The doors could be wide open for additional growth of the only FDA-approved over-the-counter product in light of the general underachievement of the weight loss drug category.
However, one of the major obstacles standing in its way are dietary supplements, which currently snatch up some of alli 's potential market share.
GlaxoSmithKline's (GSK) recent petition to the US Food and Drug Administration (FDA), which requests all weight loss claims be considered drug claims, could eliminate this competition.
As part of a series on the GSK petition and its impact on the US dietary supplements industry, NutraIngredients-USA.com here examines the state of the market for weight loss drugs.
Underachievement for drugs According to a report published yesterday by Edison Investment Research, an equity research firm, the market for weight loss drugs has until now been stunted because of the side effects or limited efficacy of most products.
"Although prescription pharmaceuticals for treating obesity have been available for most of the 20 th century, their development has been beset with problems.
Most have been associated with limited efficacy - typically 5kg of placebo-adjusted weight loss - and significant side effects, including addiction potential and effects on the CNS (central nervous system) and cardiovascular system."
No currently marketed anti-obesity treatment generates blockbuster sales, says the report.
However, with several new treatments now in late-stage development, the landscape could change in the next 18 months.
"Products with an acceptable risk-benefit profile should be able to gain a significant share of this blockbuster, fast-growing and significantly under-served market."
Uphill for alli Market figures compiled by IMS Health Incorporated, a pharmaceutical market research firm, have placed GSK's alli product in third place out of all weight loss drug sales, accounting for 7 percent of all anti-obesity treatments in 2007 around the world.
Following its US launch in June 2007, GSK said alli had recorded sales of around $290m in the year ended December 31 2007.
However, this included a large stock-up in order to get the new product on the shelves.
IMS figures, which track actual consumer sales for the year to December 31 2007, placed alli sales at $121m. GSK reported Q1 2008 sales for alli of $17.5m.
The active ingredient in the product is orlistat, which is said to work by attaching to some of the natural enzymes in the digestive system and preventing them from breaking down fat.
Diarrhea is a side-effect.
The drug must be taken in combination with a reduced-calorie, low-fat diet, and GSK claims it can help people lose 50 percent more weight than dieting alone.
GSK says that orlistat has been studied in more than 100 clinical trials.
Other weight loss drugs GSK's alli is actually a low-dose version of the most popular global weight loss drug, branded Xenical and sold by Roche.
Xenical contains 120mg of orlistat, whereas alli contains 60mg.
When Xenical was launched in 1999 it was an immediate market success, recording sales of about $948m in its first full year on the market.
However, since then sales slowly slipped and have never matched the first year of revenue.
This has been put down to its side effects, which include flatulence and diarrhea.
However, Xenical remains the top-selling global weight loss drug accounting for 31 percent of the market in 2007, according to IMS.
Sales that year were $538m, falling around 8 percent from 2006.
The second biggest seller last year was Reductil, made by Knoll Pharmaceutical, a member of BASF Pharma.
This product recorded sales of $375m at retail in 2007, and held a 22 percent market share.
The overall global market for antiobesity treatments, excluding dietetics, was valued at $1.7bn in 2007 by IMS.
The market grew 19 percent at a fixed rate from 2006.
Other products on the market include Acomplia, Dinintel, Clo Sibutramina, Duromine and Ectiva.
More drugs on the way There are currently numerous anti-obesity agents in studies, with development being undertaken by a range of companies including big pharma, specialty pharma and biotech, states the new Edison report.
"The success or failure of one or more projects currently in late-stage development will shape the level of interest shown by big pharma in the obesity sector," it writes.
Anti-obesity drugs in development at Phase III include products from Merck (taranabant), Pfizer (otenabant), Arena (Iorcaserin), Orexigen (Contrave) and Vivus (Qnexa).
According to FDA guidance issued last year, Phase III trials for weight management drugs should involve 12 months of placebo-controlled exposure in 1,500 patients, followed by a second year of open-label exposure in 500 patients.
Edison estimates that this would cost firms $100m. In terms of efficacy, the guidance suggests drugs need to achieve over 5 percent weight loss from baseline.
Although the market for obesity drugs could hold potential, the side effects and limited efficacy of currently available products has led to only 2 percent of the obese population in the US being treated by drugs in 2005, according to figures from Frost & Sullivan.
And it is not just the market research firms highlighting concern with current obesity drug treatments.
A spokesperson from Phytopharm, a pharmaceutical firm also active in the functional food arena, told NutraIngredients-USA.com that "whilst it is an important area, I am not bowled over by the pharmaceutical products out there (for weight loss).
My concern is that the current products are not particularly impressive or have significant side effects".
Phytopharm holds the patent for a weight loss extract from the South African plant hoodia, which it has licensed to Unilver for use in weight loss foods.
Access previous articles in the series Drug petition could strip supplements of weight loss claims GSK petition claims weight loss supplements have no science Why weight loss supplements don't work, according to GSK