Mackenzie Cottrell, PharmD Assistant Professor Co-Director of the UNC CFAR Clinical Pharmacology and Analytical Chemistry Core Division of Pharmacotherapy and Experimental Therapeutics University of North Carolina at Chapel Hill

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2. Precision HIV PrEP: Tailoring
the Prescription for the User
17July2020
Mackenzie Cottrell, PharmD, MS
mlcottre@email.unc.edu

3. Disclosures
• No conflicts of interest to disclose

4. Disparities in PrEP Efficacy
Biological or Behavioral?
Daily Oral PrEP
RCT Population Treatment Outcome
TDF2 Heterosexual high risk men and women F/TDF Inconclusive
Partners PrEP Serodiscordant heterosexual couples F/TDF Protective
Partners PrEP Serodiscordant heterosexual couples TDF Protective
iPrEx MSM and Transgender women F/TDF Protective
Discover MSM and Transgender women F/TDF Protective
Discover MSM and Transgender women F/TAF Protective
FEM-PrEP Heterosexual high risk women F/TDF Futile
VOICE Heterosexual high risk women F/TDF Futile
VOICE Heterosexual high risk women TDF Futile
Plot adapted from Landovitz R. PrEP for HIV Prevention: What We Know and What We Still Need to Know for Implementation. CROI 2015.
% Adherence by Objective Assessment Measure
20 30 40 50 60 70 80 90 100
%Effectiveness
-60
-40
-20
0
20
40
60
80
100
Female Only
Male and Female
Male and Transgender Woman
*
*Discover % effectiveness calculated compared to background
incidence and adherence estimated based on CASI, pill count, and DBS.
F/TDF F/TAF
%Efficacy

5. PrEP Effectiveness May Differ by User
Corneli A et al. JAIDS 2014;66:324-331Grant et al. Lanced ID 2014;14(9):820-829
80% HIV risk reduction
with ≥2 doses/week
But 45-60% taking ≥ 2
doses/week in FEM-PrEP
iPrEx OLE Overall 51%  Risk FEM-PrEP Overall Futile

6. PrEP Effectiveness May Differ by User
2015 HIV Diagnoses Among Heterosexual Subpopulations in U.S.
0 1000 2000 3000 4000 5000
BlackHispanic/LatinoWhite
Male
Female
CDC. HIV Surveillance Report 2016;27:22; Bush et al. Racial characteristics of FTC/TDF for pre-exposure prophylaxis users in the U.S. Paper presented at:
2016 ASM Microbe; June 16-20, 2016; Boston. Session 371.
Overall, only 20.7% of those initiating PrEP were women, and from 2012
to 2015 the percentage of women starting PrEP decreased by 37.1%.

7. Intracellular: Inside the Nucleus
Extracellular: Blood and Tissue Intracellular: Blood and Tissue
PrEP Pharmacology & Mechanism of Action
T -PPP
PharmacokineticsPharmacodynamics
A
U
CG
U
CG
C
A
U
HIV RNA
HIV ssDNA
A -PPPA -PPP
A -PPP
Phosphatases Deactivate
Kinases Activate
TFV
-PPP
FTC
-PPP
TFV
-PP
FTC
-PP
FTC
-P
Transport into CellFTC
TDF TFV
-PEsterase Transport into Cell
TFV
-P
TAF Transport into Cell Cathepsin-A
Reverse
TranscriptaseT

8. PrEP Blood PK Scales with Dose
PBMC TFVdp Concentration (Median +/- IQR) Versus Time After a
Single 5mg, 10mg, or 25mg Dose of Tenofovir Alafenamide Over 14 Days
Time (h)
TFVdp(fmol/millioncells) 0.1
1
10
100
1000
25mg TAF; 18% BLQ
10mg TAF; 27% BLQ
LLOQ
5mg TAF; 38% BLQ
Time (h)
0 1 3 7 10
TFVdp(fmol/millioncells)
1
10
100
Adapted from Cottrell ML et al. J Infect Dis. 2016 Jul;214(1):55-64; Cottrell et al. JAC 2017 Jun;72(6):1731–1740.
Nominal Time (hr)
0 10 20 30 40 50
FTC-TPConcentration(fmol/10
6
cells)
100
1000
10000
100mg Emtricitabine Solution
200mg Emtricitabine Solution
400mg Emtricitabine Solution
Nominal Time (hr)
0 10 20 30 40 50
TFV-DPConcentration(fmol/10
6
cells)
1
10
100
150mg Tenofovir-DF
300mg Tenofovir-DF
600mg Tenofovir-DF

