Biotech stocks dropped as the markets plummeted at the start of the week, though some stock success stories broke through.

The Nasdaq and Amex biotechnology indices were down 5.3% and 4.9%, respectively. The Nasdaq global biotechnology index was off by 5.6%.

The only stock in the green on the Amex index was ImClone Systems ( IMCL), which tacked on $1.75, or 2.7%, to $6.71 after Eli Lilly ( LLY - Get Report) confirmed that it bid $70 a share or roughly $6.1 billion. Eli Lilly said the offer represents a premium of 51% to ImClone's closing stock price on July 30, the day before Bristol-Myers Squibb's ( BMY - Get Report) acquisition offer for ImClone was made public.

Meanwhile, Bristol-Myers Squibb, which had launched a hostile tender for $62 a share, indicated it would not raise its offer. But it also isn't walking away empty-handed. The company said it owns roughly 14.4 million shares, or 16.6%, of ImClone. Considering that, the transaction is worth about $1 billion in cash for Bristol-Myers.

Eli Lilly shares were down 5.4% to $39.16. Meanwhile, Bristol-Myers shares gave up 4.5% to $19.51.

Turning to study results, the wait for interim data from Dendreon ( DNDN) is over. Dendreon shares soared $2.67, or 52%, to $7.87, after the company said prostate cancer vaccine Provenge had a 20% reduction in the risk of death at the interim analysis. The FDA required a 22% reduction in order to grant approval based on these mid-study data, so the trial will continue, with investors waiting for a final readout in 2009.

In previous studies, Provenge has been shown to have a delayed positive impact on survival. Based on this, CEO Mitch Gold said the interim results are promising.

Next, Genentech ( DNA) and OSI Pharmaceuticals ( OSIP) said that a late-stage study found that a combination of cancer drugs Avastin and Tarceva as a second-line treatment in patients with advanced lung cancer failed to increase the overall survival rate.

The "BeTa Lung" study looked at Avastin in combination with Tarceva in comparison to Tarceva alone in patients for whom chemotherapy had not stopped cancer progression. Median survival in the Tarceva and placebo group was 9.2 months. The companies said the median survival in the combination arm was similar but did not give specific data. The full data will be presented at a U.S. conference in November.

Wall Street analysts said that the trial's potential success wasn't factored into any Genentech revenue estimates, giving Monday's outcome little impact. Genentech shares were down $4.40, or 5%, at $83.13. OSI shares lost value on the study data, shedding $7.90, or 17%, at $37.94.

Also Monday, Salix Pharmaceuticals Ltd. ( SLXP) said at the American College of Gastroenterology that its rifaximin met its goals improving quality of life for patients with irritable bowel syndrome in a midstage clinical trial. Its shares were up $1.09, or 19.2%, at $6.77.

And CombinatoRx Inc ( CRXX) shares plunged $2.22, or 74%, to 78 cents, after osteoarthritis drug Synavive missed its main goal in a midstage trial, as it didn't significantly improve knee symptoms vs. placebo.