in vitro assessment of tipranavir to inhibit cytochrome P450 pathways in the absence of ritonavir

1
in vitro assessment of tipranavir to inhibit
cytochrome P450 pathways in the absence of
ritonavir
I ? 95 µM Order CYP 2C9 gt CYP 3A4 gt CYP 2C19 gt
CYP 2D6 gt CYP 1A2
2
Study 1182.12 Number of patients taking
co-medications that are substrates for cytochrome
P450 enzymes that tipranavir inhibits in vitro
Substrate Substrate Substrate Substrate Substrate Substrate
CYP1A2 CYP2C19 CYP2C9 CYP2D6 CYP3A4 PGP
N N N N N N
Total Number Patients 582
Alprazolam . . . . 14 .
Amitriptyline 15 . . 15 15 .
Dapsone . . . . 24 .
Dexamethasone . . . . 11 11
Diazepam . 23 . . 23 .
Diclofenac . . 30 . 30 .
Ibuprofen . . 36 . . .
Itraconazole . . . . 26 .
Ketoconazole . . . . 18 .
Loperamide . . . . . 80
Loratadine . . . 20 20 20
Omeprazole . 49 . . 49 .
Pentamidine . 26 . . . .
Prednisone . . . . 13 .
Rofecoxib . . 10 . . .
Zolpidem . . . . 16 .
3
Planned in vitro studies

• Evaluate induction in human hepatocytes by
  measuring increases in the relevant proteins,
  namely CYP3A4, CYP2C9, CYP2B6, UGT, Pgp (MDR1),
  and MRP2, by quantitative PCR. These results
  will be compared to data for other relevant
  protease inhibitors to rank order tipranavir with
  respect to its induction potency.
• Evaluate the possible interaction with the
  nuclear receptors PXR, CAR and FXR, which are
  responsible for induction of drug metabolizing
  enzymes and transporters. Derive EC50 and Emax
  values using a reporter gene construct assay.
  Interaction with these receptors will be used to
  indicate the potential for induction of various
  drug-metabolizing enzymes and transporters by
  comparisons with the scientific literature.

4
Percentage of patients who do and do not develop
LFT abnormalities is similar among TPV/r
recipients who do and do not develop rash
HIV Positive HIV Positive HIV Negative HIV Negative
Skin AEs No Skin AEs Skin AEs No Skin AEs
ALT n ()
Grade 1 9 (15.8) 116 (25.3) 1 (11.1) 32 (16.9)
Grade 2 8 (14.0) 53 (11.6) 0 (0.0) 9 (4.8)
Grade 3 2 (3.2) 25 (5.5) 0 (0.0) 2 (1.0)
Grade 4 0 (0.0) 11 (2.4) 0 (0.0) 2 (1.0)
All grades 19 (33.3) 205 (44.8) 1 (11.1) 45 (23.8)
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Onset and Duration of Rash Associated with TPV/r

HIV
-
Negative
Trial 1182.22

Trials

HIV
-
Positive
(n
28
)

(n
9)

Trials

(n5
6
)

Time to O
nset



Range

3
-
14

1
-
10

1
-
582

10.5

4.9

87.5

Mean
Median

11

4.0

15.5


Duration of Skin


Rash

(n28)

(n9)

(n45)

Range

1
-
24

2
-
19

2
-
49

Mean

6.7

8.8

13.5

Median

4.0

10

11

HIV-negative trials 1182.37, 1182.41, 1182.42,
1182.46 HIV-positive trials 1182.2, 1182.4,
1182.6, 1182.52
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TPV/r Exposure During Pregnancy
Maternal Age Trimester Exposure Started Delivery Birth outcome
34 1st Elective C-section Normal
38 1st Elective C-section Normal, HIV (-)
30 1st Elective C-section Normal, HIV (-)
32 3rd Elective C-section Normal
36 1st Elective termination N/A
36 1st Elective termination N/A
33 1st Spontaneous abortion Small for gestational age and oligohydramnios
Source ARISg query March 22, 2005
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Risk of MST Rash Among TPV Recipients in
RESISTCD4 Baseline
Factor Comparator Odds Ratio 95 C.I. P Value
Age NA 0.998 0.969, 1.027 0.8825
Gender Females 0.673 0.352, 1.286 0.2306
Baseline CD4 (cells/µL)
gt200 gt200 1 NA NA
50 200 1.203 0.704, 2.057 0.5
lt50 2.060 1.119, 3.793 0.02
TPV trough (µMol) NA 1.003 0.993, 1.012 0.5961
RTV trough (mcg/mL) NA 2.034 0.728, 5.682 0.1755
Race Non-white 1.973 0.911, 4.273 0.0846
Hepatitis coinfection No 0.657 0.282, 1.527 0.3289
Weight (Kg) NA 1.005 0.986, 1.024 0.6040
Fixed logistic regression model among TPV/r
recipients in RESIST. Variables shown are all
variables tested in the model.
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Determination of Protein Adjustment Factor

