Current and Emerging Transporter Regulatory Themes in Drug Development: Relevance to Understanding PK/PD, DDIs, and Toxicity

Transcription

1 Current and Emerging Transporter Regulatory Themes in Drug Development: Relevance to Understanding PK/PD, DDIs, and Toxicity Maciej Zamek-Gliszczynski, Ph.D.

2 1940 s Probenecid & anion secretion 1950 s Dubin-Johnson Syndrome P-gp in MDR cells MRP OCT OATP P-gp & ivermectin [CNS] OAT BCRP MATEs FDA DDI Guidance ITC White Paper EMA Draft Guidance EMA &FDA Guidances &ITC2 ITC2 White Papers MDR1 (and MRP) inhibitors to reverse MDR Landmarks in Drug Transporters: Why 2013 is an Exciting Time

3 Giacomini et al., Nature Rev Drug Discov 9: , Zamek-Gliszczynski et al., Clin Pharmacol Ther 92: , ITC2 Whitepapers (Clin Pharmacol Ther, July 2013, 1. Emerging transporters of clinical importance 2. Transport IVIVE/PK best practices 3. Transporter pharmacogenomics 4. Transporters in CNS distribution 5. Transport in vitro methods 6. Transporters in drug development 7. Intracellular concentrations in efflux interactions

4 (Draft released in 2010)

5 How Transport Differs from Metabolism: Fexofenadine Gut Lumen Blood OATP1B1 OATP1B3 Bile OATP MRP3 OATP2B1 MRP2 P-gp MRP3? Attenuation of intestinal absorption, brain and tumor penetration by P-gp is a single-step process occurring at a single membrane simple enzyme kinetics Vectorial transport through intestine, liver, and kidney is a two-step process Opposing transport on same membrane: ex. OATP/MRP3 Transport mechanisms may differ between tissues Blood Brain P-gp BBB OAT3 Blood? Urine Matsushima et al., Mol Pharmacol 73: , Tahara et al., Drug Metab Dispos 34: , Tahara et al., Drug Metab Dispos 33: , Shimizu et al., Drug Metab Dispos 33: , 2005.

6 DISCOVERY DEVELOPMENT POST MARKETING Major transport issues --Low CNS exposure (P-gp) --Low oral F (P-gp ± BCRP) --OATP1B1 inhibition (DDI) -- Rapid CL,excretory Transporter Drug Delivery --PEPT1 prodrugs --OATP hepatic targeting Controversial & Inconsistent --BSEP inhibition (tox) Bulk of transporter studies that drive clinical DDI evaluation. Inhibition studies for OATP1B1 & 1B3, OCT1 & 2, MATE1/2-K, OAT1 & 3, P-gp, BCRP (retrospective BSEP & MRP2) DDI perpetrator studies by I/Ki Substrate studies for P-gp and BCRP; OATP1B1 & 1B3 when >25% CL,biliary OAT1/3, OCT2/MATE1/2-K when >25% CL,renal secretory DDI victim studies by substrate Post-marketing commitments for gaps identified by regulators or for observed DDIs. Typically clinical studies to clarify lower-risk DDIs. Drive labeling revisions.

7 EMA (2012) EMA (2012) ITC(2010)/FDA(2012) ITC2(prospective) ITC2(retrospective) Zamek-Gliszczynski et al., Clin Pharmacol Ther 92: , 2012.

8 Absorption Zamek-Gliszczynski et al., Clin Pharmacol Ther 92: , 2012.

9 % F (rat or mouse) Bioavailability and Permeability: Strong P-gp and Bcrp Substrates Compounds within a chemical series of strong P-gp and Bcrp substrates Papp (LLC-PK1 or MDCK) 10-6 cm/s IVIVE of efflux transport in absorption is confounded by permeability As permeability increases, in vivo attenuation of intestinal absorption decreases Efflux-limited absorption requires low passive permeability Xiaoyan Chu, AAPS Drug Transport Workshop: 2011.

