Biotech indices were largely flat on Monday with the exception of a few clinical, regulatory and analyst catalysts.

Penwest Pharmaceuticals

(PPCO)

said Monday that a midstage trial on its lead product candidate, chronic-pain drug nalbuphine ER, didn't meet its primary endpoint, but the company will go ahead with a phase IIb study anyway.

Penwest theorized that the trial missed the primary endpoint (the sum of pain intensity differences between baseline and day 21) primarily because of patient dropouts in the first week of dosing, noting that it still felt the secondary endpoints demonstrated proof of concept. And so, it will conduct a phase IIb to try to show the drug has statistically significant efficacy compared to placebo based on an accepted clinical endpoint, and that the efficacy is sustained over the 12-hour dosing period, among other things. The company predicts the study will take about a year to complete.

Investors, perhaps less convinced, took shares down $1.01, or 19%, to $4.29. The Nasdaq biotechnology index, of which the stock is a component, was down ajust slightly at 821.34.

Heading the other direction

Schering-Plough

(SGP)

was moving -- and for once not because of Vytorin and the Enhance study. The company said Monday that the Food and Drug Administration approved once-daily inhaler Asmanex for asthma maintenance in children aged 4 to 11 years old. The preventive therapy was approved for patients 12 and older in March of 2005. Shares were trading up 63 cents, or 3.1%. at $21.20 on typical-to-light volume.

Sirtris Pharmaceuticals

(SIRT)

was trading up 9.3% to $13.19. Piper Jaffray analyst Edward Tentoff upgraded the stock to buy from neutral, maintaining a $15 price target, citing data due out in 2008 from a phase Ib study on the company's SIRT-501 twice daily in type II diabetes and data from a three-month phase II trial on SIRT-501 plus metformin in type II diabetes.

The company is developing drugs to target a class of enzymes called sirtuins -- SIRT-501 is an enhanced formulation of resveratrol (the healthful agent found in red wine) that targets one of those enzymes, SIRT1. The company has also discovered new chemical entities that are significantly more potent activators of SIRT1 and should enter the clinic in 2008, according to the research note.

"With proof-of concept data in hand, we look for Sirtris to enter into a major SIRT1 partnership in 2009 providing significant upside potential to shareholders," noted Tenthoff in the report.

More analyst actions -- Canaccord Adams increased its price target for

Orexigen Therapeutics

(OREX)

to $32 from $29, and Lazard decreased its price target for

Vertex Pharmaceuticals

(VRTX) - Get Report

to $13 from $16. Vertex traded down 27 cents, or 1.3%, at $20.30, while Orexigen was up 60 cents, or 5.5%, to $11.59.