• Adjustment Factor
• 4-fold
• 3 to 4-fold
• 3.75-fold

• Method
• Serum shift of IC50 (PNU)
• Serum shift of IC50 (BI)
• Equilibrium dialysis (BI)

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Calculation of Inhibitory Quotient (IQ)

• Protein Binding Correction Factor (PBCF 3.75x)
• TPV is highly bound in plasma (99.96 - 99.98)
• Cell culture media only contains 6 fetal bovine
  serum (99.88)
• PBCF estimated using 2 methods
• Method 1 Equilibrium Dialysis 0.120 free /
  0.034 free 3.5x
• Method 2 Addition of 75 human plasma to
  antiviral assay resulted in a 4x shift
• IQ Cmin / (IC50 fold WT ? mean WT HIV IC50 ?
  3.75)

standardized TPV susceptibility
susceptibility in patient isolate
PBCF
PK
10
Choice of Pre-selected Protease Inhibitor
RESIST Trials
Total Total Total Total
TPV/r TPV/r CPI/r CPI/r
N () N ()
Total treated 582 (100.0) 577 (100.0)
New or ongoing pre-selected PI
New PI 375 (64.4) 363 (62.9)
Ongoing PI 207 (35.6) 214 (37.1)
Resistance to pre-selected PI
Susceptiblea 76 (13.1) 80 (13.9)
Possibly Resistantb 135 (23.2) 112 (19.4)
Resistantc 369 (63.4) 385 (66.7)
Missing 2 (0.3) 0
Genotypically available and new pre-selected PI 152 (26.1) 140 (24.3)
a TruGene No evidence of resistance. Virtual
Phenotype within normal susceptibility range or
resistance unlikely for IDV lt 3.0, for SQV lt
2.5, for APV lt 2.0, and for LPV lt10. b TruGene
Possible resistance. Virtual Phenotype for LPV
only 10 to lt40. c TruGene Resistance. Virtual
Phenotype resistance or resistance likely as
defined by being above normal susceptibility
range for IDV gt3.0, for SQV gt2.5, for APV gt2.0,
and for LPV gt 40.
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Treatment Response at Week 24 by Prior Use of
the Pre-selected Comparator PI
Treatment Group Treatment Group Treatment Group Treatment Group Treatment Group Treatment Group
TPV/r TPV/r TPV/r CPI/r CPI/r CPI/r
n () N N () N
Total Treated 240 (41.2) 582 109 (18.9) 577
Patients with an ongoing pre-selected CPI 75 (36.2) 207 21 (9.8) 214
Patients with a new pre-selected CPI 165 (44.0) 375 88 (24.2) 363
Patients not entirely naïve to pre-selected CPI 60 (40.3) 149 21 (13.0) 161
Patients entirely naive to pre-selected CPI 105 (46.5) 226 67 (33.2) 202
n Number of patients with response N Number of randomized and treated patients n Number of patients with response N Number of randomized and treated patients n Number of patients with response N Number of randomized and treated patients n Number of patients with response N Number of randomized and treated patients n Number of patients with response N Number of randomized and treated patients n Number of patients with response N Number of randomized and treated patients n Number of patients with response N Number of randomized and treated patients
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Where did L90M Go?

• L90M when combined with V82T or I84V was
  associated with decreased TPV susceptibility in
  the VIRCO panel of isolates
• Combinations of Key mutations which include L90M
  are associated with decreasing TPV susceptibility
  and decreased virologic responses to TPV/r
• L90M is not included in the TPV Score
• Not selected by TPV exposure in vitro or in
  clinical HIV isolates
• Not associated with TPV phenotype in multivariate
  analysis of 99 HIV-1 protease amino acids
• Not associated with TPV/r antiviral responses in
  multivariate analyses of 99 HIV-1 protease amino
  acids
• It appears that L90M when combined with mutations
  at codons 82 or 84 serves as a marker for highly
  mutated viruses which contain other mutations
  associated with decreased TPV susceptibility.

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Impact of Key Mutations at Codons 33, 82, 84, 90
Baseline Phenotypic Susceptibility all TPV trials
0 1 2 3 4
0 1 2 3 4
0 1 2 3 4
0 1 2 3 4
0 1 2 3 4
0 1 2 3 4
0 1 2 3 4
0 1 2 3 4
Key mutations
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Tipranavir BI 1182.518 Week Viral Load Response
0
-0.2
-0.4
-0.6
HIV RNA (log10 copies)
-0.8
-1
-1.2
Single Boosted PI Phase
TPV added to LPV/APV/SQV
-1.4
0
2
4
6
8
Weeks of Treatment
TPV n 66 60 60 57
APV n 74 64 64 61
SQV n 74 67 70 64
LPV n 78 74 72 62