Update on DDI Guidance of the FDA -In Vitro

Xinning Yang, Ph.D.Policy lead

Guidance & Policy Team (GPT)Office of Clinical Pharmacology (OCP)Office of Translational Sciences (OTS)

Center for Drug Evaluation and Research (CDER), FDA

www.fda.gov 2

Outline

• DDI with CYP enzymes

– NME as a substrate

– NME as an inhibitor

– NME as an inducer

• DDI with transporters – NME as a substrate

– NME as an inhibitor

• Case example

www.fda.gov 3

In Vitro → In Vivo

• In vitro guidance –

– Define potential for drug interactions of an investigational drug

Metabolic enzymes – CYP isoformsTransporters

– Help determine what in vivo interaction studies are needed

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In Vitro evaluation- CYP enzymes

CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6*, 3A4/5

• Evaluate an NME as a substrate - routine

– If 25% clearance by an enzyme (in vitro phenotyping; human PK), need further clinical evaluation, i.e., evaluate effect of inhibitor and inducer of the enzyme on the PK of the NME

• Evaluate an NME as a perpetrator (inhibitor and/or inducer) - routine

– Apply equations with cut-off values to determine whether in vivo studies are needed

*CYP2D6 is not inducible by drugs, though its activity is increased in pregnancy women.

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Determine whether drug is an inhibitor of CYP enzymes- Basic model

If the R value is above the cut-off, further evaluation of the DDI potential is needed.

- Reversible inhibitionR1 = 1 + (Imax,u / Ki) ≥ 1.02 Imax: steady-state Cmax of the inhibitor in plasma;

‘u’ means unbound (free) drug (Imax,u = Imax x fu,p);Ki is unbound inhibition constant determined in vitro

R1,gut = 1 + (Igut / Ki) ≥ 11 For CYP3A, R 1,gut should also be calculated; Igut: Dose/250mL (a rough estimate of intestinal luminal

concentration of inhibitor.

- Time-dependent inhibition (TDI)R2 = (kobs + kdeg) / kdeg ≥ 1.25

Where kobs = (kinact × 50 × Imax,u) / (KI + 50 × Imax,u)

https://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/UCM581965.pdf

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Updates from 2012 FDA Guidance

• Inhibitor concentration for R1 (reversible) and R2 (TDI):

total (unbound + plasma protein bound) → unbound (same as EMA DDI guideline)

• Threshold for R1: Imax/Ki ≥ 0.1 → Imax,u/Ki ≥ 0.02 (same as EMA)

Imax,u/Ki ≥ 0.02 is equal to R1 ≥ 1.02

• TDI: Multiple a factor of 50 for Imax,u (same as EMA)

• TDI: no need to calculate ratio using Igut. (different from EMA)

• Rationale for the change?

Our recent analysis (see Table 3 in the reference) suggests these criteria performed

similarly in predicting positive DDIs mediated by CYP3A inhibition, e.g.

sensitivity, specificity, positive predictive value, negative predictive value, fold error

Viera ML, et al. Clin Pharmacol Ther 95(2):189-198 (2014).

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Determine if NME is an Inducer of CYP enzymes

– Evaluate CYP1A2, CYP2B6, and CYP3A4/5 initially.

– If no induction of CYP3A4/5 is observed, evaluating the induction potential of CYP2C enzymes is not necessary because both CYP3A4/5 and CYP2C enzymes are induced via activation of the pregnane X receptor (PXR).

– If the drug induces CYP3A4/5, evaluate the drug’s potential to induce CYP2C enzymes.

– P-gp and certain Phase II enzymes (e.g., UGT) may be co-induced with CYP3A.

Modified from Lei Zhang

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Evaluate Induction Potential• Fold-change method

– Examine the fold-change in CYP enzyme mRNA levels when incubated with the investigational drug

– Use a cutoff determined from known positive and negative controls to calibrate the system. (e.g., a ≥ 2-fold increase in mRNA and a response ≥ 20% of the response of the positive control)

• Correlation method – Predicted positive criteria defined by known positive (e.g., known inducers of the

same enzyme) and negative controls (e.g., relative induction score (RIS))

• Basic kinetic model R3 = 1 / [1 + (d × Emax × 10 × Imax,u) / (EC50 + 10 × Imax,u)] ≤ 0.8(compared to 2012 guidance, Imax → 10 x Imax,u;

the cut-off changed from 0.9 → 0.8)

• Compared to the 2012 guidance, correlation method was mentioned and activity measurement was added back (besides mRNA).

