Diet drugs under the microscope

Dieters, doctors and investors get
their first extensive look at the first of a trio of new weight loss drugs this
week. The hope is that the new drugs can succeed where many others have failed:
delivering significant weight loss without risky side effects.

With
U.S. obesity rates nearing 35 per cent of the adult population, expectations
are high for the first new prescription drug therapies to emerge in more than a
decade. Even a modestly effective drug has blockbuster potential.

None
of the three medicines represents a breakthrough in research. Drug makers have
made little headway in understanding and treating the causes of overeating. Two
of the drugs submitted for approval simply combine existing drugs — an anticonvulsant
and an amphetamine — but have worrying side effects. The third, a new
medication, is safer but less effective.

The
quest for a blockbuster weight loss drug has been plagued for decades by safety
issues. The most notable was Wyeth’s diet pill drug combination fen-phen, which
was pulled off the market in 1997 due to links to heart valve damage and lung
problems.

The
FDA is expected to post its review of Vivus Inc.’s pill Qnexa Tuesday and will
hold a public meeting Thursday to review the data. Orexigen Therapeutics Inc.’s
Contrave is set for review in October, and Arena Pharmaceuticals Inc.’s
lorcaserin is set for December.

Qnexa
showed the best weight loss results in clinical trials, with patients losing
between 13 per cent and 15 per cent of their body weight. But the drug also had
the highest rate of patient dropouts due to side effects, which include memory
and concentration problems.

Qnexa
is a combination of two older drugs: the amphetamine phentermine and
topiramate, an anticonvulsant drug sold by Johnson & Johnson as Topamax.
According to the company, phentermine helps suppress appetite, while topiramate
makes patients feel more satiated.

Contrave
is also a combination pill, mixing an antidepressant with an anticonvulsant
drug. The drug has shown weight loss between 5 percent and 10 percent with side
effects such as nausea.

The
one truly novel drug under FDA review showed the weakest results in clinical
trials. Arena Pharmaceuticals’ lorcaserin is a first-of-a-kind drug that acts
on serotonin, a brain chemical associated with feelings of well-being and
satiation. But patients in company trials lost just 5 per cent of their body
weight.

While
Arena’s drug trails its competitors in weight loss, it appears to have the
least side effects, an important factor in FDA approval.

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