However, XBI has previously proven that even a small allocation to a stock that puts in a Puma-esque one-day surge can benefit the ETF. XBI surged in January on the day when shares ofIntercept Pharmaceuticals (NasdaqGM: ICPT) nearly quadrupled after trials for the company’s liver disease treatment proved successful. [The One ETF Really Benefiting From the Intercept Pharma News]

Other biotech ETFs have seen similar one-day pops, including the First Trust NYSE Arca Biotechnology Index Fund (NYSEArca: FBT). FBT surged on June 24 after shares of Vertex Pharmaceuticals (NasdaqGS: VRTX) soared when the company said two Phase III trials for its cystic fibrosis treatment showed encouraging results. [Vertex Lifts Biotech ETFs]

FBT and the Market Vectors Biotech ETF (NYSEArca: BBH) are each up about 2% today, although neither holds shares of Puma.

The PowerShares Dynamic Biotechnology & Genome Portfolio (NYSEArca: PBE), which soared early last month on news of Merck’s (NYSE: MRK) takeover of Idenix Pharmaceuticals (NasdaqGS: IDIX), is also up 2% despite not holding Puma, either.

SPDR S&P Biotech ETF