According to a new report, the number of victims claimed by the South-East Asian tsunami is likely to rise due to the lack of drugs in active development for post-tsunami diseases. The report identified only 87 drugs in active development for some of the diseases most likely to be threatening the disaster victims.
Although only isolated cases of diarrhoea and respiratory diseases have occurred so far outbreaks of diseases most likely to occur are in malaria, dengue haemorrhagic fever, Japanese encephalitis virus, measles, respiratory diseases and cholera. Indeed, the World Health Organisation predicted that post-tsunami disease could kill as many people as were killed in the floods.
With no vaccines or drugs available for prevention or treatment of dengue haemorrhagic fever (DHF) the disease is potentially fatal to the elderly, the very young and those who are immuno-compromised.
Difficulty in developing a vaccine arises because there are four types of virus, which may cause DHF. Protection against only one or two dengue viruses could increase the risk of more serious disease. Although no vaccines have been launched, Pharmaprojects reports nine drugs in active development, including GlaxoSmithKline's tetravalent vaccine, currently in Phase II trials.
Even before the disaster struck dengue fever was a disease that had no major discovery effort directed to new treatments despite figures suggesting it was long overdue. The >World Health Organisation (WHO) cited 58,000 new cases of dengue fever in Indonesia alone during 2004 leading to 650 deaths. Worldwide, there are about 500,000 hospitalisations to treat dengue patients each year.
At present only supportive treatment for dengue fever patients is available. Antiviral medications offer much and advances in genetic research are aiding their development. Areas of the dengue genome involved in virus replication have been identified, and are potential targets for new broad acting anti-viral agents.
One particular area of promise is Acambis' ChimeriVax-Dengue vaccine. The "tetravalent" vaccine has shown in advanced pre-clinical trials to induce high levels of protective antibodies against all four dengue virus serotypes. There were no serious adverse events reported.
Despite a need for cheaper and better products, only four drugs are being actively developed for Japanese encephalitis (JE) virus. JE is an infection of membranes around the brain and while there is a prophylactic vaccine available, but it is expensive and requires two boosts after the initial vaccination.
The most advanced programmes are Acambis' and Intercell's prophylactic vaccines, both of which are in Phase II trials.
Vero cell-derived inactivated JE vaccines have been developed in China, where the vaccine is now licensed and 2 million doses are produced annually, as well as in Japan, where Biken and Chemo-Sero Therapeutic Research Institute are testing in Phase I-II trials two Vero cell-derived JE vaccines.
Diseases that can be easily treated, such as the acute intestinal disease cholera, still pose a threat to South-East Asia. Up to 90 per cent of cholera cases can be treated with oral rehydration, but in communities unprepared for the disease, case-fatality rates can be as high as 50 per cent.
A potential solution is to vaccinate with cholera vaccines, but two launched vaccines, Mutacol (Berna) and Dukoral (Chiron), are available in only a few countries and are in limited supply. The only other vaccine in active development for cholera is CholeraGarde (Avant), which is in Phase II trials.
>Pharmaprojects reports 36 drugs in active development for the prevention and treatment of malaria. Although many scientists doubt that a single cure for malaria will ever exist, treatments such as Artemisinin - based combination therapies are being effectively used.
In clinical trials, GlaxoSmithKline's (GSK) Bio's Mosquirix (RTS.S/AS02A) malaria vaccine candidate protected a significant percentage of children against uncomplicated malaria, infection and even severe forms of the disease for at least six months.
This trial also re-confirmed the vaccine's safety in one- to four-year-old children. However, further efficacy studies will be needed before the company can consider filing for approval of the vaccine.
With so few drugs in development for this range of diseases, and even fewer drugs close to launch, the situation for improving treatment options is not ideal. With several campaigns currently giving money to fund drug development programmes, such as the Bill and Melinda Gates Foundation donating $750 million (€573 million) over the next 10 years to the Global Alliance for Vaccines and Immunisation (GAVI), we may begin to see some improvement.
Amongst the diseases mentioned, malaria is one of the world's biggest killers and is estimated to result in one to three million deaths in the world's poorest countries every year, as well as killing more children in sub-Saharan Africa than any other infectious disease.
A licensed malaria vaccine is not expected to be commercially available before 2010, by which time it is projected that half the world's population, or 3.5 billion people, will be living in areas in which malaria is transmitted. The economic costs of the disease for Africa alone are equivalent to $12 billion annually, it is estimated.