10 P-gp-Limited Intestinal Absorption 3X 5X 7X 6X 9X 12X 11X Preclinical-to-clinical translation of P-gp-limited absorption was observed (formulation differences can be a confounding factor) Extensive inhibition of intestinal P-gp (approx. P-gp knockout effect) can be observed in vivo in animals and also in the clinic ( note: I 1 and I 2 approach to systemic vs. intestinal P-gp inhibition) Breedveld et al., Trend Pharmacol Sci 27: 17-24, 2006.

11 BCRP-Limited Absorption of Topotecan 6X Mouse Human Preclinical-to-clinical translation of BCRP-limited absorption was observed (formulation differences can be a confounding factor) Extensive inhibition of intestinal BCRP can be observed in vivo in animals and also in the clinic ( note: [I] 1 and [I] 2 approach to systemic vs. intestinal BCRP inhibition) 2-3X Breedveld et al., Trend Pharmacol Sci 27: 17-24, 2006.

12 CNS Distribution Zamek-Gliszczynski et al., Clin Pharmacol Ther 91: in press, 2012.

13 Functional Importance of P-gp at the BBB: Why No Major Clinical DDIs? Ivermectin LD X Similar examples: Loperamide 2 nd generation antihistamines Schinkel et al., Cell 77: , 1994.

14 P-gp Inhibition in Clinical Studies PET Tracer P-gp Inhibitor Dose Fold Increase in Distribution Volume or Tracer Uptake P-gp Inhibtion a [ 11 C]-verapamil Tariquidar 8 mg/kg b % [ 11 C]-verapamil Tariquidar 6 mg/kg b % [ 11 C]-verapamil Tariquidar 4 mg/kg b % [ 11 C]-verapamil Tariquidar 3 mg/kg b % [ 11 C]-verapamil Tariquidar 2 mg/kg % [ 11 C]-verapamil Tariquidar 2 mg/kg % [ 11 C]-N-des-Loperamide Tariquidar 2 mg/kg % [ 11 C]-verapamil Cyclosporin A 2 mg/kg/hr % [ 11 C]-verapamil Cyclosporin A 2 mg/kg/hr 1.9 c 47% [ 11 C]-loperamide Cyclosporin A 10 mg/kg 2 50% [ 11 C]-loperamide Quinidine 600 mg 1 0%

15 Why Clinical Modulation of Transport at the Blood-Brain Barrier is Unlikely: The ITC Evidence-Based Position Clin Pharmacol Ther 93: in press: July Altered CNS distribution of efflux transport substrates has been commonly observed in animal models due to BBB efflux inhibition, saturation, or induction. In contrast, overall clinical evidence indicates that modulation of BBB efflux has not translated to humans. Why not?

16 Why No Clinically-Relevant BBB DDIs? Loperamide brain-to-serum ratio ~50% P-gp inhibition elicits a 2-fold increase in brain Kp not half of max effect In vitro potency and C max of clinically-tested P-gp inhibitors Inhibitor Inhibitor K i or IC 50 K i or Ki f u IC 50 C max f u Total C max Unbound Total (µm) (µm) (µm) plasma C max (µm) /K i C max max /K /K i i cyclosporin A cyclosporin A GF (Elacridar) GF (Elacridar) < < < ketoconazole ketoconazole LY (Zosuquidar) LY (Zosuquidar) * * OC (ONT-093) OC (ONT-093) na 8.9 na na 280 PSC833 (Valspodar) PSC833 (Valspodar) quinidine quinidine quinine quinine > 2.4 > < 1124 < < rifampin rifampin ritonavir ritonavir R (Laniquidar) R (Laniquidar) ~0.085 ~0.085 < 0.02 < ~ < ~ R-verapamil R-verapamil verapamil verapamil XR9576 (Tariquidar) XR9576 (Tariquidar) na > 0.31 na > > na > 19 Fold Change in CNS Distribution f e I/K i = (gene knockout) I ~ K i (clinical inhibition) Clinical Iu/Ki ratio 1 is too low to elicit increased CNS distribution comparable to KO mice Since Ki ~ Km, P-gp substrate concentrations are insufficient to saturate efflux Unlike in the gut and liver, BBB P-gp is not inducible in humans Clin Pharmacol Ther 93: in press, July, 2013.

