LONDON (Reuters) - Antiretroviral drugs have transformed HIV infection from a death sentence to a manageable, chronic disorder for many people in the West. But they are still not getting to millions who need them in the developing world. The following are some key facts about anti-AIDS drugs:

- Antriretrovirals suppress replication of HIV, the virus that causes AIDS, by interfering with its genetic workings. But they cannot eradicate it from the body completely, so patients must take the medicines for life.

- There are two dozen AIDS drugs on the market that are used in various combinations called highly active antriretroviral therapy (HAART). When successful, HAART can keep virus levels very low, enabling many people to lead virtually normal lives.

- Existing drugs fall into four groups known as nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, protease inhibitors and fusion inhibitors. They fight HIV at different stages of its life cycle.

- New drugs are needed because the virus mutates constantly and eventually develops resistance. Several companies are working on new ways to stop HIV infecting cells, including a promising class of experimental drugs known as CCR5 inhibitors.

- The cost of AIDS drugs in developing countries has plunged by more than 90 percent in recent years as drug companies have bowed to pressure to offer concessionary rates and generics have entered the market.

- Yet only one million of the six million people with HIV/AIDS in developing countries who need urgent treatment are receiving the drugs, according to the United Nations.

- GlaxoSmithKline dominates the $6 billion-a-year HIV/AIDS market with a share of more than 40 percent, according to market research firm Datamonitor. Other major players include Bristol-Myers Squibb, Roche, Pfizer, Abbott Laboratories, Merck, Boerhinger Ingelheim and Gilead Sciences.

((Reporting by Ben Hirschler; editing by Joe Ortiz))