British pharmaceutical firm BTG said the first of two U.S. trials of its varicose vein treatment Varisolve had met all its goals, bringing a launch of the long-delayed product a step closer.

Varisolve is a ground-breaking treatment that uses an injectable foam to dissolve the veins as an alternative to removing them surgically. The company has forecast peak sales of between $250 million and $500 million if it is approved.

Its development, however, received a major setback in 2003 when regulators in the United States halted a trial of the drug over concerns about side effects of the foam and its active agent Polidocanol entering the bloodstream.

BTG said the final-stage, Phase III trial showed significant benefits on all end points and no major safety concerns, such as stroke or pulmonary emboli, for the 590 patients in the entire program.

Shares in BTG, which have gained 15 percent in the last three months, were 3.7 percent higher at 335.5 pence by 4:41 a.m. ET, the top performer in the mid-cap index.

Analysts at Deutsche Bank said the results of the trial significantly reduced the risks of the regulatory process for the drug.

Overall success rates for Varisolve were expected to be in line with prior clinical data, in the mid 80s percent, they said.

"This combined with benefits on ease of use, speed, lower pain and likely reduced treatment cost should make Varisolve a highly competitive option vs alternatives," they said.

Jefferies said the results bode well for future Varisolve data, but it remained cautious on the treatment's commercial potential and regulatory risks.

"We believe lingering safety concerns could ultimately preclude FDA approval, although we do not expect a decision until at least second half of 2013," the broker said.

"If BTG is able to secure approval, we believe the competitive varicose vein market, in addition to pricing and reimbursement difficulties, could limit future sales and we forecast only $100m at peak."

Chief Executive Louise Makin said the results of a second study would follow, and the group was on track to submit an application to U.S. regulators by the end of the year.

BTG, which also sells niche anti-poison treatments, decided in 2010 to market Varisolve itself in the United States rather than sharing development costs with a partner.