The HealthShares Emerging Cancer ( HHJ) exchange-traded fund was Wednesday's worst performer, recently down 4.7%. Dendreon ( DNDN) and Nuvelo ( NUVO) both faced downgrades and were lower by 13.7% and 17.6%, respectively. The ETF was recently down $1.33 to $27.09.

The B2B Internet HOLDRs ( BHH) ETF was also lower due to rating changes. Holding Checkfree ( CKFR) sank 6.7% after JMP Securities downgraded the stock to market perform from strong buy. The ETF was off 10 cents, or 4.6%, to $2.08.

Bundled securities tracking homebuilders were also losing ground, a day after D.R. Horton ( DHI) eased after the company said fiscal second-quarter new-home orders fell 37% from a year ago. The stock was recently down 2.1%, while Hovnanian ( HOV) was losing 3.3% and Lennar ( LEN) was off 3.2%.

The iShares Dow Jones U.S. Home Construction ( ITB) ETF was recently down 62 cents, or 1.8%, at $33.82. The SPDR Homebuilders ( XHB) ETF was losing 54 cents, or 1.6%, to $32.32.

On the other hand, the Internet Infrastructure HOLDRs ( IIH) ETF was among few winners of the day. Major holding BEA Systems ( BEAS) was recently adding 1.6%, and the ETF was climbing a cent, or 0.3%, to $5.34.

Energy-related ETFs were inching higher as crude oil climbed in a volatile session. Earlier, the Energy Department said gasoline stores sank by 5.5 million barrels last week, a much steeper drop than had been expected. Crude stocks were up by 700,000 barrels. May oil futures were adding 9 cents to $61.98 a barrel.

The PowerShares DB Oil ( DBO) ETF was higher by 7 cents, or 0.3%, to $26.40. The iPath Goldman Sachs Crude Oil Index ( OIL) was gaining 6 cents, or 0.2%, to $36.88.