9. PrEP Blood PK Scales with Frequency
Hendrix et al. AIDS Res Hum Retroviruses. 2016 Jan;32(1):32-43.

10. Tissue:BloodPlasmaRatio
0.1
1
10
100
Tenofovir
Emtricitabine
Cervix/Vagina Male Rectum
PrEP PK Differs by Transmission Site
 TFV Exposure in Female Genital
Tract vs Male Rectum
 TFVdp Exposure in Female Genital
Tract vs Female Rectum
Patterson KB Sci Transl Med. 2011 Dec 7;3(112):112re4.
TFV TFV-dp FTC FTC-tp
AUC0-48(ngorfmol*hr*mg
-1
)
1
10
100
1000
10000
Rectal tissue
FGT tissue
Adapted from Cottrell ML et al. J Infect Dis. 2016 Jul 1;214(1):55-64.

11. PrEP PK Differs by Transmission Site
TFVdpFTCtp
0.8 (0.6, 1.1) 7 (2, 19)
111 (64, 194)1450 (898, 2340)
Total Cervical Cells (N=13)Rectal Mononuclear Cells (N=40)
Seifert. ARHR (2016) 32: 981-991

12. TAF Distributes into FGT Tissue
Single Dose Study Multiple Dose Study
Treatment
Arm
TAF
25mg
TDF
300mg*
TAF
10mg
TAF
25mg
TDF
300mg
BLQ
values
(n,%)
12; 75% 4; 25% 73; 94% 69; 69%* 85; 85%
Cmax
(pmol/g)
7.1 7.8 44.8 144.0 46.9
AUC0-last
(pmol*h/g)
132.1 170.7 1668.4 3471.8 1884.8
Adapted from Schwartz. Oral Abstract Presentation HIV Prevention in Healthy Women: Safety and Pharmacokinetics of a Potential New Tenofovir Alafenamide
Fumarate (TAF)-based Oral PrEP Regimen. HIVR4P 2018; Cottrell et al. JAC 2017 Jun;72(6):1731–1740

13. Time (hr)
0 6 12 24 48 72
TFVorTFVdp(pM)
103
104
105
106
107
Time (hr)
0 6 12 24 48 72
TFVorTFVdp(pM)
103
104
105
106
107
Time (hr)
0 6 12 24 48 72
TFVorTFVdp(pM)
103
104
105
106
107
TAF Results in Lower TFVdp in the Rectum
TAF 25mg
TFVdp LLOQ
TDF 300mg 10-fold 
13-fold 

14. TAF Results in Higher TFVdp in Lymph Node MNCs
Fletcher et al. Clin Pharmacol Ther 2020 May 8. [Ahead of print]

15. FTCtp Generally High in Lymph Node MNCs
Fletcher et al. Clin Pharmacol Ther 2020 May 8. [Ahead of print]

16. PK/PD: How much is enough?
Time (hours)
0 20 40 60 80 100 120
NaturalLogConcentration
SS Cmax
SS Trough
SS PK Principles
1. In=Out
2. Achieved by ~5 T1/2
3. Time to SS independent of:
• Dose
• Dose frequency
• Concentration
Trough

17. PrEP Time to Steady State Differs by Compartment
Compartment
TFVdp t1/2
(hrs)
TFVdp 90% Tss
(days)
Blood Plasma 17 3
Blood derived
CD4+ cells
112
(100, 118)
16.3
(14.6, 17.2)
Colon CD4+
cells
60
(52, 72)
8.8
(7.6, 10.5)
FGT CD4+ cells
139
(121, 167)
20.3
(17.6, 24.4)
Louissaint, et al. AIDS Res Hum Retrovir 2013; Wang, et al. AIDS Res Hum Retrovir. 2004; 20: 1173-1182.
Day after initiating daily dosing
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30Concentration
1
10
100
Below assay limits of quantification
17 hour half-life
120 hour half-life
17 hour half-life
139 hour half-life

18. Dose vs Response Relationship
Drug Concentration
1 10 100 1000 10000 100000
PercentInhibition
0
10
20
30
40
50
60
70
80
90
100
EC50→
EC90→
EC99→
PK/PD: How much is enough?

