Simulating the lower intestine based on in vivo data

Transcription

1 HELLENIC REPUBLIC National & Kapodistrian University of Athens SCHOOL OF HEALTH SCIENCES FACULTY OF PHARMACY Dpt of Pharmaceutical Technology Simulating the lower intestine based on in vivo data Christos Reppas AAPS 214 Annual Meeting, San Diego, CA Symposium #32 Exploiting vivo studies to improve predictive in vitro models for oral drug delivery: are leveraging this new body of knowledge? November 4, 214

2 Outline Overview of the (aqueous) environment in the lumen of lower intestine and its impact on drug solubility Translating the environment in the lower intestinal lumen into in vitro and in silico models

3 Ascending Colon, Cecum, Terminal Ileum in the fasted state

4 Ascending Colon, Cecum, Terminal Ileum in the fed state

5 Ascending lumen / healthy adults / white-fasted, grey-fed Volume of contents (ml) fasted fed % Aqueous fraction of contents 1 n=12 n= fasted fed * (similar to Schiller et al. 25) ph * n=12 Buffer Capacity (mmol/l/δph) n=12 n=8 * n=12 * n=8 5 fasted Diakidou et al. Pharm Res. 29 fed fasted fed Measured with NaOH Measured with HCL

6 Ascending lumen / healthy adults / white-fasted, grey-fed Short Chain Fatty Acids Short Chain Fatty Acids Concentration (mm) * * * AA PA IBA BA IVA VA CA Acetic Acid Propionic Acid IsoButyric Acid Butyric Acid IsoValeric Acid Valeric Acid Caprionic Acid AA PA IBA BA IVA VA CA - AA and BA levels are higher in the fed state. IBA levels are lower - Concentrations are lower than those measured previously at autopsies (about 4 hours after death) Diakidou et al. Pharm Res. 29

7 Ascending lumen / healthy adults / white-fasted, grey-fed Surface Tension (mn/m) * Osmolarity (mosmol/kg) * 3 fasted fed fasted fed Protein Content (mg/ml) fasted Similar to previously measured levels fed Carbohydrate Content (mg/ml) fasted fed Diakidou et al. Pharm Res. 29

8 Ascending lumen / healthy adults / white-fasted, grey-fed Colloidal species forming agents: Bile acids.8 Bile Acid Concentration (mm) * * C CDC LC DC UDC GC TC Cholic Acid Chenodeoxycholic Acid Lithocholic Acid Deoxycholic acid Ursodeoxycholic acid Glychocholic Acid Taurocholic Acid. C LC DC UDC GC TC CDC - Higher levels in the fed state - Minimal presence of conjugated bile acids - In the fasted state most subjects had higher levels of secondary bile acids - In the fed state most subjects had higher levels of primary bile acids (fresh material, inhibition of breakdown in the fed state) Diakidou et al. Pharm Res. 29

9 Ascending lumen / healthy adults / white-fasted, grey-fed Colloidal species forming agents: Glycerides, fatty acids, cholesterol (from cellular debris, microorganisms, secretions in the lumen) 6 5 Concentration (mm) PA LA OA PC CHO Palmitic Acid Linoleic Acid Oleic Acid Phosphatidylcholine Cholesterol 1 PA LA OA PC CHO (Cholesterol: net absorption from the proximal SI is ~56%, is eliminated in feces, colonic volumes are small)

10 Colloidal structures are present in the contents of upper as well as lower intestine, regardless of dosing conditions End of duodenum / Fasted state A Ascending colon / Fasted state B * C D Α. Open bilayers (black arrows) and vesicles (white arrows) B. Open bilayer (white arrow) and vesicles (black arrow) C. Vesicles Black dots: Μicelles Α. Vesicles (arrows) adhere to plate like structures (*) B. Open bilayers (arrows) C. Vesicles D. Vesicles and discoidal vesicle Cryogenic transmission electron (Cryo-TEM) micrographs Muellerz et al. JPP 213 Muellerz et al. JPP in press

11 Drug solubility in the fluid of ascending colon vs. solubility in the upper GI contents in fasted state (μg/ml, 37 o C) No brackets: Mean using a pooled sample Brackets: Mean or range of means created from data in individual samples collected at a single time point or at several time points post water administration, respectively Ketoconazole (pka 6.5) Danazol (non-ionizable) Felodipine (non-ionizable) HGF fasted 925 [1.6].41 HIF fasted 29 [ ] [2.] 4.9 [13-18] HCF fasted [51] [7.7] [11.6] 14 Vertzoni et al. Pharm. Res. 21a In the fasted state, solubility in contents of ascending colon is not much different than that in upper intestinal lumen

