Circassia seeks $285 mln in bumper UK biotech IPO

* Allergy firm tests European market for larger biotech IPOs

* Follows boom in biotech offerings in United States

* Funds to help bring cat allergy vaccine to market

By Paul Sandle

LONDON, Feb 6 (Reuters) - Circassia, a company developing allergy treatments based on a discovery by scientists at Imperial College in London, aims to raise about 175 million pounds ($285 million) of new funds in one of Europe's biggest biotechnology IPOs.

The stock market debut in London will help to bring its cat allergy vaccine to market.

Chief executive and co-founder Steve Harris said the proceeds of the flotation in London would also support the firm's programmes in other common allergies such as house dust mites, grass and ragweed.

Biotechnology has proven to be a hot investment in the past year in the United States, triggering dozens of initial public offerings (IPOs) - but the sector has been slow to catch fire in Europe.

That makes Circassia an important test of investor appetite for larger biotech offerings, according to Robin Davison, an analyst at Edison (Milan: EDNR.MI - news) .

A successful flotation could encourage more biotech firms to raise money in London rather than crossing the Atlantic (Frankfurt: 98S.F - news) , as Dutch gene therapy company uniQure did this week for its IPO.

Circassia was formed in 2006 to commercialise innovative technology developed at Imperial College, which synthesises part of the allergens that cause reactions in sufferers.

The approach is quicker and has none of the side effects of treatments that expose sufferers to small samples of the allergen to build up resistance, Harris (Frankfurt: HRS.F - news) said on Thursday.

"We are not based on whole allergen-immunotherapy," he said.

"We take T-cell epitopes that are identified from the whole allergen, we make them synthetically, and we give four injections that treat the underlying disease rather than injections over weeks, months or years."

The company had already received 105 million pounds of funding from investors including Imperial Innovations, which holds just under 20 percent, Goldman Sachs (NYSE: GS-PB - news) , Invesco (Frankfurt: 3IW.F - news) Perpetual and Lansdowne Partners, he said.

They had indicated they would support the fundraising, he said. A small number of existing shares could also be included in the offer, he added.

The company has conducted over 15 clinical studies for its programmes, he said, and the results of late-stage trials in cat allergy in Europe, Canada and the United States were expected in the first half of 2016.

It has also demonstrated proof-of-concept for treatments for house-dust mite, grass and ragweed allergies, common conditions that affect millions of people.

"Over the course of the last six months, we've had some excellent data on our other programmes and we are now in a position to push forward on multiple fronts with a lot of confidence," Harris said.

JP Morgan Cazenove and Peel Hunt are the joint book runners on the offer.