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* GSK vaccine cuts risk of shingles by 97.2 pct in over 50s
* Potentially strong competitor for Merck's Zostavax
* Shares in GSK partner Agenus jump 10 percent (Adds sales figures for Merck vaccine, forecast for GSKproduct)
By Ben Hirschler
LONDON, Dec 18 (Reuters) - An experimental shingles vaccinefrom GlaxoSmithKline has produced impressive results ina late-stage study, giving the group's expanding vaccine unit apotential $1 billion boost.
The data suggests the British company's new shot could be astrong competitor for Merck & Co's established vaccineZostavax, which is currently the only product on the market.
GSK's vaccine, known as HZ/su, reduced the risk of shinglesby 97.2 percent in adults aged 50 years and older compared toplacebo in the Phase III clinical trial involving more than16,000 individuals, the drugmaker said on Thursday.
That result looks compelling compared to Zostavax, which hasshowed 69.8 percent efficacy in patients aged 50 to 59 years,and lower efficacy in older people. However, the design ofdifferent clinical trials means direct comparisons are tricky.
The two vaccines work in different ways. Zostavax is aso-called live attenuated virus vaccine while HZ/su combines aprotein found on the virus that causes shingles with anadjuvant, or booster, which is intended to enhance theimmunological response.
The adjuvant includes a component from U.S. biotech firmAgenus, which is entitled to royalties on any futuresales. Shares in Agenus jumped 10 percent in early U.S. tradingon news of the good results.
GSK has not said when HZ/su might reach the market and acompany spokeswoman said more data would be collected on theexperimental shot next year. Additional trials to evaluate theability of HZ/su to prevent shingles are also underway in peopleaged 70 and older and in immunocompromised patients.
The full set of safety data from the Phase III trial iscurrently being analysed and will be disclosed in the comingmonths, the company added.
Merck's Zostavax, which was approved by the U.S. Food andDrug Administration in 2006, generated sales of $758 millionlast year and is still growing strongly, since only a minorityof elderly people have so far been vaccinated. Its sales areexpected to reach $1.1 billion by 2019, according to consensusforecasts compiled by Thomson Reuters Cortellis.
With potential superior efficacy, UBS said in a researchnote that sales of GSK's vaccine might exceed $1 billion a year.
Shingles is caused by the varicella-zoster virus, the samevirus that causes chickenpox. After an attack of chickenpox, thevirus lies dormant in certain nerve tissue but in older peoplein can reappear in the form of shingles. (Editing by Vincent Baby)
