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Bayer Offers New Antibiotic With Promise in Fight on TB
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NY Times
October 18, 2005
By DONALD G. McNEIL Jr.
Dr. Wafaa El-Sadr, who treats tuberculosis patients in central Harlem and in Durban, South Africa, believes that a new drug for tuberculosis is needed "absolutely desperately."
No new medication has been registered for 40 years, she points out. And one of the four drugs she prescribes for new patients clashes with an important H.I.V. drug, meaning that patients who have both the AIDS virus and tuberculosis - as more than half of her New York patients and 80 percent of her African patients do - cannot fight both at the same time. "Every new TB drug is precious," Dr. El-Sadr said. "That's why what Bayer is doing is a big deal."
In an unusual step, Bayer Healthcare announced yesterday that it had agreed to allow its most promising new antibiotic, moxifloxacin, be tested against tuberculosis, a disease that kills 5,000 people a day and is the immediate cause of death for a third of the world's AIDS victims. If the antibiotic substantially shortens TB treatment, which now typically lasts six months, the company will make millions of doses and sell them at low prices to poor countries.
Bayer's decision is unusual because major drug companies rarely test their best-selling patented antibiotics against diseases of the poor - and virtually never test them against tuberculosis - for fear of hurting sales in rich countries. Bayer makes about $500 million a year from moxifloxacin, which it sells in the United States as Avelox and elsewhere as Avalox, Avelon, Megaxin, Actira and Izilox.
The company hopes to have $1 billion in annual sales of the drug soon, according to Dr. Wolfgang Plischke, head of Bayer's pharmaceutical division. First marketed in 1999, moxifloxacin the company's heir apparent to ciprofloxacin, a related antibiotic that, sold as Cipro and other names, has earned billions of dollars but its patent will soon expire.
Bayer's decision is part of a contract with the Global Alliance for TB Drug Development, a public-private partnership. The clinical trials of moxifloxacin, involving thousands of patients in eight countries including Brazil and Zambia, will be paid for by the Bill and Melinda Gates Foundation and by the Centers for Disease Control and Prevention, the new European and Developing Countries Clinical Trials Partnership and the Food and Drug Administration.
"As someone who's been working on TB for 12 years, this is one of the most exciting advances I've seen," said Dr. Kenneth G. Castro, director of TB elimination at the C.D.C.
Even Doctors Without Borders, the Nobel Prize-winning medical charity that is often harshly critical of the pharmaceutical industry, praised Bayer.
"Moxi is a very promising drug for TB, so it's very good news," said Dr. Tido von Schoen-Angerer, research chief of the charity's global campaign for cheaper drugs. He questioned only why the decision took nearly three years, saying, "valuable time has been lost."
Dr. Plischke said in a telephone interview that Bayer had "an underlying commitment to TB" and pointed out that isoniazid, a 50-year-old drug that is one of the mainstays of TB treatment, is a Bayer drug. The company also works on low-profit-margin drugs for tropical diseases like sleeping sickness and Chagas' disease, he said.
Many powerful antibiotics made by many companies can kill the Mycobacterium tuberculosis germ that causes tuberculosis.
But the more lucrative antibiotic sales lie in curing the ills of the relatively wealthy residents of North America, Europe and Japan: pills for infections of the ears, sinuses, lungs and urinary tracts, and intravenous infusions for dangerous hospital infections.
Beside the small profits made serving poor countries, there are other risks to registering a drug for TB. For example, the cheaper pills may be shipped back to rich countries for "gray market" sale.
In nations with broken-down health systems, the drug may be sold openly and overused, leading to drug-resistant germs that make their way to rich countries and render the company's best-seller useless. And when millions use a drug for months, rare side effects can emerge, forcing its withdrawal, much as unexpected reports of heart attacks forced Merck to pull Vioxx, its best-selling painkiller, from the market.
"Companies are much more likely to offer drugs that have no commercial value, or to piggyback a drug from the veterinary sector and give it a human application," said Dr. Mary Moran, an expert on drugs for neglected diseases at the London School of Economics. "Big companies say 'TB muddies the water.' If it works, governments may try to restrict it for TB use. And if you get a side effect, you've just trashed your best commercial antibiotic."
Dr. Plischke said he believed that new side effects were unlikely because moxifloxacin had already been taken by 40 million people. Overuse leading to resistance and gray-market sales were unlikely, he said, because the drug would be mixed into a four-drug pill.
Four old antibiotics with expired patents - isoniazid, ethambutol, rifampicin and pyrazinamide - are the mainstays of first-line tuberculosis treatment. A typical patient takes cocktails of them for six months.
In tests in mice with tuberculosis, the substitution of moxifloxacin for one of them cuts treatment time to four months, Dr. Castro said.
Also, he said, moxifloxacin's close chemical relatives ciprofloxacin and levofloxacin have been used for a decade to treat multidrug-resistant strains of TB. Ideally, tuberculosis specialists want to get treatment down to a few weeks, because many patients stop taking their pills when they stop coughing up blood and start feeling better. Ending treatment early encourages drug-resistant strains.
To prevent that, patients are put on "directly observed therapy," or D.O.T., meaning a nurse or someone else who will not let the patient slip up must watch them take their pills every other day.
Six months of that, Dr. El-Sadr said, is very taxing for patients in New York who have to get to jobs, as well as for those who are homeless or have drug problems. It is equally hard, she said, for her African patients many miles from clinics.
In the last few years, several pharmaceutical companies have begun drug-donation programs, though they often limit them to drugs without lucrative Western markets or limit which diseases the drugs may be used against.
Pfizer, for example, donates millions of doses of its best-selling antibiotic Zithromax to programs fighting trachoma, an eyelid infection common in rural Africa that slowly causes blindness. Merck and GlaxoSmithKline donate their veterinary deworming pills to poor countries to treat human worm diseases.
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