ADVERTISEMENT
See Inside The Science Behind Your Health

Pro-Drug Gets Attention

The latest on drug approvals, warnings and research

ALL-DAY RELIEF FROM ADHD: The U.S. Food and Drug Administration is now considering whether to approve the marketing of Vyvanse (lisdexamfetamine dimesylate, made by Shire) to adults with attention-deficit hyperactivity disorder (ADHD).

Shire filed for that application in June, following up on the FDA's approval of Vyvanse last February as a treatment for ADHD in children.

Like many ADHD medications, Vyvanse acts as a stimulant. (Paradoxically, stimulants can help offset such hyperactivity problems, possibly by leveling out inconsistencies in how fast different parts of patients' brains process information.) Vyvanse, however, is a “pro-drug” compound that does not exert its therapeutic effect until after the body has metabolized it. That delayed action can stretch out how long the drug works: in studies, a dose of Vyvanse was able to combat ADHD symptoms for a full day. (The delay may also make it less appealing for abuse than conventional amphetamine stimulants are.)

The review period for the adult application is 10 months; look for a decision in spring 2008.

Last June the FDA also issued an “approvable letter” to Shire for another of its pending anti-ADHD products, Intuniv (guanfacine), a once-a-day extended-release tablet. An approvable letter indicates that the FDA is prepared to approve a new drug application once certain specified conditions, such as a request for additional information, are met. According to the filed application, Intuniv, which is not a stimulant, acts specifically on the brain's prefrontal cortex to improve executive functions, such as working memory, impulse control, tolerance of frustration and regulation of attention.

MORE: www.shireadhdtreatments.com

EASING FIBROMYALGIA: Sufferers of fibromyalgia, a painful and frustratingly mysterious affliction of the muscles and connective tissue, can finally hope for some relief. Lyrica (pregabalin, made by Pfizer) became the first FDA-approved drug treatment for fibromyalgia in June. Not all fibromyalgia patients have found that Lyrica reduced their discomfort, and common side effects have included dizziness and sleepiness. The drug had previously been approved for use in treating the nerve pain of shingles. Still more applications may yet emerge: Lyrica is also in advanced clinical trials as a treatment for epilepsy and for generalized anxiety disorder.

MORE: www.lyrica.com

NEW HOPE AGAINST RESISTANT BREAST CANCER: Ixabepilone, a compound being investigated by Bristol-Myers Squibb, shows some encouraging effectiveness against metastatic breast cancers that are resistant to three other standard chemotherapy drugs (anthracycline, taxane and capecitabine). That was the finding of a phase II clinical trial published in the Journal of Clinical Oncology in August. Ixabepilone belongs to a new class of potential chemotherapy agents called epothilones that inhibit the growth of cancer cells. In June the FDA accepted the company's New Drug application for ixabepilone, and, based on expectations, a decision should have been announced in October.

MORE: www.bms.com

NEW HIV TREATMENT: For the first time in 10 years, the FDA has approved a member of a new class of oral HIV medication. Selzentry (maraviroc, made by Pfizer) prevents HIV from entering white blood cells. The FDA granted the approval in August on an accelerated basis, after only 24 weeks of data collection during a clinical trial. The drug, however, is so far meant for use only by patients infected with a particular strain of the virus—CCR5-tropic HIV-1—that is resistant to many other antiretroviral therapies.

MORE: www.pfizer.com

LIVING WELL IS THE BEST PROVENGE? One of the most contentious and closely scrutinized decisions before the FDA concerns Provenge, a proposed therapeutic vaccine made by Dendreon for use against prostate cancer. Better options for controlling or treating prostate cancer are desperately in demand because existing treatments often fail or carry undesirable consequences (such as impotence or incontinence). A therapeutic vaccine would not be intended to prevent the disease but rather to help patients' immune systems mobilize against the cancer cells, without recourse to surgery or radiation.

An advisory panel to the FDA recommended approval of Provenge on the basis of good early clinical results, but the FDA instead requested more information last May after a second phase III clinical trial seemed more equivocal. Outraged patient groups (and investors in Dendreon) have protested this decision, at times alleging that hidden interests sabotaged the drug's approval.

Turning up the heat was a July report in the journal Clinical Cancer Research, which argued that clinical trials often misjudge cancer vaccines: in the case of Provenge, its failure to shrink tumors may be less significant than its success in raising survival rates. Dendreon is planning a new trial for Provenge that focuses on survival, and it could submit preliminary data from that work during 2008.

MORE: www.dendreon.com, www.provengenow.org

PULLING THE PLUG ON A NOVEL PAINKILLER: Neuromed Pharmaceuticals and Merck announced in early August that they were suspending development of a compound called MK-6721 as a treatment for chronic pain, after disappointing results in a phase II clinical trial.

MK-6721 belongs to an innovative class of analgesic compounds, called N-type calcium channel blockers, that block pain signals in the nervous system. It reportedly showed no adverse side effects in earlier trials, but according to the pharmaceutical makers, in the more recent tests MK-6721 lacked “the ideal pharmaceutical characteristics considered necessary” to justify further development. Nevertheless, Neuromed and Merck indicated they would continue to investigate other N-type calcium channel blockers for treating pain.

MORE: www.neuromed.com, www.merck.com

HEARTBURN DRUGS OKAY FOR HEART: Two studies released in May had suggested that two popular prescription heartburn drugs made by AstraZeneca, Prilosec (omeprazole) and Nexium (esomeprazole), might increase users' risks of heart problems. In August, however, the FDA concluded that the preponderance of available evidence did not support that worry and recommended that consumers continue to take the pills while investigations continued. The FDA expects to have concluded a more thorough review of the evidence by November.

MORE: www.astrazeneca.com

NEW MEDS FOR FIDO: Two recently approved veterinary drugs made by Pfizer Animal Health can help keep the family dog feeling fit.

Cerenia (maropitant citrate) is the first FDA-approved prescription medication specifically for the prevention and treatment of canine nausea. Motion sickness strikes one in six dogs during car trips and other travel. Moreover, acute vomiting from other causes is a common reason for owners to take their dogs to the vet. Unlike some other nausea remedies, Cerenia does not make dogs drowsy.

Another problem for dogs that is increasingly widespread is obesity: as many as 40 percent of American dogs are overweight, according to Pfizer. The new prescription compound Slentrol (dirlotapide) decreases dogs' appetite and food consumption: almost 98 percent of the animals in tests lowered their weight by an average of 11.8 percent. (Sorry, Garfield—Slentrol is not suitable for cats or humans.)

MORE: www.pfizerah.com

The Editors

Information on new medications and approvals is presented only for general educational purposes. Decisions about taking specific drugs and selecting therapies should always be made in consultation with the appropriate medical authorities.

Scientific American Dinosaurs

Get Total Access to our Digital Anthology

1,200 Articles

Order Now - Just $39! >

X

Email this Article

X