19. PBMC TFVdp Correlated with PrEP Efficacy
Anderson PL et al. Sci Transl Med 2012; 4(151)
EC90 = 16fmol/million vPBMC

20. Endogenous Nucleotides Mediate Potency
Adapted from: García-Lerma J G et al. J. Virol. 2011;85:6610-6617
Lower TFVdp:dATP associated with
infection in 4/6 macaques dosed with
tenofovir PrEP
Molar TFVdp:dATP ratio of ≥1
associated with 100% reverse
transcriptase inhibition
%RTInhibition
dATP, mM
Treated with 0.005 mM TFVdp
00.10.010.0010.0001
100
80
60
40
20
0
1000
100
10
1
TFVdp:dATPratios
Weeks

21. Metabolite:Nucleotide Correlates with in vitro Inhibition
▲CD4+
○ TZM-bl
Cell EC50 (±SE) Hill (±SE) EC90
TZM-bl 0.01 (±0.001) 1.02 (±0.11) 0.086
CD4+ 0.086 (±0.011) 1.81 (±0.39) 0.29
Cell EC50 (±SE) Hill (±SE) EC90
TZM-bl 0.059 (±0.004) 1.42 (±0.11) 0.27
CD4+ 0.022 (±0.005) 1.86 (±0.67) 0.07
▲CD4+
○ TZM-bl
Cottrell ML et al. J Infect Dis. 2016 Feb 24 [Epub ahead of print].
%Protection
%Protection
TFVdp:dATP (Molar Ratio) FTCtp:dCTP (Molar Ratio)

22. TFVdp and FTCtp Inhibit HIV Synergistically
Ψ=0.632 (±0.074; p<0.001)Chakraborty A and Jusko W. J Pharm Sci. 2002;91(5):1334-1342.

23. v v
PK/PD Modeling can Predict Effective Dosing
Doses of TDF/FTC PrEP per Week%PopulationAchievingTargetExposure
0
10
20
30
40
50
60
70
80
90
100
1 2 3 4 5 6 7 1 2 3 4 5 6 7
100% 100%
Female Genital Tract Lower GI Tract
Adapted from Cottrell ML et al. J Infect Dis. 2016 Jul 1;214(1):55-64.
Female Genital Tract vs Lower GI Tract
Time (hr)
0 48 96 144 192 240 288 336
%PopulationAchievingTargetExposure
0
10
20
30
40
50
60
70
80
90
100
Sex

24. Female Sex Hormones May Mediate PK/PD
Median (IQR) Estradiol in 16 TGW starting FHT
Baseline 6 months
29 (16) pg/ml 258 (812) pg/ml
Deutsch et al. Obstet Gynecol 2015; 125 (3): 605-610
Estradiol and progesterone mediate ADME pathways
Absorption
 gastric pH
 gastric emptying
 intestinal motility
Delayed drug absorption –
SR formulations particularly
impacted
Decreased absorption for
acid dependent drugs
Distribution
 intravascular volume
 sodium and water
retention
Altered plasma
concentrations of
hydrophilic and lipophilic
drugs

25. Female Sex Hormones May Mediate PK/PD
Shieh et al. Oral abstract OA23.03. R4P 2018; Shen Z et al. PLoS One. 2013 Jul 25;8(7):e69854; Shen Z et al. PLoS One. 2014 Jun 30;9(6):e100863.
FGT Cells treated with Estradiol
1. Gender affirming-FSH do not
alter kinase expression in
PBMCs or colon tissue
2. In vitro FSH  nucleotidase
activity in epithelial cells
3. In vitro FSH  TFVdp in FGT
derived CD4+ cells
FGT Derived CD4+s Blood Derived CD4+s

26. PrEP Effectiveness in Transgender Women
Deutsch et al. Lancet HIV 2015 Dec;2(12):e512-e519
Lower TFVdp in DBS amongst TGW

27. Gender Affirming FHT May  Systemic PrEP in TGW
Shieh et al. J Int AIDS Soc. 2019 Nov;22(11):e25405Cirrincione et al. JAC 2020 Jan [Epub ahead of print]
PlasmaTFV(ng/m)
PlasmaTFV(μg/m)
Time (hours) Time (hours)
 CG adults (n=17)
 TGW (n=15)
 CGM (n=8)
 TGW (n=8)
27%  AUC
20%  Ctrough*
24%  AUC*
11%  Ctrough
 Plasma TFV and FTC in TGW vs CGM  Plasma TFV in TGW vs Cisadults
* p<0.05

