(Biotech Winners & Losers item updated for closing stock prices.)

NEW YORK (

TheStreet

) --

Lexicon Pharmaceuticals

(LXRX) - Get Report

stock was one of the leading gainers among biotech shares Monday on a day when most names in the land of experimental medicaments were in the green.

The Nasdaq Biotechnology Index jumped 6.24 points to 930.20

Shares of Lexicon, a Houston-based outfit that's attempting to develop treatments for diabetes, irritable bowel syndrome and rheumatoid arthritis, among other diseases, gained 4% to $1.79 Monday after earlier going as high as $1.91. Volume exceeded 1.9 million shares; average daily turnover has been about 750,000 shares.

Lexicon is expected to release results of a Phase Two clinical study of its rheumatoid arthritis drug LX2931. The firm launched the 12-week study in August 2009. On Friday, the company's CEO, Arthur Sands, is scheduled to deliver a presentation at the Biotech Industry Conference in New York.

Elsewhere,

Exelixis

(EXEL) - Get Report

shares added 21 cents, or 4.6%, to $4.81, on brisker-than-average volume. Earlier in the session, the stock hit $4.99.

Last week, the company licensed a pair of drugs still under development to

Bristol-Myers Squibb

(BMY) - Get Report

for an initial payment of $60 million. The two companies will collaborate on developing the drugs, which could be used to treat diabetes and inflammatory illnesses, Exelixis says.

If certain milestones are hit, Exelixis said the Bristol-Myers deal could eventually result in payments of more than $500 million. Both drug programs are in preclinical trials.

Bristol-Myers in June walked away from a deal with Exelixis under which the companies were to have worked on a cancer drug. The two companies have five other licensing agreements in place.

SIGA Pharmaceuticals'

(SIGA) - Get Report

stock continued to ride higher Monday, gaining more than 7% to $14.21. Last week,

SIGA announced a tentative agreement

to supply $500 million worth of smallpox antiviral treatments to the Department of Health and Human Services.

To make the deal official, though, SIGA needs to address a protest filed by a rival bidder for the government contract, one of the conditions of which is that the winner be certified as a small business. The Small Business Administration will rule on the protest.

Among other biotech gainers,

Luminex

(LMNX) - Get Report

shares rose 4% to $16.59,

Isis Pharmaceuticals

(ISIS)

added 3.7% to $9.46 and

Celera Corp.

( CRA) ended the day up 3.7% to $6.10.

Earnings season is upon us, and

Gilead Sciences

(GILD) - Get Report

was

set to report third-quarter numbers after the bell Monday

, with investors cued on sales of the company's HIV drug in European markets, where governments have ordered price cuts.

Gilead shares ended Monday's regular session down 0.5% to $37.54.

Other leading biotech decliners during the session included

Acorda Therapeutics

(ACOR) - Get Report

, which lost 4.7% to $27.57,

Auxilium Pharmaceuticals

(AUXL)

, which closed Monday down 3.75% to $25.69, and

Biodel

(BIOD)

, which fell 5% to $4.

Meanwhile,

Molecular Insight Pharmaceuticals

( MIPI) shares were declining Monday after

rocketing by as much as 80% Friday

. The troubled company -- on the verge of being delisted by Nasdaq -- said an early-stage clinical trial of a cancer diagnostic test showed positive results vs. a rival technology.

The stock finished Monday by sinking 15.8% to $1.07. Also on Friday, Molecular Insight received another waiver extension from its bondholders as it struggles to refinance its debt load.

-- Written by Scott Eden in New York

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