17 SS brain/plasma ratio was ~3.5-fold higher in P-gp KO mice ~30% higher in Bcrp KO mice ~40-fold higher in P-gp/Bcrp KO mice Fold Change in Exposure Efflux-Limited Exposure at the BBB f e Polli et al., Drug Metab Dispos 37: , f e The observed increase in P-gp/Bcrp null mice is not unexpected synergism or some far-fetched biochemical interaction, it is simply the result of adding the contribution (Fe) of P-gp and Bcrp together. This phenomenon is not relevant to inhibition of both efflux pumps in the clinical setting. Consider co-administration of lapatinib with both cyclosporine and efavirenz in humans. The resulting clinical DDI would be a 1.9-fold increase in CNS distribution. =0.968 Zamek-Gliszczynski et al., Drug Metab Dispos 37:

18 Renal Clearance Bile CL, renal > fu * GFR Urine Metabolism Clearance Pathways For Top 200 Drugs (2004) 2009 Pfizer analysis of 391 compounds with human clearance data (internal + literature): 31% predominant CLr ( > 50% CLtotal) Williams et al., Drug Metab Dispos 32: , Varma et al., J Med Chem 52: , 2009 Zamek-Gliszczynski et al., Clin Pharmacol Ther 91: in press, 2012.

19 Example 1: The Old Approach Prescribing Information: 2011 Prescribing Information Alimta (pemetrexed) Prescribing Information

20 Uptake (ng pemetrexed/mg protein/min) Uptake (ng pemetrexed/mg protein/min) Example 1: Secretion by OAT3/4 HEK OAT3 HEK VC Pemetrexed concentration (µm) Selection of NSAIDs from US and EU oncology cases (>400K patients) Inhibitor OAT3 [Cmax,u] (µm) IC50 (µm) [Iu]/IC Inhibitor OAT Pemetrexed concentration (µm) [Cmax,u] (µm) IC50 (µm) HEK OAT4 HEK VC [Iu]/IC50 Probenecid Ibuprofen Naproxen Diclofenac Celecoxib Probenecid Ibuprofen Naproxen Diclofenac Celecoxib Courtesy J. Bacon and K. Hillgren, 2010.

21 Example 2: Contemporary Approach 50/50 GFR/ATS (OAT1/4) Identify secretory mechanism in vitro Follow-up clinical DDI study if victim risk identified Approx. equal contribution of GFR and ATS to CLr. The limit of decrease in CLr by ATS inhibition (I/Ki ) is GFR,u. LY mg + Inhibition of ATS would be expected LY to reduce Probenecid CLr 1000mg < 50%. 80mg (n=24) (n=23) Observed decrease in renal clearance with high-dose probenecid Geo Mean (Geo CV%) (OAT1/4 inhibition) was 30%. LY Cumulative amount (mg) 25.4 (50.6) LY (41.7) 80mg + LY Control Probenecid 1000mg LY mg (n=24) (n=23) Fraction Excreted (50.6) (41.7) Geo Mean (Geo CV%) LY LY CLr (L/h) Cumulative amount (mg) 12.3 (17.6) 25.4 (50.6) 8.55 (19.2) 27.5 (41.7) Clr/GFR,u ~2 ~1.3 LY Fraction Excreted (50.6) (41.7) Courtesy Jennifer Witcher, 2011.

22 OCT1: Metformin hepatic distribution/pd Hepatic Transport EMA OATP1B1/1B3: Largest transport DDIs Pharmacogenetics Statin DDIs BSEP: Follow up in cholestasis BCRP, P-gp, MRP2: Parent/metabolite biliary excretion MRP2 inhibition: conj. hyperbilirubinemia MATE1: Metformin distribution/pd ITC(2010)/FDA(2012) ITC2(prospective) ITC2(retrospective)

23 HIGH DDI POTENTIAL Giacomini et al., Nat Rev Drug Discov 9: , 2010.

24 Biliary Clearance Bile Urine Metabolism Clearance Pathways For Top 200 Drugs (2004) ~5% of drugs are cleared by biliary excretion But can be very important for metabolite disposition Williams et al., Drug Metab Dispos 32: , Varma et al., J Med Chem 52: , 2009

25 Co-administration of MMF with CsA Reduced MPA Exposure in Patients Pou et al., Ther Drug Monit 23: 35-38, 2001.

26 Clinical DDI Reproduced in Mrp2-Deficient Rats Plasma Bile MPA-G MPA 40X 2X MPA-G MPA-G 25% X Kobayashi et al., J Pharmacol Exp Ther 309: , 2004.

