CYP2B6 Genetics and Drug Interactions in Healthy Volunteers

Schedule of assessment

PHASE 1 (CONTROL PHASE)

Phase 1 (day 1 to day 4): baseline (control) activities of CYP2B6, CYP2C8 and OATP1B1 will be
measured using selective probe substrates. Eligible subjects will receive simultaneously a
single 100 mg dose of bupropion (CYP2B6), a single 10 mg dose montelukast (CYP2C8) and a
single 5 mg dose of rosuvastatin (OATP1B1) by mouth on empty stomach together at least 10
days before phase 2. Frequent plasma samples will be collected for 72 hours and urine for 48
hours after dosing. Safety assessment will be made for the first 24 hours. Phase 1 is
completed after the last blood draw on day 4 (72 hours).

PHASE 2 (INHIBITION PHASE)

In phase 2 (days 11 to 16), the metabolism and pharmacokinetics of a single 600 mg oral dose
efavirenz will be determined along with the activities of CYP2B6, CYP2C8 and OATP1B1.
Subjects receive a single 600 mg oral dose of efavirenz and blood samples will be obtained at
30 min and 1 hour. Immediately after the 1 hour blood draw, the three probe drugs (10 mg
montelukast, 100 mg bupropion, and 5 mg rosuvastatin) will be administered simultaneously.
Frequent plasma samples will be collected for 120 hours and urine for 48 hours after
efavirenz dosing. Safety assessment will be made for the first 24 hours. Phase 2 is completed
after the last blood draw on day 16 (120 hours). Note: The additional time points (compared
to phase 1) are needed because of the long elimination half-life of efavirenz.

PHASE 3 (EFAVIRENZ TREATMENT PHASE).

In phase 3 (days 16 to 32), subjects will take efavirenz (600 mg/day) every evening for 17
days (Note: Phase 3 starts when the subject takes the first dose that evening on Day 16).
Prior to taking the evening dose, they will be requested to return to the Indiana Clinical
Research Center on day 19, day 22, day 25, day 28 and day 31 for a brief outpatient visit to
have vital signs checked, draw blood sample (~10 ml, approximately 2 teaspoonful), and to
fill out the brief central nervous system (CNS) symptoms questionnaire. They will be reminded
not to take the evening dose of efavirenz on these days until after their blood draw. Since
efavirenz has a long half-life (~76 hours after single dose and ~50 at steady state), a total
of 17 days of efavirenz treatment is required to achieve steady-state plasma concentrations
of efavirenz and steady-state autoinduction of metabolism. Subjects will be instructed to
take efavirenz at bed-time to minimize efavirenz-induced central nervous side effects. Minor
rescheduling (±3 days) of the subject's fixed inpatient/outpatient visits will be allowed
including adjusting the amount of study medication (up to 3 doses less or up to 3 doses more)
to be given prior to the subject's 4th inpatient visit.

PHASE 4 (INHIBITION/INDUCTION PHASE)

In phase 4 (days 33 to 38), the steady-state metabolism and pharmacokinetics of efavirenz
will be determined along the activities of CYP2B6, CYP2C8 and OATP1B1. The procedures
described in phase 2 will be repeated. On day 38, an exit exam will be performed consisting
of a repeat of a repeat of the screening laboratory tests including blood and urine tests.
The study diary will be collected. Medication bottles with left over pills (if any) will be
returned and pills remaining will be counted for compliance purposes. The total duration of
the study will be 38 days.

A total of 60 healthy female and male volunteers (18 to 49 years old) who meet all
inclusion and exclusion criterion listed below will be enrolled to participate in this
study. All subjects will sign an Institutional Review Board (IRB) approved written informed
consent prior to participation in the study after subjects read and carefully explained of
the study to them. Then, potential subjects will undergo a pre-enrollment screening
examination (a maximum of six weeks prior to enrollment into the study) for any medical
abnormalities which will include medical histories, vital signs and electrocardiography,
demographic variables, and standard laboratory blood and urine tests. The screening will be
performed at the Indiana Clinical Research Center. During the screening, a blood sample (15
ml) will be collected from each subject for laboratory tests and urine for urine analyses.
An additional ∼10 ml will be obtained from each subject to extract genomic DNA for
genotyping purposes.

INCLUSION CRITERIA:

- 18 to 49 years old healthy male and female participants within 32% of their ideal body
weight

- Individuals who agree to refrain from taking any prescriptions medications,
over-the-counter medications, hormonal agents, and herbal, dietary, and alternative
supplements that may interact with the metabolism of those study drugs at least 2
weeks prior to the start of the study and until study completion

- Nonsmoker or individuals willing to refrain from smoking or use of tobacco or
marijuana for at least one month prior to and until the completion of the study (the
entire study lasts for approximately 38 days)

EXCLUSION CRITERIA:

- Are underweight (less than 114 lb) or overweight (BMI greater than 32)

- Have history or current alcohol or drug abuse (more than 4 alcoholic drinks per day on
a regular basis)

- Have history of intolerance, allergic reactions (e.g. rash) or other forms of
hypersensitivities to any of the study medications (efavirenz, montelukast, bupropion
and rosuvastatin)

- Have history or current significant health conditions such as heart, liver, or kidney

- Have history or current psychiatric illness such as depression, anxiety, or
nervousness that may be exacerbated by participation in study

- Have a history of suicidality including suicide attempts

- Have history or current gastrointestinal disorders such as persistent diarrhea or
malabsorption that would interfere with the absorption of orally administered drugs

- Have a serious infection within the last week before study enrollment

- Have a baseline EKG readings that is abnormal that could place the patient at the
higher risk as decided by the study medical doctor (MD)

- Have donated blood within the past two months

- Have blood results that do not fall in a healthy range

- Are taking on regular basis substances that may interfere with the metabolism of study
medications by the body, including prescription medications, over-the-counter, herbal
or dietary supplements, alternative medications, or hormonal agents

- Are female with a positive pregnancy urine test obtained just prior to each study

- Are female breastfeeding

- Are child-bearing potential unable or unwilling to either practice abstinence or use
two non-hormonal forms of birth control up until the study completion, which will take
a total of 38 days

- Have a life style that places subjects at a higher risk for contracting HIV (e.g. drug
abuse, excessive alcohol drinking, and having multiple sexual partners)

- Have a history or current HIV infection

- Have participation in a research study or use of an investigational drug in the last
one month

- Are employed or are student under supervision of any of the investigators of this
study

- Cannot state a good understanding of this study including risks and requirements; are
unable to follow the rules of this study

- Cannot commit the time requested for this study