BOSTON ( TheStreet) -- Biotech investors will be happy with the chart above as the sector's benchmark index continues to outperform the broader market in the second quarter. The iShares Nasdaq Biotechnology Index Fund closed the June quarter up 8.9 percent compared to a 2.8 percent rise in the S&P 500. The biotech index has been on a consistent downtrend since the middle of May, which bears watching. Here are the five top-performing bio-pharma stocks in the second quarter: No. 5: Vanda Pharmaceuticals ( VNDA) VNDA data by YCharts Vanda is developing tasimelteon as a treatment for a rare sleep disorder which affects blind people. Vanda shares fell in June after questions were raised about the company's clinical development of tasimelteon, raising the risk that the drug would be rejected by FDA. No. 4: Stemline Therapeutics ( STML) STML data by YCharts Stemline is developing drugs which target cancer stem cells. The company's shares rose following the presentation of clinical data at the American Society of Clinical Oncology annual meeting in early June. No. 3: Immunomedics ( IMMU) IMMU data by YCharts Immunomedics will be presenting results from a phase I study of the experimental radio-labeled monoclonal antibody Clivatuzumab tetraxetan at a medical meeting, July 3-6. No. 2: Acadia Pharmaceuticals ( ACAD) ACAD data by YCharts Acadia continues to be one of the strongest-performing stocks in the biotech sector this year, supported by investor excitement for the company's Parkinson's psychosis drug pimavanserin. No. 1: Clovis Oncology ( ACAD) CLVS data by YCharts Clovis is not only the best-performing stock in the second quarter, but it's also No. 1 for all of 2013 so far. Why? The experimental lung cancer drug CO-1686. Not all bio-pharma stocks enjoyed success in the second quarter. The worst-performing stocks for the June quarter were: No. 5: Cardium Therapeutics ( CXM) -56% No. 4: Aveo Pharmaceuticals ( AVEO) -66% No. 3: Infinity Pharmaceuticals ( INFI) -67% No. 2: Echo Therapeutics ( ECTE) -68% No. 1: GenVec ( GNVC): -75% -- Reported by Adam Feuerstein in Boston. Follow Adam Feuerstein on Twitter.