Modified from Lei Zhang

Yoshida K, et al. J Pharm Sci. 2017 Sep;106(9):2209-2213

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Determine if NME is an Inhibitor or Inducer of Metabolizing Enzymes

• Mechanistic, static

• Mechanistic, dynamic (e.g., PBPK)

Determine in vitro parameters

Basic Model

CYP inhibitor(CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, 3A)

CYP inducer(CYP1A2, 2B6, 2C8, 2C9, 2C19, 3A)

In vivo DDI studyFrom Lei Zhang

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Transporter-MediatedDrug Interactions

• Determine if NME is a substrate of transporters

• Determine if NME is an inhibitor of transporters

* Current knowledge about transporter induction is quite limited; consider evaluating P-gp induction if CYP3A induction is observed.

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Investigational Drug as a Substrate of Transporters

• P-gp and BCRP (efflux transporters, in intestine, liver, kidney, blood-brain barrier, etc.)Intestinal absorption is likely to be a major cause of the variability in drug PK and response.The drug needs be transported into certain tissues to exert a pharmacological effect (e.g.,

brain)

• OATP1B1 and OATP1B3 (hepatic uptake transporters)Hepatic/biliary elimination is significantPhysiological properties (e.g., anion at physiological pH, high hepatic concentrations

relative to other tissues, low passive permeability)

• OAT1, OAT3, OCT2, MATE1, MATE2/K (renal uptake or efflux transporters)

Signiant active renal secretion (≥ 25% of systemic clearance of the drug) or concerns about renal toxicity

• If a drug is a transporter substrate, the need for clinical DDI studies is determined by: drug’s putative site of action, route of elimination, likely concomitant drugs, and safety considerations.

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• Evaluate an NME as an inhibitor for– P-gp, BCRP;

OATP1B1, OATP1B3;OAT1, OAT3, OCT2, MATE1, MATE-2K

– Applicable for most drugs (a drug not as a substrate of a transporter doesn’t mean it cannot be an inhibitor)

• Basic Models for predicting in vivo inhibition potential of transporters by the NMEIs relevant inhibitor concentrations [I]/IC50 ≥ cutoff value? If yes, inhibition is possible.

• Induction? - in vitro methods are not well establishedP-gp is also regulated by PXR, but less sensitive than CYP3A.

Investigational Drug as an Inhibitor of Transporters

Does the drug affect a given transporter?

Modified from Lei Zhang

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Decision for In Vivo Study mediated by Transporter Inhibition

• If the ratio is above the cut-off, the sponsor should further investigate the DDI potential by either using mechanistic static models or PBPK or conducting a clinical DDI study.

Transporters 2012 Draft guidance 2017 Draft Guidance

P-gp I1/IC50 ≥ 0.1 or I2/IC50 ≥ 10 I2/IC50 ≥ 10 (for oral drugs)

OATP1B1/ OATP1B3Step 1: Itotal, max/IC50 ≥ 0.1

Step 2: Iunbound, inlet, max/IC50 ≥ 0.25Iunbound, inlet, max/IC50 ≥ 0.1

OAT1/OAT3 Iunbound, max/IC50 ≥ 0.1 Remained the same

OCT2/MATE1/ MATE2-K

Iunbound, max/IC50 ≥ 0.1 (only for OCT2)Iu, max/IC50 ≥ 0.1 for OCT2

ORIu, max/IC50 ≥ 0.02 for MATEs

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P-gp: Comparison of Prediction Performance with Different Cut-off Criteria

EMA1 PMDA& FDA2I2/IC50 alone

(#1)

I2/IC50 alone

(#2)

I1u/IC50 ≥0.02

OR I2/IC50≥10

I1/IC50 ≥0.1

OR I2/IC50≥10I2/IC50≥10 I2/IC50≥45

FN (#) 6 (11%) 6 (11%) 6 (11%) 8 (15%)

