Cheap Viagra clone lifts Dong-a

Successful trials of a Viagra substitute have lifted the share price of its developer, Dong-a PharmTech of Korea. The drug, Zydena, or Udenafil, is already one of Korea's best selling pills, despite facing a stiff challenge from Viagra.

What the company describes as 'intercourse completion rates', were doubled to almost 70 percent for couples using the highest doses of the drug in the trial. The rate for those using a placebo was 38 per cent.

Dong-A described the 12-week trial as a 'multi-center test, conducted in the US', but it did not identify the researchers. Following the completion of this phase 2b trial the company anticipates it will be able to proceed to Phase 3 clinical trials in the US and Europe – the final critical step before regulatory approval can be granted.

Dong-A's Zydena is already one of Korea's best selling drugs, despite stiff competition from Viagra. In Korea, Zydena sells for approximately half the price of Viagra.

The drug was approved for sale in Korea at the end of 2005, but has not yet been approved abroad. Within six months, it had achieved 11 percent market penetration, deflating Viagra's share to below 50 percent of the market for anti-impotence drugs. By last December, sales were worth $13m in the country's $100m-a-year erectile dysfunction treatment market, the Korea Times reported.

The drug, is also known under its generic name Udenafil, which hints at its chemical similarity to the Sildenafil Citrate molecule which is the active ingredient of Pfizer's Viagra. Udenafil is said to have more rapid onset, greater endurance, and fewer side effects, according to local media reports. Dong-A reported no serious side effects in its most recent trial, but said 4 out of 340 participants dropped out because they believed the drug, or placebos, were having an adverse effect on them.

Dong-A released news of the successful trials yesterday in advance of a contentious shareholders meeting.

Former President and CEO Moon-Seok Kang has accused the board of attempting to 'illegally' disenfranchise shareholders by boycotting his investor group's proposals and not revealing them to shareholders.