The fund, expected to be called Polar Capital Biotechnology, will be a Dublin-domiciled Oeic investing mainly in US biotechnology stocks.
Mr Pinniger joined Polar Capital at the end of August this year from SV Life Sciences, where he had been managing the £180.6m International Biotechnology Trust since April 2008.
Under his tenure, the trust delivered a return of 127.8 per cent, compared to a rise of 215.8 per cent in the Nasdaq Biotech Cap index, as the unlisted stocks in the portfolio hampered performance.
The Polar Capital fund is yet to be registered with the Irish regulator, but the firm expects to launch it towards the end of October or in early November.
Biotechnology has been the best-performing investment sector in recent years and the £229.3m Axa Framlington Biotech fund is the best-performing fund in the IMA universe in the past three years.
Polar Capital hired a former manager of the Axa fund, Deane Donnigan, earlier this year, but a spokesperson for Polar Capital said she would be working as an analyst across the healthcare team.