Pfizer Succumbs to Temptation (Again) on "Viagra for Women"

Last Updated Apr 19, 2010 11:55 AM EDT

Pfizer (PFE) has gotten back into the search for Viagra for women. The news is a surprise only in the sense that the company officially said it had given up testing Viagra for women in 2004. That turned out to be only partially true -- a Pfizer-funded study of Viagra in depressed women was published in 2008, in the Journal of the American Medical Association.

The study is a reminder of the way that marketers often attempt -- and fail -- to take a product that is successful with one gender and double its sales by introducing it to the other, no matter what the differences (cultural, biological, you name it) may be. Five other companies have developed mostly unsuccessful products in this area. And yet research money has never really stopped flowing.

This time around, Pfizer looked beyond sildenafil, the active ingredient in Viagra, to a new potion, a selective neutral endopeptidase inhibitor, UK-414,445. Results published in the British Journal of Pharmacology show that the chemical increased vaginal and clitoral blood flow.

UPDATE: Pfizer said the results weren't good enough and has ended its studies of the compound:*
... Pfizer has conducted a number of studies over the past 15 years designed to understand the causes and nature of female sexual dysfunction (FSD) and its impact on women and their partners. ... the chemical compound studied in this research did not prove appropriate for further development. Pfizer has no current plans to develop medicines for FSD.
If you read this press release, you'd be forgiven for thinking that this study has something to do with women, but it doesn't:
A team of researchers based at Pfizer's labs in Sandwich, Kent, found that electrically stimulating the pelvic nerve increases blood flow to the genitalia, and that this effect was enhanced if they also gave a prototype drug (UK-414,495). They believe that the drug acts by blocking the breakdown of an internal chemical messenger that plays a key role in increasing blood flow during sexual arousal.
When women become aroused, blood flow increases to the vagina, labia and clitoris. This causes the organs to swell, and the vagina to relax, as well as increasing vaginal lubrication and the sensitivity of the genitalia.
In fact, the study was conducted on terminally anesthetized rabbits who were dosed up with ketamine (a veterinary anesthetic often used by humans as a party drug) before having their pelvic nerves electrically stimulated. Only then was UK-414,445 administered. No women were harmed -- or stimulated -- during the making of this research.

Pfizer's demurral leaves Boehringer Ingelheim, with its compound, flibanserin, alone in the development race. The contrast between the two drugs is interesting: flibanserin is an antidepressant, and thus may have some action on desire (but perhaps not blood flow and lubrication). UK-414,495 may have some action on blood flow and lubrication (but perhaps not desire).

Joint venture, anyone?

*This item was updated to reflect Pfizer's statement that it is no longer pursuing UK-414,445 as a treatment for female sexual disorder. Related: Image: "Jack-in-the-Pulpit" by Georgia O'Keefe.

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