28. Gender Affirming FHT May  PrEP in Tissues
Trend towards  TFVdp/FTCtp in
TransWomen vs CisMen in Colon Cells
 TFVdp in TransWomen vs CisMen
and Women in Rectal Tissues
Active
Metabolite
Ctau PBMC Colon Cells
TFVdp
% Reduction 16% 36%
P value 0.3 0.44
FTCtp
% Reduction -1% 44%
P value 0.98 0.38
Cottrell et al. Clin Infect Dis. 2019 Apr 9. pii: ciz290.
Shieh et al. Oral abstract OA23.03. R4P 2018
7-fold lower
TFVdp FTCtp
PBMCsRectalTissues

29. How Can We Monitor PrEP Dose Taking Behavior?
State of the Evidence for PrEP in 2011
RCT Population Treatment Outcome
Partners
PrEP
Serodiscordant
heterosexual couples
TDF/FTC Protective
Partners
PrEP
Serodiscordant
heterosexual couples
TDF Protective
iPrEx
MSM and Transgender
women
TDF/FTC Protective
TDF2
Heterosexual high risk
men and women
TDF/FTC Inconclusive
FEM-PrEP
Heterosexual high risk
women
TDF/FTC Futile
VOICE
Heterosexual high risk
women
TDF/FTC Futile
VOICE
Heterosexual high risk
women
TDF Futile
Plot adapted from Landovitz R. PrEP for HIV Prevention: What We Know and What We Still Need to Know for Implementation. CROI 2015. Statistics: Pearson
correlation of extracted data using PlotDigitizer v2.6.8.
% Adherence by Objective Assessment Measure
20 40 60 80 100 120%Effectiveness
-60
-40
-20
0
20
40
60
80
100
FEM-PrEP (TDF/FTC)
PartnersPrEP (TDF)
PartnersPrEP (TDF/FTC)
TDF2 (TDF/FTC)
VOICE (TDF)
VOICE (TDF/FTC)
iPrEx (TDF/FTC)
Pill Count
r=0.60, p=0.2
% Detectable Drug Concentration
r=0.89, p=0.006

30. Day after initiating daily dosing
2 4 6 8 10 12 14 16 18 20
Concentration
1
10
100
Below assay limits of quantification
17 hour half-life
Short Term Adherence Measures
• Concentrations of short half-
life compounds in urine and
plasma overlap for single and
multiple doses
• No overlap for long half-life
compounds in cells or hair
Concerns: White Coat Adherence
Day after initiating daily dosing
2 4 6 8 10 12 14 16 18 20
Concentration
1
10
100
Below assay limits of quantification
17 hour half-life
120 hour half-life
No overlap between Dose 2 and 20 concentrations
Overlap between Dose 2 and 20 concentrations

31. Day after initiating daily dosing
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Concentration
1
10
100
Below assay limits of quantification
17 hour half-life
120 hour half-life
Long term Adherence Measures
• Long time to steady state
increases risk of
misinterpretation following
recent changes in behavior
• Concentrations of 0 doses for
>1 week similar to those after
recently initiating daily dosing
Concerns: Misclassification Following Recent Changes

32. Long Term Adherence Measures
RBCs: DOT of 100, 67, 33% TDF doses per week (N= 48)
Anderson PL et al. AAC 2017;62(1):1710-17
Steady-state exposure by 8 week
Daily dosing misclassified up to 1
month on therapy
700 fmol/punch = 4+ doses/week
1 month after discontinuing therapy

33. Long term Adherence Measures
RBCs (DOT of 100, 67, and 33% of TAF doses/week (N=36)
Yager J. TFVdp in DBS Following Escalating TAF/FTC Dosing (Abstract 463 CROI 2019).
TAF #2
7mm
TDF #1
3mm
Week
1-12
Week
24-36
TDF=518
TDF=946
TDF=1542
Steady-state exposure by week 12?

34. Long Term Adherence Measures
Hair (HPLC-MS/MS)
Liu A et al. PLOSone 2014;9(1) Koss et al. CID 2018;66(2):213-9
2 Doses/Week
0.01 (0.008-0.02)
7 Doses/Week
0.04 (0.02-0.05)
Median (Range)

35. Summary
• PK studies and PK/PD modeling indicate PrEP pharmacology
differs between HIV transmission sites for TDF and TAF
•  TFVdp and  FTCtp in FGT vs GI tissues
• Based on modeling higher levels of adherence are required to achieve
PrEP target exposure in female genital tract
• Gender Affirming FHT may  Systemic and Rectal PrEP exposure
by enhancing phosphatase activity
• Pharmacologic measures of PrEP (i.e. DBS and hair) correlate with
PrEP effectiveness and may more accurately indicate adherence
than subjective measures

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