Why only Norvir for boosting?
May 13, 2008
I am curious as to why Norvir is the only drug used for "boosting"? Many people simply cannot tolerate Norvir and others refuse to take it because of Abbott's price gouging of the drug. Are there any other older P.I.'s being studied for their boosting capabilities? Thanks for your time! Joseph Peer Advocate
Response from Dr. DeJesus
Hi Joseph: Your question is something that has been haunting the HIV research community at all levels for over a decade.
Ritonavir works for boosting other protease inhibitors because it is a very strong inhibitor of some enzymes in the cytochrome P540, a complex enzyme system with in the body (mainly in the liver and guts) that we all use to metabolize some drugs. There are many other medications that can also inhibit these enzymes at different degree, including among many others ketoconazole and delavirdine. Unfortunately, ritonavir appears to do a much better job that any other agent so far found, using a small dose, with potentially less side effects.
I have referred your questions also to Dr. Ben Young, which I am sure will have something interesting to add to my response.
Response from Dr. Young
Thanks for your question, Joseph.
The Norvir question indeed has been an important one- ritonavir boosted protease inhibitors are central to HIV therapy and outside of Kaletra, Abbott Laboratories has systematically made the development of coforumulated PIs impossible. As you may know, both Dr. DeJesus and I strongly protested and objected to the price increase of Norvir in Black December, 2003.
As my good friend, Dr. DeJesus points out, gram for gram, the pharmaceutical industry hasn't found a better inhibitor of P450. Even if such a medication were to be found, the extensive testing for effectiveness and safety would mean that it would take a very long time to replace the ritonavir that we already use.
Short of a new medication booster, I believe that it remains incumbent upon community groups and physicians alike to support careful and balanced review of how drugs are developed and priced. It should be of some solace that the class action- and other civil law suits against Abbott's price gouging are ongoing. Stay tuned.
Response from Dr. Young
Well, stay tuned.
There are a couple of drugs in development that may herald a new period of PK boosters. Neither has antiviral activity and appear to be better tolerated than ritonavir (Norvir). One from Gilead, called GS9350 is being developed to boost their integrase inhibitor (elvitegravir) and protease inhibitors. The other, from Sequoia Pharmaceuticals is also a P450 inhibitor and has been studied with a variety of protease inhibitors.
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