year shelf life (25ºC/60%RH) = 75% ln k 70/75 %RH 80/40 60/40 50/75 Ln A 70/ 5 25ºC/60%RH B 1/T E a /R Calculated using Monte-Carlo simulation process 18
Error Bars for Predicted Shelf-Life ln k Example: Confidence Interval For 2 year shelf life (25ºC/60%RH) = 99% For 3 year shelf life (25ºC/60%RH) = 95% 70/75 %RH 80/40 60/40 50/75 40/75 Ln A 70/ 5 25ºC/60%RH B 1/T E a /R 19
Likely Causes for Poor Fit/Prediction Form/Phase change caused by T/RH: melts, glass transitions, anhydrate/hydrate formation ln k 80/40 70/75 %RH 60/40 50/75 40/75 30/75 Ln A 30/65 25/60 70/5 B E a /R 1/T 20
Protocol Example Final protocol may require several iterations! T ( C) %RH Days % Degradant 50 75 14 0.45±0.05 60 40 14 0.24±0.02 70 5 14 0.09±0.02 70 75 1 0.68±0.07 80 40 2 0.59±0.06 Specification Limit = 0.2% 25 C/60%RH shelf-life (PVC blister) 25 C/60%RH shelf-life (HDPE bottle) 30 C/65%RH shelf-life (HDPE bottle) 30 C/65%RH shelf-life (HDPE bottle, desiccant) 2.4-13.2 yrs 4.2-18.8 yrs 1.8-5.6 yrs 3.5-8.8 yrs 21
Protocol Example Final protocol may require several iterations! T ( C) %RH Days (screening protocol) %Degradant using screening (generic) protocol Days: Product specific protocol 50 75 14 045 0.45 7 60 40 14 0.24 14 70 5 14 0.09 Not tested 70 75 1 0.68 Not tested 80 40 2 0.59 1 40 75 Not tested --- 21 80 5 Not tested --- 11 22
Protocol Example Final protocol may require several iterations! T ( C) %RH Days: Protocol 2 (product specific) %Degradant using product specific protocol 40 75 21 0.23±0.02 50 75 7 0.20±0.02 60 40 14 0.22±0.02 80 40 1 0.31±0.02 80 5 11 0.18±0.02 25 C/60%RH shelf-life (PVC blister) 25 C/60%RH shelf-life (HDPE bottle) 30 C/65%RH shelf-life (HDPE bottle) 30 C/65%RH shelf-life (HDPE bottle, desiccant) 2.9-6.0 yrs 5.4-9.4 yrs 2.3-3.4 yrs 4.3-6.0 yrs 23
ASAP Protocol Validation Over 50 drugs have now been studied at Pfizer! 24
Packaged-Product Stability H 2 O H 2 O H 2 O H 2 O Moisture transfer depends on MVTR + RH Moisture inside packaging equilibrates between headspace (RH), tablets, desiccant (vapor sorption isotherms) 25
Moisture Sorption Isotherm Microcrystalline Cellulose % H 2O 2 10 9 8 7 6 5 4 3 2 1 0 0 20 40 60 80 %RH 26
Moisture Sorption Isotherm Desiccants 35 30 %H 2 O 25 20 15 10 5 0 10 20 30 40 50 60 70 80 %RH Silica Gel Molecular Sieves Clay Mineral 27
Moisture Equilibration in Bottle 35 Tablets introduced 30 25 %RH 20 15 10 500-mg tablets (2) 1:1 spray-dried lactose:mcc (RH 32%) in N 2 - purged120-cc bottle 5 0 0 10 20 30 40 50 60 70 80 90 Time (min) 28
Moisture Vapor Transmission Rate permeability moisture transferring into a package at a fixed difference in RH; fixed T P = MVTR/ RH difference in RH inside and outside package m = P RH t mass of water entering/leaving container unit of time 29
MVTR Values Vary with T in Arrhenius manner Proportional to surface area Bottles 60-cc HDPE (75%RH) 20 C 0.198 30 C 0.534 40 C 1.352 180-cc HDPE (75%RH) 30 C 1.061 Blisters (30 C;75%RH) Aclar 0.027 PVDC 0.148 30
Empty Bottle/Blister Equilibration 65 60 55 %RH 50 45 40 35 30 Aclar Blister 60-cc bottle 0 20 40 60 80 Days 25ºC/60%RH Oven 31
Bottle/Blister Equilibration with Tablets 60 55 50 %RH 45 40 35 30 0 2 4 6 8 10 years 25ºC/60%RH Oven 60 500-mg tablets 2:1 MCC:lactose 60-cc bottle + 60 tablets Aclar blister + 1 tablet 32