FP (#) 12 (23%) 12 (23%) 11 (21%) 7 (13%)

TN (#) 16 (30%) 16 (30%) 17 (32%) 21 (40%)

TP (#) 19 (36%) 19 (36%) 19 (36%) 17 (32%)

PPV 61% 61% 63% 71%

NPV 73% 73% 74% 72%

1 2012 EMA DDI guideline. 2 2014 PMDA draft DDI guideline and 2012 FDA draft DDI guidance. 3 Lee SC, et al., Adv Drug Deliv Rev. 2017 Jul 1;116:100-118

• I2/IC50 ≥10 alone (I2 = Dose/250 mL, reflecting inhibitor concentration in intestine) seems sufficient for reasonable prediction of P-gp mediated DDIs for oral drugs.

• For drugs given parentally or metabolite that are the inhibitors, a different cut-off with systemic concentrations (e.g., Imax or Imax,u) will be more appropriate and needs further evaluation.

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Case Example - Dolutegravir

• Dolutegravir is an orally administered anti-HIV drug. Cmax of dolutegravir was 4.1 μg/mL at 50 mg b.i.d. It is highly bound (≥ 98.9%) to human plasma proteins.

• An in vitro experiment was conducted to measure the uptake of metformin (OCT2 substrate) with the absence or presence of dolutegravir, generating an IC50 value of dolutegravir as 1.93 μM (or 0.81 μg/mL).

• Is there a potential for dolutegravir to inhibit OCT2 in vivo and cause clinically significant drug interactions? Is there a need to further conduct an in vivo DDI study with OCT2 substrate(s)?

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Case Example - Dolutegravir• Cmax,u/IC50 = 0.05 < 0.1 thus, it would be concluded that dolutegravir

won’t cause clinically relevant DDIs mediated by inhibition of OCT2 in humans. No further DDI assessment is needed.

• There is 20-30 fold difference in IC50 of dolutegravir against OCT2, i.e., 0.11 μM (or 0.047 μg/mL) using metformin as the substrate. This was confirmed by another source reporting an IC50 of 0.21 μM.

• Using the new data, Cmax,u/IC50 = 0.89 > 0.1, it would be concluded that dolutegravir may cause clinically relevant DDI.

Lepist EI, Kidney Int. Kidney Int. 2014 Aug; 86(2):350-7.

Chu X, et al. Drug Metab Dispos. 2016 Sep;44(9):1498-509

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Dolutegravir – Metformin DDI

Song IH, et. al. J Acquir Immune Defic Syndr. 2016 Aug 1;72(4):400-7.

Dolutegravir USPI: With concomitant use,

limit the total daily dose of metformin to

1,000 mg either when starting metformin or

TIVICAY. When stopping TIVICAY, the

metformin dose may require an adjustment.

Monitoring of blood glucose when initiating

concomitant use and after withdrawal of

TIVICAY is recommended.

Also contraindicate with dofetilide, an

OCT2 substrate, considered as a narrow

therapeutic index drug

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Why there was discrepancy in the in vitro data?

Dr. Yong Huang, Optivia Biotechnology Inc. April 2015

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Conclusions• In Vitro experiment results inform in vivo DDI evaluation

strategy (the need, the timing, etc.).

• An integrated approach can be used to leverage available in vitro/in vivo information to evaluate DDI potential (e.g., simple model, mechanistic static and/or dynamic model).

• The criteria of simple models (the matrix, the cut-off values) will be continuously evaluated for their prediction performance with more data becoming available and may be updated.

• Standardize and validate in vitro assay conditions to ensure data with good quality (e.g., including proper controls, check recovery/mass balance, pay attention to potential non-specific binding)

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Acknowledgements

Kellie Reynolds Arya Vikram

Lei Zhang Zhongqi Dong*

Shiew-Mei Huang Tian Zhou

Joseph Grillo Dinko Rekic*

Ping Zhao* Kenta Yoshida*

Darrell Abernethy

Issam Zineh

Jayabharathi Vaidyanathan

*former FDA colleagues

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OATP1B1: Comparison of Prediction Performance with Different Cutoff Criteria

Method 1: Imax/Ki≥0.12: Iu,max/Ki

≥0.023: R≥1.04

(EMA)4: R≥1.1

5: R≥1.25(PMDA)

