Back to the Top
Hello,
I wonder if anyone can advise, any information would greatly appreciated. I am
currently designing an in vivo xenograft study for an anti-tumor drug. I am
thinking of starting with an IP single dose study, also considering going
straight to o.p and iv. Can anyone advise or have any suggestions as what the
first in vivo PK studies should include. Your views would be most helpful
Regards,
Szah
Back to the Top
The following message was posted to: PharmPK
First of all you'll need to decide what you want to get from the xenograft
study. Do you want proof-of-concept? Do you want to measure a biomarker or
surrogate marker or tumour growth by volume/size measurements etc?
What is the mechanism of action? Is it cytotoxic or cytostatic? Is it likely to
be efficacious after a single administration or will it require repeat
administration?
What is your target? This will help to choose an appropriate xenograft model.
Obviously, you will have to formulate your compound. Does it have good aqueous
solubility? The choice of vehicle also depends on the route of administration.
Intraperitoneal injections generally work fine but you always have to be careful
for drug precipitation in the peritoneal cavity. Intravenous injection is harder
to do on mice and may lead to acute reactions, besides extravasation of the drug
and/or haemolysis, which may be attenuated by ip administration. I would not
start with oral dosing and I personally see very little point in doing this with
mice but that is my personal opinion.
Generally, you first determine the maximum tolerated dose (MTD), which is often
unachievable because of solubility limitations. If the achievable maximum dose
is very low you could stop then & there.
You could determine plasma PK, for example at the MTD or maximum achievable
dose, and then decide whether it is worth setting up tumour-bearing mice for an
activity study. However, rather than relying on assumptions about total plasma
concentrations & AUCs on the one hand and expected activity in vivo on the other
you may need to bite the bullet and test in tumour-bearing mice. However, if you
have good reliable validated PK/PD model then you could consider making a
go/no-go decision based on plasma PK alone.
Some xenograft models are slow-growing, which also depends on the strain, sex,
and age of the mice. It may take time and practice to get good reliable results
from xenograft studies. Inoculation or implantation and also measuring tumours
are a skill & art that some people never fully master.
Obviously, you need ethics approval to undertake animal studies. This will
require of all of the above plus estimates of the numbers of animals required;
many committees like to see power calculations if possible.
HTH but please keep in mind that your question was too basic and general to give
a more adequate and specific answer.
Frederik
Back to the Top
The following message was posted to: PharmPK
Hello,
If you are interested in establishing in vivo xenograft models for cancer drug
efficacy studies, the following publication is an excellent reference:
Advancing bioluminescence imaging technology for the evaluation of anticancer
agents in the MDA-MB-435-HAL-Luc mammary fat pad and subrenal capsule tumor
models.
Zhang C, Yan Z, Arango ME, Painter CL, Anderes K. Clin Cancer Res. 2009 Jan
1;15(1):238-46.
http://clincancerres.aacrjournals.org/content/15/1/238.full.pdf+html
With imaging one can non-invasively assess tumor growth/regression and
metastasis, drug efficacy, compound biodistribution, and molecular pathways
(apoptosis, MMP activity, cathepsin activity, hypoxia etc.) in a live lab
animal. I'd be glad to further discuss.
Best wishes,
Alexandra
Back to the Top
Dear Frederik,
Many thanks for your email, it is indeed very helpful. Apologies for sending out
a question that was too basic, but I just wanted to get a brief overview before
I ask more specific questions.
My plan is to determine basic PK parameters and the best administrative route
for drug ie I.P I.V or O.P. I will start with using normal mice (ie non-tumor
bearing mice) and deliver the drug by I.P at a concentration of 1mg/ml, 5mg/ml
10 mg/kg to obtain plasma levels of drug in the region of ng/ml - ug/ml which
can be easily be detected via LC/MS/MS to determine basic PK parameters of drug
and metabolite breakdown. This will be preceded with observing bioavailability
of drug via iv and oral. This will give a general idea on the PK properties of
the drugs. However, you mentioned that there is very little point in
administrating the drug orally to the mice and I am wondering if you could
explain this further to me.
Also I believe that i should determine the MTD dose for the above study design
and I am wondering if determining the MTD using the i.v route would be
sufficient or even ip, but I believe i.v route produces are more unwanted
adverse side effects so its best to determine MTD via i.v?
Having determined the optimal dose and route to use then I would expand into
determining PK/PD parameters in in vivo xenograft models. ie look at the effect
of drug on tumor growth inhibition and its PK profile in these mice.
If you have any suggestions or comments on this current PK study plan or any
suggestions on how I could improve this study to make in more concise or
effective that would be very helpful. I thank you very much again for your time
and help. Please if anyone has any further comments do send me an email.
Kind regards,
Szah
Back to the Top
The following message was posted to: PharmPK
Hi Sahka,
In addition to the comments already shared by experts, I have few minor points.
During the PK-PD study in xenograft mouse models, you can also look at proteins
or biomarkers quantification using western blotting or IHC techniques . These
proteins may be upregulated or downregulated based on your pathway. This way you
can use simple PD models like Emax models to show target pathway engagement.
Also give a thought on the number of days you would dose the mice. Generally
these studies are for 2 weeks (depends on clinical dosage).
Hope it helps.
Tausif Ahmed, Ph.D.
Asst. Director, Translational Research, Piramal Healthcare Limited, Mumbai, India
Back to the Top
Dear Frederik,
Many thanks for your email, it is indeed very helpful. Yes this anti-tumor
compound developed is the lead candidate been planned to be taken to the
clinical after obtaining sufficient pre-clinical PK and toxicity data. You
mentioned that
depending on the mechanism of action you'll have to design a suitable dosing
schedule or simply do single-dose administration.
This compound is a small molecule inhibitor aimed at inhibiting cancer growth
through targeting genetic dysregulation within these cells. Therefore, to
actually determine the dosing regimen, would one not have to determine the basic
PK parameters in the mouse, such as clearance rate of drug? Or alternatively I
was thinking of using the MTD or max achievable dose via IP route and
determining the anti-tumor activity over a timecourse of 0-24h. Please let me
know your views on this. Many thanks to everyone who has replied and shared
their views. It is indeed been very helpful and very much appreciated.
PS: I am involved at looking at the in vitro development of this potential
drug. This stage has been successful and the patent application to extend into
clinical for this drug has been accepted and will be put through if sufficient
PK and tox study data is provided. I have 12 mths to achieve this! Currently I
am writing a proposal to obtain funding for this and need to develop a concise
effective PK stud design to put on the proposal.
Best regards,
Szah
|
Want to post a follow-up message on this topic?
If this link does not work with your browser send a follow-up message to PharmPK@boomer.org with "Designing in vivo xenograft study" as the subject | Support PharmPK by using the |
Copyright 1995-2011 David W. A. Bourne (david@boomer.org)