Predicted (Lines) vs. Measured RH 70 60 50 empty bottle 2 tablets %R RH 40 30 20 10 0 15 tablets 15 tablets + desiccant 0 10 20 30 40 50 60 70 Days 500 mg tablets of CP-481715 60-cc HDPE Bottles (40 C/75%RH) 33
Example 1: Very Unstable (When Unprotected) Drug Product (B = 0.068) 4 %D Degradant 3 2 1 PVC blister (open bottle) 2 tablets/60-cc bottle 15 tablets/60-cc 15 tablets + bottle desiccant/60-cc bottle 0 0 10 20 30 40 50 60 70 Days Lines: predicted (ASAP + calculated RH) Diamonds: experimental CP-481,715 in 60-cc HDPE Bottles (40 C/75%RH) 34
Example 2: More Stable Drug Product (B = 0.015) Real time ASAP Varenicline tablets (500 0.5 mg in 180-cc bottle); 30 C/65%RH 35
ASAP vs. Real Time Example 3 (25 C/60%RH in Bottles with Desiccant) B = 0.022 ASAP Prediction Real Time 36
Bridging Science and Regulations Early Clinical Trials Use ASAP to support Clinical Use Period assignments During Development Use ASAP to predict stability for changes in: Formulations/processes o ocesses Synthetic routes Packaging At Registration Use ASAP as supportive data or as an alternative to traditional stability to minimize stability commitments Post-Approval Use ASAP to justify changes that will not affect stability Replace annual commitment with ASAP commitment 37
Conclusions ASAP provides a scientific basis for setting shelf-lives Dramatically shorter time Better understanding Lower risk Allows package selection without screening lowers risk + saves time 38
Acknowledgments Pfizer scientists Groton and Sandwich Paul Gerst Bruce MacDonald Mike Roy Anthony Carella Garry Scrivens 39
Related Publications Waterman, K.C.; MacDonald, B.C. Package selection for moisture protection for solid, oral drug products, J. Pharm. Sci. 99 (2010) 4437-4452; (on line) DOI 10.1002/jps.22161 (2010) Waterman, K.C. Accelerated stability assessment program (ASAP): using science to set shelf life, accepted in American Pharm. Rev. Waterman, K.C. Understanding and predicting pharmaceutical product shelf-life. In Handbook of Stability Testing in Pharmaceutical Development: Regulations, Methodologies and Best Practices, Huynhba, K., Ed. Springer Science and Media Publishing, Chapter 6 (2008) 115-135. Waterman, K.C.; Colgan, S.T. A science-based approach to setting expiry dating for solid drug products. Regulatory Rapporteur 5 (2008) 9-14. Waterman, K.C.; Carella, A.J.; Gumkowski, M.J.; Lukulay, P.; MacDonald, B.C.; Roy, M.C.; Shamblin, S.L. Improved protocol and data analysis for accelerated shelf-life estimation of solid dosage forms. Pharmaceutical Research 24 (2007) 780-790. Waterman, K.C.; Adami, R.C. Accelerated aging: prediction of chemical stability of pharmaceuticals. Intern. J. Pharm. 293 (2005) 101-125. Waterman, K.C.; Adami, R.C., Hong, J. Impurities in drug products. In Handbook of Isolation and Characterization of Impurities in Pharmaceuticals. S. Ajira and K.M. Alsante, Eds. 2003, pp. 75-85. Waterman, K.C.; Adami, R.C.; Alsante, K.M.; Antipas, A.S.; Arenson, D.R.; Carrier, R.; Hong, J.; Landis, M.S.; Lombardo, F.; Shah, J.C.; Shalaev, E.Y.; Smith, S.W.; Wang, H. Hydrolysis in pharmaceutical formulations. Pharm. Dev. Tech. 7 (2002) 113-146. Waterman, K.C.; Adami, R.C.; Alsante, K.M.; Hong, J.; Landis, M.S.; Lombardo, F.; Roberts, C.J. Stabilization of pharmaceuticals to oxidative degradation. Pharm. Dev. Tech. 7 (2002) 1-32. 40