6: Imax/Ki≥0.1 and R≥1.25

(FDA 2-step)

FN 12 (11%) 17 (16%) 8 (7%) 12 (11%) 15 (14%) 17 (16%)

FP 27 (25%) 16 (15%) 33 (31%) 22 (21%) 16 (15%) 13 (12%)

TN 28 (26%) 39 (36%) 22 (21%) 33 (31%) 39 (36%) 42 (39%)

TP 40 (37%) 35 (33%) 44 (41%) 40 (37%) 37 (35%) 35 (33%)

PPV 60% 69% 57% 65% 70% 73%

NPV 70% 70% 73% 73% 72% 71%

R ≥ 1.1 (Iu,inlet,max/IC50 ≥ 0.1, unbound liver inlet concentrations of inhibitor) seems providing a better balance between false negative and false positive predictions.

Lee SC, et al., Adv Drug Deliv Rev. 2017 Jul 1;116:100-118

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OAT1/OAT3: Comparison of Prediction Performance with Different Cut-off Criteria

Cmax,u/

IC50

All substrates

(59 DDI Studies)

OAT1-specific substrates (13 DDI Studies)

OAT3-specific substrate (32 DDI Studies)

EMA

≥0.02a

FDA

≥0.1b

PMDA

≥0.25c

EMA

≥0.02a

FDA

≥0.1b

PMDA

≥0.25c

EMA

≥0.02a

FDA

≥0.1b

PMDA

≥0.25c

FN 0 1d 1d 0 0 0 0 1d 1d

FP 20 12 8 4 1 1 13 9 6

TP 22 21 21 6 6 6 10 9 9

TN 17 25 29 3 6 6 9 13 16

PPV 52% 64% 72% 60% 86% 86% 43% 50% 60%

NPV 100% 96% 97% 100% 100% 100% 100% 93% 94%

The cut-off value 0.02 (EMA) yielded more false positives. The value 0.1 (FDA) or even 0.25 (PMDA) seems to be a reasonable cut-off.

Lee SC, et al., Adv Drug Deliv Rev. 2017 Jul 1;116:100-118

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OCT2/MATEs: Comparison of prediction performance of different cut-off criteria

EMAa ITCb PMDAc #4 #5 #6 #7 #8 #9

Cmax,u/

IC50

OCT2 ≥

0.02 OROCT2

≥0.1 OR

OCT2

≥0.25 OR

OCT2 ≥0.02

OR

OCT2 ≥0.1

OR

OCT2 ≥0.25

OR

MATEs

≥0.02

MATEs

≥0.1

MATEs

≥0.25

MATEs

≥0.1

MATEs

≥0.25

MATEs

≥0.02

MATEs

≥0.25

MATEs

≥0.02

MATEs

≥0.1

FN 0 2d 3d 0 0 0 2d 0 3d

FP 10 9 5 10 10 10 6 9 8

TP 18 16 15 18 18 18 16 18 15

TN 5 6 10 5 5 5 9 6 7

PPV64% 64% 75% 64% 64% 64% 73% 67% 65%

NPV 100% 75% 77% 100% 100% 100% 82% 100% 70%

a A cut-off of 0.02 applied to unbound Cmax/IC50 for OCT2 or for MATEs was suggested in 2012 EMA DDI guideline; b A cut-off of 0.1 for OCT2 or for MATEs was suggested in ITC paper (Hillgren KM, et. al, Clin Pharm Ther, 94(1):52-63, 2013). As of note, 2012 FDA’s draft DDI guidance has a cutoff of 0.1 only for OCT2; c A cut-off of 0.25 was suggested in 2014 PMDA draft DDI guideline. d Among these false negatives, two DDI records were between ranolazine (inhibitor, different doses) and metformin (substrate) (Zack J, Clin Pharm in Drug Develop, 4(2) 121–129, 2015). The other DDI study was between isavuconazole and metformin (Clinical Pharmacology and Biopharmaceutical review for NDA 207-500 from Drugs@FDA). Z. Dong, X. Yang, V. Arya, L. Zhang, CPT, 2016, Vol. 99, Issue Supplement S1, S94-95.

From Lei Zhang