For the first time, Teva (TASE, Nasdaq: TEVA)  faces competition over its flagship original drug Copaxone, used to treat relapsing-remitting multiple sclerosis.

The Indian company Natco Pharma today announced the launch of a generic version of Copaxone (glatiramer acetate), which is Teva's biggest earner. Global sales of the drug run at about $1.4 billion a year.

Natco, the first company to launch a generic version of the drug, says it will sell glatimir at 60% below the price of the original drug.

Teva launched Copaxone - the first non-interferon treatment for multiple sclerosis - in 1996. Sales of the drug increased by 20% in 2006 compared with the year before.

Copaxone was responsible for 8.5% of Teva's turnover last year.

However, Natco - a smaller company, traded in India at a market capitalization of $92 million, compared to Teva's market cap of $30.74 billion - is unlikely to pose an immediate threat to Teva, as sales to India's population of MS patients - 50,000 out of the world's 2.5 million sufferers from the neurological disease - are low.

Also, a launch in the U.S. market will be contingent on Natco challenging Teva's patents in court.

The original patent protecting Copaxone has expired, but other patents protecting the drug only expire in 2014 in the U.S., and in 2015 in most other countries. It will probably take some 30 months before a wider generic launch can be expected.

Moreover, Teva may try to fight the generic by shifting patients to the 40-milligram version of the drug. The current dosage is 20 mg.

MS is an incurable degenerative condition of the nervous system. Copaxone, injected once a day, reduces the incidence of MS attacks.

Shares of Teva are losing 0.6% on Wall Street as of writing.