Investors tread lightly in health stocks on Thursday in anticipation of the public release this evening of thousands of research abstracts with potentially investible data.

At 9 p.m. EDT, the American Society of Clinical Oncology will release many of the roughly 5,000 abstracts due to be presented at this year's annual meeting by posting them to its Web site,

Analysts, doctors, investors and reporters will be diligently searching for study results from the likes of Genentech , ImClone ( IMCL), Amgen ( AMGN) and basically every biotech and pharma company in the public sphere. (For a useful guide on searching through the abstracts, check out Adam Feuerstein's ASCO Abstract Preview.

The Amex biotechnology and pharmaceutical indices were both up, but by less than a percentage point each. Pharma stocks Astra Zeneca ( AZN - Get Report) and Sanofi-Aventis ( SNY - Get Report)both were trading up more than 2%.

Biotech stocks ImClone, PDL Biopharma ( PDLI - Get Report) and Vertex ( VRTX - Get Report) recorded gains of 2.5% or more, with Amylin , in particular, adding 3.3% to $30.51.

Elsewhere, shares of Geron ( GERN - Get Report) recovered a bit a day after the Food and Drug Administration put a clinical hold on the biopharmaceutical company's GRNPPC1, a cell therapy for spinal cord injuries. Geron said the agency verbally notified it and that it will have more information when it receives an official letter regarding the hold. After losing 20% on Wednesday, shares added 1.5% to $4 Thursday.

Incyte ( INCY - Get Report) shares climbed 2.4% to $10.48 (on lower-than-average volume) after Piper Jaffray analyst Thomas Wei and Bank of America Securities analyst Katherine Kim reaffirmed buy ratings with $19 and $15 price targets, respectively. They expecting the company to present positive data at the American College of Rheumatology meeting in June.

In other analyst action, RBC Capital Markets dropped its price target for development stage biopharmaceutical company Molecular Insight Pharmaceuticals to $14 from $18, but the stock was relatively unaffected, gaining 1.9% to $8.54 on very light volume.

In earnings, Abraxis BioScience said it turned a first-quarter profit of $4.3 million, or 11 cents a share, vs. a loss of 14 cents a share in the year-ago quarter. Revenue rose 14% to $82.1 million, from $71.9 million, leveraged by higher sales of its breast cancer drug Abraxane. Shares were off by nearly 1% at $62.65 on very light volume.