Cubist Pharmaceuticals ( CBST) swung to a second-quarter profit from a loss one year ago as sales of its antibiotic Cubicin met reduced Street expectations. The Lexington, Mass.-based drug maker reiterated 2009 sales guidance for Cubicin in the range of $520 million to $540 million. Net income for the June quarter totaled $23.8 million, or 40 cents a share, compared to a net loss of $1.3 million or 2 cents a share in the year-ago quarter. Second-quarter revenue rose 28% to $130.8 million, just a tad shy of Street expectations. Cubicin sales for the quarter rose 27% to $126.1 million, matching the estimates of analysts, although many of those forecasts had been reduced in recent weeks based on weak prescription tracking data. Cubist shares closed Thursday up 1.5% to $17.31.