Biotech stocks climbed Wednesday amid positive regulatory and clinical news, while health insurers took another blow.

Amgen ( AMGN) got a boost after a Food and Drug Administration advisory panel unanimously voted to recommend approval for Nplate, a treatment of low platelet counts in patients with chronic immune thrombocytopenia purpura, or ITP. The FDA isn't bound to follow the recommendations of such panels, but usually does.

ITP is an autoimmune disorder that puts patients at risk for severe bleeding. Lehman Brothers analyst Jim Birchenough has projected peak sales of $500 million for Nplate.

Amgen shares were up 81 cents, or 1.9%, at $45.48 Wendesday, one day before the biotech company's top-selling anemia drug, Aranesp, comes under review before another FDA advisory panel due to safety questions.

Also up on FDA news was Dendreon ( DNDN), which said that the agency agreed to let it hasten clinical testing for its prostate cancer vaccine, Provenge. Dendreon still now expects final results from the trial in the second half of 2009 instead of 2010.

Shares jumped 46 cents, or 9.3%, to $5.39.

Elsewhere, Third Wave Technologies ( TWTI) surged after the company said its test for high-risk HPV and an HPV genotyping test were successful in a clinical trial. Used with a Pap test, the company's HPV test checks for 14 strains of HPV. The genotyping product checks for HPV types 16 and 18, which cause 70% of cervical cancer cases.

The company, which said it would submit the results to the FDA in April, saw its shares soar $1.95, or 31.5%, to $9.34.

Third Wave, Dendreon and Amgen helped to prop up the Nasdaq Biotechnology Index, which was adding 1.7% to 749.41.

On the downside, Progenics ( PGNX) shares plummeted after the company said its experimental bowel drug, being developed with Wyeth ( WYE), failed in a late-stage study in patients undergoing surgery.

Progenics shares plunged $8.62, or 67%, to $4.93. Wyeth fell 97 cents, or 2.3%, to $40.69. The companies are expecting results from a second phase III study for intravenous methylnaltrexone later this year.

Elsewhere, health insurers took another blow. The sector was slammed on Tuesday when WellPoint ( WLP) scaled back guidance, and on Wednesday Humana ( HUM) followed suit.

The company warned that profits will fall far short of expectations in light of high costs associated with its Medicare prescription drug coverage. Humana slashed its full-year profit forecast to $4 to $4.25 a share from its previous guidance of $5.35 to $5.55.

Humana shares fell $8.43, or 17.8%, to $39.08.