12 Drug solubility in the fluid of ascending colon vs. solubility in the upper GI contents in fed state (μg/ml, 37 o C) No brackets: Mean using a pooled sample Brackets: Mean or range of means created from data in individual samples collected at a single time point or at several time points post water administration, respectively Ketoconazole (pka 6.5) Danazol (non-ionizable) Felodipine (non-ionizable) HGF fed not available HIF fed [437-15] [6-37] HCF fed [82] [6.1] [12] Vertzoni et al. Pharm. Res. 21a In the fed state, solubility in contents of ascending colon is lower than that in upper GI lumen

13 Medium Simulating the Environment in the Ascending Colon FaSSCoF FeSSCoF ph Tris/maleates Buffer Capacity 1 (mmol/l/δph) 16/26 15/14 Osmolality (mosm/kg) Surface tension (mn/m) Albumin 3 (mg/ml) 3 3 Glucose (mg/ml) 14 Total bile acids 4 (μm) 15 6 Palmitic acid (μm) 1 2 Phosphatidylcholine (μm) By titrating with HCl / by titrating with NaOH 2 Adjusted with NaCl (34mM) 3 Bovine serum albumin 4 Bile salt extract Vertzoni et al. Pharm. Res. 21a

14 Ketoconazole Solubility (μg/ml) Felodipine Solubility (μg/ml) Danazol Solubility (μg/ml) buffer ph 7.8 HCF fasted FaSSCoF buffer ph 6. HCF fed FeSSCoF Solubility of non-ionizable compounds in the lumen of the ascending colon is well predicted by data in FaSSCoF and FeSSCoF buffer ph 7.8 HCF fasted FaSSCoF buffer ph 6. FeSSCoF HCF fed - It is more difficult for ionized APIs (?) buffer ph 7.8 HCF fasted FaSSCoF buffer ph 6. HCF fed FeSSCoF Vertzoni et al. Pharm. Res. 21a Reppas and Vertzoni JPP 212

15 Asacol 4 mg Initiation of dissolution of coating polymers may be delayed in bicarbonate buffers Fadda et al. IJP 56-6 (29) also, in: Garbacz et al. EJPS 51: (214) Are bicarbonates important in the fed state? / Correlation with in vivo data?

16 Effects of ulcerative colitis on the pchem environment in the fasted ascending colon - ph is lower than in healthy adults - Buffer capacity, osmolality, and soluble protein are higher than in healthy adults - Treatment with prednisolone increases volume of intracolonic contents in the fasted state in patients in relapse [37(14)ml] compared with patients untreated with prednisolone [19(6)ml] and compared with healthy adults [22(8)ml] Vertzoni et al. Pharm Res. 21b

17 Outline Overview of the (aqueous) environment in the lumen of lower intestine and its impact on drug solubility Translating the environment in the lower intestinal lumen into in vitro and in silico models When and why? How far should we go and how well are we doing?

18 When and why in vitro simulation of the environment in the lumen of lower intestine is of interest Extended release products Release / Dissolution / Bacterial degradation Colon targeting products Release / Dissolution / Bacterial degradation Immediate release or enteric coated products of highly dosed APIs, i.e. APIs which belong to Development Classification System (DCS) Class IIb or IV (Butler and Dressman, 21) Locally acting APIs, e.g. mesalazine prodrugs Dissolution / Bacterial degradation Bacterial degradation

19 In vitro simulation of the environment in the lumen of lower intestine: How far should we go and how well are we doing? Extended release products Depends on technology (and size?) of the product as well as API characteristics An easy case: Osmotic pump / API without solubility, permeability, stability issues e.g. Salbutamol (DCS/BCS Class I API) in a 5mm osmotic pump Fotaki et al. EJPB 29

20 Amount absorbed (mg) Amount absorbed (mg) % released Plasma Concentration (ng/ml) Neither medium composition nor hydrodynamics were important for the release profile of salbutamol from the osmotic pump formulation USP II Time (h) SGF FaSSIF SCoF A Time (h) USP III Time (h) USP IV Time (h)

21 In vitro simulation of the environment in the lumen of lower intestine: How far should we go and how well are we doing? Extended release products Depends on technology (and size?) of the product as well as the API characteristics Colon targeting products Published data are limited DCS Class IIb/IV APIs Published data are limited Mezalazine prodrugs Published data are limited

