Emergence of Virulent Drug-Resistant Strain Focuses Attention on TB Drugs

Concern in South Africa

Following a high-level meeting in Johannesburg (South Africa) yesterday, between the World Health Organization (WHO), South African health officials and the U.S. Centers for Disease Control and Prevention (CDC), a seven-point plan has been devised by the Medical Research Council to tackle the alarming rise in XDR-TB cases in the country. A total of 53 cases were reported between January 2005 and March 2006, with 52 deaths already accounted for. Of the 53 reported cases in South Africa, 44 patients were found to have HIV/AIDS, and it comes as little surprise that the country's health authorities are currently detailing a joint TB-HIV/AIDS programme, to combat the dangers of the new virus. The virulent XDR-TB strain has been found to be high in Latvia and South Africa, with a WHO survey, cited by the Times of India, classifying Asia as being at high risk—particularly India, which had almost 5.7 million people with HIV last year, according to the UNAIDS 2005 report. The South Africa health ministry revealed that 3% of new TB infections involved XDR-TB, while 12% of cases currently undergoing treatment have also been infected with this new strain.

Available Therapies and Future Prospects

The WHO currently follows a TB treatment programme involving two months of multi-drug observed therapy, using isoniazid, rifampicin, streptomycin, ethambutol and pyrazinamide, which form the first line of resistance drugs. Second-line drugs include ethionamide, cycloserine, thiocetazone, quinolones (ofloxacin, ciprofloxacin and sparfloxacin), macrolides (clarithromycin), amoxicillin and clavulanic acid. With the new XDR-TB strain seemingly resistant to all the first-line drugs and most of the second-line drugs, health authorities are now turning their attention to drug candidates in the R&D pipelines of pharma firms and research organisations. The table below lists some of the hopefuls..

Outlook and Implications

The WHO's survey on the virulent strain has underscored the significance of new TB drugs. The infectious diseases sector in general, and the TB market in particular, are not sufficiently attractive for global pharma firms to deploy millions of dollars in R&D. For example, the entire market for TB drugs is estimated at just US$500 million, which does not provide much motivation when measured against a single cardiovascular drug such as Lipitor (atorvastatin; Pfizer (U.S.)), which achieved sales of US$12.2 billion last year. The therapeutic segment itself has not had a new class of drugs in the last four decades. TB drugs are usually subsidised under the WHO’s projects, or form part of national treatment campaigns, resulting in a market driven by volume rather than value. There are also concerns that TB drugs could face the same pressures that have been observed in the HIV/AIDS market, where companies have been forced to slash drug prices and/or allow greater flexibility in patent protection.

However, as the table above illustrates, attitudes are steadily changing, as pharmaceutical firms recognise the amounts being pumped into discovery research and drug distribution by organisations such as the Bill and Melinda Gates Foundation, which has injected US$132 million into TB research so far. The opportunity offered by the new strain will not unnoticed, and pharma firms are likely to look into the TB segment—particularly with the increase in the number of AIDS patients also infected with TB.