Despite the massive release of generic copies with the expiration of Tamiflu’s patent in August last year, the original drug (oseltamivir) has maintained a robust sales growth in the latest flu season, industry data showed.

According to data from U-BIST, a pharmaceutical market researcher, Tamiflu marked the largest outpatient prescription sales among flu treatments in the flu season between December and February.

Tamiflu, developed by Roche and sold locally by Chong Kun Dang, posted 11.62 billion won ($10.9 million) prescription sales during the cited period.

Among the generic drugs, Hanmi Pharmaceutical’s copy Hanmi Flu ranked second with 7.92 billion won prescriptions.

Hanmi Flu’s prescription sales of 2.76 billion won in December and 4.08 billion won in January failed to exceed those of the original. In February, however, the No.2 closely trailed the top seller, with a sales gap narrowing to 500 million won.

Kolon Pharmaceutical’s generic Comy Flu also showed a meaningful result in the generics market.

Comy Flu sold 1.83 billion won for the three months, showing a large gap from the No. 2 Hanmi Flu. However, the third-ranking treatment’s 860 million won prescriptions helped the drug nearly reach a 1 billion won monthly revenue mark.

Yunhan Corp.’s Yuhan N Flu sold 1.56 billion won in the same period.

Yuhan N Flu beat Kolon’s Comy Flu in January, signaling that the two generics can be rivals going forward.

Yuhan expects more sales growth of the flu treatment, as it has completed releasing a set of influenza test kit Capilia and flu vaccine Fluarix Tetra.

In the oseltamivir market, the supply of flu diagnosis kits will have a significant impact on flu treatment sales, observers said.

Analysts attribute the robust growths of influenza therapies by Hanmi and Yuhan to their co-marketing of test kits.

The Quick Navi-Flu is the most popular influenza test kit, used by Chong Kun Dang to promote Tamiflu, and by Hanmi, for Hanmi Flu.

“The flu season normally abates after February,” an industry executive said. “In the second half of this year, companies with large sales are expected to boost marketing activities by selling the drugs in packages with testing kits.”