22 Concentration (μg/ml) Concentration (μg/ml) Sodium Salt of L-87,81 (NaA) DCS Class IIb pka of the acid: 7.3 LogP of the acid: 2.9 In vitro dissolution data time (min) time (min) Mean ± SD (n = 3) concentration (μg/ml) during the dissolution of 8 mg NaA granules (4 mg dose) in HCl ph 1.6 ( ), in blank FaSSGF-V2 ( ), and in FaSSGF-V2 ( ). Horizontal lines indicate previously measured solubility of HA in blank FaSSGF-V2 (dashed) and in FaSSGF-V2 (continuous). Mean ± SD (n = 3) concentration (μg/ml) during the dissolution of 8mg NaA granules (4 mg dose) in maleates buffer ph 6.5 ( ), in blank FaSSIF-V2 ( ), and in FaSSIF-V2 ( ). Horizontal lines indicate previously measured solubility of HA in blank FaSSIF-V2 (dashed), and in FaSSIF-V2 (continuous). Petrakis et al. JPP in press

23 PBPK model for the description of oral PKs of NaA Petrakis et al. JPP in press

24 Continuous grey lines: Continuous black line: Dashed black line: Actual individual plasma levels in healthy adults Predicted plasma levels based on dissolution kinetics in upper small intestine Predicted plasma levels assuming reduced solubilization and/or dissolution rates 1.5h after administration Petrakis et al. JPP in press

25 Bacterial degradation of olsalazine in the large intestine Reaction mediated by anaerobic bacteria in the large intestine Wadworth and Fitton, 1991; Sousa et al. 28

26 Evaluation of bacterial degradation of therapeutic agents in the ascending colon? Typically, evaluation is based on data collected in fecal slurry prepared from human feces using water, buffers or normal saline with dilution factors varying from 2 to 1 We evaluated two types of media: - Feces, homogenized with 3.8 parts normal saline - Precipitates, obtained after ultracentrifugations of individual samples from the lumen of the ascending colon, homogenized with volumes of normal saline equal to the supernatants after ultracentrifugation

27 % olsalazine % olsalazine Evaluation of bacterial degradation of olsalazine in the ascending colon Individual fecal materials [n=6 (3 adults, 2 fecal materials from each adult)] Individual colonic contents prepared from contents of ascending colon collected in the fasted state (n=7) A1 A2 B1 B2 C1 C #5 #6 #7 #9 #1 #11 # t (min) t (min) Degradation rate constant in the material from the contents of the ascending colon collected in the fasted state is highly variable significantly lower than that observed in fecal material Vertzoni et al. IJP 211

28 % olsalazine % olsalazine Evaluation of bacterial degradation of olsalazine in the ascending colon Individual fecal materials [n=6 (3 adults, 2 fecal materials from each adult)] Individual colonic contents prepared from contents of ascending colon collected in the fed state (n=7) A1 A2 B1 B2 C1 C #5 #6 #7 #9 #1 #11 # t (min) t (min) Practically stable in the material from the contents of the ascending colon collected in the fed state The slower degradation in the fed state relates with the arrival of fermentable substrates from the small intestine, i.e. a competitive inhibition mechanism operates. Vertzoni et al. IJP 211

29 In vitro simulation of the environment in the lumen of lower intestine: How far should we go and how well are we doing? Extended release products Depends on technological and perhaps physical characteristics of the product and API characteristics works in progress Colon targeting products Published data are limited works in progress DCS Class IIb/IV APIs Published data are limited works in progress Mezalazine prodrugs Published data are limited works in progress Could food effects be of interest? 29

30 Back up slides

31 Pchem characteristics along the intestinal lumen Fed state Upper SI Fed State Ascending Colon (4) ph (1) 6. [ ] Buffer capacity (mmol/l/ph) Osmolality (mosm/kg) Bile salts/acids (mm) SCFAs (mm) 18-3 (2) 4 [ ] ~4 (5) 266 [-35] 8-2 (salts) (1).3 [.9-.85] (perhaps traces) (3) 39 [23-18] 1. Sjoegren et al Fadda et al Schmitt et al Diakidou et al Kalantzi et al. 25

32 Pchem characteristics along the intestinal lumen Fasted State Upper SI Fasted State Ascending Colon (5) ph (1) 7.8 [ ] Buffer capacity (mmol/l/ph) Osmolality (mosm/kg) Bile salts/acids (mm) SCFAs (mm) 4-13 (3) 2 [7.5-35] (3) 33 [-291] 2-1 (salts) (1).1 [.1-.46] (perhaps traces) (4) 29 [6.4-54] 1. Sjoegren et al Fadda et al Banwell et al Schmitt et al Diakidou et al. 29

33 If video does not play: Control panel Display Settings Advanced Troubleshoot None Full