27 Irinotecan: SN-38 Glucuronide Biliary Excretion and Diarrhea Vehicle Probenecid SN-38 Glucuronide Biliary Excretion 80% in Mrp2-Deficient Rats Horikawa et al., Pharm Res 19: , Chu et al., J Pharmacol Exp Ther 281: , 1997.

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29 Transporter DDI? Decreased Ethinyl Estradiol (EE) Sulfate Exposure EE-Sulfate (pg/ml) EE + placebo EE + drug Time (hr)

30 Transporter DDI? Ethinyl Estradiol (EE) Sulfate EE EE EE blood EE-S EE-G liver intestinal lumen bile EE-S EE-G EE intestinal epithelium EE Ethinylestradiol EE-S Sulfate conjugate EE-G Glucuronide conjugate Abcg2 (Bcrp) Abcc2 (Mrp2) Abcc3 (Mrp3)

31 EE Metabolites: Transporter DDI EES Concentration (pg/ml) IV AUC 3X PO AUC 9X WT IV TR- IV WT PO TR- PO EEG Concentration (pg/ml) IV AUC 20X PO AUC 100X WT IV TR- IV WT PO TR- PO Time (hr) Mrp2-deficient rats: Comparable EE PK (Cl, V, t 1/2, F, Cmax, Tmax) EES exposure was decreased due to increased EES desulfation secondary to impaired excretion EEG exposure was increased due to impaired GI luminal and biliary excretion and increased compensatory secretion into blood Findings supported by perfusions and KO mice EE Concentration (pg/ml) Time (hr) Time (hr) WT IV TR- IV WT PO TR- PO Zamek-Gliszczynski et al., Drug Metab Dispos 39: , 2011.

32 BSEP BSEP Inhibition and DILI transports bile acids from hepatocytes into bile does NOT transport drugs in vivo (few examples of very low in vitro transport): DILI not a DDI concern inhibition by drugs is hypothesized to result in elevated hepatic concentrations of bile acids Chronic BSEP inhibition can elicit cholestasis, which may lead to DILI: ~30% of DILI cases are attributed to cholestasis Rational Strategy BSEP inhibition without in vivo cholestasis does not predict DILI Prospective screening to eliminate BSEP inhibitors is unwarranted Potency of BSEP inhibition in relation to clinical and toxicology exposures may be helpful in implementing safety monitoring. Observations of cholestasis should be followed up to understand BSEP inhibition as a potential mechanism.

33 Metformin + Cimetidine DDI: More than Inhibition of Renal Secretion? Liver Bile MATE1? Bile PD? Blood Kidney Urine Cimetidine OCT1? X OCT2 MATE1 MATE2/2-K [Metformin]? [Metformin] CL Somogyi et al., Br J Clin Pharmacol 23: , 1987.

34 Metformin + Cimetidine DDI Cimetidine inhibits the renal tubular secretion of metformin in man, resulting in higher circulating concentrations. Because of its propensity for causing dose and concentration-dependent adverse effects, the dose of metformin should be reduced when cimetidine is co-prescribed. ABOVE CONCLUSION SEEMS REASONABLE, EXCEPT: Blood lactate to pyruvate ratios were 64% increased by metformin or metformin+cimetidine vs. cimetidine alone (p = 0.003). However, overall the lactate to pyruvate ratio was comparable between metformin alone and metformin+cimetidine (p = 0.4) Somogyi et al., Br J Clin Pharmacol 23: , 1987.

35 Overlap in OCT/MATE Inhibitors Inhibitors: OCT1 (n = 46) OCT2 (n = 66) MATE1 (n = 17) MATE2-K (n = 23) Inhibitor Drug Overlap: OCT1/OCT2 (72%) MATE1/MATE2-K (74%) OCT/MATE (70%) UCSF-FDA Transportal, March Wittwer et al., J Med Chem, 56: , Overlap in Renal/Hepatic Potency Renal Hepatic Renal Renal/Hepatic (IC 50 or K i, mm) OCT2 OCT1 MATE2-K MATE1 Cimetidine Pyrimethamine UCSF-FDA Transportal, March Ito et al., J Pharmacol Exp Ther 333: , 2010.

