Shortage of resistant TB meds looms

While countries are rolling out new tests that will enable them to diagnose more patients with drug-resistant tuberculosis (DR-TB), a worldwide shortage of the drugs to treat these patients is likely, Médecins Sans Frontières (MSF) warns.

DR-TB can occur when TB patients do not complete their initial course of TB treatment. The only way to test for DR-TB is through cultures or via molecular testing - neither of which has been widely available in many high incident countries - until the advent of the GeneXpert, a two-hour molecular TB test released in 2010.

South Africa, which has the world's fifth-largest burden of multi-drug resistant (MDR) TB cases, will replace all microscope-based TB diagnoses with faster, more sensitive GeneXpert testing within two years, making it the world's largest user of the machine, according to Norbert Ndjeka, director of DR-TB, TB and HIV at the South African National Department of Health.

The GeneXpert machine - about the size of a milk crate - provides a fully automated nucleic acid amplification test (NAAT) that is effective in the early diagnosis of TB, MDR-TB, and TB patients co-infected with HIV, which is more difficult to diagnose.

Double the number of diagnosed

Speaking at a recent meeting co-hosted by South African Aids lobby group, the Treatment Action Campaign, human rights organisation SECTION27 and MSF, Ndjeka said that national use of the GeneXpert machine could double the number of MDR-TB cases diagnosed.

But while more patients may get diagnosed, their access to treatment remains precarious as a limited number of approved drug producers keep many DR-TB prices high and supply uncertain, according to Dr Eric Goemaere, MSF's senior regional adviser.

Higher prices

The country cures about 42% of MDR-TB patients nationally, according to Ndjeka, but the national success rate masks provincial cure rates as low as 10%.

Treating MDR-TB patients takes up about half South Africa's TB budget and this proportion is expected to rise as the country diagnoses more cases with technology like the GeneXpert.

While DR-TB drugs remain expensive worldwide, South African activists have long complained that the country paid more than other countries that were able to access prices negotiated by the international procurement body, the Global Drug Facility. South Africa recently negotiated a US$33.8 million savings in TB drugs through its new TB drug tender, which also included DR-TB drugs such as capreomycin, kanamycin and moxifloxacin.

MSF has estimated that without lower DR-TB costs, South Africa will be spending as much as $630 million on treatment by 2015. At present, para-aminosalicylic (PAS), one of the world's oldest TB drugs - which has been reintroduced to MDR-TB treatment due to a lack of alternatives - can account for as much as half of MDR-TB treatment costs generally.

Ndjeka admitted that South Africa continues to pay higher-than-average prices for PAS as the drug has not been registered for use by South Africa's regulatory Medicines Control Council (MCC), which has been labouring for years under a backlog in drug registrations, including those of some fixed-dose antiretrovirals. The country now pays a private company to import the drug through a special application to the MCC.

Behind the shortages

The answer to why the prices of DR-TB drugs - even for an antiquated and highly toxic drug such as PAS - remain high is wrapped up in a range of market and regulatory dynamics that will likely mean a shortage, says Goemaere.

A drug starts with the active pharmaceutical ingredient (API), but the number of API producers for DR-TB is extremely low, and for some drugs there is only one, says Goemaere.

Many countries struggle to accurately forecast DR-TB drug needs, leaving API producers unable to forecast not only possible increases in demand but also the market: without an accurate idea of potential financial returns, would-be API producers have little reason to enter the DR-TB drug market.

In addition, difficulties in obtaining regulatory approval is another disincentive. "Because of this, our experience in MSF with stock supply is that we go from stock failure to stock failure," Goemaere remarked.

DR-TB drug capreomycin for example, has more than doubled in price in the past 10 years, according to a recent MSF report, DR-TB Drugs Under the Microscope.

MSF has called for countries to avert the looming crisis by improving drug forecasting, negotiating better prices and accelerating national medicines registrations.

- (PlusNews, August 2011)

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