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Monday, August 09, 2004

AZT, not toxic enough

One very key part of the AIDS dissent is concerning the antiretroviral drugs. In particular, due to an early series of papers by Prof Peter Duesberg, AZT (Azidothymidine) has been targetted. It is said to be an anti-cancer drug that was canned due to being too toxic. This is false for lots of reasons.

The original inventor of AZT, Dr Richard Beltz, is quoted as saying that AZT was in fact inactive against cancer cells in the lab and in mice. This quote comes from an email to an AIDS dissident (see link) - what better source can you imagine?

"It proved to be completely inactive in all of the test systems [Dr Sartorelli] employed. In my laboratory I found AZT incapable of inhibiting the growth of Jensen sarcoma cells in vitro at very high concentrations. Thus, AZT showed no activity as a potential anticancer drug at that time."

As regards various quotes that have Dr Beltz saying that "AZT was shelved for two reasons: My studies showed that it caused cancer at any dose and it was too toxic even for short term use":

"Now let me say that I am aware of the existence of certain quotes attributed to me on the Internet, such as the one you mentioned in your letter. Such quotes are completely untrue!"

Duesberg also makes an assumption that AZT was stopped due to toxicity. From his book "Inventing the AIDS virus".

"However, when he tested the compound on cancerĀ­ ridden mice, it failed to cure the cancer. Horowitz was so disappointed he never bothered publishing the experiment and eventually abandoned that line of research. The drug MUST HAVE killed the tumors, which contain dividing cells, but it so effectively destroyed healthy growing tissues that the mice died of the extreme toxicity." [Emphasis my own]

Duesberg also says that even with enzyme specificity there is so little viral DNA compared to human DNA that it must kill many more healthy cells than virally-infected cells. The evidence doesn't bear this out, with up to 100-10,000 times more drug needed to kill cells compared to virus. [refs 1-4 below]

Some have said that AZT is currently used in cancer therapy. A drug that has the same abbreviation, Azathioprine is used in treating leukaemias, but it is not Azidothymidine.

All in all, far from being a toxic anti-cancer drug that was abandoned due to toxic effects, it doesn't kill enough cells. It is, unarguably, a nasty drug. Many (perhaps a quarter to a third) of patients require blood transfusions while on it, at least they did on the older doses which were twice those of today. However, it is quite clearly not, and never was, an anti-cancer drug.

Refs:
(1) J Virol 2002, 76(12):5966-73

(2) J Biol Chem 1989, 264:6127-33

(3) Antimicrobial Agents and Chemotherapy 1990, 34:637-641

(4) NEJM 1987, 317:192-197

2 Comments:

Blogger Steve Inrig said...

Not that it really matters, since this post is so old, but I wanted to echo Dr. Bennett's assertion that Beltz and Horowitz shelved AZT owing to its ineffectiveness against cancer, not its toxicity. Horowitz reported this to reporters at the New York Times back in 1986, so Duesberg et al. didn't have to assume why. Cf. "A Failure Led To Drug Against AIDS," New York Times, September 20, 1986, section 1, page 7.

Cheers,

S. Inrig

9:52 AM  
Blogger rj said...

I think it does still matter, because this is one of the foundation myths of AIDS denial. As is often the case, Duesberg's error/duplicity is worse than you might at first think. The section of his book that you quote in this post contains three citations:

17. B. Nussbaum, Good Intentions: How Big Business' Politics, and Medicine Are Corrupting the Fight Against AIDS (New York: Atlantic Monthly Press, 1990).

18. S. S. Cohen, "Antiretroviral Therapy for AIDS," New England Journal of Medicine, 317 (1987): 629; J. Lauritsen, Poison by Prescription-The AZT Story (New York: Asklepios Press, 1990).

Not only do these citations not support his statements, but the Cohen NEJM letter explicitly states:

"The compounds were inactive in screening trials for cancer"

The first paper describing AZT's antiretroviral activity, from 1974, is available online:
http://www.pnas.org/content/71/12/4980.full.pdf

It specifically discusses "the low toxicity of azidothymidine for the cell but high toxicity for the virus" and suggests the drug could have potential as an antiviral.

So Duesberg's statment: "The drug must have killed the tumors, which contain dividing cells, but it so effectively destroyed healthy growing tissues that the mice died of the extreme toxicity."

Is a fantasy, but it has been repeated as fact over and over again (and still is).

8:03 PM  

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