Sulforaphane as an Antagonist to Human PXR-mediated Drug-drug Interactions

Summary

Adverse drug-drug interactions (DDIs) are responsible for approximately 3% of all hospitalizations in the US, perhaps costing more than $1.3 billion per year. One of the most common causes of DDIs is the when one drug alters the metabolism of another. A key enzyme in the liver and intestine, called "cytochrome P450 3A4 (CYP3A4) is generally considered to be the most important drug metabolizing enzyme. The gene for CYP3A4 can be 'turned on' by the presence of certain other drugs, resulting in much higher levels of CYP3A4 in the liver and intestine. Thus, when a drug that induces CYP3A4 is given with or before another drug that is metabolized by 3A4, a 'drug-drug' interaction occurs because the first drug (the inducer) greatly changes the rate at which the second drug (CYP3A4 substrate) is removed from the body. Many drugs increase CYP3A4 activity by binding to a receptor called the Pregnane-X-Receptor (PXR), which is a major switch that controls the expression of the CYP3A4 gene. Using human liver cells we have demonstrated that sulforaphane (SFN), found in broccoli, can block drugs from activating the PXR receptor, thereby inhibiting the switch that causes CYP3A4 induction. The purpose of this project is to determine if SFN can be used to block adverse DDIs that occur when drugs bind to and activate the PXR receptor and subsequently induce CYP3A4 activity. We will recruit 24 human volunteers to participate in the study. This project will determine whether SFN can prevent the drug Rifampin from binding to PXR and increasing CYP3A4 activity in humans following oral administration of SFN (broccoli sprout extract). The rate of removal of a small dose of the drug midazolam will be used to determine the enzymatic activity of CYP3A4 before and following treatment with Rifampin, in the presence or absence of SFN, since midazolam is only eliminated from the bloodstream by CYP3A4. . We predict that SFN will prevent the increase in midazolam clearance (metabolism) that normally follows treatment with the antibiotic, rifampicin.

This research is important because it could potentially lead to a simple, cost-effective way of preventing one of the most common causes of adverse drug-drug interactions that occurs today. For example, rifampicin, which is a cheap and effective antibiotic used to treat TB, cannot be used in HIV/AIDS patients because it increases the metabolism of many of the antiretroviral drugs used to treat HIV/AIDS. TB is a major opportunistic infection in AIDS patients, so this is a serious clinical problem, especially in developing countries where more expensive alternative drug therapies are not available. We hypothesize that co-formulation of rifampicin with SFN could block this drug-drug interaction without altering its efficacy, thereby allowing its use in HIV/AIDS patients infected with TB. This is but one example of numerous drug-drug interactions that occur via this mechanism.

Conditions

• Adverse Drug Interactions

Interventions

DRUG

Rifampicin

Rifampicin, an antibiotic used to treat TB, is administered at a dose of 300 mg day x 7 days to induce CYP3A5.

DIETARY_SUPPLEMENT

sulforaphane plus rifampicin

Sulforaphane (SFN) is an isothiocyanate derived from the plant phytochemical, glucoraphinin. It appears to inhibit ligand binding to the ligand activated nuclear transcription factor, Pregnane X-Receptor (PXR). This arm tests the hypothesis that SFN can block ligand binding to the PXR, thereby inhibiting transcriptional activation of PXR-regulated genes. Sulforaphane is administered daily for 7 days as a broccoli sprout extract, at a dose rate of 75 mg (\~420 umoles)per day for 7 days. Rifampicin is also administered once per day at a dose rate of 300 mg/day for 7 days.

DIETARY_SUPPLEMENT

sulforaphane alone

Sulforaphane (SFN) is an isothiocyanate derived from the plant phytochemical, glucoraraphinin. It appears to inhibit ligand binding to the ligand activated nuclear transcription factor, Pregnane X-Receptor (PXR). This arm tests the hypothesis that SFN can block ligand binding to the PXR, thereby inhibiting transcriptional activation of PXR-regulated genes

Sponsors & Collaborators

• Fred Hutchinson Cancer Center

  collaborator OTHER

• National Institute of General Medical Sciences (NIGMS)

  collaborator NIH

• University of Washington

  lead OTHER

Principal Investigators

• David L Eaton, PhD · University of Washington

Study Design

Allocation

RANDOMIZED

Purpose

OTHER

Masking

NONE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

40 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2008-03-31

Primary Completion

2010-06-30

Completion

2010-09-30

Countries

• United States

Study Locations