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From: "Bonate, Peter"
Date: Wed, 11 Jun 2003 09:38:25 -0500
To: david.aaa.boomer.org
Subject: When is PK not needed
The following message was posted to: PharmPK
Hello, everyone. I
have a question to the collective conscious of the group that is sure to bring
out some interesting discussion. In clinical studies, particularly in Phase 3,
when it is NOT necessary to collect PK information. Basically, when is enough
enough? This question goes right to the heart of why do we collect PK in the
first place.
Any thoughts on this would be appreciated.
Thank you in advance,
pete
Peter L. Bonate, PhD, FCP Director, Pharmacokinetics ILEX Oncology, Inc
4545 Horizon Hill Blvd San Antonio, TX 78229 phone: 210-949-8662 fax:
210-949-8487 email: pbonate.at.ilexonc.com
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From: "Prof. Walter Wolf"
Date: Sat, 14 Jun 2003 21:46:03 -0700
Subject: Re: PharmPK When is PK not needed
The following message was posted to: PharmPK
Peter:
There are basically two reasons why we need to know the biodistribution and the targeting of drugs: one if because this information is required by the FDA, and the second is because this information may (and should, if pertinent) be used to direct and optimize therapy. One would assume that the two reasons overlap, but they do not do so always.
Let me concentrate on the second reason: what do we need to know about how much of the drug goes where in an individual patient, so that we can develop an individualized and optimized therapeutic regimen for that particular patient?. That is not a trivial answer, and when we depend only on measurements of drug concentrations in blood, we may not really have always a valid measure of how much of that drug can be delivered to the target site(s).
One set of answers is when blood levels really give you sufficient and valid information. I will let others answer your question for those cases.
The second set of answers is when we are trying to target tumors or other tissues/organs where transport to and uptake by the target site are not controlled solely by blood levels. In that case we need to be able to measure drug levels at the target site, and noninvasive methods (e.g., nuclear imaging of radiolabeled drugs or MR spectroscopic measurements of drugs with NMR measurable atoms) are two of the key available methods. One of the drugs with which I work very actively is 5-Fluorouracil (5-FU). Although it has been in clinical use now for over 40 years, we still do not know all we need to know, and we still are not using, routinely, good methods to screen and select those patients likely to respond from those who do not.
Professor Walter Wolf, Ph.D.
President, Correlative Imaging Council, Society of Nuclear Medicine Distinguished Professor of Pharmaceutical Sciences Director, Pharmacokinetic Imaging Program Department of Pharmaceutical Sciences, School of Pharmacy University of Southern California
1985 Zonal Ave., Los Angeles, CA 90089-9121 E-Mail: wwolfw.-at-.usc.edu
Telephone: 323-442-1405
Fax: 323-442-9804
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