New weapons to fight hepatitis
HEPATITIS B is a major public health problem in the Asia-Pacific region, according to the World Health Organisation. And you only have to look at the Hong Kong statistics to understand why.
Worldwide there are more than 300 million people with asymptomatic or symptomatic hepatitis B.
In Hong Kong, about 10 per cent of the population are carriers of the disease, and of these, 25 per cent will die from liver-related diseases such as cirrhosis or liver cancer.
Currently, the sole-accepted therapy for chronic hepatitis B is interferon-alpha. But, at recommended doses, it only helps 30-40 per cent of Caucasian patients in the long term, and the chances of success in Chinese and other Asians, who typically acquire the disease early in life, are much lower.
About 70-90 per cent of Chinese people are infected at birth and develop 'immune tolerance' to the hepatitis B virus, which is why they do not respond to interferon-alpha.
Chinese with the active liver disease are just as likely to benefit from interferon as their Caucasian counterparts, but this only gives them a 40-per-cent chance of success.
Dr C. L. Lai, a reader in medicine at the University of Hong Kong and Queen Mary Hospital, says that studies at the Queen Mary Hospital did not show any significant statistical differences between treatment with the interferon-alpha drug and a placebo.
He does not recommend the use of interferon-alpha to treat Chinese hepatitis B patients.
Dr Lai, however, is more enthusiastic about two new drugs which should be available within the next 12 months.
Thymosin-alpha has been registered in Singapore since the beginning of this year and is expected to be approved for registration in Hong Kong within the next few months.
Thymosin-alpha acts as an immune system activator and would be typically prescribed when a patient's hepatitis B condition becomes 'chronic persistent'.
Another bonus is that thymosin-alpha appears to be free of the toxic side-effects of interferon-alpha, such as flu-like symptoms, fever, rashes, vomiting and depression.
Dr Lai will be studying the effects of thymosin-alpha in children with hepatitis B later this year.
The second drug under investigation, lamivudine, is also well-tolerated and, according to Dr Lai, has shown 'tremendous potential'.
It works by interfering with the way in which the hepatitis B virus replicates within the body.
In a local four-week study with lamivudine, levels of hepatitis B virus fell by 95 per cent and remained low for the remaining three weeks of treatment. However, two weeks after lamivudine therapy had stopped, the virus reappeared, returning to pre-treatment levels.
In June, Dr Lai started people on a one-year course of lamivudine therapy. His team will be collaborating with other researchers in Southeast Asia, and all are hoping for the long-term elimination of the hepatitis B virus.
The results of this study could be the key to determining which patients might benefit from life-long therapy with lamivudine. Because it is taken as a tablet, lamivudine is more convenient than both interferon-alpha and thymosin-alpha, which have to be injected.
There were few complaints from the people who took lamivudine for a month: fewer than 10 per cent complained of transient headaches or transient fatigue.
'The ultimate aim is to prevent cirrhosis and liver cancer. We are trying to halt the immune attack on the liver but it will take three to four decades to see if this approach works,' said Dr Lai, who will be presenting his results with lamivudine to medical professionals in the United States next month.
Clinical trials with these drugs in Chinese people are of special interest worldwide because of the high prevalence of hepatitis B carriers in Chinese populations; the high number of people who die from liver cirrhosis and cancer of the liver; and their poor response to interferon-alpha.
In the meantime, hepatitis B experts have warned of some unscrupulous doctors in private practices overcharging for interferon treatment, and prescribing doses lower than those recommended and to patients who cannot be helped by interferon.