36 Do Changes in Metformin Systemic Exposure Translate Directly to Hepatic Exposure and PD? Liver Blood Kidney Bile X OCT/MATE Inhibitor (ex. Cimetidine) MATE1 X OCT1 X OCT2 Bile PD??? [Metformin]??? [Metformin] CL Vd??? Urine X MATE1 MATE2/2-K X

37 Similarity of Rodent/Human Metformin PK Similar oral absorption (F = 50-60%) Renal clearance: 20% GFR + 80% secretion in both mice and humans Tubular secretion: OCT2&MATE1/2/2-K in humans; Oct1/2&Mate1 in mice Hepatic distribution is active (OCT1&MATE1 in humans; Oct1&Mate1 in mice) Oct1/2- and Mate1-KO mice represent worst-case OCT/MATE inhibition scenario Mate1 function is not altered by Oct1/2 knockout Rodent Liver Mate1 Bile Bile Human MATE1 Oct1 Blood OCT1 Oct1 Oct2 Kidney OCT2 Mate1 MATE1 MATE2/2-K Urine

38 What Happens to Metformin PK, Distribution and PD Following Ablation of Oct1/2? Liver Bile Mate1 Bile PD? [Metformin]? Blood X Oct1 [Metformin] Kidney X Oct1 X Oct2 [Metformin]? Mate1 Urine

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40 Metformin Pharmacokinetics 5 mg/kg IV 10 mg/kg PO CL 4.5X; Qr GFR Vd 3.5X F wild type Oct1/2 KO AUC 2.9X Cmax 2.4X

41 Metformin Distribution Liver Kp 4.2X AUC, systemic 2.9X AUC, liver 40% Liver Kp 4.2X wild type Oct1/2 KO Kidney Kp 2.5X Kidney Kp 2.5X AUC, systemic 2.9X AUC, kidney

42 Metformin Pharmacodynamics 10 mg/kg metformin PO (lowest dose level) 300 mg/kg metformin PO (highest dose level) Inefficacious Dose Complete hyperglycemic control ED 50 Emax wild type Oct1/2 KO wild type + metformin Oct1/2 KO + metformin EAUC 50 3X Emax

43 Metformin PK, Distribution and PD Following Ablation of Oct1/2 Liver Bile Mate1 Bile PD [Metformin] Blood X Oct1 [Metformin] Kidney X Oct1 X Oct2 [Metformin] Mate1 Urine

44 What Happens to Metformin PK, Distribution and PD Following Ablation of Mate1? Liver Bile X Mate1 Bile PD? [Metformin]? Blood Oct1 [Metformin]??? Oct1 Oct2 Kidney [Metformin]? X Mate1 Urine

45 Metformin PK and Distribution wild type Mate1 KO Kidney Kp 2X Liver Kp 10X 3.2 Liver CL 4X AUC 4X Blood Oct1-70 mv ~10X [Metformin] u Kidney Urine Mate1 X H + Oct2 Bile X Mate1 Oct1 C, kidney 4X Bile [Metformin] C, liver 20X [Metformin]?? ~10X 3.2 [Metformin] Tsuda et al., Mol Pharmacol 75: , PD

46 Metformin PK, Distribution and PD Following Ablation of Mate1 Liver Bile X Mate1 Bile PD [Metformin] Blood Oct1 [Metformin] Oct1 Oct2 Kidney [Metformin] X Mate1 Urine

47 Changes in Metformin Systemic Exposure Do NOT Translate to Hepatic Exposure and PD Liver Blood Kidney Urine Bile X OCT/MATE Inhibitor During OCT/MATE Inhibition MATE1 X X OCT1 X OCT2 MATE1 MATE2/2-K X Bile PD?????[Metformin] [Metformin] CL??Vd??[Metformin]

48 EMA (2012) EMA (2012) ITC(2010)/FDA(2012) ITC2(prospective) ITC2(retrospective) Zamek-Gliszczynski et al., Clin Pharmacol Ther 92: , 2012.